Global patterns and drivers of beta diversity facets of reef fish faunas

Aim: Exploring the relationships between the different facets of beta
diversity and both past and current environmental conditions can unveil
the processes that have shaped spatial patterns of biodiversity. In the
marine realm, large-scale patterns and processes of beta diversity have
been less investigated. Our study aimed to investigate the patterns and
drivers of multiple facets of beta diversity and its components,
contrasting pairs of reef fish assemblages among marine realms. Location:
Tropical reefs. Taxon: Reef fishes. Methods: Based on trait data and
phylogenetic relationships for 5,182 tropical reef fish species, we
calculated compositional differences between pairs of reef fish
assemblages across the Atlantic, Tropical Eastern Pacific (TEP), and
Indo-Pacific realms. We also applied a partitioning approach to
distinguish between the turnover and nestedness components. We then
evaluated the relative importance of several variables related to
historical and contemporary environmental conditions in shaping spatial
patterns of beta diversity using Constrained Analysis of Principal
Coordinates (CAP) models. Results: Both the turnover and nestedness
components contributed to total phylogenetic and taxonomic beta diversity
in the TEP and Indo-Pacific realms, while the turnover component was found
to be more important in the Atlantic realm. In contrast, total trait beta
diversity displayed very low values and was primarily explained by the
nestedness component. Taxonomic and phylogenetic differences in the
composition of tropical reef fish assemblages were influenced by both
historical and contemporary factors or solely by historical variables.
Main conclusions: Our results suggest that past climate changes
and historical contingency left an imprint in the present-day composition
of tropical reef fish assemblages. The very low levels of trait beta
diversity indicate that reef fish assemblages display similar trait
composition even among geographically distant assemblages with contrasting
evolutionary histories, which may result from environmental filtering or
evolutionary convergence, or the combination of both processes.