Species in the genus Hypoplectrus (hamlet fish) have been recognized primarily on the basis of colour morphology, which varies substantially. Limited differentiation in other morphological characters, however, has led to ongoing debate about their taxonomy. Our analysis of mtDNA sequences demonstrates neither reciprocal monophyly nor significant genetic differentiation among hamlet colour morphs. These data are potentially consistent with a model of recent speciation due to sexual selection on colour morphology. The presence within hamlets of two divergent mtDNA clades, however, suggests a longer history during which hybridization and gene flow have prevented the differentiation of hamlet colour morphs, at least in neutral genetic markers.

No abstract

No abstract

AbstrAct.-Working in the Galápagos Islands and surrounding areas, we examined the relationship between population structure, a precursor to allopatric speciation, in species of reef fishes that exhibit different life history traits and three types of distributions in a nested setting: endemic (restricted to the Galápagos Islands), insular (Galápagos and neighboring islands), and Panamic (tropical eastern Pacific). We used a combination of population structure and coalescent approaches to assess the degree of genetic population structure in the three groups of fish species. In addition, we evaluated the level of inter-island genetic diversity in endemic species to determine if Galápagos fishes, like their terrestrial counterparts, could be used as a system to study allopatric speciation in the sea. We found that in general, there was no correlation between distribution ranges, life history traits, and population structure, except for Dialommus fuscus Gilbert, 1891, a Galápagos endemic that lives in the uppermost intertidal area, and as predicted, shows very strong population structure. We found the highest number of statistically significant population pairwise F st comparisons in endemic species. In addition, three out of four endemic species showed significant population pairwise F st [D. fuscus, Lepidonectes corallicola (Kendall and radcliffe, 1912), and Lythrypnus gilbert (Heller and snodgrass, 1903)]. These results suggest that endemic Galápagos Islands reef fishes may be a promising group of species to study phylogeographic patterns of speciation. "The (Galápagos) archipelago does not appear to offer a good laboratory for researching the impact of isolation, because the barren islands do not harbor many isolated fish pools. "David starr Jordan (in a letter to robert Evans snodgrass, 1898)