MAJOR DISTRIBUTION PATTERNS OF SAWFLIES

Table 2. Number of native species of Symphyta in the Mixedwood Plains Ecozone recorded in each major distribution pattern types for each family and subfamily. Distribution pattern code: "3" Carolinian species,"4" southern species matching the ecotone, "5" southern species extending well North of the ecotone, "7" boreal species reaching southern limit in ecotone, "8" boreal species occurring well south of ecotone, "9" prairie disjunct, "10" Atlantic coast species. Patterns 1 (southern strays), 2 (migrants) and 6 (very widespread species) are not recorded for any of our species.

TAXON NAME       Family      Subfamily	3	4	5	6	8	9	10	Total
Argidae	1	9	6	3	-	-	-	19
Cephidae	-	-	5	-	-	-	-	5
Cimbicidae	-	3	1	-	3	-	-	7
Diprionidae	-	3	12	1	-	-	-	16
Orussidae	-	2	2	-	-	-	-	4
Pamphiliidae	-	16	24	-	3	-	-	43
Pergidae	-	1	2	-	-	-	-	3
Siricidae	-	-	5	2	2	-	-	9
Tenthredinidae
Allantinae	-	8	20	-	8	-	-	36
Blennocampinae	-	12	9	-	3	1	2	27
Heterarthrinae	-	4	8	-	-	-	-	12
Nematinae	-	5	29	4	22	-	-	60
Selandriinae	2	6	24	2	15	-	-	49
Tenthredininae	1	27	49	6	7	1	1	92
Xiphydriidae	1	1	2	1	1	-	-	6
Xyelidae	1	1	2	1	1	-	-	6
Total	7	98	199	21	67	2	3	397

Table 2 is a summary of the main types of distribution for species of the Mixedwood Plains Ecozone. Four types of distributions were not recorded among native species: southern stray species, regular southern migrants, very widespread species, and species endemic to MWPE. The most common range type is the one with ranges extended well north of MWPE (50% of species), then with ranges matching MWPE (25% of species). Of the native species recorded 105 (27%) of species are found in Canada only in the MWPE. Other distribution types are less prevalent. About 20% of species are widely established in the boreal regions and usually are transamerican in distribution (i.e. with ranges extending from the Atlantic to the Pacific coasts or almost so). The low proportion of species restricted to the Carolinian zone reflects a generally lower diversity in this life zone. However, more sampling is needed as most of the 34 expected species are species expected in the Carolinian zone. Sawflies are more diverse in temperate and boreal regions. Three species have basically Atlantic coast ranges, and two species are disjunct relative to their main range in the prairie region. Most species (81%) have ranges centred east of the prairies as far west as the eastern slopes of the Alberta Rockies north and west of the prairie region, and 68% are found east of the 100th meridian.

In some groups, there is divergence from the general trend within families and families of Symphyta. About 50% of the Argidae, Cimbicidae and Blennocampinae are restricted to the Ecozone. Species with boreal ranges are more prevalent in the Nematinae and Selandriinae (about 40% of species).

Table 2 gives important clues about the general pattern of post-glacial re-invasion of the Ecozone. As much as 3,000 m of ice covered MWPE. As the climate became warmer, the ice sheet retreated, an open tundra-like vegetation developed (one species, Amauronematus amentorum (Foerster), is well adapted to high arctic conditions and is still in the Ecozone), followed by an open boreal forest vegetation (66 species of MWPE with ranges extending into this life zone) and by a close boreal forest vegetation (21 species of MWPE adapted to this zone). Two species have a relictual distribution: Blennogeneris spissicornis (Cresson) and Zaschizonyx montana (Cresson). They are associated with alvars and originally adapted to the tall grass prairie ecozone. Alvars are open habitats with thin soil over a flat sedimentary rock. These habitats are maintained by drought periods. During the warmer hypsithermal period, these species extended their ranges eastward in larger and more contiguous alvars in Minnesota, Michigan and Ontario than seen today.

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