Speciation in the Simulium arcticum Species Complex in the Pacific Northwest

Abstract

Sequences of the mitochondrial genes, cytochrome oxidase 1 and II {COI and COII) were used to estimate the phylogenic relationships of five siblings and eight cytotypes of the Simulium arcticum complex from cytogenetically identified larvae. These 13 taxa are all differentiated by unique Y chromosome inversions, and in the present study a phylogeny based on chromosome types was tested molecularly. Bayesian analysis showed that taxa are non-monophyletic, in that sequences of different taxa are more closely related than are those of the same taxon. I conclude that incomplete lineage sorting as well as interspecific gene flow may explain these findings. These molecular data support and modify the model of chromosome speciation previously proposed by Rothfels and suggest that taxa within the S. arcticum species complex are likely in the early stages of differentiation and speciation. This thesis forms the basis of the manuscript, Good Species Behaving Badly: Apparent Non-monophyly ofBlack Fly Sibling Species in the Simulium arcticum Complex (Diptera: Simuliidae), submitted, January, 2010 to Molecular Phylogenetics and Evolution.