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

气候变化是全球海洋和陆地生态系统物种分布范围变化的主要驱动因素。范围的变化和扩张预计会在发生得太快时侵蚀遗传多样性，降低物种对正在进行的气候/环境变化的适应潜力。沿海物种在这方面研究不足，但特别脆弱，因为它们的生命周期经常在海洋和(半)陆地系统之间交替，而海洋和(半)陆地系统都受到全球变化的影响。自然历史收藏越来越被认为是独特的分子数据档案，用于研究气候变化在进化过程中的重大影响。在这个项目中，红树林蟹Aratus pisonii将作为研究系统。在20世纪沿着佛罗里达东海岸向北扩张之后，根据一份全面的收集记录，最近(自2012年)pisonii殖民了迄今为止的外国栖息地，红树林分布界限以北的盐沼。它为研究气候变化引起的范围扩大对(亚)热带甲壳类物种遗传多样性和种群结构的影响提供了一个极好的机会。该项目的主要目标是在空间和时间尺度上调查水仙种群的遗传多样性和种群结构格局，作为了解该物种在其正在进行的范围向北扩展过程中栖息地转移的基线。超常保护元素(UCE)将被用于目标丰富的高通量测序，以从现代和历史标本中获得基因组数据，作为种群基因组分析的基础。基因组数据将进一步用于物种分布建模，采用最近开发的集合建模方法。该项目将为种群结构和遗传多样性的变化提供经验性的见解，该物种具有很好的范围扩展历史。该研究系统作为一个案例研究，突出了遗传多样性对沿海物种在气候变化下的适应能力的重要性。此外，还将创建新的基因组资源，特别是为十足类甲壳类动物设置的第一个UCE探测器。该项目将分为两个阶段，分别在剑桥/马萨诸塞州哈佛大学比较动物学博物馆和不来梅莱布尼茨热带海洋生物学中心主办。

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.