Convergent evolution and divergent selection: lizards at the White Sands ecotone

Area of Science:

• Ecology
• Evolutionary Biology
• Genetics

Background:

• Ecological transition zones showcase the balance between local adaptation and gene flow.
• Organismal phenotypes in these zones are shaped by natural selection and migration.
• Understanding these dynamics is crucial for predicting species' responses to environmental change.

Purpose of the Study:

• Investigate how natural selection and gene flow influence phenotypic adaptation in a species assemblage across an environmental gradient.
• Quantify color and genetic variation in three lizard species along the White Sands gypsum dune ecotone.
• Determine the role of gene flow in modulating adaptive responses to selection.

Main Methods:

• Quantified phenotypic (color) and genetic variation across an environmental gradient.
• Analyzed population connectivity and genetic isolation within and among three lizard species.
• Compared phenotypic variation with habitat and genetic similarity to understand adaptive drivers.

Main Results:

• Three lizard species at White Sands exhibit convergent evolution of blanched coloration, adapting to gypsum dunes.
• Species show varying degrees of background matching and genetic connectivity across the ecotone.
• Higher gene flow correlates with less pronounced phenotypic responses to selection, indicating modulated adaptation.
• Phenotypic variation is better explained by habitat similarity than genetic similarity, suggesting strong ecological selection.

Conclusions:

• Convergent evolution of blanched coloration at White Sands is driven by strong divergent selection.
• Adaptive responses are modulated by gene flow and demographic history, aligning with divergence-with-gene-flow models.
• Ecologically mediated divergence is evident in White Sands lizards, with habitat influencing adaptation more than genetic similarity.