Trophic niche and adaptation in highland lizards: sex has greater influences than species matching.

The plateau environments are typically arid, cool, and high altitude, posing formidable challenges to wildlife survival due to resource scarcity and harsh conditions. Unraveling ecological adaptability in severe conditions requires a deeper understanding of the niche characteristics of plateau species. Trophic niche, which is a comprehensive indicator describing the energy acquisition strategy of animals, remains relatively understudied in plateau species. Here, by combining stable isotopes and morphological data, we quantified the trophic niches of two allopatric lizard species (Phrynocephalus vlangalii and P. erythrurus) that live in the hinterland of the Qinghai-Tibetan Plateau, and explored how their trophic niches correlate with morphological and environmental factors. While both trophic niche and morphological traits were similar between species, noteworthy distinctions were observed between male and female Phrynocephalus lizards. The morphological traits associated with predation (i.e. limb length and head size) and reproduction (i.e. abdomen length), annual mean temperature, and sex played influential roles in shifting trophic niches. These results imply that sexual dimorphism may facilitate inter-sex divergence in resource utilization, leading to trophic niche variations in the highland lizards. Furthermore, extreme environmental stress can constrain interspecific divergence in morphological and trophic traits. Our findings illustrate the dynamic variations of trophic niches in highland lizards, contributing to a more comprehensive understanding of the adaptation strategies employed by lizard species in plateau environments.