Instituto de Biociências, Universidade Federal de Mato Grosso do Sul, Campo Grande, Brazil.
Department of Biology, University of Vermont, Burlington, VT, USA.
J Anim Ecol. 2022 Mar;91(3):618-629. doi: 10.1111/1365-2656.13660. Epub 2022 Jan 16.
Understanding the effects of random versus niche-based processes on biodiversity patterns is a central theme in ecology, and an important tool for predicting effects of habitat loss and fragmentation on biodiversity. We investigated the predictive power of random processes to explain species richness and species dissimilarity of amphibian assemblages in a fragmented tropical landscape of the Atlantic Forest of South America. We analyzed a large database of amphibian abundance and occupancy, sampled in 21 forest fragments ranging in size from 1.9 to 619 ha. We compared observed species richness and species dissimilarity with the outcomes of two null (random placement) models: 1- the traditional Coleman's area-based model and 2- an abundance-based model (based on the number of individuals observed in each fragment). We applied these models for all species combined, and separately for forest-dependent and habitat-generalist species. The abundance-based model fitted the observed species richness data better than the area-based model for all species, forest-dependent species, and generalist species. The area-based and the abundance-based models were also able to significantly explain species dissimilarity for all species and for generalists, but not for forest dependent species. The traditional area-based model assigned too many individuals to large fragments, thus failing to accurately explain species richness within patches across the landscape. Although niche-based processes may be important to structuring the regional pool of species in fragmented landscapes, our results suggest that part of the variation in species richness and species dissimilarity can be successfully explained by random placement models, especially for generalist species. Evaluating which factors cause variation in the number of individuals among patches should be a focus in future studies aiming to understand biodiversity patterns in fragmented landscapes.
理解随机过程与生态位过程对生物多样性模式的影响是生态学的一个核心主题，也是预测生境丧失和破碎化对生物多样性影响的重要工具。我们调查了随机过程对解释在南美的大西洋森林的破碎热带景观中的两栖动物组合的物种丰富度和物种相似性的预测能力。我们分析了一个大型的两栖动物丰度和占有量数据库，这些数据是在 21 个森林片段中采样的，这些片段的大小从 1.9 公顷到 619 公顷不等。我们将观察到的物种丰富度和物种相似性与两个零假设（随机放置）模型的结果进行了比较：1-传统的科尔曼基于面积的模型和 2-基于每个片段中观察到的个体数量的丰度模型。我们将这些模型应用于所有物种的组合，以及对依赖森林的物种和生境广适物种分别进行了应用。丰度模型比基于面积的模型更适合所有物种、依赖森林的物种和广适物种的观察到的物种丰富度数据。基于面积和丰度的模型也能够显著解释所有物种和广适物种的物种相似性，但不能解释依赖森林的物种的物种相似性。传统的基于面积的模型将太多的个体分配给了大的片段，因此无法准确地解释景观中斑块内的物种丰富度。虽然生态位过程可能对构建破碎景观中的区域物种库很重要，但我们的结果表明，部分物种丰富度和物种相似性的变异可以通过随机放置模型成功解释，特别是对于广适物种。评估哪些因素导致斑块之间个体数量的变化应该是未来研究的重点，目的是了解破碎景观中的生物多样性模式。
