Molecular and morphological divergence in the inland silverside (Menidia beryllina) along a freshwater-estuarine interface

• Published in: Environmental biology of fishes 2011-07, Vol.91 (3), p.311-325
• Main Authors: Fluker, Brook L., Pezold, Frank, Minton, Russell L.
• Format: Article
• Language: English
• Subjects: Agnatha. Pisces; Animal and plant ecology; Animal populations; Animal Systematics/Taxonomy/Biogeography; Animal, plant and microbial ecology; Animals; Autoecology; Biological and medical sciences; Biomedical and Life Sciences; Brackish; Brackish water; Brackish water ecosystems; Environment; Estuaries; Fish; Fresh water; Freshwater & Marine Ecology; Fundamental and applied biological sciences. Psychology; Gene flow; Genetic diversity; Habitats; Life Sciences; Menidia audens; Menidia beryllina; Molecular biology; Morphology; Nature Conservation; Population genetics; Speciation; Synecology; Vertebrata; Zoology
• ISSN: 0378-1909; 1573-5133
• DOI: 10.1007/s10641-011-9786-2

Populations that vary across ecological gradients or that have invaded novel habitats are important to elucidate the association between adaptive divergence and gene flow, factors that may play an important role in speciation of silverside fishes. The inland silverside, Menidia beryllina , is an ideal organism for this kind of research, displaying a great diversity in morphology among freshwater and coastal brackish habitats. Using a combination of geometric morphometrics and mitochondrial (mt) DNA, we investigated patterns of variation within and among the nominal freshwater Menidia audens and coastal M. beryllina , spanning the transition from freshwater to tidally influenced semi-brackish waters of the lower Mississippi River to brackish waters of the Lake Pontchartrain estuary. Although we found no evidence for a phylogenetic split between M. audens and M. beryllina , our results indicate that significant genetic divergence corresponds with body shape differences among the two, with a clear distinction at the interface of freshwater and brackish water. Patterns in mtDNA suggest that freshwater populations referred to as M. audens are of recent origin with evidence for habitat-based divergence compared to coastal populations referred to as M. beryllina . Our findings add to a growing body of evidence that ecological shifts, following colonization of novel habitats, may promote rapid adaptive divergence and reduced gene flow among silverside populations in adjacent environmental regimes.