Research Centre for Ecosystem Resilience, Australian Institute of Botanical Science, The Royal Botanic Garden, Sydney, New South Wales, Australia.
Queensland Alliance of Agriculture and Food Innovation, University of Queensland, Brisbane, Queensland, Australia.
Evolution. 2022 Jun;76(6):1209-1228. doi: 10.1111/evo.14460. Epub 2022 Apr 26.
The expansions and contractions of a species' range in response to temporal changes in selective filters leave genetic signatures that can inform a more accurate reconstruction of their evolutionary history across the landscape. After a long period of continental decline, Australian rainforests settled into localized patterns of contraction or expansion during the climatic fluctuations of the Quaternary. The environmental impacts of recurring glacial and interglacial periods also intensified the arrival of new lineages from the Sunda shelf, and it can be expected that immigrant versus locally persistent taxa responded to environmental challenges in quantifiably different manner. To investigate how such differences impact on species' distribution, we contrast landscape genomic patterns and changes in habitat availability between a species with a long continental history on Doryphora sassafras and a Sunda-derived species (Toona ciliata), across a distributional overlap. Extensive landscape-level homogeneity across chloroplast and nuclear genomes for the Sunda-derived T. ciliata, characterize the genetic signature of a very recent invasion and a rapid southern "exploratory" expansion that had not been previously recorded in the Australian flora (i.e., of Gondwanan origin or Sahul-derived). In contrast, D. sassafras is consistent with other Sahul-derived species characterized by strong geographical divergence and regional differentiation. Interestingly, our findings suggest that admixture between genetically divergent populations during expansion events might be a contributing factor to the successful colonization of novel habitats. Overall, this study identifies some of the mechanisms regulating the rearrangements in species distributions and assemblage composition that follow major environmental shifts, and reminds us how a species' current range might not necessarily define species' habitat preference, with the consequence that estimates of past or future range might not always be reliable.
物种范围的扩张和收缩是对选择过滤器随时间变化的反应，这些变化留下了遗传特征，可以更准确地重建它们在景观中的进化历史。在经历了漫长的大陆衰退之后，澳大利亚雨林在第四纪气候波动期间，逐渐形成了收缩或扩张的局部模式。反复的冰川和间冰期的环境影响也加剧了巽他陆架上新谱系的到来，可以预期，外来种与本地持续种对环境挑战的反应方式在数量上存在明显差异。为了研究这些差异如何影响物种的分布，我们对比了具有长期大陆历史的物种（麻疯树）和源自巽他陆架的物种（香椿）之间的景观基因组模式和栖息地可利用性变化，这些物种在分布上存在重叠。源自巽他陆架的香椿在叶绿体和核基因组上具有广泛的景观水平同质性，这体现了其非常近期入侵和快速向南“探索”扩张的遗传特征，而这种扩张在澳大利亚植物区系中以前没有记录过（即起源于冈瓦纳或源自萨赫尔）。相比之下，麻疯树与其他源自萨赫尔的物种一致，具有强烈的地理分化和区域分化。有趣的是，我们的研究结果表明，在扩张事件中，遗传上不同的种群之间的混合可能是成功殖民新栖息地的一个因素。总的来说，这项研究确定了一些调节物种分布和组合组成在重大环境变化后重新排列的机制，并提醒我们，一个物种当前的分布范围不一定能定义其对栖息地的偏好，因此，对过去或未来范围的估计可能并不总是可靠的。
