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Environmental determinants of interpopulation variation in chemical and visual signals in an insular lizard
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DOI：10.1002/oik.12150.png)
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Abstract
En 中文
Understanding how communication systems evolve across heterogeneous environments requires examining multiple signalling modalities. In 2017 and 2018, we examined geographic variation in chemical signals of the insular lizard Gallotia galloti across 16 sites on Tenerife (Canary Islands). We analysed interpopulation variation in the lipophilic fraction of male femoral gland secretions in relation to vegetation cover (NDVI), local sex ratio, ectoparasite load and macroclimatic factors. In 2023, we also analysed visual signals of two lizard phenotypes that occur in contrasting habitats of Tenerife. We modelled the chromatic and achromatic conspicuousness of colour patches under both a conspecific (lacertid) and an avian predator visual system to examine habitat-dependent divergence in signal detectability. Chemical signal diversity decreased with increasing shrub vegetation cover, while males from sites with male-biased sex ratios exhibited greater individual chemical richness, consistent with heightened intrasexual competition. Populations in xeric habitats and with higher mite loads showed relatively higher proportions of α-tocopherol, whereas greener habitats were associated with higher proportions of steroids. In contrast, visual analyses revealed that lizards from densely vegetated habitats exhibited greater chromatic conspicuousness and larger chromatic volumes, particularly under the conspecific visual model. Achromatic contrast showed weaker habitat-dependent differentiation, consistent with the hypothesis that luminance divergence is constrained by predator-mediated selection due to the high luminance sensitivity of avian visual systems. Thus, in open habitats, persistent and chemically diverse secretions may enhance communication efficiency under increased exposure, whereas in vegetated environments chromatic visual signals appear to be amplified, potentially driven by sexual selection while constrained by predation risk. These findings suggest that environmental heterogeneity can promote complementary divergence across signalling modalities, highlighting the importance of integrating sensory ecology and social context to understand the evolution of animal communication.
Keywords:
animal communication
ecological gradients
Gallotia galloti
local adaptation
sexual versus natural selection
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