Variation in intraspecific demography drives localised concordance but species-wide discordance in responses to Plio-Pleistocene climatic change

Understanding how species biology may facilitate resilience to climate change remains a critical factor in detecting and protecting species at risk of extinction. Many studies have focused on the role of particular ecological traits in driving species responses, but less so on demographic history and levels of standing genetic variation. We used environmental and genomic datasets to reconstruct the phylogeographic histories of two ecologically similar and largely co-distributed freshwater fishes to assess the degree of concordance in their responses to Plio-Pleistocene climatic changes. Although several co-occurring populations demonstrated concordant demographic histories, idiosyncratic population size changes were found at the range edges of the more spatially restricted species. Discordant responses between species were associated with low standing genetic variation in peripheral populations. This might have hindered adaptive potential, as documented in recent population declines and extinctions of the two species. Our results highlight both the role of spatial scale in the degree of concordance in species responses to climate change, and the importance of standing genetic variation in facilitating range shifts. Even when ecological traits are similar between species, long-term genetic diversity and historical population demography may lead to discordant responses to ongoing and future climate change

探究物种生物学特性如何助力物种抵御气候变化，仍是甄别与保护濒临灭绝物种的关键所在。既往诸多研究多聚焦于特定生态性状在驱动物种响应气候变化中的作用，而对种群历史与现存遗传变异水平的关注相对匮乏。本研究借助环境与基因组数据集，重建了两种生态相似、分布范围大体重合的淡水鱼类的系统发育地理历史，以评估二者对上新世-更新世气候变化的响应一致性程度。尽管多个共存种群展现出一致的种群历史，但在空间分布更受限的物种的分布范围边缘，却观测到了独特的种群规模变化模式。物种间响应的不一致性，与边缘种群较低的现存遗传变异水平密切相关。正如近期两种物种种群衰退与灭绝的记录所证实的那样，这种低遗传变异水平可能削弱了其适应潜能。本研究结果既凸显了空间尺度在物种响应气候变化的一致性程度中的关键作用，也强调了现存遗传变异在推动物种分布范围迁移中的重要性。即便物种间的生态性状相似，长期遗传多样性与历史种群动态仍可能导致其对当前及未来气候变化产生不一致的响应。