AMPHIBIANS AND REPTILES
Patrick T. Gregory and Linda A. Gregory
THE DIVERSITY OF AMPHIBIANS AND REPTILES IN THE MONTANE CORDILLERA ECOZONE
The herpetofauna of the Montane Cordillera is a mixture of essentially western forms, western representatives of more-or-less transcontinental species, and perhaps a few prairie species that reach the mountains in western Alberta. The number of currently recognized species recorded for the region is 29 (including a few peripheral species), a large number relative to other areas of comparable size in Canada (except for southern Ontario). The amphibians and reptiles of the Montane Cordillera are spread across 14 Families (7 amphibian, 7 reptilian), representing a very high diversity at this taxonomic level. Moreover, of these 14 families, two (Anguidae, Boidae) are represented nowhere else in Canada; a third (Ascaphidae), the most primitive anuran family extant, is otherwise restricted in Canada to the nearby Pacific coast.
The known herpetofauna of the Montane Cordillera Ecozone has not changed greatly in recent years, although species known from surrounding areas, but previously unrecorded in the region, still are occasionally discovered (e.g. the Night Snake in 1980; Lacey et al., 1996). At least two species have been introduced (Green Frog and Bullfrog). On the opposite side of the ledger, at least one species seems to have been extirpated from the ecozone in this century (Pigmy Short-Horned Lizard). Although relatively little is known about the genetic diversity of the amphibians and reptiles of the Montane Cordillera, research in this area has been increasing in recent years, sometimes revealing new species (e.g. Columbia Spotted Frog; Green et al., 1997). Geographic variation in diversity also is indicated by the fact that many of the species in the Ecozone either represent regional subspecies of more widely distributed species or are divided into two or more subspecies within the region.
The herpetofauna of the Montane Cordillera represents a reservoir of immensely important biodiversity. We summarize salient features of this diversity by Family. Distributions of the various species are based on maps presented in Green and Campbell (1984), Gregory and Campbell (1984), and Russell and Bauer (1993); nomenclature (ignoring subspecies) is based on Green (1997b) and Gregory and Gregory (1998).
FAMILY ASCAPHIDAE – The forest-dwelling Tailed Frog (Ascaphus truei, Fig. 1) is the sole member of this primitive family, whose closest relatives occur in New Zealand. It is unique in that the cloaca of the male is extended into a tail-like appendage, which is really a copulatory organ for internal fertilization. The multi-year tadpole inhabits pools in fast-flowing streams and its mouth disc is large and suctorial, allowing it to cling to rocks. In the Montane Cordillera, this species is known only from the southeast and the extreme southwestern corner. This is a strictly western species.
FAMILY RANIDAE – Members of this globally widespread family are often described as “typical” frogs. They occupy a range of ecological “niches” as adults, from highly aquatic to quite terrestrial, depending on species. Several species occur in the Montane Cordillera. The Columbia Spotted Frog (Rana luteiventris, Fig. 6) is a western North American species that is distributed throughout the ecozone. A related species, the Red-Legged Frog (Rana aurora), a coastal species, may occur in the extreme southwestern part of the zone. Another close relative is the Wood Frog (Rana sylvatica, Fig. 4) is found through most the Montane Cordillera, but is known only patchily from southern British Columbia; this species has a country–wide distribution. The Northern Leopard Frog (Rana pipiens) is also a transcontinental species, whose populations have declined significantly in recent years in western Canada (including the Montane Cordillera); it is found patchily across the southern part of the ecozone. Two introduced species from eastern North America (including eastern Canada) are known from a few locations in British Columbia in the southern part of the Montane Cordillera; these are the Green Frog (Rana clamitans) and the Bullfrog (Rana catesbeiana).
FAMILY BUFONIDAE – This globally widespread family comprises the animals commonly known as toads. The Western Toad (Bufo boreas, Fig. 6), a strictly western species, occurs through most of the Montane Cordillera, but records are sparse for northern British Columbia. Although occupying a wide range, the species is not common everywhere. Spotty abundance and concern about declining numbers of this species in the western U.S.A. have raised concerns about it here. The Canadian Toad (Bufo hemiophrys), a prairie species, may just make it into the eastern Montane Cordillera Ecozone in southern Alberta.
