Smith, I.M., Lindquist, E.E., and V. Behan-Pelletier. 1998. Mites (Acari) in Smith, I.M., and G.G. Scudder, eds. Assessment of species diversity in the Montane Cordillera Ecozone. Burlington: Ecological Monitoring and Assessment Network, 1998.

MITES (ACARI)

Ian M. Smith, Evert E. Lindquist and Valerie Behan-Pelletier

CASE STUDY - WATER MITES (HYDRACHNIDA) - I.M. Smith

Water mites comprise 7 superfamilies belonging to the cohort Parasitengona, along with Stygothrombidioidea and their terrestrial relatives in the superfamilies Trombidioidea, Calyptostomatoidea and Erythraeoidea. This large and diverse clade is characterized by an essentially holometabolous life history. Larval water mites are ectoparasites of aquatic insects while the active post-larval instars (deutonymphs and adults) are fully aquatic predators of small invertebrates. The parasitic associations of larvae were discussed by I.M. Smith and Oliver (1986) and B.P. Smith (1988).

The first reports of water mites from the Montane Cordillera Ecozone were published by Koenike (1895, 1912), based upon collections made by J.B. Tyrrell during the original C.P.R. surveys. Extensive knowledge of the water mite fauna of the Ecozone began to develop in the early 1960's as a result of field work conducted by staff of the Royal Ontario Museum and by John Conroy of the University of Winnipeg. The following treatment is based largely on collections made during the past 30 years by the senior author, now housed in the Canadian National Collection (CNC) of Acari in Ottawa. I consider available data on species occurrence to provide at least preliminary coverage of the Okanagan Range (E.C. Manning Provincial Park), the Okanagan Highland (south Okanagan Valley), the Selkirk-Bitterroot Foothills (several localities along Hwy. 3), parts of the Thompson-Okanagan Plateau (Okanagan Valley and Sicamous - Kamloops corridor), parts of the Columbia Mountains and Highlands (Creston Valley and Revelstoke - Golden corridor), the Southern Rocky Mountain Trench, the Northern Continental Divide (Waterton Lakes National Park and lower elevations of Banff National Park), the Chilcotin Ranges (Upper Bella Coola Valley) and parts of the Fraser Plateau (Clinton - Williams Lake corridor and Smithers area). Occurrence data from other ecoregions is rudimentary or lacking. Information on some species has previously been published, and additional data for these and many more species are available in a large relational database associated with the CNC. The faunas associated with wetland and spring habitats were treated by I.M. Smith (1987 and 1991a, respectively).

Over 800 species representing 98 genera and 34 families of water mites occur in Canada, and nearly 350 species in 73 genera and 31 families have been collected in the Montane Cordillera. About 170 species, mostly in lotic habitats, have yet to be identified with certainty, and many of them are undescribed and unnamed taxa. A taxonomic census of the families of water mites for North America, Canada, and the Montane Cordillera Ecozone is summarized in Table 7, using estimates based upon published reports supplemented by at least preliminary study of taxa represented in major North American collections, especially the Canadian National Collection. Numbers of species in large families with numerous unidentified species are approximate. Both named and unnamed species of the representative superfamily Arrenuroidea from the Ecozone are considered in more detail in Table 8. A list of named species known from the Montane Cordillera is presented in Table 9.

Water mite species of the Montane Cordillera exhibit a variety of distribution patterns with six apparent centres of origin. The names for some of the ecological regions used to describe these patterns are derived from the publication entitled "Ecological Regions of North America - Toward a Common Perspective" (Commission for Environmental Cooperation 1997).

Marine West Coastal Forests (MWCF). A number of species have distributions centred on or largely restricted to the Coast Ranges between central California and central British Columbia, but extending inland through part or all of the watershed of the Columbia River and its tributaries. Populations of these species apparently inhabited Pleistocene refugia with temperate conditions on and around the Siskiyou Highlands of northern California and southern Oregon well south of the maximum extent of the Cordilleran Ice Sheet during the Wisconsinan.

Western Interior Basins and Ranges (WIBR). Many species have extensive distributions in the Great Basin and adjacent desert regions between the Rocky Mountains and the Cascade and Sierra Nevada Ranges in the United States, and reach their northern limit in the Southern Interior Ecoregion of the Montane Cordillera Ecozone. These species probably inhabited Pleistocene refugia with warm temperate conditions in southern regions of the major mountain ranges of the western United States.

Western Cordillera (WC). Many species occur at higher elevations on several mountain ranges extending through the Montane Cordillera as far south as Colorado and northern California. Some of them are also widely distributed in Taiga and Tundra ecozones, and apparently inhabited periglacial Pleistocene refugia along the ice front during the Wisconsinan Glacial Maximum.

Boreal. Many species have extensive distributions throughout the Boreal Plains and Boreal Shield and reach their southern limit in western North America in the Montane Cordillera Ecozone. These species apparently inhabited periglacial Pleistocene refugia with boreal conditions in coniferous forest biomes just south of the maximum extent of the Cordilleran Ice Sheet.

Prairies. Some species are widespread in the Temperate Prairies and the West-Central Semi-Arid Prairies as far east as Manitoba and Minnesota. They probably inhabited Pleistocene refugia on steppes in the southern Great Plains region.

Widespread. Some species have distributions that essentially cover all of temperate North America. Populations of these species apparently inhabited Pleistocene refugia with temperate conditions in various biomes south of the ice front across North America.

CLASSIFICATION AND DIVERSITY OF WATER MITES IN THE MONTANE CORDILLERA ECOZONE

The basic classification, ecology and distribution of North American water mites is summarized at the generic level by Smith, Cook and Smith (1999).

Hydrovolzioidea. Members of Hydrovolzia marshallae Cook, the only species of the holarctic family Hydrovolziidae known from the Montane Cordillera, inhabit cold springs and seepage areas with water temperatures below 10·C. Deutonymphs and adults crawl slowly through moss mats and detritus, and larvae are parasites of adult Empididae (Diptera). This species is widely distributed in the Marine West Coastal Forests and Western Cordillera, and occurs throughout the Montane Cordillera and adjacent regions of British Columbia and the northwestern United States (Smith 1991a). Other species of Hydrovolzia live in similar habitats throughout North America and Eurasia.

Eylaoidea. Limnochares americana Lundblad is widespread in North America and common in the Montane Cordillera. Adults are commonly seen swimming in ponds and lakes; their larvae are parasites of adult Odonata. Another species of this genus, Limnochares aquatica Linnaeus, lives in ponds and bog pools throughout the Boreal ecozones of Canada and is common in the Maritime Pacific Ecozone, but has not yet been found in the Montane Cordillera.

About 10 species of Eylais, the only North American genus of the worldwide family Eylaidae, inhabit vernal temporary pools and ponds in the Montane Cordillera (B.P. Smith 1986, CNC). The conspicuous red adults of this genus are among the largest water mites, often reaching 5 mm. in length, and feed voraciously on ostracod crustaceans. Larvae of Eylais parasitize aquatic bugs (Hemiptera) and beetles (Coleoptera) (Lanciani 1969, 1970a, 1970b; B.P. Smith 1986) and those of species that breed in temporary pools spend much of the year attached to hosts, completing development only after their habitats refill with water in spring (Wiggins et al. 1980). Recent systematic studies of Eylais have shown that the most reliable morphological characters for diagnosing species are found on the larval instar. Scudder (1983) concluded that parasitism by larval Eylais and Hydrachna excludes one of their hosts, Cenocorixa expleta (Uhler), from living in fresh and low salinity lakes and ponds on the Fraser Plateau.

