Seascape continuity plays an important role in determining patterns of spatial genetic structure in a coral reef fish

Abstract

Detecting patterns of spatial genetic structure (SGS) can help identify intrinsic and extrinsic barriers to gene flow within metapopulations. For marine organisms such as coral reef fishes, identifying these barriers is critical to predicting evolutionary dynamics and demarcating evolutionarily significant units for conservation. In this study, we adopted an alternative hypothesis-testing framework to identify the patterns and predictors of SGS in the Caribbean reef fish Elacatinus lori. First, genetic structure was estimated using nuclear microsatellites and mitochondrial cytochrome b sequences. Next, clustering and network analyses were applied to visualize patterns of SGS. Finally, logistic regressions and linear mixed models were used to identify the predictors of SGS. Both sets of markers revealed low global structure: mitochondrial ΦST=0.12, microsatellite FST=0.0056. However, there was high variability among pairwise estimates, ranging from no differentiation between sites on contiguous reef (ΦST=0) to strong differentiation between sites separated by ocean expanses≥20 km (maximum ΦST=0.65). Genetic clustering and statistical analyses provided additional support for the hypothesis that seascape discontinuity, represented by oceanic breaks between patches of reef habitat, is a key predictor of SGS in E. lori. Notably, the estimated patterns and predictors of SGS were consistent between both sets of markers. Combined with previous studies of dispersal in E. lori, these results suggest that the interaction between seascape continuity and the dispersal kernel plays an important role in determining genetic connectivity within metapopulations.

Patterns, causes, and consequences of marine larval dispersal

“…4B). This prediction is qualitatively consistent with previous estimates of spatial genetic structure for E. lori in Belize (35). This consistency suggests that the logistic model predicts both short-term patterns of dispersal and long-term patterns of gene flow.…”

Insight into the population structure of hardhead silverside,Atherinomorus stipes(Teleostei: Atherinidae), in Belize and the Florida Keys usingnd2

“…Additionally, high levels of larval dispersal among populations may diminish signals of IBD at smaller spatial scales over time (D'Aloia et al., 2014). The lack of barriers to larval dispersal may explain why geographic distance did not correlate with the amount of genetic differentiation at the island‐group scale.…”

“…However, the identification of genetic structuring within marine species is notoriously difficult due to the lack of clearly identifiable barriers to gene flow and dispersal commonly found within terrestrial systems. Early genetic studies on marine systems worked under the assumption that populations existed in a state of panmixia in the absence of extrinsic barriers, such as ocean currents and continental barriers (Avise, 2000; Taylor & Hellberg, 2006; D'Aloia, Bogdanowicz, Harrison, & Buston, 2014). However, studies have demonstrated clearly that other factors, such as habitat fragmentation and limited dispersal capabilities, may also act as reproductive barriers that restrict gene flow and result in subsequent isolation (Johnson & Black, 1991; Shulman & Bermingham, 1995; Fauvelot, Bernardi, & Planes, 2003; Gonzalez, Knutsen, & Jorde, 2016).…”

Geographic isolation and larval dispersal shape seascape genetic patterns differently according to spatial scale

“…Larval dispersal is then expected to influence seascape genetic variations, and the resulting genetic patterns often differ from the classical theory of isolation by distance (Selkoe et al., 2016). Hence, a comprehensive assessment of the drivers of spatial genetic variation in marine populations needs to include in a same framework environmental heterogeneity, geographic isolation, and larval dispersal (D'Aloia, Bogdanowicz, Harrison, & Buston, 2014; Selkoe et al., 2016). To this aim, large‐scale datasets and novel analytical methods are required (Manel & Holderegger, 2013).…”