Island Biogeography Theory and Habitat Amount Hypothesis postulate species richness and densities to increase with connectivity and habitat amount, while niche theory highlights the importance of environmental heterogeneity for species coexistence. Additional ecological niches in heterogeneous landscapes increase species richness and functional and phylogenetic diversity, but larger, less isolated habitats are expected to enlarge species densities by mass effects without effects on functional or phylogenetic diversity. We assessed the relative contribution of habitat amount, isolation and environmental heterogeneity on taxonomic, functional and phylogenetic diversity of the particular canga vegetation, i.e., rupestrian savannas associated to banded ironstone outcrops from the Carajas Massif, Eastern Amazon. We sampled vegetation at 48 sampling points comprising different physiognomies from 5 canga patches. Diversity measures were modelled as response variables in linear mixed models, using non-collinear predictors of habitat amount, isolation and environmental heterogeneity. Diversity and species composition differed among canga physiognomies, indicating that environmental filters segregate canga plant metacommunity in physiognomy-specific species pools. Landscape roughness, a proxy for heterogeneity on the landscape level, increases species densities and functional richness. Additionally, habitat amount was positively associated with the degree of phylogenetic relatedness and functional diversity in communities. Our results suggest that configurational landscape heterogeneity increases the number of available ecological niches, while larger habitat amounts select for functionally and phylogenetically convergent species. These different underlying mechanisms need to be considered for management plans and reserve design for canga ecosystems, so that functional canga portions can be protected.

中文翻译：

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景观异质性和栖息地数量驱动亚马逊canga生态系统中的植物多样性

岛屿生物地理学理论和栖息地数量假设假设物种丰富度和密度随着连通性和栖息地数量的增加而增加，而生态位理论则强调了环境异质性对物种共存的重要性。异质景观中的额外生态位增加了物种丰富度以及功能和系统发育多样性，但预计更大、更不孤立的栖息地会通过质量效应扩大物种密度，而不会影响功能或系统发育多样性。我们评估了栖息地数量、隔离和环境异质性对特定 canga 植被的分类、功能和系统发育多样性的相对贡献，即与亚马逊东部 Carajas 地块带状铁岩露头相关的 rupestrian 稀树草原。我们在 48 个采样点对植被进行了采样，这些采样点包括来自 5 个 Canga 斑块的不同地貌。多样性测量被建模为线性混合模型中的响应变量，使用栖息地数量、隔离和环境异质性的非共线预测因子。坎加地貌的多样性和物种组成不同，表明环境过滤器将坎加植物元群落隔离在地貌特定物种库中。景观粗糙度是景观水平异质性的代表，增加了物种密度和功能丰富度。此外，栖息地数量与群落系统发育相关程度和功能多样性呈正相关。我们的结果表明，配置景观异质性增加了可用生态位的数量，而较大的栖息地数量选择功能和系统发育趋同的物种。坎加生态系统的管理计划和保护区设计需要考虑这些不同的潜在机制，以便保护功能性坎加部分。