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ABSTRACT Aim Location Methods Results Main Conclusions Marine organisms are responding to warming by altering their distribution ranges, causing biogeographic range shifts and in some cases, favouring the community homogenisation. Transition zones can act as natural laboratories to explore the consequences of homogenisation. However, these habitats are relatively poorly studied in coastal areas. In this study, we aimed to investigate biotic homogenisation and changes in reef fish community composition from both a taxonomic and trait‐based perspective.Seven islands in the South‐western Atlantic transition zone.We used a long‐term survey data set of reef fish species abundances and traits of communities to calculate beta‐diversity indices. By analysing the data, we derived temporal trends of beta‐diversity values by separately comparing the North and South regions of the transition zone and performed pairwise comparisons to explore their dynamics when considered together.Contrary to previous expectations, we found no sign of homogenisation. The colder islands (Southern) experienced a decrease in taxonomic and trait richness metrics, whereas for the warmer islands (Northern), the taxonomic and trait richness fluctuated without any significant temporal trends.While taxonomic composition may change over time, the trait composition is generally more conserved, highlighting the trait redundancy in South‐western Atlantic communities and supporting the idea that these communities can maintain a range of ecological processes despite changes in taxonomic composition. Finally, the study revealed that despite non‐homogenisation, the species that contribute most to variation, especially in the South, have common trait combinations indicating an increase in the trait redundancy of fish communities over time. We underline that local‐scale conservation efforts may be particularly effective in preserving and protecting species and ecological functions in areas experiencing unique and fast changes in biodiversity. [ABSTRACT FROM AUTHOR]

Human activities and climate change have accelerated species losses and degradation of ecosystems to unprecedented levels. Both theoretical and empirical evidence suggest that extinction cascades contribute substantially to global species loss. The effects of extinction cascades can ripple across levels of ecological organization, causing not only the secondary loss of taxonomic diversity but also functional diversity erosion. Here, we take a step forward in coextinction analysis by estimating the functional robustness of reef fish communities to species loss. We built a tripartite network with nodes and links based on a model output predicting reef fish occupancy (113 species) as a function of coral and turf algae cover in Southwestern Atlantic reefs. This network comprised coral species, coral‐associated fish (site occupancy directly related to coral cover), and co‐occurring fish (occupancy indirectly related to coral cover). We used attack‐tolerance curves and estimated network robustness (R) to quantify the cascading loss of reef fish taxonomic and functional diversity along three scenarios of coral species loss: degree centrality (removing first corals with more coral‐associated fish), bleaching vulnerability and post‐bleaching mortality (most vulnerable removed first), and random removal. Degree centrality produced the greatest losses (lowest R) in comparison with other scenarios. In this scenario, while functional diversity was robust to the direct loss of coral‐associated fish (R = 0.85), the taxonomic diversity was not robust to coral loss (R = 0.54). Both taxonomic and functional diversity showed low robustness to indirect fish extinctions (R = 0.31 and R = 0.57, respectively). Projections of 100% coral species loss caused a reduction of 69% of the regional trait space area. The effects of coral loss in Southwestern Atlantic reefs went beyond the direct coral‐fish relationships. Ever‐growing human impacts on reef ecosystems can cause extinction cascades with detrimental consequences for fish assemblages that benefit from corals. [ABSTRACT FROM AUTHOR]

The emergence of functional ecology has changed the focus of ecological research from investigating patterns of species diversity to understanding how species traits relate to specific ecological processes generating these patterns. Traits, ecological patterns and processes can be shared and driven by species from distantly related taxonomic groups.Crossing the boundaries among distantly related taxonomic groups is still a challenge and a critical knowledge frontier in functional ecology. A cross‐taxa approach, merging trait data across distantly related taxonomic groups, could fill this gap. In this context, functionally analogous traits, that is traits that may have distinct ontogenetic origins yet represent similar processes, comprise an important recent advance in functional ecology. However, which taxa and traits (be them analogous or not) have been used in research with multiple taxa, and whether (and how) these data have been combined, still needs to be elucidated.We reviewed articles published in the last 75 years to investigate the use of traits in functional research involving multiple taxa. Our search returned 1006 articles, and a subset of 96 was filtered for data extraction. Studies covered a total of 134 taxa and 491 different traits; they were predominantly observational, and focussed on community ecology and ecosystem monitoring.Our review showed that current knowledge in this field relies on a limited number of response variables, particularly taxonomic diversity (e.g. species richness and abundance within functional groups). Also, the field relies on a limited number of taxa (e.g. plants, birds and mammals) and trait types (diet, size, habitat and dispersal). Two‐thirds of the articles (n = 72) used functionally analogous traits, and one‐third of them (n = 32) employed a cross‐taxa approach.We mapped the limitations of current research in functional ecology involving multiple taxa, presented ecological questions to a functional cross‐taxa research and showed directions to pushing the limits of this research field. Our review aimed to encourage researchers in the field of functional ecology to move beyond single taxa and traits, and to integrate more branches and dimensions of the Tree of Life in their research. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

We investigated the feeding rates, agonistic behaviour and diet of two blenny species, Entomacrodus vomerinus and Ophioblennius trinitatis, by direct observation and gut content analysis. Both species coexist in small and shallow tide pools in the St Peter and St Paul's Archipelago, equatorial North Atlantic Ocean. The feeding rate of O. trinitatis was c. 55% higher than E. vomerinus. On the other hand, agonistic rate of O. trinitatis was negatively related to body size, whereas in E. vomerinus was positively related. Both species showed a high diet overlap, in which detritus was the most important food item (86% in O. trinitatis and 80% in E. vomerinus). Feeding activity was more intense during the morning for O. trinitatis but afternoon for E. vomerinus. These behavioural observations support the importance of temporal feeding partitioning as the main strategy allowing species co‐existence in tide pools. [ABSTRACT FROM AUTHOR]

Diversity patterns are determined by biogeographic, energetic, and anthropogenic factors, yet few studies have combined them into a large‐scale framework in order to decouple and compare their relative effects on fish faunas. Using an empirical dataset derived from 1527 underwater visual censuses (UVC) at 18 oceanic islands (five different marine provinces), we determined the relative influence of such factors on reef fish species richness, functional dispersion, density and biomass estimated from each UVC unit. Species richness presented low variation but was high at large island sites. High functional dispersion, density, and biomass were found at islands with large local species pool and distance from nearest reef. Primary productivity positively affected fish richness, density and biomass confirming that more productive areas support larger populations, and higher biomass and richness on oceanic islands. Islands densely populated by humans had lower fish species richness and biomass reflecting anthropogenic effects. Species richness, functional dispersion, and biomass were positively related to distance from the mainland. Overall, species richness and fish density were mainly influenced by biogeographical and energetic factors, whereas functional dispersion and biomass were strongly influenced by anthropogenic factors. Our results extend previous hypotheses for different assemblage metrics estimated from empirical data and confirm the negative impact of humans on fish assemblages, highlighting the need for conservation of oceanic islands. [ABSTRACT FROM AUTHOR]