Parallel evolution of toepads in rock-dwelling lineages of a terrestrial gecko (Gekkota: Gekkonidae:Heteronotia binoei)

Abstract

Selection for effective locomotion can lead to specialized morphological structures. Adhesive toepads, which have arisen independently in different lizard clades, facilitate the use of vertical and inverted substrates. Their evolution is poorly understood because functionally intermediate morphological configurations between padless and pad-bearing forms are rare. To shed light on toepad evolution, we assessed the subdigital morphology of phylogenetically distinct lineages of the Bynoe’s gecko species complex (Heteronotia binoei). Most populations of H. binoei are terrestrial, but two relatively distantly related saxicoline (rock-dwelling) lineages have enlarged terminal subdigital scales resembling toepads. We reconstructed the ancestral terminal subdigital scale size of nine lineages of H. binoei in eastern Australia, including these two saxicoline lineages. Additionally, we compared the subdigital microstructures of four lineages: the two saxicoline lineages and their respective terrestrial sister-lineages. Surprisingly, all four lineages had fully developed setae, but the setae of the two saxicoline lineages were significantly longer, branched more often and were more widely spaced than the terrestrial sister-lineages. We conclude that the saxicoline lineages represent examples of parallel evolution of enlarged adhesive structures in response to vertical substrate use, and their morphology represents a useful model as an intermediate state in toepad evolution.

Composition of a chemical signalling trait varies with phylogeny and precipitation across an Australian lizard radiation

“…There is strong ML bootstrap support for nearly all terminal lineages (i.e. candidate species), consistent with mtDNA phylogenies produced in previous studies (Fujita et al, 2010; Moritz et al, 2016; Riedel et al, 2021; Zozaya et al, 2019), although deeper relationships vary and typically have lower support (Figure S1). Our phylogeny reveals two new deeply divergent H. binoei mtDNA lineages from central and southeastern Queensland: the Kroombit lineage from Kroombit Tops; and the nearby Biloela lineage, found in the vicinity of Biloela and the Blackdown Tableland sandstone plateau (Figure S1).…”

“…We obtained 905–1041 bp ND2 sequences from 69 new individuals of H. binoei . These, combined with an additional 592 ND2 sequences from Zozaya et al (2019), Moritz et al (2016) and Riedel et al (2021), yielded a final alignment of 661 ND2 sequences. The RAxML analysis of these sequences confirms the lineage identity of geckos sampled for pheromones (Table S3).…”

“…Sequences were edited and aligned using Geneious version , 2019 .1.3 (2019) and then visually inspected and verified by translating the ND2 coding region into amino acids. The resulting sequences were then combined with the ND2 alignment from Zozaya et al (2019) and an additional 241 sequences from Moritz et al (2016) and 20 sequences from Riedel et al (2021), thus representing all major lineages of H. binoei , all lineages of H. planiceps sampled herein, and, as outgroups, two individuals of the H. spelea complex. We used this combined alignment of 661 ND2 sequences (see Section 3) for phylogenetic analysis via maximum‐likelihood with RA x ML version 8.2.11 (Stamatakis, 2014).…”

“…We sequenced the gene NADH dehydrogenase subunit 2 (ND2) for at least three individuals from sites not previously sampled (i.e. not represented in Moritz et al, 2016, Zozaya et al, 2019, or Riedel et al, 2021 and all individuals at sites where more than one lineage occurs. DNA extraction and polymerase chain reaction (PCR) protocols followed the methods of Zozaya et al (2019), which used the ND2 primers ('tRNAI' and 'tRNAA') 2016) and 20 sequences from Riedel et al (2021), thus representing all major lineages of H. binoei, all lineages of H. planiceps sampled herein, and, as outgroups, two individuals of the H. spelea complex.…”

“…Here, we use a multivariate phylogenetic comparative approach to investigate how phylogenetic history and climate have shaped the chemical composition of epidermal pore secretions in Australia's Heteronotia lizard radiation. Heteronotia (Gekkonidae) is a genus of five recognized species (Wilson & Swan, 2017), two of which— H. binoei (Gray, 1845) and H. planiceps Storr, 1989—are complexes of deeply divergent genetic lineages, many representing undescribed ‘cryptic species’ (Fujita et al, 2010; Moritz et al, 2016; Oliver et al, 2017; Pepper et al, 2013; Riedel et al, 2021; Zozaya et al, 2019). Similar to many lizard groups (Mayerl et al, 2015), male Heteronotia have epidermal pores (Figure 1b) that exude waxy secretions with complex and variable chemistry.…”