National Herbarium of New South Wales, Royal Botanic Gardens & Domain Trust, Sydney, Australia.
School of Life and Environmental Sciences, University of Sydney, Sydney, Australia.
Heredity (Edinb). 2019 Oct;123(4):532-548. doi: 10.1038/s41437-019-0243-x. Epub 2019 Jun 26.
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.
生态位分割可以通过影响栖息地的可利用性、扩散或选择影响定居和持续的特征，导致植物物种的分布范围动态差异。我们调查了两种在澳大利亚东部密切相关且同域的树种——山地水胶（Tristaniopsis collina）和水胶（T. laurina）——是否通过向旱地和河岸生境的生态位分割来区分其分布范围动态。我们使用来自 480 个样本 SNP 基因分型的基因组数据，评估了生物地理障碍的影响，并测试了范围扩张的信号。电路理论用于在三个古环境情景下模拟隔离阻力：末次冰期最大值、全新世气候最适宜期和现代（1950-2014 年）。尽管存在明显的环境生态位分化和不同的冰河后生境转移，但这两种树在历史上干燥的障碍中都表现出相似的遗传结构。Tristaniopsis collina 表现出与最近或快速分布范围扩张一致的连续奠基者效应的特征，而 T. laurina 的遗传模式则与长期在地理隔离的种群中持续存在一致，尽管它占据了更广泛的生物气候生态位。我们发现隔离阻力对这两个物种的影响较小，但其他未知因素似乎影响了遗传变异。我们假设，专门的繁殖特征（适应洪水干扰模式）而不是栖息地的可利用性限制了 T. laurina 的冰河后分布范围扩张。我们的研究结果表明，生态位宽度并不总是通过跨越障碍的定居和迁移来促进分布范围的扩张，尽管它可以促进原地的长期持续存在。
