Data from: Humidity levels drive reproductive modes and phylogenetic diversity of amphibians in the Brazilian Atlantic Forest

AIM: The diversity of reproductive modes among amphibians provides a striking example of how differences in the biology of species furnish can provide important explanations for species distribution patterns on a broad scale. We hypothesized that sites with a higher humidity level will support more different modes of reproduction than drier sites and will consequently exhibit a higher phylogenetic diversity. Furthermore, we predict that if there is a gradient in the tolerance of reproductive modes to desiccation, there will be a nested pattern in the composition of reproductive modes among sites. LOCATION: Twenty-seven forest sites in the Brazilian Atlantic Forest. METHODS: Through a path analysis approach, we evaluated the direct and indirect effects of the humidity level on the number of reproductive modes as well as the relative importance of both variables on amphibian phylogenetic diversity. A nestedness analysis was used to quantify the extent to which the composition of both species and reproductive modes in drier sites correspond to non-random subsets of those in sites with higher annual precipitation. RESULTS: We found that the reproductive modes present in drier sites are non-random subsets of those present in sites with higher humidity levels. Because reproductive modes are phylogenetically conserved among amphibians, sites with a greater number of reproductive modes supported greater phylogenetic diversity. Sites with high precipitation throughout the year provided adequate environmental conditions for a larger number of reproductive modes, whereas sites with low precipitation and typical seasonal climates supported only those reproductive modes specialized to resist desiccation. MAIN CONCLUSIONS: Our results show that humidity-related variables are key environmental factors related to both the richness of reproductive modes and phylogenetic diversity. We hypothesized that the higher phylogenetic diversity found in moister sites reflects differences in the tolerance to desiccation among different reproductive modes. Given that reproductive modes are associated with susceptibility to desiccation, their incorporation into explanatory models may trigger a great advance in the understanding of the mechanisms regulating the species richness and composition of amphibian communities.

研究目的：两栖动物的繁殖模式（reproductive modes）多样性，堪称阐释物种生物学差异可为大范围物种分布格局提供重要解释的绝佳范例。我们提出假说：湿度更高的生境，相较于干旱生境，可支持更多样的繁殖模式，因此其系统发育多样性（phylogenetic diversity）也更高。此外，我们预测：若不同繁殖模式对干旱（desiccation）的耐受性存在梯度差异，则不同生境的繁殖模式组成将呈现嵌套格局。
研究区域：巴西大西洋森林分布的27处森林生境。
研究方法：本研究采用路径分析（path analysis）方法，评估湿度对繁殖模式数量的直接与间接效应，以及二者对两栖动物系统发育多样性的相对贡献。同时通过嵌套性分析（nestedness analysis），量化干旱生境中的物种与繁殖模式组成，是否为高年降水量生境中非随机的子集。
研究结果：本研究发现，干旱生境中的繁殖模式，实为高湿度生境繁殖模式的非随机子集。由于两栖动物的繁殖模式具有系统发育保守性，因此拥有更多繁殖模式的生境，其系统发育多样性也更高。全年降水充沛的生境，可为更多样的繁殖模式提供适宜环境；而降水稀少且具典型季节性气候的生境，仅能容纳特化以抵御干旱的繁殖模式。
主要结论：本研究结果表明，与湿度相关的变量，是影响繁殖模式丰富度与系统发育多样性的关键环境因子。我们推测，湿润生境中更高的系统发育多样性，源于不同繁殖模式对干旱的耐受性差异。鉴于繁殖模式与干旱易感性密切相关，将其纳入解释模型，或可极大推动我们对调控两栖动物群落物种丰富度与组成的机制的认知。