Up to the north and down from the trees: Genetic signatures of expansion over a century of climate change and of a recent habitat shift in the Mangrove tree crab Aratus pisonii

• Applicant: Dr. Jonas Geburzi
• Subject Area: Evolution, Anthropology ; Ecology and Biodiversity of Animals and Ecosystems, Organismic Interactions
• Term: from 2020 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 447933111

Climate change is a major driver of changes in species’ distribution ranges in marine and terrestrial ecosystems worldwide. Range shifts and expansions are predicted to erode genetic diversity when occurring too quickly, reducing the adaptive potential of species towards ongoing climate/environmental change. Coastal species are understudied in this respect, but are especially vulnerable since their life cycles often alternate between marine and (semi-)terrestrial systems that are both affected by global change. Natural history collections are increasingly recognised as unique archives of molecular data to investigate such consequences of climate change over evolutionary significant time spans.In this project, the Mangrove tree crab Aratus pisonii will serve as study system. After expanding northwards along the Florida east coast during the 20th century, documented by a comprehensive collection record, A. pisonii recently (since 2012) colonised a hitherto foreign habitat, the salt marshes north of the distribution limit of mangroves. It provides an excellent opportunity to study the impacts of climate change-induced range expansions on genetic diversity and population structure in a (sub-)tropical crustacean species. The project’s main objective is an investigation of patterns of genetic diversity and population structure in A. pisonii at both, spatial and temporal scales, as a baseline for understanding the species’ habitat shift during its ongoing northward range expansion.Ultraconserved elements (UCE) will be used for target-enriched high-throughput sequencing to obtain genomic data from modern and historical specimens, as a basis for population genomic analyses. The genomic data will further be used to inform species distribution modelling, employing a recently developed ensemble modelling approach. The project will provide empirical insight into changes of population structure and genetic diversity in a species with a well-documented history of range expansion. The study system serves as a case study for highlighting the importance of genetic diversity for coastal species’ resilience under climate change. Additionally, new genomic resources, particularly the first UCE probe set for decapod crustaceans, will be created. The project will be divided in two phases, hosted at the Museum of Comparative Zoology at Harvard University, Cambridge/MA, and the Leibniz-Centre for Tropical Marine Biology, Bremen, respectively.

• DFG Programme: WBP Position