Phylogenetic community structure as an ecological indicator of anthropogenic disturbance for endemic lizards in a biodiversity hotspot

摘要

The expansion of human-altered landscapes affects biodiversity on every continent. In the Cerrado biodiversity hotspot of central Brazil, Eucalyptus plantations increasingly claim large tracts of native habitats thanks to favorable soils, climate and booming pulp firm profits. Yet, the highs and lows of the economy including government incentives over the years riddled the landscape with abandoned plantations, which are not subject to active restoration. Despite the well-documented pattern anthropogenic disturbances negatively affect Cerrado biodiversity, little is known about the processes driving species co-existence within these abandoned plantations.Herein, we use phylogenetic community structure indices to test if potential processes assembling lizard communities differ between undisturbed Cerrado habitats and disturbed abandoned Eucalyptus plantations; and if so, are these processes predictable. In addition, we explore the applicability of phylogenetic community structure indices as ecological indicators of anthropogenic disturbance in the Cerrado biodiversity hotspot.We address these questions at a local scale, recording lizard species richness and abundance along transects of undisturbed Cerrado and adjacent disturbed abandoned Eucalyptus plantations. Morphological measurements were collected from captured lizards to test for trait conservatism. We investigated if phylogenetic community structure is altered in a predictable manner by comparing (i) phylogenetic species variability, (ii) phylogenetic species richness and (iii) phylogenetic species evenness. To test for significant differences between undisturbed and disturbed communities, we performed two-tailed paired t-tests for each phylogenetic community index. We also test for phylogenetic clustering and overdispersion to determine if potential processes assembling lizard communities differ between undisturbed and disturbed communities. Furthermore, we compare phylogenetic community structure indices to other commonly used diversity indices (taxonomic, functional and phylogenetic diversity) to evaluate their applicability as ecological indicators of anthropogenic disturbance in the Cerrado.We demonstrated phylogenetic clustering in two out of three of the undisturbed Cerrado lizard communities supporting habitat filtering as the potential dominant assembly process; whereas 67% of the disturbed Eucalyptus communities showed phylogenetic overdispersion supporting competition as the potential predominate assembly process. This indicates anthropogenic disturbance, in the form of abandoned Eucalyptus plantations, may alter phylogenetic community structure in a predictable manner, leading to the loss of closely related species in the disturbed plantation forests. The highly endemic biota of the Cerrado is composed of closely related species that share similar traits for survival, most likely a consequence of frequent episodic fires during the dry season. Interestingly, phylogenetic community structure indices and diversity indices did not converge on the same disturbed site to prioritize for active restoration; thereby, providing a cautionary tale on the applicability of the indices as ecological indicators for the Cerrado biodiversity.