Hydrachnoidea. Adults of Hydrachna, the only genus in this worldwide group, are large (< 5 mm in diameter), rotund mites living in temporary pools and ponds. They apparently feed on eggs of aquatic insects. Members of the estimated 15 species inhabiting the Montane Cordillera Ecozone (Conroy and Scudder 1975, B.P. Smith 1987, CNC) are often abundant and readily observed in vernal temporary pools during May and June. Their larvae are parasites of aquatic bugs (Hemiptera) and beetles (Coleoptera) and may spend up to 9 months of the year on the host during the dry phase of the vernal temporary pool cycle (Wiggins et al. 1980). As in the case of Eylais, recent studies of the species in temperate North America confirm that larval features provide the most reliable characters for identifying the various species.

Hydryphantoidea. Over 20 species, representing 8 holarctic genera, 3 nearctic genera and 1 genus with species in western North America, South America and Australia, of the family Hydryphantidae occur in the Montane Cordillera (Koenike 1895; Cook 1955; I.M. Smith 1987, 1991a; CNC). Adults of these species live in a wide variety of habitats and feed on eggs or early instar larvae of insects. Their larvae parasitize various adult insects, typically nematocerous flies (Diptera), stoneflies (Plecoptera) or caddisflies (Trichoptera). Members of Notopanisus, Albertathyas, Panisopsis, Panisus, Columbiathyas, Thyopsella, Protzia, Tartarothyas, and certain species of Thyas live in springs or riffles of cold streams (I.M. Smith 1991a, I.M. Smith and Cook 1998a, 1998b). Species in the genera Hydryphantes and Thyopsis, and other species of Thyas, live primarily in vernal temporary pools (I.M. Smith 1987, Wiggins et al. 1980). Notopanisus canadensis Smith and Cook is a rare species known only from cold rheocrenes in Waterton Lakes National Park and the Mount Hood region of Oregon (I.M. Smith and Cook 1998a). Other species of Notopanisus live in the Andes Mountains of Chile and Argentina and in Australia, suggesting an ancient origin for the genus. Members of Albertathyas montana Smith and Cook are locally abundant in riffles of mountain streams in the Rockies of southern Alberta and Montana, and have also been reported once from eastern Oregon (I.M. Smith and Cook 1998a). Another recently described species, Columbiathyas crenicola Smith and Cook occurs in seepage areas at high elevation in the Southern Interior Mountains and Southern Interior Ecoprovinces, in the Cascade Mountains of Washington and the Coast Range in Oregon (I.M. Smith and Cook 1998a). Members of Tartarothyas occidentalis Smith and Cook occur in small mountain streams in southern areas of the Columbia Mountains and Highlands Ecoregion, and are also common in the Coast Range from southern Vancouver Island to Curry County, Oregon (I.M. Smith and Cook 1998b). Species of the genera Hydryphantes, Thyas, Thyopsis, Thyopsella, Panisus, Panisopsis and Protzia occurring in the Montane Cordillera all have widespread Boreal distributions. Adults of several undescribed species of the worldwide genus Wandesia occur in hyporheic habitats in the Montane Cordillera. Larvae of Wandesia parasitize stoneflies (Plecoptera). Members of Pseudohydryphantes latipalpus Marshall are widely distributed in the Montane Cordillera in stream pool and cold lake habitats, and occur across the Boreal and Taiga ecozones of North America (Marshall 1924b, 1929; CNC).

Adults of Hydrodroma despiciens (Müller), the only species of the worldwide family Hydrodromidae known from the Montane Cordillera, are common in permanent lentic habitats throughout temperate North America (I.M. Smith 1987). This species is one of the few water mites able to live in highly alkaline ponds and lakes in the Southern Interior and Central Interior Ecoprovinces (Conroy and Scudder 1975, CNC). Larvae of this species parasitize chironomid midges (Chironomidae) and phantom midges (Chaoboridae).

Lebertioidea. Adults of most species of the holarctic genera Sperchon and Sperchonopsis (Sperchontidae), Bandakia (Anisitsiellidae), Lebertia (Lebertiidae) and Torrenticola and Testudacarus (Torrenticolidae) inhabit riffles in streams. The western North American species Bandakiopsis fonticola Smith, Cookacarus columbiensis Barr, Utaxatax newelli (Habeeb) and Estelloxus californiensis Habeeb live mainly in cold springs and all have essentially Marine West Coastal Forests distributions that extend into the Montane Cordillera (I.M. Smith 1979, 1982, 1991a; CNC). Spring inhabiting species of Sperchon, Bandakia, Lebertia, Estelloxus and Testudacarus appear to have similar distributions. Springs and fast flowing streams are abundant in the Montane Cordillera and adjacent Ecozones, and the large genera Sperchon, Lebertia and Torrenticola all exhibit relatively high levels of species diversity. These genera have not been well studied in western North America, and many species remain undescribed or incompletely known. In contrast, species of the holarctic genus Teutonia (Teutoniidae) and the worldwide genera Oxus and Frontipoda (Oxidae) are adapted for living in lentic habitats. Most species of these genera inhabiting the Montane Cordillera, such as Teutonia lunata Marshall, Oxus connatus (Marshall) and Frontipoda americana Marshall, are widely distributed in Boreal ecozones (Marshall 1924b, CNC). One species, Oxus occidentalis (Marshall), is restricted to western North America where it occurs throughout the Montane Cordillera, Boreal Cordillera and Pacific Maritime Ecozones (Marshall 1924b, CNC). Larvae of most Lebertioidea parasitize chironomid midges (Chironomidae), but those of some species of Sperchontidae attack blackflies (Simuliidae).

Hygrobatoidea. Species of 8 families of this large superfamily inhabit the Montane Cordillera. Adult hygrobatoid mites live in a wide variety of habitats and feed on either early instar insect larvae or crustaceans. Larvae of nearly all taxa are parasites of chironomid midges (Chironomidae).

Most species of Limnesiidae living in the Ecozone belong to holarctic species groups of the genus Limnesia (Conroy and Scudder 1975, CNC). Adults inhabit stream pools, ponds and mesotrophic lakes, and most have Boreal distributions (I.M. Smith 1987). Larvae parasitize chironomid midges. All other North American taxa of Limnesiidae apparently originated in South America and have their greatest species diversity in the southern United States. Members of Tyrrellia circularis Koenike occur in the Selkirk-Bitterroot Foothills (CNC). Adults of this genus are unusual among Hygrobatoidea, inhabiting the surface film on wet detritus at the edges of ponds and streams; larvae parasitize ceratopogonid midges.

The large worldwide family Hygrobatidae is represented in the Montane Cordillera by several species of the holarctic genera Atractides and Hygrobates living in springs, streams and lakes (Conroy and Scudder 1975; I.M. Smith 1987, 1991a). Most of the species of Atractides inhabit stream riffles and appear to have their distributions centred in either Marine West Coastal Forests or Western Interior Basins and Ranges, but one, Atractides nodipalpis (Thor), is widespread in Boreal Ecozones. Adults of several species of Hygrobates inhabit springs in the Montane Cordillera and have either Western Cordillera or Boreal distributions (I.M. Smith 1991a). Other species inhabit ponds and lakes and are distributed widely in boreal ecoregions (I.M. Smith 1987).

The tiny and strongly flattened adults of several species of Feltria, the only genus in the holarctic family Feltriidae, live in cold springs and both hyporheic and riffle habitats in streams in the Montane Cordillera (CNC). Most species inhabiting surficial substrata have either Marine West Coastal Forests or Western Cordillera distributions (Cook 1961, 1963, 1970), but some restricted to subsurface gravels (eg. Feltria cornuta Walter) are also well represented in the Western Interior Basins and Ranges and several of them reach the northern limit of their distribution in the Southern Interior or Southern Interior Mountains Ecoprovinces.

