Delimiting species in recent radiations with low levels of morphological divergence: a case study in Australian Gehyra geckos

Abstract

Recent conceptual and methodological advances have increased the ability to apply multifaceted approaches to species delimitation, which is particularly useful in delimiting recently diversified species where single lines of evidence lead to incorrect species delimitation or assignment of individuals to species (e.g. cryptic, morphological species and paraphyletic, hybridizing species). Species of the Australian Gehyra gecko radiation have historically proven difficult to delimit due the group's uniform, almost continent-wide geographic distribution and conservative morphology, contrasting high chromosomal and genetic diversity. Using an integrated approach to species delimitation taking advantage of morphological, geographic distributional and multi-locus genetic data, we investigate the diversity within three Gehyra species from the Australian arid zone. Our results show that these species represent eight distinct phylogenetic lineages, which display different patterns of morphological distinction and reproductive isolation. Using a recently developed Bayesian species delimitation method, we also find different levels of support for putative species dependent on priors for population size and timing of diversification assumed. Our results show that the current taxonomy does not adequately account for the diversity of the group. Discrepancies between lines of evidence indicate that diversification of the group is recent and ongoing, thus posing challenges for both species concepts and delimitation.