Habitat preference modulates trans-oceanic dispersal in a terrestrial vertebrate

Abstract

The importance of long-distance dispersal (LDD) in shaping geographical distributions has been debated since the nineteenth century. In terrestrial vertebrates, LDD events across large water bodies are considered highly improbable, but organismal traits affecting dispersal capacity are generally not taken into account. Here, we focus on a recent lizard radiation and combine a summary-coalescent species tree based on 1225 exons with a probabilistic model that links dispersal capacity to an evolving trait, to investigate whether ecological specialization has influenced the probability of trans-oceanic dispersal. Cryptoblepharus species that occur in coastal habitats have on average dispersed 13 to 14 times more frequently than non-coastal species and coastal specialization has, therefore, led to an extraordinarily widespread distribution that includes multiple continents and distant island archipelagoes. Furthermore, their presence across the Pacific substantially predates the age of human colonization and we can explicitly reject the possibility that these patterns are solely shaped by human-mediated dispersal. Overall, by combining new analytical methods with a comprehensive phylogenomic dataset, we use a quantitative framework to show how coastal specialization can influence dispersal capacity and eventually shape geographical distributions at a macroevolutionary scale.

Keywords: Cryptoblepharus; biogeography; exon capture; long-distance dispersal.

Figure 1.

Time-calibrated phylogeny for the major Cryptoblepharus lineages based on a summary-coalescent species tree analysis of 1225 loci. Confidence intervals for the node ages are highlighted in grey. The geographical region of origin has been annotated for each species using coloured orbs (see legend). Moreover, internal nodes have been annotated with the most probable ancestral regions as inferred using ancestral range estimation (see the electronic supplementary material, figure S2 for further details) and the colour scheme corresponds with figure 2. All nodes with multi-locus bootstrap support below 90 have been annotated and the blue arrow highlights the inferred branch where species switched from a non-coastal to coastal habitat (also see the electronic supplementary material, figure S3).

Figure 2.

Distribution map of the genus with the 17 geographical regions used in the biogeographic analyses. The colours and outlines of each region match with the orbs that highlight the geographical region of origin for each species (figure 1). Five geographical regions have been magnified to improve visualization, while regions within the Indonesian and Malagasy archipelagoes have been combined to improve clarity (though each of these regions were used independently in biogeographical models).