Energetic and ecological constraints on population density of reef fishes

Abstract

Population ecology has classically focused on pairwise species interactions, hindering the description of general patterns and processes of population abundance at large spatial scales. Here we use the metabolic theory of ecology as a framework to formulate and test a model that yields predictions linking population density to the physiological constraints of body size and temperature on individual metabolism, and the ecological constraints of trophic structure and species richness on energy partitioning among species. Our model was tested by applying Bayesian quantile regression to a comprehensive reef-fish community database, from which we extracted density data for 5609 populations spread across 49 sites around the world. Our results indicate that population density declines markedly with increases in community species richness and that, after accounting for richness, energetic constraints are manifested most strongly for the most abundant species, which generally are of small body size and occupy lower trophic groups. Overall, our findings suggest that, at the global scale, factors associated with community species richness are the major drivers of variation in population density. Given that populations of species-rich tropical systems exhibit markedly lower maximum densities, they may be particularly susceptible to stochastic extinction.

Body size, reef area and temperature predict global reef‐fish species richness across spatial scales

“…The sub‐linear nature of this relationship corroborates the suggestion of recent studies that species richness estimated at small spatial scales might not necessarily resemble that at the province scale (Dornelas et al, ; Vellend et al, ). We speculate that this observed phenomenon reflects the interaction between body size, local abundance and geographic range (Supporting Information Appendix S1: Figure A4a), as smaller species are generally more abundant (Ackerman et al, ; Barneche et al, ) and often exhibit smaller geographic range sizes than larger species (Belmaker, ; Luiz et al, ). Consequently, it is expected that species at the extremes of the body size distribution are detected in only a small fraction of transects: for small species this may relate to smaller home range sizes and difficulties in visual detection, whereas for large species low abundance should result in a small representation across those transects within their geographic range ( Preston's veil ; Preston, ).…”

Consumption explains intraspecific variation in nutrient recycling stoichiometry in a desert fish

“…, Barneche et al. ). Careful mechanistic tests of these hypotheses will be particularly illuminating in advancing our understanding of variation in consumer‐driven nutrient recycling among populations and species.…”

“…At the ecosystem scale, the energetic constraints imposed by temperature and predation pressure are most likely to impact small‐bodied, abundant consumers at lower trophic levels because these abundant species garner most of the energy entering a system and are thus most likely to be limited by its supply (Barneche et al. ). For these same reasons, small‐bodied consumers are often the most important nutrient recyclers in aquatic environments (Elser et al.…”

Temperature effects on mass‐scaling exponents in colonial animals: a manipulative test

“…Isometric energy gains and allometric energy expenditure in colonial marine invertebrates may explain why they are often competitively dominant, outgrowing and excluding unitary organisms (which generally present allometric scaling of both feeding and metabolic rates, see e.g., Kooijman 2009, Kearney and in a range of systems (Buss 1980(Buss , 1990. Importantly, if that is the case, this scenario would add a new mechanism to explain deviations from energetic equivalence, which are thought, for example, to be a consequence of size-dependent mortality rates in eusocial insects (DeLong 2011) and energetic subsidies in reef fishes (Barneche et al 2016b). Importantly, if that is the case, this scenario would add a new mechanism to explain deviations from energetic equivalence, which are thought, for example, to be a consequence of size-dependent mortality rates in eusocial insects (DeLong 2011) and energetic subsidies in reef fishes (Barneche et al 2016b).…”