Several species of Neumania, and a few each of Koenikea and Unionicola, represent the family Unionicolidae in the stream pools, ponds and lakes of the Montane Cordillera (I.M. Smith 1987; Conroy 1991a-b, 1992 a-b; CNC). Most of the about 10 species of the worldwide genus Neumania represent holarctic species groups and have either Marine West Coastal Forests and Western Cordillera or Boreal distributions. Unionicola crassipes (Müller) is a widespread Boreal species. Two widely distributed species of the genus Koenikea are known from southern ecoregions of the Ecozone. Koenikea wolcotti Viets inhabits ox-bow ponds in the southern Okanagan Valley near Osoyoos and Koenikea haldemani Viets lives in similar habitats in the Creston Valley Wildlife Management Area. These are the only two of the approximately 20 nearctic species of Koenikea to occur in British Columbia. This genus apparently originated in Gondwanaland, and species groups occurring in North America represent invasions during late Tertiary times.

About 25 species representing 10 genera of the family Pionidae occur in the Montane Cordillera (I.M. Smith 1976, 1987; CNC). At least 3 species of the holarctic genus Hydrochoreutes live in stream pools and lakes in the Montane Cordillera (I.M. Smith 1976, 1987). Two of these, Hydrochoreutes intermedius Cook and H. microporus Cook, are distributed throughout the Boreal ecozones of Canada and probably reach their southern limit in western North America in the Montane Cordillera.

Two species of the holarctic genus Pseudofeltria inhabit springs in the Montane Cordillera (CNC). Pseudofeltria laversi Cook has a Western Cordillera distribution and an undescribed species has been collected at a few sites in the Rocky Mountains of Alberta and British Columbia. At least three species of the related holarctic genus Forelia live in stream pools, ponds and lakes in the Ecozone (I.M. Smith 1976, 1987; CNC), and appear to have widespread Boreal distributions.

Members of Huitfeldtia rectipes Thor, a holarctic mite that occurs throughout Boreal and Arctic ecozones, inhabit oligotrophic lakes in the Montane Cordillera at the southern limit of the distribution for the species (I.M. Smith 1976, CNC). One species of the nearctic genus Neotiphys, N. marionensis (Conroy), occurs in stream pools and lakes throughout northern regions of the Western Cordillera and Marine West Coastal Forests and an undescribed species of Pionopsis inhabiting temporary pools has a similar distribution (CNC). Two species of the holarctic genus Tiphys occur in temporary pools in the Ecozone (I.M. Smith 1976, 1987; CNC), and both of them have widespread Boreal distributions. These mites survive the dry phase of the temporary pool cycle as deutonymphs, becoming quiescent until water returns to the pool basin during the following Spring (Wiggins et al. 1980).

The holarctic genus Nautarchna is represented in the Montane Cordillera by two species with transcontinental Boreal distributions (I.M. Smith 1972, 1976; CNC). Members of N. muskoka Smith live in stream pools and those of N. queticoensis inhabit springs. About 15 species of the holarctic genus Piona occur in standing water habitats in the Montane Cordillera (Conroy and Scudder 1975; I.M. Smith 1976, 1987). Many of them, such as Piona conglobata (Koch) and P. neumani (Koenike), live primarily in permanent ponds and small lakes and are widely distributed in Boreal and Prairie ecozones. A few others, including Piona constricta (Wolcott) and P. mitchelli Cook, inhabit vernal temporary pools and are adapted to survive drought in the same way as species of Tiphys do. Members of Piona carnea (Koch) are common in many of the shallow lakes and ponds in the Southern Interior and Central Interior Ecoprovinces.

Frontipodopsis nearctica Cook, the only described nearctic species of the world-wide family Frontipodopsidae, is common in hyporheic habitats throughout the Marine West Coastal Forests and parts of the Western Cordillera (CNC). In the Montane Cordillera Ecozone, it has been reported from the western part of the Chilcotin Range Ecoregion of the Central Interior Ecoprovince and the southern ecoregions of the Southern Interior Ecoprovince.

At least 40 species of the worldwide family Aturidae are known from the Montane Cordillera (Smith 1984, CNC). Several holarctic genera are represented in the Ecozone by one or two common species with either Marine West Coastal Forests and Western Cordillera or Boreal distributions. Adults of Ljania bipapillata Thor and an undescribed species of Ljania occur in stream riffles and interstitial habitats, respectively. The holarctic species Neobrachypoda ekmanni (Walter) is widespread in Arctic ecozones and occurs in both cold mountain pools and limnocrene habitats throughout the Montane Cordillera and Maritime Pacific Ecozones. The widespread Boreal species Estellacarus unguitarsus (Habeeb) inhabits both stream pools and alpine lakes throughout the Ecozone. Two species with extensive distributions in the Marine West Coastal Forests, Brachypoda setosicauda Habeeb and Woolastookia setosipes Habeeb, are common in stream pool habitats in southern ecoregions of the Montane Cordillera. Many species in the holarctic genera Aturus and Kongsbergia are among the most common mites in stream riffles and hyporheic habitats in the Ecozone, but these taxa have not yet been well studied and many species identities remain uncertain.

Arrenuroidea. Forty-seven species representing 10 genera and 8 families of this superfamily have been recorded from the Montane Cordillera. Thirty-two of these species belong to the genus Arrenurus, and four of them have not yet been described.

Momoniidae. Five species of this ancient worldwide family occur in the Montane Cordillera Ecozone (I.M. Smith 1989a, 1989c, 1991b; CNC). Members of Cyclomomonia andrewi Smith, the only known species of the genus, live in interstitial habitats associated with small streams. They have been reported from scattered localities in the Marine West Coastal Forests between southern Oregon and central Vancouver Island, and from both the Bella Coola Valley at the western edge of the Chilcotin Range and Bonanza Pass in the Selkirk-Bitterroot Foothills. Four species of the holarctic genus Stygomomonia also live in hyporheic gravels. Three of them, Stygomomonia (Allomomonia) mitchelli Smith, S. (A.) atnarkicola Smith and S. (s. s.) neomexicana Cook are widespread throughout the Marine West Coastal Forests, Western Cordillera and Western Interior Basins and Ranges. All of these species occur in the headwaters of the Bella Coola watershed in the Chilcotin Range and in streams of the Southern Interior, and S. mitchelli is also common in the Southern Interior Mountains as far east as Waterton Lakes National Park. The fourth species, Stygomomonia (s. s.) separata Cook, has a more limited distribution in the southern Marine West Coastal Forests, central Western Cordillera and northern Western Interior Basins and Ranges, and has been reported from the Montane Cordillera only in the Similkameen River near Princeton.

Nudomideopsidae. One species of this ancient world-wide family, Paramideopsis susanae Smith, inhabits springs and hyporheic gravels throughout the Marine West Coastal Forests, Western Cordillera and Western Interior Basins and Ranges (I.M. Smith 1990, CNC). In the Montane Cordillera, this species is moderately common in the Southern Interior and Southern Interior Mountains Ecoregions, with populations as far east as Waterton Lakes National Park.

Mideidae. Members of Midea alata Young live in beaver ponds and boggy pools throughout the Boreal and Taiga ecozones, and occur southward in western North America as far as coastal Oregon in the Marine West Coastal Forests and Colorado in the Western Cordillera (CNC). This species is locally common in all regions of the Montane Cordillera Ecozone.

Mideopsidae. Five species representing two subgenera of the holarctic genus Mideopsis are known from the Montane Cordillera (CNC). Members of Mideopsis (s. s.) americana Marshall, a common species from coast to coast throughout much of temperate North America, inhabit shallow lakes and ponds of the Southern Interior and Southern Interior Mountains Ecoregions of the Ecozone. The common transcontinental species Mideopsis (s. s.) borealis Habeeb has been collected from Okanagan Lake near Summerland, and probably occurs in other deep oligotrophic lakes in the Ecozone. Mideopsis (s. s.) barri Cook is a common mite in springs throughout the Marine West Coastal Forests and southwestern areas of the Western Cordillera. Populations of this species have been found in the Montane Cordillera Ecozone near Clinton at the southern edge of the Fraser Plateau Ecoregion, in the Kettle Valley of the Okanagan Highlands Ecoregion and two localities in the Columbia Mountains and Highlands Ecoregion, one near Kootenay Lake and the other in the Selkirk Mountains. Two species of the subgenus Xyxtonotus with very different habits occur in the Montane Cordillera. Adults of Mideopsis (X.) robusta (Habeeb), a species with transcontinental Boreal distribution, are locally abundant in thick detritus substrata of stream pools, bog pools and ponds in the Thompson- Okanagan Plateau and the Northern Continental Divide Ecoregions. Members of Mideopsis (X.) pumila Cook inhabit hyporheic gravels of streams throughout the Marine West Coastal Forests, Western Cordillera and Western Interior Basins and Ranges and are common in the southern ecoregions of the Montane Cordillera.

