Data from: Effects of climate and topography on the diversity anomaly of plants disjunctly distributed in eastern Asia and eastern North America

Aim: Differences in physiography have been proposed to explain
the diversity anomaly for vascular plants between environmentally similar
regions of eastern Asia (EAS) and eastern North America (ENA). Here, we
use plant species within disjunct genera to examine whether differences in
topography contribute to the diversity anomaly and whether the
richness–environment relationships differ between regions. Disjuncts are
used to ensure that the diversity anomaly relates to post-disjunction
evolution and diversification rather than regional differences in clade
ages or immigration. Location: EAS and ENA. Time period: Current.
Major taxa studied: Plant taxa disjunctly distributed in EAS and ENA.
Method: We compiled county-level plant distribution data, and calculated
species richness and variables of topography and climate within unit grid
cells. We compared estimated coefficients of region effects among models,
where richness was fitted with or without topography and climate.
Topography and climate were also used to separately model within-region
spatial diversity patterns using spatial simultaneous autoregressive error
models. Results: The coefficients of region effects varied from -0.776 for
the model only including region to -0.309 when topography was controlled
for, but remained significant. Climate dominated the spatial diversity
patterns in ENA. In contrast, the influence of climate (14.2%) on species
richness was weaker than that of topography (18.3%) in warm EAS. Relations
to elevation and temperature varied between regions, shifting between
positive and negative relationships in several cases. Main conclusion: Our
results demonstrate that variability in local topography contributes to
the strong regional anomaly in plant species richness between EAS and ENA.
Nevertheless, the diversity anomaly persists after controlling for local
topography and climate. EAS and ENA also exhibit contrasting
richness–environment relationships, providing another divergent aspect
between the EAS-ENA disjunct floras. Our findings highlight that regional
differences in topography or other environmental factors may underlie the
diversity anomaly.

研究目的：此前有研究提出，地貌差异可用于解释环境相似的东亚（Eastern Asia, EAS）与北美东部（Eastern North America, ENA）区域之间维管植物（vascular plant）的多样性异常现象。本研究以间断分布属（disjunct genera）内的植物物种为研究对象，旨在探究地形差异是否为该多样性异常的成因，同时比较两地的物种丰富度-环境关系是否存在差异。选用间断分布类群作为研究对象，可确保该多样性异常与物种分化后的演化和多样化过程相关，而非由支系年龄或区域迁入的差异导致。
研究区域：东亚与北美东部。
时间范围：当前。
研究类群：间断分布于东亚与北美东部的植物类群。
研究方法：本研究收集县级植物分布数据，计算单位网格单元内的物种丰富度、地形与气候变量。构建以物种丰富度为因变量的模型，分别纳入/不纳入地形与气候因子，比较不同模型的区域效应估计系数。此外，采用空间同时自回归误差模型（spatial simultaneous autoregressive error model）分别模拟两个区域内的空间多样性格局。
研究结果：仅包含区域效应的模型其区域效应系数为-0.776，加入地形控制后的模型系数为-0.309，且两类系数均具有统计学显著性。北美东部的空间多样性格局主要受气候因子主导。与之相反，在温暖的东亚区域，气候对物种丰富度的解释度（14.2%）弱于地形（18.3%）。海拔与温度对物种丰富度的影响在两地间存在差异，部分案例中二者的相关性方向发生正负转变。
主要结论：本研究结果表明，局地地形的异质性是导致东亚与北美东部植物物种丰富度呈现显著区域差异的重要成因。尽管如此，在控制局地地形与气候因子后，两地间的多样性异常现象依然存在。东亚与北美东部的物种丰富度-环境关系也呈现出显著差异，这进一步体现了东亚-北美东部间断分布植物区系的另一分化特征。本研究结果凸显出，区域间地形或其他环境因子的差异可能是植物多样性异常现象的潜在驱动因素。