Diversification across biomes in a continental lizard radiation

Abstract

Ecological opportunity is a powerful driver of evolutionary diversification, and predicts rapid lineage and phenotypic diversification following colonization of competitor-free habitats. Alternatively, topographic or environmental heterogeneity could be key to generating and sustaining diversity. We explore these hypotheses in a widespread lineage of Australian lizards: the Gehyra variegata group. This clade occurs across two biomes: the Australian monsoonal tropics (AMT), where it overlaps a separate, larger bodied clade of Gehyra and is largely restricted to rocks; and in the larger Australian arid zone (AAZ) where it has no congeners and occupies trees and rocks. New phylogenomic data and coalescent analyses of AAZ taxa resolve lineages and their relationships and reveal high diversity in the western AAZ (Pilbara region). The AMT and AAZ radiations represent separate radiations with no difference in speciation rates. Most taxa occur on rocks, with small geographic ranges relative to widespread generalist taxa across the vast central AAZ. Rock-dwelling and generalist taxa differ morphologically, but only the lineage-poor central AAZ taxa have accelerated evolution. This accords with increasing evidence that lineage and morphological diversity are poorly correlated, and suggests environmental heterogeneity and refugial dynamics have been more important than ecological release in elevating lineage diversity.

Spots before the eyes: revision of the saxicoline geckos of the Gehyra punctata (Squamata: Gekkonidae) species complex in the Pilbara region of Western Australia

“…nov. (lineage C on Figure 1), as this was recovered inside G. micra sp. nov. (lineage B) in the mtDNA data, yet in the nDNA analysis of Ashman et al (2018) it was recovered as the sister of G. media sp. nov. (lineage A) + G. micra sp.…”

“…New specimens and tissues for genetic analyses were integrated into the revision, and recently the missing type of Fry was located to help resolve the application of names. Preliminary mtDNA phylograms generated by Sistrom et al (2013) and for this study informed the study of Ashman et al (2018), who drew samples from within mtDNA lineages and used exon capture techniques to carry out a detailed phylogenomic assessment of nearly all Gehyra species that firmly established independently-evolving lineages. Similar to Kealley et al (2018), we use the findings of Ashman et al (2018) based on few individuals per lineage and coupled them with our expanded mtDNA sampling to provide sufficient genotyped specimens for morphological analyses and for mapping distributions.…”

“…However, recognition of species-level taxonomic units was also guided by the unpublished allozyme data set and mtDNA phylograms. In addition, we drew from an extensive phylogenomic analysis of Australian Gehyra (Ashman et al 2018), which recovered with high support all the lineages described as new species here. Thus we have employed an integrative taxonomic approach (Padial et al 2010), whereby we base taxonomic decisions on multiple lines of evidence.…”

“…In practical terms, we have focussed on the operational criteria that permit us to infer independently-evolving lineages (Wiens and Penkrot 2002;Marshall 2003, 2004;Bauer et al 2006;Camargo and Sites 2013). Such criteria may be either tree-based or character-based and we employ both approaches in this paper, basing our taxonomic decisions on the conjunction of data from mtDNA phylograms, the phylogenomic analysis of Ashman et al (2018), the unpublished pilot allozyme analysis and diagnostic morphological traits. Although distribution patterns alone should not be used in erecting initial hypotheses of species boundaries, geographic concordance with other evidence of lineage independence may be corroborative of taxonomic decisions based on tree-and character-based delimitations (Bergmann and Russell 2007).…”

“…Therefore it is timely to reassess the status of the many forms of G. punctata from the region using evidence from morphology, mtDNA, distribution and habitat preferences. We also draw on a recent phylogenomic analysis of Gehyra (Ashman et al 2018) and an unpublished pilot study using allozyme electrophoresis (M. Adams and P. Doughty, unpublished data). The combined genetic and morphological evidence indicates that G. punctata as currently conceived is paraphyletic, with two major clades: one with four larger-bodied species and one small-bodied species, and a second clade with three smaller-bodied species, resulting in the description of seven new species from the Pilbara region herein.…”