About This Project

Adaptive radiations occur when an evolutionary lineage diversifies and adapts to use a previously unoccupied niche or underutilized resource, such as Darwin’s Finches. We seek to test hypotheses about the patterns and processes that generate an adaptive radiation by quantifying the morphological diversity of a secretive species-rich group, the New World leaf-litter geckos. We will compare the morphology of island and mainland gecko species using x-rays and photos of preserved specimens.

Ask the Scientists

What is the context of this research?

Adaptive radiations occur when an evolutionary lineage diversifies into new forms to exploit previously unoccupied niches (e.g., new habitats). Island ecosystems contain multiple instances of adaptive radiations as mainland forms colonize new islands, leading to their rapid diversification. New World (NW) leaf-litter geckos (i.e., sphaerodactyls) are a group of small-bodied and species-rich group of lizards (7 genera; 172 species) that have a circum-Caribbean distribution, including all of the Caribbean Islands, Central America, and parts of South America. Due to their secretive nature and small size, these species have not garnered much attention from biologists as compared to more conspicuous species with which they co-occur (e.g., Anole lizards, genus Anolis).

What is the significance of this project?

East African cichlids and Darwin’s Finches are exceptional classic examples of adaptive radiations. Biologists still debate as to how generalizable these examples are and whether existing case studies allow us to derive general principles of what an adaptive radiation is and how it proceeds. Therefore, identifying and studying additional instances of adaptive radiation should be a high priority, particularly if these new examples can help test existing hypotheses, such as whether adaptation occurs in predictable stages. We hypothesize that NW sphaerodactyl geckos represent an undescribed adaptive radiation and that island species have undergone greater morphological diversification compared to mainland species.

What are the goals of the project?

Sphaerodactyl geckos co-occur with Anolis lizards through much of their range and share many spatial and temporal biogeographic similarities with the iconic model group of adaptive radiation. This study provides a unique opportunity to test the generality of the stages of adaptive radiation to help answer whether sphaerodactyl geckos exhibit evolutionary patterns consistent with adaptive radiation, as observed with Anolis lizards, including exceptional diversity and adaptation.

We will visit the Smithsonian Institution Herpetology Collection to obtain X-rays and photographs of preserved gecko specimens. From the X-rays and photos, we will measure and compare the adaptive traits associated with feeding (skull shape) and habitat use (scale type) of island and mainland species.