Abstract
The diversity of the vertebrate cranial shape of phylogenetically related taxa allows conclusions on ecology and life history. As pleurodeline newts (the genera Echinotriton, Pleurodeles and Tylototriton) have polymorphic reproductive modes, they are highly suitable for following cranial shape evolution in relation to reproduction and environment. We investigated interspecific differences externally and differences in the cranial shape of pleurodeline newts via two‐dimensional geometric morphometrics. Our analyses also included the closely related but extinct genus Chelotriton to better follow the evolutionary history of cranial shape. Pleurodeles was morphologically distinct in relation to other phylogenetically basal salamanders. The subgenera within Tylototriton (Tylototriton and Yaotriton) were well separated in morphospace, whereas Echinotriton resembled the subgenus Yaotriton more than Tylototriton. Oviposition site choice correlated with phylogeny and morphology. Only the mating mode, with a random distribution along the phylogenetic tree, separated crocodile newts into two morphologically distinct groups. Extinct Chelotriton likely represented several species and were morphologically and ecologically more similar to Echinotriton and Yaotriton than to Tylototriton subgenera. Our data also provide the first comprehensive morphological support for the molecular phylogeny of pleurodeline newts.
Highlights
One of the most complex structures in tetrapods is the cranium, an almost static component
As we had no access to specimens of T. pseudoverrucosus, we could not draw a conclusion about the morphological distinctness and validity of Liangshantriton and rather follow the opinion placing T. taliangensis in Tylototriton subgenera
Climate zone had no effect on cranial shape of pleurodeline newts, confirming their quite conservative morphology (Hernandez et al, 2018)
Summary
One of the most complex structures in tetrapods is the cranium, an almost static component. Ribbed and crocodile newts occupy various habitats along the latitudinal and altitudinal gradient from tropical lowland rainforests to montane forests and grassy landscapes (Bernardes et al, 2013; Hernandez et al, 2017; Hernandez et al, 2019) Their diverse ecology may result in indistinct morphological adaptations hard to access with traditional morphological approaches. Based on unique morphological characters, Chelotriton was assigned to the tribe Pleurodelini by various authors and is regarded as more closely related to crocodile newts, i.e. the genera Echinotriton and Tylototriton, than to Pleurodeles (Marjanović and Witzmann, 2015; Schoch et al, 2015). The overall aim was to obtain novel insights into the evolution of cranial shape in relation to ecology of selected, phylogenetically basal salamandrids
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