Environmental correlates of morphological diversity in Australian geckos

Abstract

Aim Climatic variation has long been regarded as a primary source of morphological variation. However, there is mixed support for the adherence of reptiles to ecogeographical hypotheses, such as Bergmann’s rule (body size decreases with temperature) and Allen’s rule (limb length increases with temperature). We quantified body and limb morphology among the diverse Australian gecko fauna (4 families, 30 genera, 226 of the 231 described species) to investigate environmental correlates of morphological variation in this radiation. Location Australia. Major taxa studied Geckos (Squamata: Gekkota; the families Gekkonidae, Carphodactylidae, Diplodactylidae and Pygopodidae). Methods We measured 20 external features of ethanol‐preserved museum specimens. We investigated whether principal component axes of morphology were correlated with three key environmental variables, and the microhabitat occupied by each species. Results Morphology varied greatly among Australian gecko families and genera, although there was a strong phylogenetic signal in morphology. After accounting for phylogeny, morphology was correlated with a species’ microhabitat use. Saxicolous species and species with variable microhabitat requirements (i.e., generalists) had larger body dimensions than terrestrial species. Saxicolous species also had longer proportional forelimbs and hindlimbs than terrestrial species. Main conclusions Our results highlight the importance of phylogeny and microhabitat use in shaping the morphology of Australian geckos. We find little evidence that Australian geckos adhere to Bergmann’s rule or Allen’s rule, suggesting that these ecogeographical hypotheses provide limited insight into the adaptive potential of lizard species to altered environmental conditions.

From Bioinspired to Bioinformed: Benefits of Greater Engagement From Biologists

“…How do toe pads vary across species with different environmental challenges? There is considerable morphological variation in geckos, which is linked to habitat (Kulyomina et al, 2019;Norris et al, 2021). These insights from basic biological research are crucial to address current performance gaps and can only be achieved through the involvement of biologists (Higham et al, 2019).…”

Living in difficult situations: Lizards living in high altitudes have smaller body sizes due to extreme climatic conditions and limited resources

“…Indeed, almost all endotherms adhere to Bergmann's rule (see reviews by Blackburn et al, 1999;Freckleton et al, 2003). However, ectotherms often do not (Forsman and Shine, 1995;Sears and Angilletta, 2004;Norris et al, 2021); with some ectotherm species showing no observable clines in body size and others reversing Bergmann's rule (Forsman and Shine, 1995;Sears and Angilletta, 2004;Olalla-Tárraga and Rodríguez, 2007;Meiri et al, 2013;Lu et al, 2018a;Norris et al, 2021). This is perhaps not surprising, as the original explanation for Bergman's rule does not apply to ectotherms (Watt et al, 2010), since they generate little internal body heat, and a larger body would therefore heat up more slowly as well (Stevenson, 1985).…”

“…Plastic and evolutionary responses to altitudinal clines may influence inter-and intraspecific variation in body size among ectotherms (Lu et al, 2018a;Meiri, 2018;Norris et al, 2021;Giovanna et al, 2022), due to the often rapid changes in annual and seasonal variation in temperature and precipitation across altitude (Liang et al, 2021;Anderson et al, 2022). For instance, studies have suggested that ectotherm body sizes may increase at low elevations with optimal seasonal environments (seasonal environments that allow ectotherms to have more active time) (Slavenko et al, 2019), likely because optimal seasonal environments allow for increased time available for ectotherms to acquire resources (Horváthová et al, 2013).…”

“…For example, female lizards inhabiting colder environments at higher gradients within China (from tropical to temperate regions) were found to possess small body sizes as adaptive plasticity for reproductive ecology (Lu et al, 2018a;Deme et al, 2022b), suggesting that the body sizes of the female lizards may as well follow climatic clines for adaptation to environmental (climatic) conditions (Feldman and Meiri, 2014;Brusch et al, 2022). Indeed, this is a large gap considering that the impact of climate conditions on lizard body size has been extensively studied in other regions of the world (e.g., Ashton and Feldman, 2003;Angilletta et al, 2004;Sears, 2005;Olalla-Tárraga et al, 2006;Olalla-Tárraga and Rodríguez, 2007;Olalla-Tárraga, 2011;Pincheira-Donoso and Meiri, 2013;Zamora-Camacho et al, 2014;Rivas et al, 2018;Slavenko et al, 2019;Tarr et al, 2019;Wishingrad and Thomson, 2020;Norris et al, 2021). To address this gap in our knowledge, we set out to evaluate the predictors of female body size within populations of the Lacertid lizard, the Mongolia racerunner (Eremias argus ), a widespread species occupying a wide altitudinal range across China (30 m to 2975m asl, Figure 1).…”

Traits, landmarks and outlines: Three congruent sides of a tale on coral reef fish morphology

“…The integration of species morphology and occurrence data is fundamental in ecology because it holds the potential of revealing spatial patterns of morphological diversity and how these relate to environmental variables. This is key to understanding the complex processes contributing to evolution and diversification, disentangling natural and anthropogenic drivers of global biodiversity, and assessing the vulnerability of biogeographic realms to species loss (Norris et al, 2021 ; Su et al, 2019 ; Toussaint et al, 2016 ). Several morphological attributes are strongly linked to species feeding modes and functions (Villeger et al, 2017 ; Wainwright & Bellwood, 2002 ).…”