Collaborative Research: Developmental and functional mechanisms of complex trait re-evolution: Limb loss and gain in skink lizards

University Of Massachusetts Amherst, Amherst MA

Investigators

Abstract

Understanding how complex characters evolve is central to developing fundamental theories of trait evolution. One such theory, Dollo?s Law, which states that once lost, complex characters cannot be re-evolved, has challenged biologists for more than a century. Despite recent evidence suggesting that complex characters can and do re-evolve, there is a lack of understanding of how and why these evolutionary reversals take place. The proposed study will address these questions by elucidating the functional underpinnings and the developmental mechanisms of complex trait re-evolution. This project will result in an unprecedented integration of functional morphology and developmental genetics in an evolutionary framework, facilitating communication between these fields. The research project will use an integrative approach that synthesizes developmental genetics and functional morphology in a phylogenetic framework to study limb and digit loss and subsequent re-evolution in the Southeast Asian burrowing lizard genus Brachymeles. Objectives of the proposed research are to determine whether a phenotypic trait that has been lost re-evolves with the same or different functional capacities, and whether re-evolved digits develop via the same or different developmental mechanisms as ancestral digits. Surface locomotor velocity, acceleration, and burrowing speed and force will be quantified using high-speed video and a force transducer for ancestrally and re-evolved pentadactyl, intermediate, and limbless species. The developmental basis of limb and digit reduction and re-evolution in Brachymeles will be characterized to identify hypothesized developmental constraints on limb and digit re-evolution. Mesenchymal condensations of digits in embryos will be identified using histochemistry and in situ hybridization of nine genes associated with limb and digit patterning. The project will be also involve and train undergraduate and graduate students in research methods and will promote international collaborations. Minority and female students will be actively recruited and encouraged to participate in the research training opportunities provided by the project. Biologically themed outreach programs resulting from this project will target disadvantaged communities and local K-12 schools. Findings from the proposed project will be publicly disseminated online as part of an established biodiversity information website (http://philbreo.lifedesks.org/), at scientific conferences, in peer-reviewed journals, and through other existing databases (http://datadryad.org/).