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中物种分布范围变化的主要驱动因素。据预测，如果范围转移和扩张发生得太快，将侵蚀遗传多样性，降低物种对持续气候/环境变化的适应潜力。沿海物种在这方面的研究不足，但由于它们的生命周期经常在海洋和（半）陆地系统之间交替，这两个系统都受到全球变化的影响，因此它们特别脆弱。自然历史收藏品越来越被认为是研究气候变化在进化过程中重大时间跨度的影响的独特的分子数据档案。本项目将以红树蟹（Aratus pisonii）为研究对象。根据一份全面的收集记录，在20世纪沿着佛罗里达东海岸向北扩张后，皮索尼a.p asonii最近（自2012年以来）殖民了一个迄今为止的外国栖息地，即红树林分布界限以北的盐沼。这为研究气候变化引起的范围扩展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很好的机会。该项目的主要目标是在空间和时间尺度上调查皮索尼的遗传多样性和种群结构模式，作为了解该物种在其不断向北扩展的过程中栖息地转移的基线。超保守元件（UCE）将用于富集靶点的高通量测序，从现代和历史标本中获得基因组数据，作为群体基因组分析的基础。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。该项目将为一个物种的种群结构和遗传多样性的变化提供经验见解，该物种有充分的范围扩张历史。该研究系统为强调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提供了一个案例研究。此外，新的基因组资源，特别是十足甲壳类动物的第一个UCE探针将被创建。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举办。

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.