Understanding the factors and mechanisms shaping differences in species composition across space and time (β-diversity) in human-modified landscapes has key ecological and applied implications. This topic is, however, challenging because landscape disturbance can promote either decreases (biotic homogenization) or increases (biotic differentiation) in β-diversity. We assessed temporal differences in intersite β-diversity of medium-bodied and large-bodied mammals in the fragmented Lacandona rainforest, Mexico. We hypothesized that, given the relatively short history of land-use changes in the region, and the gain and loss of some species caused by landscape spatial changes, β-diversity would increase through time, especially its nestedness component. We estimated β-diversity between 24 forest sites (22 forest patches and two continuous forest sites) in 2011 and 2017 to assess whether β-diversity is decreasing or increasing in the region, and calculated its turnover and nestedness components to understand the mechanisms responsible for changes in β-diversity, separately assessing mammal groups with different body mass, feeding guild, and habitat specialization. We then related such temporal changes in β-diversity to temporal changes in five landscape variables (forest cover, matrix openness, number of patches, edge density and interpatch distance) to identify the landscape drivers of β-diversity. In contrast with our expectations, β-diversity decreased over time, suggesting an ongoing biotic homogenization process. This pattern was mostly driven by a decrease in species turnover in all mammal groups, especially in landscapes with decreasing forest cover and increasing forested matrices. Although the nestedness component showed a three-fold increase through time, species turnover was 22 and six times higher than nestedness in 2011 and 2017, respectively. The decreased turnover appears to be driven by an increase in dispersal (i.e., spillover) of native species among patches. The prevalence of species turnover over nestedness indicates that different forest sites have a fairly distinct subset of species (i.e., high complementarity in species composition). Therefore, conserving all remaining forest patches and increasing forest cover is of utmost importance to effectively maintain β-diversity and conserve the total diversity (γ) of mammal assemblages in this Mesoamerican biodiversity hotspot.

中文翻译：

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破碎雨林中陆生哺乳动物的同质化：物种周转的丧失及其景观驱动因素

了解在人类改造的景观中影响物种组成跨时空差异（β-多样性）的因素和机制具有关键的生态和应用意义。然而，这个主题具有挑战性，因为景观干扰可以促进 β 多样性的减少（生物同质化）或增加（生物分化）。我们评估了墨西哥拉坎多纳雨林中中型和大型哺乳动物的位点间 β 多样性的时间差异。我们假设，考虑到该地区土地利用变化的历史相对较短，以及景观空间变化引起的一些物种的得失，β-多样性会随着时间的推移而增加，尤其是其嵌套成分。我们估计了 2011 年和 2017 年 24 个森林地点（22 个森林斑块和两个连续森林地点）之间的 β-多样性，以评估该地区的 β-多样性是减少还是增加，并计算其周转率和嵌套性分量以了解负责的机制β-多样性的变化，分别评估不同体重的哺乳动物群体、饲养行会和栖息地专业化。然后，我们将 β 多样性的这种时间变化与五个景观变量（森林覆盖、矩阵开放度、斑块数量、边缘密度和斑块间距离）的时间变化联系起来，以确定 β 多样性的景观驱动因素。与我们的预期相反，β-多样性随着时间的推移而下降，表明生物同质化过程正在进行中。这种模式主要是由所有哺乳动物群体的物种更新减少造成的，特别是在森林覆盖率下降和森林基质增加的景观中。尽管嵌套部分随时间增长了三倍，但物种周转率分别比 2011 年和 2017 年的嵌套高出 22 倍和 6 倍。减少的周转似乎是由本地物种在斑块之间的扩散（即溢出）增加所驱动的。物种周转超过嵌套的流行表明不同的森林地点具有相当不同的物种子集（即物种组成的高度互补性）。所以，