1. ¹Department of Biology, University of Vermont, Burlington, VT, USA
2. ²Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
3. ³Griffin Laboratory, The Wadsworth Center, New York State Department of Health, Slingerlands, NY, USA

Correspondence: Dr DA Joy, NIH/NIAID/Laboratory of Malaria and Vector Research, 12735 Twinbrook Parkway, Room 3E-20B, Rockville, MD 20850, USA. E-mail: djoy@niaid.nih.gov

Received 18 May 2006; Revised 1 May 2007; Accepted 26 May 2007; Published online 4 July 2007.

Abstract

Geographic isolation is widely viewed as a key component of insular radiations on islands. However, strong ecological affinities may also reinforce isolation and promote genetic divergence. The black fly fauna in the Society Islands French Polynesia is notable for the number of closely related endemic species (31), and the morphological and habitat diversity of the larvae. Here, we measure ecological and morphological differences within and between two closely related species, Simulium oviceps and Simulium dussertorum and relate these differences to genetic distance. Phylogenetic analyses of a 920 bp fragment of the cytochrome oxidase I (COI) gene revealed a well-supported, ecologically divergent S. oviceps clade (larvae found in rivers instead of cascades) that shows little morphological differentiation. For both S. oviceps and S. dussertorum, genetic distance among populations is related to larval habitat, with cascade populations showing greater isolation from each other than river populations. Our data support the hypothesis that larval ecological shifts have played a role in the radiation of this black fly fauna.