Evaluating life‐history strategies of reef corals from species traits

Abstract

Classifying the biological traits of organisms can test conceptual frameworks of life-history strategies and allow for predictions of how different species may respond to environmental disturbances. We apply a trait-based classification approach to a complex and threatened group of species, scleractinian corals. Using hierarchical clustering and random forests analyses, we identify up to four life-history strategies that appear globally consistent across 143 species of reef corals: competitive, weedy, stress-tolerant and generalist taxa, which are primarily separated by colony morphology, growth rate and reproductive mode. Documented shifts towards stress-tolerant, generalist and weedy species in coral reef communities are consistent with the expected responses of these life-history strategies. Our quantitative trait-based approach to classifying life-history strategies is objective, applicable to any taxa and a powerful tool that can be used to evaluate theories of community ecology and predict the impact of environmental and anthropogenic stressors on species assemblages.

Cryptic regime shift in benthic community structure on shallow reefs in St. John, US Virgin Islands

“…for instance, underwent large relative changes in cover, with declines following high temperature in 1998 and 2005, and recovery thereafter; Porites astreoides in creased in cover from 2002 to 2010, before declining after 2010; and branching Porites generally increased in cover throughout the study. Changing abundances of juvenile scleractinians (< 40 mm diameter) that differ among genera have been found in adjacent shallow water (~5 m) (Edmunds 2013), and more broadly, similar effects involving taxonomic variation in the response of scleractinians to environmental conditions are widespread (Darling et al 2012). Three of the 6 common scleractinians in St. John brood their larvae and have traits generally characterized as a weedy life history strategy (e.g.…”

“…branching Porites, P. astreoides, and Agaricia;Fadlallah 1983). The traits associated with this strategy (Darling et al 2012) may have been important factors contributing to the high relative ecological stability of this community (Gross & Edmunds 2015). The results indicate that not all scleractinians are ecological losers (or winners) under present-day conditions (Loya et al 2001), and it is possible that this scleractinian community in St. John is an example of regional-scale biotic homogeni zation favor-ing eurytopic species and ecological stability (Burman et al 2012).…”

The future of evolutionary diversity in reef corals

“…As an additional test, we also applied the vulnerabilities of species inferred by the trait-based approach of Darling et al [65]. Their analyses clustered 143 coral species into four groups representing competitive, weedy, stress-tolerant and generalist taxa.…”

“…To quantify the declines in PD and PSV specifically, we computed the excess loss of each metric under the 'observed' scenario relative to random, as a percentage of the random result [74]. All calculations were performed for each of the 1000 posterior trees obtained from the phylogenetic analysis, and repeated for the 143 species classified according to life-history strategy [65] with the predicted extinction of 'competitive' corals.…”

“…Their analyses clustered 143 coral species into four groups representing competitive, weedy, stress-tolerant and generalist taxa. The 46 competitive species were predicted to be the most sensitive to anthropogenic impacts and environmental change [65], so we used this category as an analogue of the threatened species on the IUCN Red List. However, as this classification was only available for 17% of all living reef coral species, we focus primarily on results using the IUCN Red List classification.…”