Meeting Abstract
24.6 Wednesday, Jan. 5 Indications of Incipient Ecological Speciation in a Polymorphic Coral Reef Fish WHITNEY, JL*; KARL, SA; Hawai`i Institute of Marine Biology, University of Hawai`i, Mānoa; Hawai`i Institute of Marine Biology, University of Hawai`i, Mānoa jw2@hawaii.edu
A long-standing challenge in marine evolutionary biology has been explaining the origin of high levels of species diversity observed in tropical seas. Unlike in terrestrial and freshwater systems, the prevalence of planktonic larvae in most marine taxa offers the potential for high rates of gene flow over large geographic distances, thereby significantly reducing opportunities for classic allopatric speciation. Alternatively, ecological speciation, the process by which barriers to gene flow arise as a result of ecologically-based divergent selection in sympatry, may be an important means of diversification in marine environments supporting high biodiversity, such as coral reefs. Although ecological speciation is theoretically plausible and potentially significant in these systems, surprisingly few empirical studies of marine taxa currently exist. Here, we provide evidence suggesting that disruptive natural selection on color pattern in combination with color-based assortative mating may be driving speciation in sympatric populations of a coral reef fish (Paracirrhites arcatus). We found that color morphs exist in adjacent, yet divergent niches characterized by a suite of ecological factors. Furthermore, we found that in zones of overlap morphs tend to segregate assortatively. Taken together, these results suggest that reproductive isolation between morphs may be arising as a by-product of divergent selection on ecological differences, and enhanced by the isolating effects of assortative mating. We anticipate that these data, once combined with genetic analyses, will provide one of the few case studies of ecological speciation in marine fishes, thereby highlighting ecology’s role in driving high biodiversity in the oceans.
