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Aim: Several drivers explain the global distribution of all reef fish. However, whether these drivers also explain the distribution and traits of a functional subgroup involving cleaner fishes remain unclear. Here we examine the variation in traits of cleaner fishes and test whether historical, environmental, ecological and geographical drivers are correlated with cleaner species richness and abundance at global reefs. Location: Tropical and subtropical reefs. Taxon: Actinopterygii. Methods: We tested whether species traits and trait space vary between facultative (i.e. species that clean only during the juvenile stages or sporadically) and dedicated (i.e. species that clean during their whole lives) cleaner types. We compiled data from local checklists (relative richness) and belt transects (standardized richness and abundance). We built four models to test whether past and current isolation (i.e. distance from Quaternary refugia and biodiversity centres), sea temperature, primary productivity, local species pool and abundance of potential clients influenced the relative richness and abundance of cleaners. Results: Facultative cleaners had high trait variability that contributed disproportionally to the trait space, whereas dedicated cleaners exhibited low trait variability. Cleaner species richness was higher in the Indo‐Pacific and Caribbean provinces, but the relative richness and standardized abundance of cleaners were higher in the Atlantic (i.e. North Eastern and Southwestern) and Eastern Pacific. Isolation influenced the relative richness of facultative cleaners, whereas the distance to Quaternary refugia, sea temperature and isolation influenced the relative richness of dedicated cleaners. Local species richness and standardized abundance of cleaner fish exhibited a strong relationship with regional diversity. The standardized abundance of both facultative and dedicated cleaners was influenced by the abundance of potential clients and the local species pool. Main conclusions: The small trait space occupied by cleaner fishes may reflect their restricted origin among lineages of reef fishes. Differences in the relative richness and standardized abundance of cleaner fishes across marine realms suggest a strong influence on biogeographical history. Our results also indicate that cleaner fishes originated mostly in peripheral areas in high latitudes due to the absence of dedicated cleaners. Our results imply that cleaner fishes do not follow the pattern of main centres of origin described for reef fishes due to opportunistic cleaning behaviour that originated with higher frequency at locations with low species richness. [ABSTRACT FROM AUTHOR]

Ecological interactions uphold ecosystem structure and functioning. However, as species richness increases, the number of possible interactions rises exponentially. More than 6,000 species of coral reef fishes exist across the world's tropical oceans, resulting in an almost innumerable array of possible trophic interactions. Distilling general patterns in these interactions across different bioregions stands to improve our understanding of the processes that govern coral reef functioning. Here, we show that across bioregions, tropical coral reef food webs exhibit a remarkable congruence in their trophic interactions. Specifically, by compiling and investigating the structure of six coral reef food webs across distinct bioregions, we show that when accounting for consumer size and resource availability, these food webs share more trophic interactions than expected by chance. In addition, coral reef food webs are dominated by dietary specialists, which makes trophic pathways vulnerable to biodiversity loss. Prey partitioning among these specialists is geographically consistent, and this pattern intensifies when weak interactions are disregarded. Our results suggest that energy flows through coral reef communities along broadly comparable trophic pathways. Yet, these critical pathways are maintained by species with narrow, specialized diets, which threatens the existence of coral reef functioning in the face of biodiversity loss. [ABSTRACT FROM AUTHOR]

Taxonomic nestedness, the degree to which the taxonomic composition of species-poor assemblages represents a subset of richer sites, commonly occurs in habitat fragments and islands differing in size and isolation from a source pool. However, species are not ecologically equivalent and the extent to which nestedness is observed in terms of functional trait composition of assemblages still remains poorly known. Here, using an extensive database on the functional traits and the distributions of 6316 tropical reef fish species across 169 sites, we assessed the levels of taxonomical vs functional nestedness of reef fish assemblages at the global scale. Functional nestedness was considerably more common than taxonomic nestedness, and generally associated with geographical isolation, where nested subsets are gradually more isolated from surrounding reef areas and from the center of biodiversity. Because a nested pattern in functional composition implies that certain combinations of traits may be represented by few species, we identified these groups of low redundancy that include large herbivore-detritivores and omnivores, small piscivores, and macro-algal herbivores. The identified patterns of nestedness may be an outcome of the interaction between species dispersal capabilities, resource requirements, and gradients of isolation among habitats. The importance of isolation in generating the observed pattern of functional nestedness within biogeographic regions may indicate that disturbance in depauperate and isolated sites can have disproportionate effects on the functional structure of their reef fish assemblages. [ABSTRACT FROM AUTHOR]