Chappuisididae. Morimotacarus nearcticus Smith is an intriguing species that lives in hyporheic gravels of mountain streams, and is currently known from only three localities, all in the Western Cordillera. One is near the headwaters of the Bitterroot River in Montana, the other two are in the Northern Continental Divide Ecoregion of the Montane Cordillera, in Waterton Lakes National Park and Kananaskis Country, respectively (I.M. Smith 1992b, CNC). The only other known species of Morimotacarus lives in Japan.

Yachatsia mideopsoides Cook inhabits hyporheic interstitial waters throughout the Marine West Coastal Forests from California to the Bella Coola Valley, and sporadically in the Western Cordillera and Western Interior Basins and Ranges of the United States (I.M. Smith 1992b, CNC). This species has been collected once in a tributary of the Atnarko River in the Upper Bella Coola Valley of the Chilcotin Ranges Ecoregion of the Montane Cordillera.

Athienemanniidae. Chelomideopsis brunsoni (Cook) has been collected in springs from southern Oregon to southern Vancouver Island in the Marine West Coastal Forests, and is abundant in helocrenes near Clinton at the southern edge of the Fraser Plateau Ecoregion of the Montane Cordillera (I.M. Smith 1992a). Members of Platyhydracarus juliani Smith inhabit hyporheic gravels in mountain streams throughout the Marine West Coastal Forests, Western Cordillera and Western Interior Basins and Ranges and are common in the headwaters of the Bella Coola River watershed of the Chilcotin Ranges Ecoregion and in southern ecoregions of the Southern Interior and Southern Interior Mountains Ecoprovinces of the Montane Cordillera (I.M. Smith 1989b, CNC).

Acalyptonotidae. Species of this family are restricted to cold water habitats in Arctic and temperate areas of North America and Eurasia. Acalyptonotus neoviolaceus Smith inhabits springs and pools at high elevations throughout the Marine West Coastal Forests and WC as far south as southern Oregon and central Colorado. In the Montane Cordillera, members of this species have been collected on Hudson Bay Mountain near the northern edge of the Fraser Plateau Ecoregion, near the headwaters of the Bella Coola River watershed in the Chilcotin Ranges Ecoregion, on Mount Revelstoke in the Columbia Mountains and Highlands Ecoregion and in Waterton Lakes National Park in the Northern Continental Divide Ecoregion (I.M. Smith 1983). Members of Acalyptonotus pacificus Smith are known from small alpine lakes and pools in only three localities, Mount Hood at the western edge of the WC in northern Oregon, Heather Mountain (southern Vancouver Island) in the Marine West Coastal Forests and along the Princeton-Summerland Road in the Thompson-Okanagan Plateau Ecoregion of the Montane Cordillera (I.M. Smith 1983, CNC).

Laversiidae. The only species of this nearctic genus, Laversia berulophila Cook, lives in cold springs with water temperature below 10·C throughout Boreal ecozones across North America (I.M. Smith 1991a, CNC), and as far south as northern Oregon and central Colorado in the Western Cordillera. Members of this species are common near the headwaters of the Bella Coola River watershed in the Chilcotin Ranges Ecoregion and in southern ecoregions of the Southern Interior and Southern Interior Mountains Ecoprovinces of the Montane Cordillera.

Arrenuridae. Thirty-four species of Arrenurus are known from the Montane Cordillera thus far, five of which are undescribed (CNC). Lavers (1945) reported 30 species and subspecies of the genus from the state of Washington.

Arrenurus (Truncaturus) - The subgenus Truncaturus is represented in the Ecozone by only Arrenurus (T.) palustris Mullen, a widespread Boreal species (I.M. Smith 1996, CNC) which has been found in seepage areas around Cameron Lake in Waterton Lakes National Park. About a dozen other species of this essentially holarctic subgenus inhabit temporary pools and helocrenes east of the Rocky Mountains, and a small group of species live in hyporheic habitats from the Ozark Plateau through the southwestern United States to Mexico. No members of Truncaturus have been reported from west of the Rockies in Canada. Known larvae of this subgenus are parasites of mosquitoes (Culicidae).

Arrenurus (Micruracarus) - There are about 20 described species of the subgenus Micruracarus in North America, and three of them have been collected from ponds and lakes in the Montane Cordillera. Known larvae of this subgenus parasitize tanypodine midges (Chironomidae).

Arrenurus (M.) infundibularis Marshall occurs in ox-bow ponds associated with the Okanagan River north of Osoyoos and the Kootenay River west of Creston (CNC), and in adjacent areas of the Marine West Coastal Forests and Western Cordillera including Oregon (Marshall 1908), Washington (Lavers 1945) and Montana (CNC). The species is common in eastern North America from the Great Lakes Basin down the Mississippi Valley to the Hill Country of Texas (Marshall 1908, Cook 1955, I.M. Smith 1996, CNC).

Arrenurus (Micr.) scutulatus Marshall is abundant in the ox-bow ponds of the Creston Valley Wildlife Management Area (CNC), and has been collected in ponds and small lakes across the continent from Washington (Lavers 1945), Saskatchewan and Idaho (CNC), the Great Lakes Basin (Marshall 1908, Cook 1955, I.M. Smith 1996, CNC) and New Brunswick (CNC).

Arrenurus (Micr.) ovalis Marshall has been collected in Waterton Lakes National Park, the Rocky Mountain Trench near Cranbrook, the Creston Valley Wildlife Management Area, and various localities on the Thompson-Okanagan Plateau (CNC). This species occurs in bog pools and ponds across the Boreal Ecozones of Canada from Newfoundland to the Montane Cordillera.

A fourth species of Micruracarus, Arrenurus (Micr.) crenellatus Marshall, also lives in ponds and small lakes across temperate North America (Marshall 1908, Cook 1955, CNC), including localities in the Marine West Coastal Forests of Washington (Lavers 1945) and British Columbia (CNC), but has not yet been found in the Montane Cordillera.

Arrenurus (Megaluracarus) - Thirteen species of the large subgenus Megaluracarus are known from the Montane Cordillera, and three of them are undescribed. Larvae of species in this subgenus are parasites of tanypodine midges (Chironomidae) or mosquitoes (Culicidae).

Seven of the described species are known only from the Western Cordillera and Marine West Coastal Forests of western North America, namely:

Arrenurus (Meg.) belonocercus Lavers lives in limnocrenes and pools in cold mountain streams, and appears to be widespread in the Montane Cordillera with known populations in Waterton Lakes National Park and adjacent Kananaskis Country of Alberta and the headwaters of the Bella Coola River and the Hudson Bay Mountain regions of British Columbia (CNC). This species also occurs in California and Oregon (CNC), Washington (Lavers 1945) and the Pacific Maritime Ecozone of British Columbia at least as far north as Ocean Falls (CNC).

Arrenurus (Meg.) capillatus Marshall is locally abundant in ponds, ox-bows and shallow lakes in southern ecoregions of the Montane Cordillera from the Thompson-Okanagan Plateau and Okanagan Valley to the Rocky Mountain Trench (CNC), and also occurs in adjacent areas of the Western Cordillera and Marine West Coastal Forests from California to Washington (Lavers 1945, CNC).

Arrenurus (Meg.) invaginatus Marshall lives in shallow ponds and pools in western ecoregions of the Montane Cordillera Ecozone from the Thompson-Okanagan Plateau to the Upper Bella Coola Valley, and adjacent areas of the Marine West Coastal Forests and Western Cordillera from Oregon to Montana (Lavers 1945, CNC).

