Rw. Lichtwardt et al., BIOGEOGRAPHIC STUDIES ON TRICHOMYCETE GUT FUNGI IN WINTER STONEFLY NYMPHS OF THE GENUS ALLOCAPNIA, Mycologia, 85(4), 1993, pp. 535-546
Winter stoneflies of the genus Allocapnia (Plecoptera, Capniidae) have
low vagility, and apparently first evolved in the Appalachian system
from where they slowly dispersed and speciated at different times duri
ng the Pleistocene. Five described genera and species of Harpellales (
Trichomycetes) live in the aquatic nymphs of Allocapnia. Two of these,
Genistelloides hibernus and Simuliomyces spica, were found widely dis
tributed in 53 stream sites in nine states that include the western an
d southern distribution limits of Allocapnia spp. This suggests that t
he fungi had already evolved in Allocapnia nymphs before major radiati
on pulses of the stoneflies during the Pleistocene. Two other fungi, E
jectosporus magnus and Capniomyces stellatus, were more limited in the
ir distribution and might have evolved subsequent to early Allocapnia
dispersals. One species, Orphella hiemalis, may be endemic to the Ozar
k Plateau and Ouachita Mountains. The presence of different extant spe
cies of Genistelloides and Orphella in the stonefly faunas of North Am
erica and Europe indicates that species of those two genera of fungi m
ust have existed prior to the final separation of the two continents d
uring the Lower Eocene. Isozymes were extracted and electrophoresed fr
om 25 axenic cultures of G. hibernus obtained from six states. When gr
ouped by geographic region, the greatest coefficient of similarity amo
ng fungal isozyme phenotypes was between the Ozarkian isolates and tho
se from northeastern Texas. However, the similarities between central
Tennessee and Kansas were greater than they were between eastern Tenne
ssee and Alabama. This apparent disparity might be explained biogeogra
phically by a southwestward Pleistocene dispersal into Alabama of G. h
ibernus-infested Allocapnia populations originally located between the
Cumberland Plateau and the mountains to the east, and a separate west
ward dispersal of other populations of fungus-infested stoneflies that
were situated to the west of the Cumberland Plateau. The isozyme data
also suggest that G. hibernus may have moved with its hosts from nort
hern Alabama into the Ozark Plateau.