• Anthropogenic impacts, global change and natural disturbances threaten coral reefs. • A multi-factor reef recovery index (RI) based on the TOPSIS method was developed. • Recovery Index is based on variables classically considered in monitoring programs. • RI adequately ranges reefs based on their potential to recover from disturbance. Over the last two decades, coral reefs have experienced dire declines due to intensifying anthropogenic disturbances and climate change. Defining and quantifying coral reef resilience now represents a critical management objective, but there is still little consensus on the approach and the indices to be used. In this study, we develop a multi-factor reef recovery index based on the Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS) method to assess the vulnerability of several insular coral reefs in the South Western Indian Ocean (SWIO) from 2016 to 2018. We showed, that in the wake of a regional bleaching event in 2016, the most isolated reefs of Europa, which is characterized by low direct human impact had the highest recovery potential. On the contrary, islands that are more prone to direct human influence (i.e. , La Reunion and Rodrigues) displayed the lowest recovery potential. [ABSTRACT FROM AUTHOR]

High species richness is thought to support the delivery of multiple ecosystem functions and services under changing environments. Yet, some species might performunique functional roleswhile others are redundant. Thus, the benefits of high species richness in maintaining ecosystem functioning are uncertain if functions have little redundancy, potentially leading to high vulnerability of functions.We studied the natural propensity of assemblages to be functionally buffered against loss prior to fishing activities, using functional trait combinations, in coral reef fish assemblages across unfished wilderness areas of the Indo-Pacific: Chagos Archipelago, New Caledonia and French Polynesia. Fish functional diversity in these wilderness areas is highly vulnerable to fishing, explained by species- and abundance-based redundancy packed into a small combination of traits, leaving most other trait combinations (60%) sensitive to fishing, with no redundancy. Functional vulnerability peaks for mobile and sedentary top predators, and large species in general. Functional vulnerability decreases for certain functional entities in New Caledonia, where overall functional redundancy was higher. Uncovering these baseline patterns of functional vulnerability can offer early warning signals of the damaging effects from fishing, and may serve as baselines to guide precautionary and even proactive conservation actions. [ABSTRACT FROM AUTHOR]

Sustained functioning of ecosystems is predicted to depend upon the maintenance of their biodiversity, structure and integrity. The large consensus achieved in this regard, however, faces to the objective difficulty of finding appropriate metrics to measure ecosystem functioning. Here, we aim at evaluating functional consequence of the phase shift occurring in meadows of the Mediterranean seagrass Posidonia oceanica , a priority habitat that is undergoing regression in many coastal areas due to multiple human pressures. Structural degradation of the P. oceanica ecosystem, consequent to increasing coastal exploitation and climate change, may result in the progressive replacement of this seagrass by opportunistic macrophytes, either native or alien. Reviewing published information and our personal records, we measured changes in biological habitat provisioning, species richness and biomass associated to each of the alternative states characterizing the phase shift. Then, ecosystem functioning was assessed by computing the exergy associated to each state, exergy being a state variable that measures the ecosystem capacity to produce work. Phase shift was consistently shown to imply loss in habitat provision, species richness, and biomass; structural and compositional loss was parallelled by a reduction of exergy content, thus providing for the first time an objective and integrative measure of the loss of ecosystem functioning following the degradation of healthy seagrass meadows. [ABSTRACT FROM AUTHOR]

