Abstract
Closely related species that show clear phenotypic divergence, but without obvious geographic barriers, can provide opportunities to study how diversification can occur when opportunities for allopatric speciation are limited. We examined genetic divergence in the coral reef fish genus Hypoplectrus (family: Serranidae), which comprises of 10–14 morphotypes that are distinguished solely by their distinct colour patterns, but which show little genetic differentiation. Our goal was to detect loci that show clear disequilibrium between morphotypes and across geographical locations. We conducted Amplified Fragment Length Polymorphism molecular analysis to quantify genetic differentiation among, and selection between, morphotypes. Three loci were consistently divergent beyond neutral expectations in repeated pair-wise morphotype comparisons using two different methods. These loci provide the first evidence for genes that may be associated with colour morphotype in the genus Hypoplectrus.
Highlights
Whether speciation can occur in the absence of geographic barriers remains controversial [1]
Through analysis of Amplified Fragment Length Polymorphisms (AFLPs) we considered whether individual loci are consistently associated with individual morphotypes across different locations
A total of 436 scorable AFLP loci were produced with an overall repeatability rate of 97.1%
Summary
Whether speciation can occur in the absence of geographic barriers remains controversial [1] In this context colour polymorphisms, which occur in a wide range of taxa, provide excellent opportunities for studies of intraspecific evolutionary divergence Many different mechanisms have been implicated in the origin and maintenance of colour polymorphism, including sexual selection, mimicry, predation, crypsis and genetic drift [3]. A highly diverse range of marine taxa produce planktonic larvae, which can facilitate dispersal over long distances Both factors enable many species to have large distributions, with the potential for strong connectivity between populations, theoretically limiting opportunities for allopatric speciation. To improve our understanding of how species can evolve under such conditions, there is a need to examine closely related groups that show clear phenotypic divergence, attempting to determine how this divergence may have arisen and whether it can lead to full reproductive isolation
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