Untitled

Abstract

Genetic studies of population or 'stock' structure in exploited marine fishes typically are designed to determine whether geographic boundaries useful for conservation and management planning are identifiable. Implicit in many such studies is the notion that subpopulations or stocks, if they exist, have fixed territories with little or no gene exchange between them. Herein, we review our long-term genetic studies of red drum (Sciaenops ocellatus), an estuarine-dependent sciaenid fish in the Gulf of Mexico and western Atlantic Ocean. Significant differences in frequencies of mitochondrial DNA haplotypes and of alleles at nuclear-encoded microsatellites occur among red drum sampled across the northern Gulf of Mexico. The spatial distribution of the genetic variation, however, follows a pattern of isolation-by-distance consistent with the hypothesis that gene flow occurs among subpopulations and is an inverse (and continuous) function of geographic distance. However, successful reproduction and recruitment of red drum depend on estuarine habitats that have geographically discrete boundaries. We hypothesize that population structure in red drum follows a modified one-dimensional, linear stepping-stone model where gene exchange occurs primarily (but not exclusively) between adjacent bays and estuaries distributed linearly along the coastline. Gene flow does occur among estuaries that are not adjacent but probabilities of gene exchange decrease as a function of geographic distance. Implications of our hypothesis are discussed in terms of inferences drawn from patterns of isolation-by-distance and relative to conservation and management of estuarine-dependent species like red drum. Based on estimates of the ratio of genetic effective population size and census size in red drum, observed patterns of gene flow in red drum may play a significant role in recruitment.

Predicting task performance from psychological ownership and innovative work behaviour: A cross sectional study

“…Finally, we evaluated the Heterotrait-Monotrait proportion of associations (HTMT) criteria for each pair of reflective variables based on the item correlations (Henseler et al, 2015). As shown in Table 4, the results from the correlations pair of variables are less than the threshold values of HTMT = 0.90 (Gold et al, 2001;Henseler et al, 2015;Teo et al, 2008), we therefore confirmed the model's discriminant validity.…”

Predicting student engagement from self-efficacy and autonomous motivation: A cross-sectional study

“…Finally, we assessed the Heterotrait-Monotrait proportion of associations (HTMT) criteria for each pair of reflective constructs based on the item correlations (Henseler et al, 2015). As shown in Table 4, the outcomes from the correlations of pair of constructs are less than threshold values of HTMT = 0.85 (Gold et al, 2001;Henseler et al, 2015;Teo et al, 2008), we therefore confirmed the model's discriminant validity.…”

Phylogeography of Bornean land snails suggests long‐distance dispersal as a cause of endemism

“…MacArthur and Wilson's (1967) stepping-stone model detailed possible migration pathways along the chains of islands. Empirical evidence supports the validity of the stepping-stone model in nature as a means of dispersal, such as in marine snails (Crandall, Treml, & Barber, 2012), coastal fish (Gold, Burridge, & Turner, 2001;Maltagliati, 1998) and plants (Harbaugh, Wagner, Allan, & Zimmer, 2009).…”