Abstract
BackgroundCongruent patterns in the distribution of biodiversity between regions or habitats suggest that key factors such as climatic and topographic variation may predictably shape evolutionary processes. In a number of tropical and arid biomes, genetic analyses are revealing deeper and more localised lineage diversity in rocky ranges than surrounding habitats. Two potential drivers of localised endemism in rocky areas are refugial persistence through climatic change, or ecological diversification and specialisation. Here we examine how patterns of lineage and phenotypic diversity differ across two broad habitat types (rocky ranges and open woodlands) in a small radiation of gecko lizards in the genus Gehyra (the australis group) from the Australian Monsoonal Tropics biome.ResultsUsing a suite of approaches for delineating evolutionarily independent lineages, we find between 26 and 41 putative evolutionary units in the australis group (versus eight species currently recognised). Rocky ranges are home to a greater number of lineages that are also relatively more restricted in distribution, while lineages in open woodland habitats are fewer, more widely distributed, and, in one case, show evidence of range expansion. We infer at least two shifts out of rocky ranges and into surrounding woodlands. Phenotypic divergence between rocky ranges specialist and more generalist taxa is detected, but no convergent evolutionary regimes linked to ecology are inferred.ConclusionsIn climatically unstable biomes such as savannahs, rocky ranges have functioned as zones of persistence, generators of diversity and a source of colonists for surrounding areas. Phenotypic divergence can also be linked to the use of differing habitat types, however, the extent to which ecological specialisation is a primary driver or secondary outcome of localised diversification remains uncertain.
Highlights
Congruent patterns in the distribution of biodiversity between regions or habitats suggest that key factors such as climatic and topographic variation may predictably shape evolutionary processes
Oliver et al BMC Evolutionary Biology (2019) 19:81 persistence in microrefugia such as deep crevices, caves and/or gorges in rocky areas that are buffered from the extremes of climate [15, 16], and 2) divergent selection and localised adaptation leading to the evolution of ecological specialists that use different habitats [17, 18]
In the eastern distribution of the australis group our sampling was relatively sparse and we conservatively identified only four generalist lineages: one unrecognised taxon “CYsp” (Cape York and the Trans-Fly region of southern New Guinea), G. catenata and G. dubia
Summary
Congruent patterns in the distribution of biodiversity between regions or habitats suggest that key factors such as climatic and topographic variation may predictably shape evolutionary processes. Oliver et al BMC Evolutionary Biology (2019) 19:81 persistence in microrefugia such as deep crevices, caves and/or gorges in rocky areas that are buffered from the extremes of climate [15, 16], and 2) divergent selection and localised adaptation leading to the evolution of ecological specialists that use different habitats [17, 18]. While these two processes may function synergistically, they may generate some contrasting predictions. If ecological diversification and habitat specialisation is driving localised diversity, phenotypic adaptations linked to occupying different niches may be predicted [20], and ecologically divergent sister species should occur in the neighbouring habitats [21]
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