Chow, C. F. Y. | bioRxiv Science

bioRxiv2022

Synthesis reveals biotic homogenisation and differentiation are both common

It is commonly thought that the biodiversity crisis includes widespread decreases in the uniqueness of different sites in a landscape (biotic homogenization). Using a typology relating homogenization and differentiation to local and regional diversity changes, we synthesize patterns across 283 metacommunities surveyed for 10-91 years, and 54 species checklists (13-500+ years). On average, there is a 0.2% increase in species shared among communities/year (i.e., weak homogenization), but across data sets, differentiation frequently occurs, with no statistically significant change being most common. Local (not regional) diversity frequently underlies composition change, and homogenization is strongly associated with checklist data that have longer durations and large spatial scales. Conservation and management can benefit from the multiscale perspective used here as it disentangles the implications of both the differentiation and homogenization currently unfolding. One-Sentence SummaryBiotic homogenization is most prevalent at large temporal and spatial scales.

ecology↗

bioRxiv2021

Coral settlement and recruitment responses to reef fish foraging and trait diversity

The process of coral recruitment is crucial to the functioning of coral reef ecosystems, as well as recovery of coral assemblages following disturbances. Fishes can be key mediators of this process by removing benthic competitors like algae, but their foraging impacts are capable of being facilitative or harmful to coral recruits depending on species traits. Reef fish assemblages are highly diverse in foraging strategies and the relationship between this diversity with coral settlement and recruitment success remains poorly understood. Here, we investigate how foraging trait diversity of reef fish assemblages covaries with coral settlement and recruitment success across multiple sites at Lizard Island, Great Barrier Reef. Using a multi-model inference approach incorporating six metrics of fish assemblage foraging diversity (foraging rates, trait richness, trait evenness, trait divergence, herbivore abundance, and sessile invertivore abundance), we found that herbivore abundance was positively related to both coral settlement and recruitment success. However, the correlation with herbivore abundance was not as strong in comparison with foraging trait diversity metrics. Coral settlement and recruitment exhibited a negative relationship with foraging trait diversity, especially with trait divergence and richness in settlement. Our findings provide further evidence that fish play a role in making benthic habitats more conducive for coral settlement and recruitment. Because of their ability to shape the reef benthos, the variation of fish biodiversity is likely to contribute to spatially uneven patterns of coral recruitment and reef recovery.

ecology↗