The extent of variation in male song, wing and genital characters among allopatric Drosophila montana populations
Kim van der Linde,
Roger K. Butlin &
Anneli Hoikkala (2007).
Journal of Evolutionary Biology
Drosophila montana, a
species of the Drosophila virilis
group, has distributed around the northern hemisphere. Phylogeographic analyses of two North
American and one Eurasian population of this species offer a good background for the studies
on the extent of variation in phenotypic traits between populations as well as for tracing the
selection pressures likely to play a role in character divergence. In the present paper, we studied
variation in the male courtship song, wing and genitalia characters among flies from Colorado
(USA), Vancouver (Canada) and Oulanka (Finland) populations. The phenotypic divergence
among populations did not coincide with the extent of their genetic divergence, suggesting that
the characters are not evolving neutrally. Divergence in phenotypic traits was especially high
between the Colorado and Vancouver populations, which are closer to each other in terms of
their mtDNA genotypes than they are to the Oulanka population. The males of the Colorado
population showed high divergence especially in song traits and the males of the Vancouver
population in wing characters. Among the male song traits, two characters known to be under
sexual selection and a trait important in species recognition differed clearly between
populations, implying a history of directional and/or diversifying rather than balancing selection.
The population divergence in wing characters is likely to have been enhanced by natural selection
associated with environmental factors, whereas the male genitalia traits may have been influenced
by sexual selection and/or sexual conflict.