Aim The delineation of regions is a critical procedure in biogeography, but there is still no consensus about the best approach. Traditionally, a compositional dissimilarity index and a clustering algorithm are used to partition locations into regions. However, the choice of index and algorithm may have a profound impact on the final result, particularly when locations display different levels of species richness and when they are nested within each other. Our objective was to estimate the influence of species nestedness among locations on the delineation of biogeographical regions. Location As a case study, we used coral reef fishes (families Chaetodontidae, Pomacentridae and Labridae) from the Indo-Pacific, where a large richness gradient extends, often as a series of nested assemblages, from the species-rich Indo-Australian Archipelago (Coral Triangle) to species-poor peripheral locations. Methods We used the turnover and nestedness components of the Sørensen and Jaccard dissimilarity indices to estimate the effect of nestedness on the delineation of biogeographical regions. In addition, we compared the results with those obtained using a parsimony analysis of endemicity ( PAE). Results Low Mantel correlation values revealed that the PAE method assembled locations in a very different way than methods based on dissimilarity indices for Indo-Pacific coral reef fishes. We also found that nestedness mattered when delineating biogeographical units because, for both the Sørensen and the Jaccard indices, reef fish assemblages were grouped differently depending on whether we used the turnover component of each index or the complete index, including the nestedness component. The turnover component ignored variation in species richness attributable to differences in habitat area between locations, and permitted a delineation based solely on species replacement. Main conclusions We demonstrate that the choice of the component used to measure dissimilarity between species assemblages is critical, because it may strongly influence regional delineations, at least for Indo-Pacific coral reef fishes. We conclude that the two components of the dissimilarity indices can reveal complementary insights into the role that history may have played in shaping extant patterns of biodiversity. [ABSTRACT FROM AUTHOR]

The global network of protected areas has rapidly expanded in the past decade and is expected to cover at least 30% of land and sea by 2030 to halt biodiversity erosion. Yet, the distribution of protected areas is highly heterogeneous on Earth and the social-environmental preconditions enabling or hindering protected area establishment remain poorly understood. Here, using fourteen socioeconomic and environmental factors, we characterize the multidimensional niche of terrestrial and marine protected areas, which we use to accurately establish, at the global scale, whether a particular location has preconditions favourable for paestablishment. We reveal that protected areas, particularly the most restrictive ones, over-aggregate where human development and the number of non-governmental organizations are high. Based on the spatial distribution of vertebrates and the likelihood to convert non-protected areas into strictly protected areas, we identify 'potential' versus 'unrealistic' conservation gains on land and sea, which we define as areas of high vertebrate diversity that are, respectively, favourable and unfavourable to protected area establishment. Where protected areas are unrealistic, alternative strategies such as other effective area-based conservation measures or privately protected areas, could deliver conservation outcomes., (© 2024. The Author(s).)

Anthropogenic pressures are restructuring coral reefs globally. Sound predictions of the expected changes in key reef functions require adequate knowledge of their drivers. Here we investigate the determinants of a poorly-studied yet relevant biogeochemical function sustained by marine bony fishes: the excretion of intestinal carbonates. Compiling carbonate excretion rates and mineralogical composition from 382 individual coral reef fishes (85 species and 35 families), we identify the environmental factors and fish traits that predict them. We find that body mass and relative intestinal length (RIL) are the strongest predictors of carbonate excretion. Larger fishes and those with longer intestines excrete disproportionately less carbonate per unit mass than smaller fishes and those with shorter intestines. The mineralogical composition of excreted carbonates is highly conserved within families, but also controlled by RIL and temperature. These results fundamentally advance our understanding of the role of fishes in inorganic carbon cycling and how this contribution will change as community composition shifts under increasing anthropogenic pressures., (© 2023. The Author(s).)

