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

842 G.B. Wiggins and C.R. Parker
FIG. 19. Distribution of Arctopora species (71, 72) (Limnephilidae); symbols superimposed indicate occurrence of
both species at the same locality.
In phylogenetic analyses of Rhyacophila, some 25 species from eastern and western
North America, Siberia, Japan, and Europe have been assigned to the sibirica species group
(Ross 1956; Schmid 1970). This group forms the major component of Rhyacophila in
Palaearctic Asia, and includes the only 2 Holarctic members of the genus known to
date—R. narvae and R. mongolica (Taxonomic Note 1). Rhyacophila mongolica is considered
the sister species of R. sibirica McLachlan (Schmid et al. 1993). Among 14 species of
Rhyacophila occurring in the Yukon, R. mongolica (Fig. 2) is recorded much farther north
than any of the others (Fig. 1, region 4), indicating that the species was ecologically adapted
for dispersal to North America across the Bering land bridge during the Pleistocene.
Leptoceridae
Ylodes kaszabi (Schmid) (67)
The genus Ylodes appears to have originated in north-central Asia (Manuel and Nimmo
1984), and Y. kaszabi occurs in Mongolia. A sister-species relationship with the Nearctic
Y. schmidi suggests the possibility of intercontinental vicariant origin during the Pliocene
or perhaps earlier; thus Y. kaszabi is inferred to have been a Palaearctic species that later
reached North America by way of the Bering land bridge during the Pleistocene.
Limnephilidae
Arctopora trimaculata (Zetterstedt) (72)