Phenotypic and genetic variation in the white croaker Micropogonias furnieri Desmarest 1823 (Perciformes: Sciaenidae): testing the relative roles of genetic drift and natural selection on population divergence

摘要

How patterns of morphological and genotypic variation co-occur in natural populations is a fundamental issue to understand underlying forces involved in the process of differentiation. Micropogonias furnieri represents a good model to test the influence of evolutionary forces in the processes of spatial differentiation, because of the variability of environments it inhabits. The main objective of this work was to characterize phenotypic variation in several populations of M. furnieri by means of geometric morphometric techniques. The phenotypic variation pattern found was compared with the genetic structure, derived from microsatellites analyses. In addition, we examined the hypothesis that genetic drift is a sufficient explanation of the patterns of phenotypic variances and covariances within and among populations. Results obtained in this work partially agree with previous surveys suggesting that specimens from Montevideo and Laguna de Rocha may represent different biological units. Our results suggest that part of the morphological divergence exhibited by white croakers among the localities sampled might be the result of diversifying selection. The apparent absence of geographic barriers among localities surveyed also support the idea that processes in addition to genetic drift may have played an important role in the morphological differentiation in this species. Further studies are needed to examine the genetic and plastic components of morphological variation found in these natural populations of white croakers.