Arrenurus (Meg.) kincaidi Lavers inhabits ponds and small lakes in southern ecoregions of the Montane Cordillera from the Okanagan Valley to the Rocky Mountain Trench (CNC) and adjacent areas of the Western Cordillera in Washington (Lavers 1945) and Idaho (CNC). It appears to be the sister species of A. (Meg.) wardi Marshall, a common mite throughout eastern North America from the Boreal Shield to the southern Mississippi Valley.

Arrenurus (Meg.) krameri Koenike was first collected from the headwaters area of the Flathead River in the Northern Continental Divide Ecoregion by J.B. Tyrrell during the initial C.P.R. surveys. The species is widespread in stream pools and ponds, especially at high elevation, throughout the Montane Cordillera, and is common throughout the Marine West Coast Forests and the Western Cordillera from California and Utah to northern British Columbia (Lavers 1945, CNC).

Arrenurus (Meg.) laversi Marshall inhabits limnocrenes, stream pools and ponds in the Montane Cordillera from the Upper Bella Coola Valley to the Northern Continental Divide on the B.C.-Alberta border (CNC), and widespread throughout the Marine West Coastal Forests from southern California north to at least the Queen Charlotte Islands (Marshall 1944, CNC).

Arrenurus (Meg.) prominulus Marshall has been collected in beaver ponds, bog pools and small lakes in the Upper Bella Coola Valley of the Chilcotin Ranges and across southern ecoregions of the Montane Cordillera (CNC). This species also occurs adjacent areas of the Marine West Coastal Forests and Western Cordillera from Washington to Colorado (Lavers 1945, CNC).

One species of Megaluracarus is also widespread in Prairie ecozones:

Members of A. (Meg.) couleensis Lavers commonly inhabit ponds and small lakes in southern ecoregions of the Montane Cordillera from the Thompson-Okanagan Plateau and Okanagan Valley to the Rocky Mountain Trench (CNC). This species also occurs in adjacent areas of the Western Cordillera of Montana and Idaho (CNC) and Washington (Lavers 1945), and across the southern Canadian Prairies from Alberta to Manitoba (CNC).

One species also occurs widely in Boreal ecozones:

Arrenurus (Meg.) morrisoni Marshall occurs in bog pools, beaver ponds and alpine lakes throughout the Montane Cordillera Ecozone. This species is widespread in the Boreal Shield and Boreal Plains of Canada, and in the Marine West Coast Forests and Western Cordillera from Idaho and Oregon to northern British Columbia (Marshall 1908, Lavers 1945, CNC). It is probably the most widespread species of Arrenurus in British Columbia.

One species is widespread across temperate North America:

Arrenurus (Meg.) intermedius Marshall occurs in southern ecoregions of the Montane Cordillera Ecozone from the Okanagan Valley to the Rocky Mountain Trench (CNC), as well as Montana and Idaho (CNC), Washington (Lavers 1945). Arrenurus intermedius belongs to the marshallae species group and is also common in lakes and ponds throughout the Mixedwood Plains and Atlantic Maritime Ecozones (Marshall 1908, Cook 1954b, I.M. Smith 1996, CNC). Further study may show that the apparently disjunct western population actually represents a distinct unnamed species.

Arrenurus (sensu stricto) - Seventeen species of the subgenus Arrenurus are known to occur in the Montane Cordillera Ecozone, including two undescribed species. Larvae of this subgenus are parasites of dragonflies and damselflies (Odonata).

Three of the described species are known only from the Western Cordillera and Marine West Coastal Forests of Western North America, namely:

Arrenurus (s. s.) auricularis Lavers is one of the rarest water mites in the Montane Cordillera Ecozone, known only from ox-bow ponds in the southern Okanagan Valley near Osoyoos (CNC) and a few localities in Washington (Lavers 1945, CNC).

Arrenurus (s. s.) cascadensis Lavers is widespread but relatively uncommon in ponds and lakes in southern ecoregions of the Montane Cordillera from the Thompson-Okanagan Plateau to the Rocky Mountain Trench (CNC). This species also occurs in the Cascade Mountains of Washington (Lavers 1945) and the Maritime Pacific Ecozone of British Columbia at least as far north as Prince Rupert (Lavers 1945, CNC).

Arrenurus (s. s.) tacomaensis Marshall lives in ponds and small lakes in the Okanagan Valley as far north as Okanagan Falls (CNC). This species also occurs throughout Washington (Marshall 1924a, Lavers 1945) and in coastal areas of Oregon and southern Vancouver Island (CNC).

Four species are also widely distributed in Prairie ecozones:

Arrenurus (s. s.) auris Lavers is a common mite in ponds and lakes in southern ecoregions of the Montane Cordillera from the Kamloops area of the Thompson-Okanagan Plateau and the Okanagan Highland to the Rocky Mountain Trench (CNC). This species is widespread in the Western Interior Basins and Ranges at least as far south as Nevada (Lavers 1945, CNC) and throughout the Prairie and Boreal Plains Ecozones of Canada (Conroy 1968, CNC).

Arrenurus (s. s.) interpositus Koenike appears to be tolerant of moderate salinity, and lives in ponds and shallow lakes in the western interior of the Montane Cordillera from the Okanagan Highland to the Fraser Plateau (Conroy and Scudder 1975, I.M. Smith 1987, CNC). This species is widespread in the Western Interior Basins and Ranges as far south as Nevada and Arizona (Lavers 1945, CNC) and occurs commonly in the Prairie ecozones of Canada and the northern United States as far east as Manitoba (CNC).

Arrenurus (s. s.) pistillatus Marshall is common in ponds and small lakes in southern ecoregions of the Southern Interior and Southern Interior Mountains Ecoprovinces of the Montane Cordillera (CNC). This species also occurs in the Western Cordillera as far south as northern California (Marshall 1908, Lavers 1945), and is widespread across the Prairie ecozones of Canada and the northern United States as far east as Manitoba and Minnesota (CNC).

Arrenurus (s .s.) ventropetiolatus Lavers inhabits temporary pools in the Clinton area of the Fraser Plateau (CNC), several localities in Washington (Lavers 1945) and the West-Central Semi-Arid Prairies as far east as southern Saskatchewan (CNC). This species is closely related to Arrenurus (s. s.) planus Marshall which lives in temporary pools from the Great Lakes Basin to New England (Cook 1954a, I.M. Smith 1996, CNC). Protonymphs of these species undergo obligatory diapause as they overwinter in the dry basins of temporary pools, before continuing their development when water returns in the Spring (Münchberg 1952, Wiggins et al. 1980).

Seven species have widespread distributions across temperate North America: Arrenurus (s. s.) americanus Marshall lives in ponds and small lakes in southern ecoregions of the Montane Cordillera from the Okanagan Valley to the Rocky Mountain Trench (CNC), and is one of the most common species of the genus from coast to coast across southern Canada and the northern United States (Marshall 1908, Cook 1954a, I.M. Smith 1996, CNC).

Arrenurus (s. s.) dentipetiolatus Marshall lives exclusively in alkaline lakes and ponds, and has been found in the Montane Cordillera only in the southern Okanagan Valley where it is locally abundant in Mahoney Lake, Blue Lake, and numerous smaller ponds (CNC). This species and Hydrodroma despiciens (Müller) (Hydryphantidae) appear to be the only water mites able to complete their life histories in these strongly saline habitats in the Montane Cordillera. Interestingly, Arrenurus dentipetiolatus has yet to be collected on the Thompson-Okanagan or Fraser Plateau Ecoregions, although it is distributed widely in the Western Interior Basins and Ranges (Lavers 1945, CNC) and southwestern deserts as far south as Arizona and Texas (CNC), and sporadically in saline habitats across North America from the San Juan Islands of Washington (Lavers 1945) to the Great Lakes Basin and coastal New Brunswick (CNC).