Human impact increasingly alters global ecosystems, often reducing biodiversity and disrupting the provision of essential ecosystem services to humanity. Therefore, preserving ecosystem functioning is a critical challenge of the twenty-first century. Coral reefs are declining worldwide due to the pervasive effects of climate change and intensive fishing, and although research on coral reef ecosystem functioning has gained momentum, most studies rely on simplified proxies, such as fish biomass. This lack of quantitative assessments of multiple process-based ecosystem functions hinders local and regional conservation efforts. Here we combine global coral reef fish community surveys and bioenergetic models to quantify five key ecosystem functions mediated by coral reef fishes. We show that functions exhibit critical trade-offs driven by varying community structures, such that no community can maximize all functions. Furthermore, functions are locally dominated by few species, but the identity of dominant species substantially varies at the global scale. In fact, half of the 1,110 species in our dataset are functionally dominant in at least one location. Our results reinforce the need for a nuanced, locally tailored approach to coral reef conservation that considers multiple ecological functions beyond the effect of standing stock biomass., (© 2022. The Author(s), under exclusive licence to Springer Nature Limited.)

Ecosystems face both local hazards, such as over-exploitation, and global hazards, such as climate change. Since the impact of local hazards attenuates with distance from humans, local extinction risk should decrease with remoteness, making faraway areas safe havens for biodiversity. However, isolation and reduced anthropogenic disturbance may increase ecological specialization in remote communities, and hence their vulnerability to secondary effects of diversity loss propagating through networks of interacting species. We show this to be true for reef fish communities across the globe. An increase in fish-coral dependency with the distance of coral reefs from human settlements, paired with the far-reaching impacts of global hazards, increases the risk of fish species loss, counteracting the benefits of remoteness. Hotspots of fish risk from fish-coral dependency are distinct from those caused by direct human impacts, increasing the number of risk hotspots by ~30% globally. These findings might apply to other ecosystems on Earth and depict a world where no place, no matter how remote, is safe for biodiversity, calling for a reconsideration of global conservation priorities., (© 2021. The Author(s).)

Climate change and consequent coral bleaching are causing the disappearance of reef-building corals worldwide. While bleaching episodes significantly impact shallow waters, little is known about their impact on mesophotic coral communities. We studied the prevalence of coral bleaching two to three months after a heat stress event, along an extreme depth range from 6 to 90 m in French Polynesia. Bayesian modelling showed a decreasing probability of bleaching of all coral genera over depth, with little to no bleaching observed at lower mesophotic depths (greater than or equal to 60 m). We found that depth-generalist corals benefit more from increasing depth than depth-specialists (corals with a narrow depth range). Our data suggest that the reduced prevalence of bleaching with depth, especially from shallow to upper mesophotic depths (40 m), had a stronger relation with the light-irradiance attenuation than temperature. While acknowledging the geographical and temporal variability of the role of mesophotic reefs as spatial refuges during thermal stress, we ought to understand why coral bleaching reduces with depth. Future studies should consider repeated monitoring and detailed ecophysiological and environmental data. Our study demonstrated how increasing depth may offer a level of protection and that lower mesophotic communities could escape the impacts of a thermal bleaching event., (© 2021 The Authors.)

We studied the food web structure and functioning of a coral reef ecosystem in the Marquesas Islands, French Polynesia, characterized by low coral cover, high sea surface temperature and meso- to eutrophic waters. The Marquesas constitute a relevant ecosystem to understand the functioning of low diversity reefs that are also subject to global change. A multi-tracer assessment of organic matter pathways was run to delineate ecosystem functioning, using analysis of fatty acids, bulk and compound specific stable isotope analysis and stable isotopes mixing models. Macroalgae and phytoplankton were the two major food sources fueling this food web with, however, some marked seasonal variations. Specifically, zooplankton relied on phytoplankton-derived organic matter and herbivorous fishes on macroalgae-derived organic matter to a much higher extent in summer than in winter (~ 75% vs. ~ 15%, and ~ 70 to 75% vs. ~ 5 to 15%, respectively) . Despite remarkably high δ 15 N values for all trophic compartments, likely due to local dynamics in the nitrogen stock, trophic levels of consumers were similar to those of other coral reef ecosystems. These findings shed light on the functioning of low coral cover systems, which are expected to expand worldwide under global change., (© 2021. The Author(s).)

