Niche and neutral assembly mechanisms contribute to latitudinal diversity gradients in reef fishes

Abstract

Aim The influence of niche and neutral mechanisms on the assembly of ecological communities have long been debated. However, we still have a limited knowledge on their relative importance to explain patterns of diversity across latitudinal gradients (LDG). Here, we investigate the extent to which these ecological mechanisms contribute to the LDG of reef fishes. Location Eastern Atlantic Ocean. Taxon Reef‐associated ray‐finned fishes. Methods We combined abundance data across ~60° of latitude with functional trait data and phylogenetic trees. A null model approach was used to decouple the influence of taxonomic diversity (TD) on functional (FD) and phylogenetic (PD) diversity. Standardized effect sizes (SES FD and SES PD) were used to explore patterns of overdispersion, clustering and randomness. Information theoretic approaches were used to investigate the role of large‐ (temperature, geographic isolation, nitrate and net primary productivity) and local‐scale (human population and depth) drivers. We further assessed the role of demographic stochasticity and its interaction with species trophic identity and dispersal capacity. Results Taxonomic diversity peaked at ~15°–20°N, with a second mode of lower magnitude at ~45°N; a pattern that was predicted by temperature, geographic isolation and productivity. Tropical regions displayed a higher proportion of overdispersed assemblages, whilst clustering increased towards temperate regions. Phylogenetic and functional overdispersion were associated with warmer, productive and isolated regions. Demographic stochasticity also contributed largely to community assembly, independently of ecoregions, although variation was dependent on the trophic identity and body size of species. Main conclusions Niche‐based processes linking thermal and resource constraints to local coexistence mechanisms have contributed to the LDG in reef fishes. These processes do not act in isolation, stressing the importance of understanding interactions between deterministic and stochastic factors driving community structure in the face of rapid biodiversity change.

Habitat configurations shape the trophic and energetic dynamics of reef fishes in a tropical–temperate transition zone: implications under a warming future

“…A standardized effect size (SES FD) was computed by iterating this procedure 999 times, and estimating the divergence between observed and expected diversity: SES = (obs–mean (null))/sd (null). We classified assemblages that were within the interquartile range of the null distribution as random, whilst assemblages below, or above, the 25th and 75th percentiles were considered to be predominantly under-dispersed and over-dispersed, respectively (Bosch et al 2021b ). Assemblages that differed significantly (> 95th percentile) were considered to be purely structured through deterministic assembly rules (i.e.…”

“…Community assembly rules shape the occurrence and relative abundance of species coexisting locally, which is in part mediated by a trade-off between ecological constraints and opportunities provided by local abiotic (e.g. temperature, nutrients, primary productivity, wave exposure) (Bejarano et al 2017 ; McLean et al 2021 ; Bosch et al 2021b ) and biotic (e.g. habitat and resource availability, biotic interactions) conditions (Chase et al 2009 ; Yeager et al 2017 ).…”

“…In reef fishes, this can be exacerbated by their generally large dispersal capacities, that enable them to colonize distant sites and compete for the available living space (Sale 1978 ). Although these community assembly processes are not necessarily mutually exclusive (Vellend et al 2014 ; Bosch et al 2021b ), the prevalence of niche-based vs. neutral mechanisms is likely mediated by the arrangement of habitats across spatial scales (Yeager et al 2011 ), and the degree to which species from the regional pool are habitat specialists or generalists (Stuart-Smith et al 2021 ).…”

Remote reef cryptobenthic diversity: Integrating autonomous reef monitoring structures and in situ environmental parameters

“…Whilst we did not investigate bleaching across ARMS communities in this study, we present methods and results of this additional analysis in the Supplementary material, as additional environmental context for future studies in this region (Supplementary File S1). Satellite-derived SST is a popular metric for ecological studies of reef benthos (Carvalho et al, 2019;Floyd et al, 2020;Bosch et al, 2021), and with climate predictions indicating an increase in water temperatures globally (IPCC, 2022), it is important we obtain accurate temperature measurements when assessing or modelling the impact of heating on shallow reef cryptobenthic communities. Recent large-scale ARMS-based studies co-analysing benthic community diversity patterns and environmental parameters have used remote sensing data, including sSST and PAR (Carvalho et al, 2019;Pearman et al, 2020).…”

Black coral forests enhance taxonomic and functional distinctiveness of mesophotic fishes in an oceanic island: implications for biodiversity conservation

“…There are precise ecological predictions concerning the importance of abiotic filters (i.e., “Environmental Filtering Hypothesis”) and biotic interactions (i.e., “Competitive Exclusion Hypothesis”) to generate biodiversity patterns across the euphotic-mesophotic zone. Shallow reef areas are less stressful environments, where high energy availability (e.g., higher light irradiance and warmer temperatures) and stronger interspecific interactions might enhance ecological specialization (i.e., trait divergence), minimizing competition for resources (i.e., niche partitioning) 25 , 26 . In contrast, increased abiotic constraints (i.e.…”