Arrenurus (s. s.) hungerfordi Cook inhabits ponds in the Clinton and Gang Ranch areas of the Fraser Plateau (CNC). This species is distributed across southern Canada from British Columbia to Newfoundland (I.M. Smith 1996, CNC) and occurs in northern Michigan (Cook 1954a).

Arrenurus (s. s.) mucronatus Lavers occurs in the Montane Cordillera only in ox-bow ponds in the southern Okanagan Valley near Osoyoos (CNC). This species also inhabits ponds and lakes in Washington (Lavers), and scattered localities across southern Canada and the northern United States as far east as New Brunswick (Cook 1954a, I.M. Smith 1996, CNC).

Arrenurus (s. s.) reflexus Marshall inhabits ponds and shallow lakes in the Creston Valley and the Rocky Mountain Trench (CNC), and occurs in similar habitats in Washington (Lavers 1945) and across southern Canada and the northern United States as far east as Quebec and Vermont (Cook 1954a, Conroy 1968, I.M. Smith 1996, CNC).

Arrenurus (s. s.) serratus Marshall has been collected only once in the Montane Cordillera, from an ox-bow pond in the southern Okanagan Valley near Osoyoos (CNC). This rare species also occurs in Wisconsin (Marshall 1919) and has been collected at profundal depths in several oligotrophic lakes in eastern Canada (I.M. Smith 1996).

Arrenurus (s. s.) superior Marshall lives in ox-bows of the Kootenay River in the Creston Valley (CNC), and also inhabits ponds and lakes in Washington (Lavers 1945) and Montana (CNC), and numerous localities across the United States and southern Canada as far east as the New England States and the Maritime Provinces (Marshall 1908, Cook 1954a, Conroy 1968, I.M. Smith 1996, CNC).

One species appears to be largely restricted to the Western Interior Basins and Ranges and adjacent ecozones:

Arrenurus (s. s.) wolcotti Marshall lives in ponds in the Okanagan Valley south of Okanagan Falls and near Osoyoos (CNC), the only Canadian localities for the species, and is widely distributed in ponds and small lakes throughout the Western Interior Basins and Ranges as far south as central Arizona and western Texas (Marshall 1908, Lavers 1945, CNC).

TABLE 8:SELECTED BIOLOGICAL DATA FOR SPECIES OF ARRENUROIDEA IN MONTANE CORDILLERA ECOZONE

Distribution Codes: Marine West Coastal Forests (MWCF), Western Cordillera (WC), Western Interior Basins and Ranges (WIBR); Thompson-Okanagan Plateau (209), Northern Cascade Ranges (210), Okanagan Highlands (211); Fraser Plateau (202), Chilcotin Ranges (204); Columbia Mountains and Highlands (205), Selkirk-Bitterroot Foothills (212), Southern Rocky Mountain Trench (213), Northern Continental Divide (214). There are no records of arrenuroid water mites from the Subboreal Interior Ecoprovince, although several species certainly occur there.

Habitat Codes: Springs (Sp), Groundwater/Hyporheos (Hyp), Stream Riffles (StRif), Stream Pools/Alpine Lakes (StPl/AL), Ponds/Lakes/Marshes (Pd/L), Vernal Temporary Pools (TPl).

HABITATS AND COMMUNITIES OF WATER MITES

Water mites form discrete communities of species based upon habitat preferences of post- larval instars that are associated with suites of morphological adaptations for particular physical conditions, primarily water depth, flow rate and substratum type. In the Montane Cordillera, six reasonably distinct communities can be identified in association with different habitat types. Most species are primarily associated with one particular type of habitat, but many are able to exploit a variety of similar types (e.g., rheocrene springs and riffle areas of cold streams, stream pools and alpine lakes, etc.), and consequently may be represented in more than one community. Water mite communities in the Montane Cordillera are richly polyphyletic assemblages of species with various biogeographic origins that may occur together nowhere else.

Freshwater habitats are especially vulnerable to physical disturbance and chemical pollution. The quantity and quality of all habitat types in the Montane Cordillera have been seriously degraded by agricultural, industrial, recreational and urban development, especially in the Okanagan Valley and adjacent ecoregions of the Southern Interior Ecoprovince. As in the case of the Mixedwood Plains Ecozone of eastern Canada, over 80% of the original wetland habitat in the Montane Cordillera has been eliminated or seriously damaged by human activities. Springs have been capped or impounded, streams have been extensively dammed, diverted, channelled, silted up and polluted. Ponds and lakes have been enriched by inorganic and organic wastes and many have been appropriated for recreational development. Entire watersheds have been affected by repeated deliberate and accidental introductions of exotic species. All of these changes have had inadvertent but profound impacts on freshwater invertebrate communities. Water mites can be robust indicators of biodiversity change in these communities because of their high taxonomic richness, abundance in all types of habitats and extensive interactions with other organisms, especially insects. Water mites are relatively easy to collect and identify compared to most other groups of freshwater invertebrates because the adult instar is a fully aquatic resident of the habitat.

Springs. About 55 species representing 28 genera and 16 families inhabit springs (limnocrenes, rheocrenes and helocrenes) in the Montane Cordillera. Communities from individual sites may include up to about 20 different species. Deutonymphs and adults of these species are typically specialized for crawling in mats formed by mosses, macrophytes and detritus. Most species are cold-adapted crenobionts, but a few (e.g., Laversia berulophila) are more generalized stenophiles also able to live in cold riffle habitats and even the profundal depths of oligotrophic lakes. Many crenophilic species are distributed widely in the Western Cordillera and Marine West Coastal Forests. Several of them show evidence of recent invasion of the Montane Cordillera from refugial areas in the Coast Mountains of northern California and Oregon. For example, Columbiathyas crenicola Smith and Cook, Cookacarus columbiensis Barr, and Bandakiopsis fonticola Smith, among other species, are widespread in Marine West Coastal Forests but found only in southwestern ecoregions of the Montane Cordillera. Similarly, Utaxatax newelli (Habeeb), Estelloxus californiensis Habeeb and Mideopsis barri Cook appear to have spread from coastal refugia, but have extended their distributions eastward in the Montane Cordillera as far as the Creston Valley. Other crenobionts with probable origins in coastal refugia, such as Paramideopsis susanae Smith, have dispersed throughout southern Ecoregions of the Montane Cordillera as far as Waterton Lakes National Park. Some spring inhabitants, such as Neobrachypoda eckmani Lundblad and Acalyptonotus neoviolaceus Smith, are widely distributed in Arctic ecozones and have relict populations that are now restricted to alpine areas in the Montane Cordillera. At least two crenophilic species, Thyopsella dictyophora Cook and Laversia berulophila Cook, have essentially transcontinental distributions and probably inhabited refugial areas along the entire ice-front during the Wisconsinan glacial maximum.

Spring habitats are abundant in the Montane Cordillera, but they and their arthropod communities are increasingly threatened with extinction by intensive agricultural, residential and recreational development, especially in the valleys and bench lands of the Southern Interior Ecoprovince. For example, at least two species of water mites, Thermacarus nevadensis Marshall and Wandesia thermalis Viets, are common in hot springs throughout the Western Interior Basins and Ranges of the western United States, but have not been reported from the Montane Cordillera Ecozone. Their apparent absence from the Ecozone may be a result of the extensive modification and degradation of hot spring habitats for recreational spa development during the past 100 years. Information on springs and their biota in the Montane Cordillera is rudimentary, despite their importance as sources for surficial watersheds and as indicators of ground water quantity and quality. Mites and other arthropods are the dominant animals in spring habitats. An inventory of springs and a relational database on their arthropod species and communities are needed to provide a baseline for assessing and monitoring biodiversity in these habitats and correlating changes with environmental variables.

