Niche partitioning can lead to differences in the range dynamics of plant species through its impacts on habitat availability, dispersal, or selection for traits that affect colonization and persistence. We investigated whether niche partitioning into upland and riparian habitats differentiates the range dynamics of two closely related and sympatric eastern Australian trees: the mountain water gum (Tristaniopsis collina) and the water gum (T. laurina). Using genomic data from SNP genotyping of 480 samples, we assessed the impact of biogeographic barriers and tested for signals of range expansion. Circuit theory was used to model isolation-by-resistance across three palaeo-environment scenarios: the Last Glacial Maximum, the Holocene Climate Optimum and present-day (1950–2014). Both trees showed similar genetic structure across historically dry barriers, despite evidence of significant environmental niche differentiation and different post-glacial habitat shifts. Tristaniopsis collina exhibits the signature of serial founder effects consistent with recent or rapid range expansion, whilst T. laurina has genetic patterns consistent with long-term persistence in geographically isolated populations despite occupying a broader bioclimatic niche. We found the minor influence of isolation-by-resistance on both species, though other unknown factors appear to shape genetic variation. We postulate that specialized recruitment traits (adapted to flood-disturbance regimes) rather than habitat availability limited post-glacial range expansion in T. laurina. Our findings indicate that niche breadth does not always facilitate range expansion through colonization and migration across barriers, though it can promote long-term persistence in situ.

中文翻译：

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栖息地偏好区分全新世范围动态，但不区分对两种同域同属树（Tristaniopsis，桃金娘科）的屏障效应

生态位划分可通过影响栖息地可用性、扩散或影响定殖和持久性的性状选择，导致植物物种范围动态的差异。我们调查了生态位划分为高地和河岸栖息地是否区分了两种密切相关且同域的澳大利亚东部树木的范围动态：山水胶（Tristaniopsis collina）和水胶（T. laurina）。使用来自 480 个样本的 SNP 基因分型的基因组数据，我们评估了生物地理障碍的影响并测试了范围扩展的信号。电路理论用于模拟三种古环境情景中的电阻隔离：末次盛冰期、全新世气候最佳期和现在（1950-2014 年）。尽管有证据表明存在显着的环境生态位分化和不同的冰川后栖息地变化，但两棵树在历史上的干旱屏障上都表现出相似的遗传结构。Tristaniopsis collina 表现出与近期或快速范围扩张一致的系列创始人效应的特征，而 T. laurina 的遗传模式与地理上孤立的种群的长期持续存在一致，尽管占据了更广泛的生物气候生态位。我们发现抗性隔离对这两个物种的影响很小，尽管其他未知因素似乎影响了遗传变异。我们假设专门的招募特征（适应洪水干扰制度）而不是栖息地的可用性限制了 T. laurina 的冰川后范围扩张。