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多样性堪称极具代表性的范例，清晰阐明了物种生物学特性的差异能够在大尺度上有效解释物种分布格局。本研究提出假说：相较于干旱生境，湿度更高的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胁迫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：巴西大西洋森林内的27处森林生境。 研究方法：本研究采用路径分析（path analysis）方法，评估了湿度水平对繁殖模式数量的直接与间接效应，以及这两个变量对两栖动物系统发育多样性的相对重要性。此外，本研究采用嵌套性分析（nestedness analysis），量化了干旱生境中物种与繁殖模式的组成，在多大程度上属于年降水量更高生境的非随机子集。 研究结果：我们发现，干旱生境中存在的繁殖模式，是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，繁殖模式更丰富的生境，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的环境条件，而降水稀少且具有典型季节性气候的生境，则仅能支持那些特化以抵御干旱胁迫的繁殖模式。 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，反映了不同繁殖模式对干旱胁迫耐受性的差异。鉴于繁殖模式与干旱胁迫易感性存在关联，将其纳入解释模型或将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取得重大进展。