Does Drainage Affect Diversity within the Simulium arcticum complex in the Clark Fork River?

Abstract

Chromosomal rearrangements seem to play a role in the speciation process of Simulium arcticum. This is an exception to the current dogma of speciation in most animals. Two models have been proposed for dispersal of S. arcticum. One relies on females returning to their natal sites to lay eggs; the other states that females choose the best available environment to lay their eggs. Chromosomal diversity has been shown to remain the same at various sites each year. With this in mind, larvae were collected from Bearmouth along the Clark Fork River, analyzed in micromorphological detail, and compared with larval chromosomes from various other sites within the Clark Fork and Blackfoot River Drainages. The goal of this analysis was to determine whether or not drainage influences chromosomal diversity. It appears that drainage does influence chromosomal diversity within the S. arcticum complex in these two drainages although the influence is slightly different within each drainage. Within the Clark Fork River Drainage, it appears that the Garrison influences Bearmouth, however, the entering Rock Creek channel has a possessive influence over Turah and Bonner, which are downstream. The opposite influence is seen in the Blackfoot River Drainage where the Clearwater River appears to have no influence on downstream sites.