Morphology and genetics reveal an intriguing pattern of differentiation at a very small geographic scale in a bird species, the forest thrush Turdus lherminieri

Abstract

Mobile organisms are expected to show population differentiation only over fairly large geographical distances. However, there is growing evidence of discrepancy between dispersal potential and realized gene flow. Here we report an intriguing pattern of differentiation at a very small spatial scale in the forest thrush (Turdus lherminieri), a bird species endemic to the Lesser Antilles. Analysis of 331 individuals from 17 sampling sites distributed over three islands revealed a clear morphological and genetic differentiation between these islands isolated by 40-50 km. More surprisingly, we found that the phenotypic divergence between the two geographic zones of the island of Guadeloupe was associated with a very strong genetic differentiation (F st from 0.073-0.153), making this pattern a remarkable case in birds given the very small spatial scale considered. Molecular data (mitochondrial control region sequences and microsatellite genotypes) suggest that this strong differentiation could have occurred in situ, although alternative hypotheses cannot be fully discarded. This study suggests that the ongoing habitat fragmentation, especially in tropical forests, may have a deeper impact than previously thought on avian populations.

Habitat specialization predicts genetic response to fragmentation in tropical birds

“…This small-scale reduction of gene flow is fairly unexpected for birds that are considered to be spatially more homogenous compared to other taxonomic groups with lower mobility (Crochet 2000). These results are, however, in line with recent studies reporting evidences of gene-flow limitation over short distances in birds (Senar et al 2006;Mil a et al 2010;Porlier et al 2012;Arnoux et al 2014;Bertrand et al 2014). In homogeneous landscapes of continuous habitat, limited dispersal may result from particular social (e.g.…”

Multilocus genetic analyses and spatial modeling reveal complex population structure and history in a widespread resident North American passerine (Perisoreus canadensis)

“…Gray jays display plumage and morphological trait variation across their range (Strickland & Ouellet, ). The presence of distinct morphs suggests the potential for reduced gene flow and population structure (Arnoux et al., ; Burg et al., ; Miller‐Butterworth, Jacobs, & Harley, ), though morphological characteristics have also been shown to vary with temperature and other environmental variables (Diniz‐Filho et al., ).…”

Islands within an island: Repeated adaptive divergence in a single population

“…Yet another option involves spatially autocorrelated natural selection, combined with localized dispersal (isolation by distance); in this scenario, dispersal and mate selection are neutral processes, but individuals are more likely to disperse to an environment that is similar to their natal habitat (and mate with individuals there) simply because they disperse locally (Mallet et al ). Despite the plausibility of these scenarios, relatively few empirical studies have tested for adaptive divergence at the spatial scale where gene flow is expected to operate across the landscape (Richardson et al ; exceptions include, but are not limited to Blondel ; Milá et al ; Kavanagh et al ; Richardson and Urban ; Arnoux et al ).…”