The overlooked underground diversity: physical and chemical edaphic structure predict morphological variation in South American amphisbaenians (Squamata: Amphisbaenidae)

ABSTRACT

Morphological patterns may vary spatially in response to adaptations to regional environmental conditions. In fossorial animals, edaphic gradients potentially predict intra and interspecific morphological variation because they can limit dispersal and select morphotypes. We measured morphological traits of South American worm lizards, including three Amphisbaena and two Leposternon species, to test whether inter- and intraspecific morphological variation and morphotype distribution are predicted by edaphic gradients measured at different soil profiles. Interspecifically, we found that the variation in head length is mainly predicted by the chemical edaphic structure, which can be explained by spatial variation in prey availability. The variation in the width of the prefrontal and frontal shields was mainly predicted by clay and sand-soil contents, which can be explained by relationships of force and friction associated with digging. Intraspecifically, we found that the effects of edaphic gradients on morphological variation reflects the level of specialization to dig, since the most adapted species were mainly affected by variables measured in deeper soil profiles. We also show that soil-mediated intraspecific morphological variation shape morphotype distribution across different biomes that form the South American dry diagonal, which are discussed in light of biological, ecological, and biogeographic premises.

KEYWORDS:

• Amphisbaenidae
• ecomorphology
• functional morphology
• neotropical
• tropics

Acknowledgments

We are also very grateful to all the herpetological collection curators and curatorial staff, who have kindly helped us collect the data. M. Teixeira and L. Vitt kindly provided us with photos of some of the sampled species.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/01650521.2022.2147046

Additional information

Funding

RF thanks National Council for Scientific and Technological Development - CNPq for a postdoc fellowship (151023/2022-0). FPW thanks CNPq for her productivity fellowship (#311504/2020-5). This study was funded by National Council for Scientific and Technological Development – CNPq, through the program to support research projects and training human resources for biological taxonomy – PROTAX 22/2020, process number 151023/2022-0 CNPq.