The relative importance of evolutionary history and ecology for traits that drive ecosystem processes is poorly understood. Consumers are essential drivers of nutrient cycling on coral reefs, and thus ecosystem productivity. We use nine consumer "chemical traits" associated with nutrient cycling, collected from 1,572 individual coral reef fishes (178 species spanning 41 families) in two biogeographic regions, the Caribbean and Polynesia, to quantify the relative importance of phylogenetic history and ecological context as drivers of chemical trait variation on coral reefs. We find: (1) phylogenetic relatedness is the best predictor of all chemical traits, substantially outweighing the importance of ecological factors thought to be key drivers of these traits, (2) phylogenetic conservatism in chemical traits is greater in the Caribbean than Polynesia, where our data suggests that ecological forces have a greater influence on chemical trait variation, and (3) differences in chemical traits between regions can be explained by differences in nutrient limitation associated with the geologic context of our study locations. Our study provides multiple lines of evidence that phylogeny is a critical determinant of contemporary nutrient dynamics on coral reefs. More broadly our findings highlight the utility of evolutionary history to improve prediction in ecosystem ecology., (© 2021. The Author(s).)

Coral reefs are diverse ecosystems that support millions of people worldwide by providing coastal protection from waves. Climate change and human impacts are leading to degraded coral reefs and to rising sea levels, posing concerns for the protection of tropical coastal regions in the near future. We use a wave dissipation model calibrated with empirical wave data to calculate the future increase of back-reef wave height. We show that, in the near future, the structural complexity of coral reefs is more important than sea-level rise in determining the coastal protection provided by coral reefs from average waves. We also show that a significant increase in average wave heights could occur at present sea level if there is sustained degradation of benthic structural complexity. Our results highlight that maintaining the structural complexity of coral reefs is key to ensure coastal protection on tropical coastlines in the future.

The largest marine biodiversity hotspot straddles the Indian and Pacific Oceans, driven by taxa associated with tropical coral reefs. Centred on the Indo-Australian Archipelago (IAA), this biodiversity hotspot forms the 'bullseye' of a steep gradient in species richness from this centre to the periphery of the vast Indo-Pacific region. Complex patterns of endemism, wide-ranging species and assemblage differences have obscured our understanding of the genesis of this biodiversity pattern and its maintenance across two-thirds of the world's oceans. But time-calibrated molecular phylogenies coupled with ancestral biogeographic estimates have provided a valuable framework in which to examine the origins of coral reef fish biodiversity across the tropics. Herein, we examine phylogenetic and biogeographic data for coral reef fishes to highlight temporal patterns of marine endemism and tropical provinciality. The ages and distribution of endemic lineages have often been used to identify areas of species creation and demise in the marine tropics and discriminate among multiple hypotheses regarding the origins of biodiversity in the IAA. Despite a general under-sampling of endemic fishes in phylogenetic studies, the majority of locations today contain a mixture of potential paleo- and neo-endemic fishes, pointing to multiple historical processes involved in the origin and maintenance of the IAA biodiversity hotspot. Increased precision and sampling of geographic ranges for reef fishes has permitted the division of discrete realms, regions and provinces across the tropics. Yet, such metrics are only beginning to integrate phylogenetic relatedness and ancestral biogeography. Here, we integrate phylogenetic diversity with ancestral biogeographic estimation of lineages to show how assemblage structure and tropical provinciality has changed through time., (© 2017 Cambridge Philosophical Society.)

The Coral Sea, located at the southwestern rim of the Pacific Ocean, is the only tropical marginal sea where human impacts remain relatively minor. Patterns and processes identified within the region have global relevance as a baseline for understanding impacts in more disturbed tropical locations. Despite 70 years of documented research, the Coral Sea has been relatively neglected, with a slower rate of increase in publications over the past 20 years than total marine research globally. We review current knowledge of the Coral Sea to provide an overview of regional geology, oceanography, ecology and fisheries. Interactions between physical features and biological assemblages influence ecological processes and the direction and strength of connectivity among Coral Sea ecosystems. To inform management effectively, we will need to fill some major knowledge gaps, including geographic gaps in sampling and a lack of integration of research themes, which hinder the understanding of most ecosystem processes., (© 2013 Elsevier Ltd. All rights reserved.)