FAMILY HYLIDAE – This is another diverse family that is widely distributed across the planet. The tree frogs are highly terrestrial and characterized by sticky, suction-cup-like tips on their toes, enabling them to climb vertically, most often in trees and bushes. Two species occur in the Montane Cordillera. The Pacific Treefrog (Hyla regilla, Fig. 7) is abundant across southern British Columbia, but is absent from the extreme southeast and Alberta; it is a strictly western species. The Boreal Chorus Frog (Pseudacris maculata), an eastern and prairie species, just makes it into the ecozone in southwestern Alberta and perhaps at the margin with the Peace River region in northeastern British Columbia; it, like the Wood Frog, is a freeze-tolerant terrestrial hibernator.
FAMILY PELOBATIDAE – This is a small family of frogs called Spadefoots, which occur in various parts of North America, mainly in the U.S.A. They are terrestrial, burrowing frogs. Western species are particularly associated with hot, dry environments such as deserts, where their activity patterns (including breeding) are keyed tightly to rainfall and moist conditions. The Great Basin Spadefoot (Spea intermontana) is restricted largely to the hot, dry interior of south- central British Columbia within the Montane Cordillera; it is a western species.
FAMILY AMBYSTOMATIDAE – This is a strictly North American, but continent-wide, family. The most widely distributed species in the Montane Cordillera is the Long-Toed Salamander (Ambystoma macrodactylum, Fig. 8), a western pond-breeding form that is found throughout the southern two-thirds of the ecozone, but has been recorded only spottily in the north. The Barred Tiger Salamander (Ambystoma tigrinum) is a western member of a continent-wide species complex that currently is undergoing taxonomic revision. Tiger Salamanders in the Montane Cordillera are restricted to the southern Okanagan Valley of British Columbia and the eastern margin of the ecozone in southern Alberta. Paedomorphosis is common in Tiger Salamanders throughout their range, but we know of no published accounts of this phenomenon for populations in the Montane Cordillera.
FAMILY PLETHODONTIDAE – This is the largest family of salamanders, originating in North America, where numerous species occur. There is also one genus in Europe, but the family is most notable for being the only group of salamanders to have invaded the tropics, in Central and South America, where it has achieved a remarkable diversity. Plethodontids lack lungs and exchange respiratory gases across the skin lining the mouth and throat and on the outside of the body. Many species lay terrestrial eggs in which direct development of embryos occurs, bypassing the larval stage. This reproductive mode characterized the sole representative of this family in the Montane Cordillera, the Coeur d’Alene Salalmander (Plethodon idahoensis). Within the ecozone, this species, which has a restricted range in the west, is confined to southeastern British Columbia, where it first was recorded in 1981.
FAMILY EMYDIDAE – The sole representative in the Montane Cordillera of this widely distributed family is the Painted Turtle (Chrysemys picta, Fig. 5), a transcontinental species that occurs across southern British Columbia. This is an aquatic turtle that moves fairly readily overland, especially to lay eggs. It is a sensitive species, easily affected by loss of ponds, suitable nesting sites, and other critical habitats. Painted turtles also are collected illegally for pets, and then sometimes released elsewhere, so that considerable artificial genetic mixing of populations may have occurred in some areas.
FAMILY ANGUIDAE – One member of this family, the Northern Alligator Lizard. (Elgaria coerulea), a western species, occurs in the Montane Cordillera. It is found across most of southern British Columbia, often locally abundant, except for the southeastern corner. This is a ground-dwelling, live-bearing species.
FAMILY SCINCIDAE – This large, globally widespread family has but one representative in the Montane Cordillera, the Western Skink (Eumeces skiltonianus, Fig. 9), a strictly western species. This is a ground-dwelling, egg-laying species that is found over a fairly wide part of south-central British Columbia, but rarely appears to be abundant in any one area.
