BARRETO, Felipe/S*; MCCARTNEY, Michael/A; University of North Carolina, Wilmington; University of North Carolina, Wilmington: Assortative Mating and Genetic Differentiation in a Coral Reef Fish Species Flock
Morphologically, species of hamlet fish (Hypoplectrus; Serranidae) can only be differentiated by their bright color patterns. Moreover, they lack allozyme differentiation, and show great similarity in allele frequencies at microsatellite DNA loci and in mitochondrial DNA sequences. Up to seven morphospecies can be found to coexist sympatrically on Caribbean coral reefs, and mixed matings have been observed in the lab and field. Previous studies have documented strong assortative mating with respect to color, suggesting that this may be the principle mechanism maintaining their reproductive isolation and color distinctiveness. However, these studies were limited to few observations, and more data are needed to determine the degree of assortative mating and hybridization among sympatric hamlet species. Our work combines detailed population census to determine the relative abundance of different morphospecies, evening observations to assess the degree of assortative mating, and molecular genetic assays for differentiation between morphospecies that coexist on Florida Keys reefs, a previously unstudied location. The Florida Keys is home to the Florida endemic blue hamlet (Hypoplectrus gemma), while the other Keys hamlets (H. puella, H. nigricans, and H. unicolor) can be found at several Caribbean locations. Amplified Fragment Length Polymorphism (AFLP) markers show evidence for great similarity among H. gemma and H. unicolor in Florida, but reveal a strong signal of non-random mating between these two most common Florida morphospecies. Our evening mating observations recorded a total of 69 mating pairs, with only one pair involving unlike morphospecies. Even the most uncommon morphospecies were observed to mate like-with-like, which lends further support to the hypothesis of strong assortative mating in this species flock.
