Contemporary and historical influences on the genetic structure of the estuarine-dependent Gulf killifish Fundulus grandis

Abstract

In comparison to species living in open marine environments, estuarine-dependent species are expected to exhibit stronger genetic population structure due to dispersal limitations. Estuarine habitats are relatively transitory on geological time scales; thus, populations may not be at migration-drift equilibrium, which could confound estimates of current day gene flow or selection. We used 8 nuclear microsatellite loci to investigate the genetic structure of the estuarine Gulf killifish Fundulus grandis across 10 populations along the northwestern and northeastern Gulf of Mexico. Patterns of isolation by distance, spatial autocorrelation, and assignment tests indicate that dispersal is limited and occurs primarily between neighboring sites. Principal component analysis and Bayesian clustering revealed evidence for genetic discontinuities located in Mobile Bay and western Florida which are near hypothesized biogeographical boundaries. There was also a significant negative relationship between genetic diversity and latitude, a pattern consistent with the presence of hypothesized refugia in the southern Gulf regions during the Pleistocene that later recolonized the northern Gulf. Results suggest that populations may be at or near migration-drift equilibrium at a regional scale (e.g the western Gulf), but that dispersal barriers and potential historical signatures on population structure will need to be taken into consideration at larger spatial scales.

THE EVOLUTIONARY RADIATION OF DIVERSE OSMOTOLERANT PHYSIOLOGIES IN KILLIFISH (FUNDULUSSP.)

“…1 and 6). Second, for Gulf Slope and Gulf Coastal species a consistent phylogeographic break consistent with the Tombigbee River discontinuity (Wiley and Mayden 1985; Avise 2000; Soltis et al 2006) occurs near Mobile Bay that separates freshwater sister species F. escambiae to the east and F. nottii to the west, brackish‐distributed F. confluentus to the east and F. pulvereus to the west, populations of the brackish distributed species F. grandis (corroborating results from Williams et al (2008)), and populations of the marine‐distributed species F. similis . Divergence across this phylogeographic break appears to be stronger for freshwater Fundulus , intermediate for estuarine species, and least severe for marine‐tolerant species (Fig.…”

Inter-population differences in otolith morphology are genetically encoded in the killifish <i>Aphanius fasciatus</i> (Cyprinodontiformes)

“…We therefore suggest that the specific salinity and hydrological parameters of the Hamdoun site have triggered the genetic divergence in this population. This assumption concurs with results from previous studies, in which specific salinity parameters have been detected as the causative agents of strong selective pressure on organisms that eventually led to reproductive isolation in spite of possible intermingling during larval and adult life stages (Bekkevold et al 2005, Fuller 2008, Williams et al 2008.…”

Genomic and physiological footprint of theDeepwater Horizonoil spill on resident marsh fishes

“…For the 646 genes that varied in expression only among sites (no significant time effect or siteby-time interaction), site variation followed a pattern of population isolation by distance, which is consistent with neutral evolutionary divergence ( Fig. 2A) and population genetic expectations (15). Most importantly, 1,500 genes indicated a pattern of site-dependent time course expression (significant interaction, false discovery rate <0.01), where the trajectory of genome expression through time was divergent at the GT site compared with all other sites ( Fig.…”