Groundwater/Hyporheos. Approximately 25 species representing 16 genera and 13 families inhabit subsurface water in the Montane Cordillera. Communities from individual sites may include up to 10 different species. Deutonymphs and adults are typically adapted for moving through subsurface interstices in hyporheic gravels. They usually lack both integumental pigment and functional eyes. Most of these species (e.g., Cyclomomonia andrewi Smith, Stygomomonia spp.) appear to have invaded the Montane Cordillera during the Holocene from refugial areas in the Coast Mountains of California and Oregon, and dispersed widely in southern ecoregions. A few species have more restricted distributions: Morimotacarus nearcticus Smith is known only from the Northern Continental Divide region of the Rocky Mountains and probably inhabited refugia in the southern Rockies during the Pleistocene. Interstitial aquatic habitats were probably extensively destroyed in the Montane Cordillera during the Wisconsinan glacial maximum, but rapidly became reestablished during the Holocene, especially in depositional areas of mountain streams. Subterranean freshwater habitats and their arthropod biotas are being degraded in the Montane Cordillera, especially in agricultural and urban areas of the Southern Interior, by siltation, compaction and chemical pollution. These habitats are also vulnerable to both excessive siltation and scouring during floods in areas of intensive forest harvesting. Knowledge of groundwater biota in the Montane Cordillera is still rudimentary. Mites and crustaceans are the dominant interstitial groups and, as in the case of spring fauna, we need to develop a relational database and initiate monitoring in selected watersheds to document biodiversity changes and correlate them with local stressors.

Stream Riffles. About 125 species representing 19 genera and 8 families inhabit flowing water in erosional zones of streams and rivers in the Montane Cordillera Ecozone. Communities from individual sites may include up to 30 different species. The dominant genera in riffle habitats, such as Sperchon, Lebertia, Torrenticola, Atractides and Aturus are among the least studied water mite taxa in the Ecozone, and most of the species are undescribed. Deutonymphs and adults of mites in these habitats are typically specialized for clinging and crawling on rocks, plants and detritus. Most rheophilic species in the Montane Cordillera are relatively cold- adapted stenophiles distributed widely in the Western Cordillera and Marine West Coastal Forests. Most of them probably inhabited one or more refugia in the mountain ranges south of the Cordilleran Ice Sheet and dispersed into the Montane Cordillera as lotic habitats stabilized during the Holocene.

Stream Pools/Alpine Lakes. About 60 species representing 26 genera and 13 families live in depositional pools of streams and rivers in the Montane Cordillera, and many of the same taxa inhabit high montane lakes. Communities from individual sites may include up to 30 different species. Deutonymphs and adults are typically specialized for swimming strongly in slow currents and burrowing in silty substrata. Some species of this fauna, including Teutonia lunata Marshall, Oxus occidentalis (Marshall) and Frontipoda americana Marshall, are among the most rapid and agile swimmers among water mites. Most species associated with this habitat in the Montane Cordillera are cool-adapted stenophiles distributed in the Western Cordillera and Marine West Coastal Forests, although a few have wider distributions including Boreal ecozones of Canada. Most of them also probably inhabited refugia in the mountain ranges south of the Cordilleran Ice Sheet and dispersed into the Montane Cordillera as lotic habitats stabilized during the Holocene.

Mountain streams are abundant in the Montane Cordillera, and their arthropod communities represent one of the most distinctive components of the Ecozone’s biodiversity. Streams and their biotas are being degraded by both erosion and siltation in areas of intensive agriculture and forestry, residential development or expanding transportation corridors. The solutions most often adopted to stabilize watersheds and inhibit destructive seasonal flooding, the construction of dams and channels, are often more deleterious to native arthropod communities than the problem they are designed to control. Although some research has been done on stream biota in certain areas of the Montane Cordillera, it has not produced well documented inventories of arthropod species to provide baselines for assessing and monitoring spatial and temporal changes. Mites and insects comprise most of the animal species diversity in streams throughout the Ecozone and, because of their short life histories can be used as sensitive indicators to detect changes in community composition and structure at an early stage. This permits remedial action to be taken before profound and irreversible degradation of community structure and function occurs, with implications for fish and other organisms at higher levels of the food chain. As in other densely populated ecozones in Canada, we urgently need to establish relational databases that can be used to link data on arthropod species with information on regional and local stressors using GIS technology. Improving taxonomic knowledge of the most diverse genera of rheobiontic water mites is a necessary but cost-effective step in this direction, because the adult mites can be more rapidly and reliably characterized and identified than the aquatic larvae of their insect hosts.

Ponds/Lakes/Marshes. About 75 species representing 20 genera and 13 families inhabit ponds, shallow lakes and marshes in the Montane Cordillera. Communities from individual sites may include as many as 30 different species. Deutonymphs and adults are typically specialized for swimming and clinging to rooted macrophytes. Most of these species exhibit broad temperature tolerance, and many have extensive distributions beyond the Western Cordillera, including adjacent ecological regions and, in numerous cases, much of temperate North America. Many of these species are restricted to the valley bottom wetlands in southern ecoregions in the Montane Cordillera. Species such as Arrenurus (s. s.) auricularis Lavers and Arrenurus (s. s.) wolcotti Marshall, inhabiting ox-bow ponds and sloughs associated with the Okanagan River near Osoyoos, are among the rarest water mites in the Montane Cordillera and occur nowhere else in Canada. One species, Arrenurus dentipetiolatus Marshall, is restricted to highly alkaline habitats within a few kilometres of the U. S. border in the southern Okanagan.

The distribution and abundance of species of mites and other arthropods associated with ponds and marshes have been greatly reduced in southern ecoregions of the Montane Cordillera by wetland drainage programs associated with agricultural and urban development. Large areas of formerly extensive marshes have been drained and filled, so that remaining populations of mite species and their insect hosts have been fragmented and isolated in small remnants patches of habitat. Some of these species are at the northern limit of their distribution and are at risk of extirpation from British Columbia and Canada. Developing a relational database for these species would provide a baseline for assessing and monitoring future spatial and temporal changes in their occurrence and abundance, and provide a measure of the sustainability of remnant wetland ecosystems in the southern Montane Cordillera.

Vernal Temporary Pools. About 25 species representing 10 genera and 7 families inhabit vernal temporary pools in the Montane Cordillera, mostly in the Okanagan Highlands, Thompson-Okanagan Plateau and Fraser Plateau Ecoregions. Communities from individual sites may include up to 15 different species. Deutonymphs and adults are typically specialized for crawling on plants and detritus or swimming. All of these species exhibit adaptations for either avoiding or withstanding drought that characteristically extends from early summer until the following spring. Most of them exhibit exceptionally broad temperature tolerance and are distributed widely in the Montane Cordillera and adjacent regions of the Western Cordillera, Western Interior Basins and Ranges, Prairies and Boreal ecozones. Mites adapted to exploit vernal temporary pools probably inhabited seasonally intermittent tundra pools in periglacial Pleistocene refugia, in regions with marked spring melting and summer drought. As they dispersed through the Montane Cordillera during the Holocene, these species established persistent populations in areas with perched water tables. Vernal temporary pools are widespread in grassland areas of the Montane Cordillera, but are often disregarded as significant wetland habitats because they are seasonal. They are often drained or polluted to reduce mosquito populations and permit agricultural or residential development. In fact, many insects breed only in temporary pools, and the mites associated with them live exclusively in these habitats (Wiggins et al. 1980).

TABLE 9: LIST OF NAMED SPECIES OF WATER MITES IDENTIFIED FROM THE MONTANE CORDILLERA ECOZONE

(Unnamed species included are only known representatives of genus in Ecozone. Potentially rare and endangered species in the Montane Cordilleran Ecozone are indicated by "R".)

