Caddisflies of the Yukon - Department of Biological Sciences ...

846 G.B. Wiggins and C.R. Parker
L. kennicotti; we have confirmed that their material from Kluane National Park and Firth
River is L. kennicotti, but that from Burwash Landing is really L. fenestratus. In the Yukon
material examined, we found some indication that male genitalic characters intergrade
between these 2 taxa. Moreover, putative distinction between females (Kimmins and
Denning 1951) has proven unreliable because of variation in genitalic characters, culminating
in our material in 2 females collected with a male of L. fenestratus (Yukon: Old Crow
Flats, ROME 810587a); one female shows characters attributed to L. kennicotti, the other to
L. fenestratus. Further evidence on variation is required before the status of these taxa can
be confirmed. [North American specimens examined: L. fenestratus 26 #, 29 !; L. kennicotti
18 #, 32 !].
Whether or not these 2 forms are distinguished as species, their distributional relationships
are informative in a Beringian context. If the very close morphological similarity
between the 2 taxa is interpreted to indicate separation during the Pleistocene, L. kennicotti
could have diverged as a disjunct population along the southern margin of the North
American glaciers. By this interpretation, L. fenestratus would have been the Holarctic
ancestor, and its present East Beringian population would be a glacial relict. As the ice
receded, widespread recolonization by L. kennicotti over northern North America evidently
led to its dispersal to Greenland, approaching the western limit of its ancestral stock
represented by L. fenestratus in Iceland (Fig. 21). Judging from material we have examined,
L. fenestratus has extended its Nearctic range little if at all beyond unglaciated Beringia;
L. kennicotti has shown marked capacity for colonizing deglaciated habitats, evidently far
into the northern Yukon where the 2 forms are now apparently sympatric. Some intergradation
in the morphological characters distinguishing the two (see above) suggests that this
postglacial sympatry has yet to reach some equilibrium.
Limnephilus stigma Curtis (118)
Records for the close sister species L. indivisus Walker, now widespread over much of
North America, approach the Nearctic limit of L. stigma in the Northwest Territories (Fort
Smith, CNCI) and northern British Columbia (Alaska Hwy. km 359, Prophet R. Prov. Park,
ROME). Specimens from Kluane in the Yukon were identified as L. indivisus by Nimmo
and Wickstrom (1984), but our examination of that same material indicates that they are
L. stigma. In the continued absence of intermediates, we infer that the 2 species do not
hybridize. It has long been recognized that L. stigma (Figs. 22 – 25) is very similar morphologically
to the widespread North American species L. indivisus Walker (e.g. Betten and
Mosely 1940). Males of L. indivisus are distinguished by the much longer intermediate
appendages and by the ventral gap in the mesal dentation of the superior appendages
(Fig. 26); females of L. indivisus are distinguished by the narrow and deeply incised apex
of segment X, especially evident in ventral aspect (Fig. 27).
Material of L. stigma from Yukon and Alaska [26 #, 24 !] differs slightly in genitalic
characters from specimens examined from Europe and northern Asia [18 #, 16 !]. In East
Beringian males (Fig. 24b), the peripheral dentate ridge on the superior appendages bears a
large point underlying the intermediate appendages which is lacking from European specimens
(Fig. 22b). Males in our Nearctic material of L. stigma bear a prominent sclerotized
point on each paramere (Fig. 24d); this sclerotized point is lacking in specimens we examined
from Europe (Fig. 22c; and Malicky 1983, p. 188), but is present in specimens examined
from Kamchatka. In East Beringian females (Fig. 25), the apex of segment X is more
narrowly tapered than in Eurasian material (Fig. 23), especially in ventral aspect.