Multi-scale determinants of small mammal and lizard dimensions of diversity across Amazonian insular forest fragments

Abstract

\n Context\n\nHydropower development is one of the primary drivers of habitat loss and insular fragmentation. Yet, studies quantifying such effects on biodiversity are mostly limited to taxonomic metrics, often overlooking species identity and their functional and phylogenetic roles.\nObjectives\n\nWe examined taxonomic, functional and phylogenetic responses to habitat loss and insular fragmentation of small mammals and lizards within (α) and between sites (β).\nMethods\n\nBoth taxa were surveyed across 25 islands within the Balbina Hydroelectric Reservoir, and adjacent continuous forest, in Central Amazonia. Each dimension of diversity was related to spatial and habitat variables. We also examined functional composition using community-weighted mean trait values, and community redundancy using functional uniqueness. β-diversity was partitioned into their richness (βrich) and replacement (βrepl) components.\nResults\n\nFunctional and phylogenetic α−diversities of both taxa mirrored the taxonomic dimension, all of which increased with forest area. Individual small mammal (body mass and matrix tolerance), and lizard traits (heliothermic mode and habitat type) were also predicted by forest area. For both taxa, species functional uniqueness decreased with forest area, and all dimensions of β-diversity were predominantly partitioned in βrich.\nConclusions\n\nThe environmental filter created by forest area resulted in the low conservation value associated with small forest islands, only occupied by a small set of species comprised by generalist lizards and matrix-tolerant small mammals. On the other side, large forest sites ensured ecosystem resilience to disturbance. To maintain ecosystem integrity, creating a myriad small island over large expanses of floodwaters should be avoided in future hydropower development.