Superfamily - Hydrovolzioidea

Family - Hydrovolzioidea

Hydrovolzia marshallae Cook

Superfamily - Eylaoidea

Family - Eylaidae

Eylais discreta Koenike

Eylais euryhalina Smith

Eylais lancianii Smith

Eylais peutrilli Smith

Family - Limnocharidae

Limnochares americana Lundblad

Superfamily - Hydrachnoidea

Family - Hydrachnidae

Hydrachna barri Smith

Hydrachna comosa Koenike

Hydrachna conjecta Koenike

Hydrachna crenulata Marshall

Hydrachna cruenta Muller

Hydrachna elongata Smith

Hydrachna davidsi Smith

Hydrachna leptopalpa Smith

Hydrachna magniscutata Marshall

Hydrachna separata Lundblad

Superfamily - Hydryphantoidea

Family - Hydryphantidae

Hydryphantes ruber (Geer)

Notopanisus canadensis Smith and Cook - "R"

Albertathyas montana Smith and Cook

Thyas barbigera Viets

Thyas pachystoma Koenike

Thyas stolli Koenike

Zschokkea bruzelii Lundblad

Thyopsis cancellata (Protz)

Thyopsella dictyophora Cook

Thyopsella occidentalis Cook

Columbiathyas crenicola Smith and Cook - "R"

Panisus cataphractus (Koenike)

Panisopsis gorhami (Habeeb)

Panisopsis pedunculata (Koenike)

Tartarothyas occidentalis Smith and Cook - "R"

Pseudohydryphantes latipalpus Marshall

Protzia constans Marshall

Wandesia n. sp.

Family - Hydrodromidae

Hydrodroma despiciens (Muller)

Superfamily - Lebertioidea

Family - Sperchontidae

Sperchon acadiensis Habeeb

Sperchon avimontis Habeeb

Sperchon glandulosus Koenike

Sperchon jasperensis Marshall

Sperchon mitchelli Habeeb

Sperchon subaureus (Habeeb)

Sperchon tenuipalpis Koenike

Sperchonopsis ovalis Marshall

Family - Teutoniidae

Teutonia lunata Marshall

Family - Anisitsiellidae

Bandakia longipalpis Cook

Bandakia oregonensis Smith

Bandakiopsis fonticola Smith - "R"

Cookacarus columbiensis Barr - "R"

Utaxatax newelli (Habeeb)

Family - Lebertiidae

Lebertia needhami Marshall

Lebertia quinquemaculosa Marshall

Lebertia setosa Koenike

Lebertia tyrrelli Koenike

Lebertia wolcotti Koenike

Estelloxus californiensis Habeeb

Family - Oxidae

Oxus occidentalis (Marshall)

Oxus connatus Marshall

Frontipoda americana Marshall

Family - Torrenticolidae

Testudacarus americanus Marshall

Testudacarus minimus Marshall

Torrenticola spp.

Monoatractides spp.

Superfamily - Hygrobatoidea

Family - Limnesiidae

Limnesia cornuta Wolcott

Limnesia fulgida Koch

Limnesia koenikei Piersig

Limnesia maculata (Müller)

Limnesia undulata (Müller)

Limnesia wolcotti Piersig

Tyrrellia circularis Koenike

Family - Hygrobatidae

Atractides americanus Marshall

Atractides nodipalpis (Thor)

Hygrobates decaporus Koenike

Hygrobates exilis Koenike

Hygrobates longipalpis (Hermann)

Hygrobates multiporus Koenike

Hygrobates neooctoporus Marshall

Family - Feltriidae

Feltria cataphracta Cook

Feltria cornuta Walter complex

Feltria curviseta Cook

Feltria geometrica Habeeb

Feltria laversi Cook

Feltria major Cook

Feltria minuta Koenike

Feltria nearctica Cook

Feltria parva Cook

Feltria rivophila Habeeb

Feltria wyomingensis Cook

Family - Unionicolidae

Neumania latifemoris Conroy

Neumania longiseta Marshall

Neumania media Conroy

Neumania ovata Marshall

Neumania pubescens Marshall

Neumania punctata Marshall

Neumania tenuipalpis Marshall

Koenikea haldemani Viets - "R"

Koenikea wolcotti Viets - "R"

Unionicola crassipes (Muller)

Family - Wettinidae

Wettina primaria Marshall

Family - Pionidae

Hydrochoreutes intermedius Cook

Hydrochoreutes michiganensis Cook

Hydrochoreutes microporus Cook

Pionacercus leuckarti Piersig

Pseudofeltria laversi Cook

Forelia siegasiana Habeeb

Forelia americana Cook

Huitfeldtia rectipes Thor

Neotiphys marionensis (Conroy)

Pionopsis lutescens (Hermann)

Tiphys americanus (Marshall)

Tiphys ornatus Koch

Nautarachna muskoka Smith

Nautarachna queticoensis Smith

Piona carnea (Koch)

Piona conglobata (Koch)

Piona constricta (Wolcott)

Piona debilis (Wolcott)

Piona interrupta Marshall

Piona media (Wolcott)

Piona mitchelli Cook

Piona neumani (Koenike)

Piona rotunda (Kramer)

Piona turgida (Wolcott)

Piona uncata (Koenike)

Piona variabilis (Koch)

Family - Frontipodopsidae

Frontipodopsis nearctica Cook

Family - Aturidae

Ljania bipapillata Thor

Neobrachypoda ekmanni (Walter)

Brachypoda setosicauda Habeeb

Estellacarus unguitarsus (Habeeb)

Woolastookia setosipes Habeeb

Aturus mirabilis Piersig

Aturus spp.

Kongsbergia spp.

Superfamily - Arrenuroidea

Family - Momoniidae

Cyclomomonia andrewi Smith

Stygomomonia atnarkicola Smith

Stygomomonia mitchelli Smith

Stygomomonia neomexicana Cook

Stygomomonia separata Cook - "R"

Family - Mideidae

Midea alata Young

Family - Nudomideopsidae

Paramideopsis susanae Smith

Family - Mideopsidae

Mideopsis americana Marshall

Mideopsis barri Cook

Mideopsis borealis Habeeb

Mideopsis pumila Cook

Mideopsis robusta (Habeeb)

Family - Chappuisididae

Morimotacarus nearcticus Smith

Yachatsia mideopsoides Smith

Family - Athienemanniidae

Platyhydracarus juliani Smith

Chelomideopsis brunsoni (Cook) - "R"

Family - Acalyptonotidae

Acalyptonotus neoviolaceus Smith

Acalyptonotus pacificus Smith - "R"

Family - Laversiidae

Laversia berulophila Cook

Family - Arrenuridae

Arrenurus (Truncaturus) palustris Mullen

Arrenurus (Micruracarus) infundibularis Marshall

Arrenurus (Micr.) ovalis Marshall

Arrenurus (Micr.) scutulatus Marshall

Arrenurus (Megaluracarus) belonocercus Lavers

Arrenurus (Meg.) capillatus Marshall

Arrenurus (Meg.) couleensis Lavers

Arrenurus (Meg.) intermedius Marshall

Arrenurus (Meg.) invaginatus Lavers

Arrenurus (Meg.) kincaidi Lavers

Arrenurus (Meg.) krameri Koenike

Arrenurus (Meg.) laversi Marshall

Arrenurus (Meg.) morrisoni Marshall

Arrenurus (Meg.) prominulus Marshall

Arrenurus (sensu stricto) americanus Marshall

Arrenurus (s. s.) auricularis Lavers - "R"

Arrenurus (s. s.) auris Lavers

Arrenurus (s. s.) cascadensis Lavers

Arrenurus (s. s.) dentipetiolatus Marshall -"R"

Arrenurus (s. s.) hungerfordi Cook

Arrenurus (s. s.) interpositus Koenike

Arrenurus (s. s.) mucronatus Lavers -"R"

Arrenurus (s. s.) pistillatus Marshall

Arrenurus (s. s.) reflexus Marshall

Arrenurus (s. s.) serratus Marshall - "R"

Arrenurus (s. s.) superior Marshall

Arrenurus (s. s.) tacomaensis Marshall

Arrenurus (s. s.) ventropetiolatus Lavers

Arrenurus (s. s.) wolcotti Marshall -"R"