Energy acquisition and allocation strategies in scleractinian corals: insights from intraspecific trait variability

Scleractinian species consist of physiologically heterogeneous individuals that can opportunistically use different resources. Yet, intraspecific variability has often been overlooked in trait-based ecology, assuming uniformity among conspecifics. This study assessed individual contributions to physiological proxies in energy acquisition and allocation of seven scleractinian species collected from various latitudes and depths and characterised collective strategies (i.e. groups of individuals with similar physiological performance). An individual trait-based approach using 15 skeletal, isotopic, and organismal traits was used to describe and compare variation within and between species physiological niches. The effect of temperature and light on the observed variation was tested, and a k-means analysis was used to characterise the optimal number of strategies among individuals. Significant differences were observed among species with physiological niches displaying large variation. This variation was partially attributed to the selected environmental factors for two branching species but had a minor influence on the variation among other species. Among all individuals, three strategies were identified, with conspecifics exhibiting two or all three strategies. These results demonstrated that individuals from various species may converge in the use of their resources and that species may stand along a gradient between two extremes: conspecifics displaying one (specialists) or several strategies (generalists). This methodology, which focuses on intraspecific variability, provides valuable insights into resource use and a tool for future investigations on individual performances in populations. Furthermore, this approach can be extended to other benthic taxa, allowing for a comprehensive assessment of ecosystem processes and ongoing changes in Anthropocene coral reefs.