FAMILY PHRYNOSOMATIDAE – This family probably is no longer represented in the Montane Cordillera, the only two specimens of the Pygmy Short-Horned Lizard (Phrynosoma douglassi) having been found in the south Okanagan of British Columbia in the early part of this century. This western live-bearing species frequently burrows in sand and is difficult to detect.
FAMILY BOIDAE – This mainly neotropical family has two members in western North America. One of them, the Rubber Boa (Charina bottae, Fig. 10), occurs right across southern British Columbia, and possibly into southwestern Alberta. This is a small, slow-moving, cryptic species that spends much of its time underground or under cover; it also seems to be largely nocturnal, so that it is somewhat hard to find and therefore of uncertain abundance. The Rubber Boa is a live-bearing species that is the most primitive snake in Canada.
FAMILY COLUBRIDAE – This is the largest, most diverse family of snakes, with a worldwide distribution. Colubrids are often called the “harmless” snakes, although some are rear-fanged and venomous, occasionally dangerously so. A large proportion of the colubrid species recorded for the Montane Cordillera Ecozone belong to one genus, the garter snakes (Thamnophis), the most speciose and widely distributed genus of snakes in North America. Garter snakes are not only widespread, they are often extremely abundant locally. Most species are strongly associated with water, although they also can be found well away from it, and all are live-bearing. Four species of garter snakes may occur in the Montane Cordillera. One, the Northwestern Garter Snake (Thamnophis ordinoides), is an essentially coastal and highly terrestrial species that just makes it into the ecozone in the southwest corner. The transcontinental Common Garter Snake (Thamnophis sirtalis, Fig. 11) is the widest ranging species of reptile in North America and is found throughout the southern two-thirds of the ecozone (and probably farther north, but records are lacking). The Western Terrestrial Garter Snake (Thamnophis elegans) occurs across the western half of North America and has a similar distribution in the ecozone to that of the Common Garter Snake. It is possible that a fourth member of the genus, the Plains Garter Snake (Thamnophis radix), a prairie species, occurs in the extreme eastern part of the ecozone. The remaining four colubrid snakes that occur in the Montane Cordillera are egg-laying species confined to southern British Columbia. One of them, the Sharptail Snake (Contia tenuis) is a very small, poorly studied western species that is mainly coastal in its British Columbia distribution, save for two specimens recorded from Chase in the southern interior. The other three species are all restricted to the dry southern interior of British Columbia. The rear-fanged Night Snake (Hypsiglena torquata) is a small, widely distributed western snake, whose range is apparently fairly patchy at its northern extreme. The Gopher Snake (Pituophis catenifer) and Western Racer (Coluber mormon) are both western members of transcontinental species complexes.
FAMILY VIPERIDAE – This family occurs on every continent except Australia. The Western Rattlesnake (Crotalus viridis, Fig. 12), a strictly western species, is the only representative of this family in the Montane Cordillera and the only truly venomous species in the ecozone. Its venomous nature makes this species of particular concern because of potential conflicts with humans. Still fairly abundant in suitable habitat, it also is restricted to the dry interior of south- central British Columbia. Rattlesnakes are live-bearing snakes.
A listing of species can give only a rough idea of the biodiversity of an area. Several of the species noted above are geographically variable and can be divided into subspecies, so that the form occurring in the Montane Cordillera is distinctive from the same species occurring elsewhere in Canada (e.g. Western Rattlesnake). In some cases, two or more subspecies occur within the Montane Cordillera Ecozone (e.g. Long-Toed Salamander, Common Garter Snake). Finally, subspecific variation is really just a point on a continuum of variation that extends to interpopulation differences within a relatively small area, all of which contributes to the total biodiversity of an area. Such interpopulation variation may be especially marked in a region such as the Montane Cordillera because its significant topographic variation increases the possibility of reduced gene flow and consequent isolation of populations; studies of genetic variation therefore should be especially rewarding.
