Species interactions and the functional role of biodiversity
The positive relationship between species richness and components of ecosystem function is often explained by the higher probability for functional complementarity (redundancy) in species-rich communities. I have been interested in further understanding the processes of species coexistence and the role of biodiversity in hyperdiverse tropical ecosystems. How do species share available resources? How are species and interactions among species and individuals affected by environmental disturbances? What are geographical disparities in richness and community composition mean for ecosystem functions and resilience? My colleagues and I have used small-scale systems to address these questions.
On coral reefs, species are stacked in small spaces and constantly interact with each other and with the foundation species (corals) of the ecosystem they inhabit. The dynamics of interactions between individuals and species can therefore have a disproportional impact on ecosystem functions (if it affects the growth and survival of reef building corals). For example, corals of the genus Pocillopora, a branching coral found across the Indo-Pacific, host numerous fishes and invertebrates, some of which are coral mutualists. Using field surveys and lab manipulations, we showed that the composition, diversity and abundance of decapod mutualists determine the cleaning services to the host coral. We showed that the composition of symbiont assemblages is variable in space, which may cause geographical disparities in the way coral populations respond to environmental changes.
In a recent paper, we used DNA analysis of gut and polyp contents to show that corals and two damselfish species have much more specialized diets than previously thought, which likely allows them to coexist (Leray et al. 2019).
Our work has also focused on mechanisms of resource partitioning to elucidate how species can coexist. We showed that the diversity of symbionts is directly linked to the surface area of live coral tissues. Additionally, we found using molecular sequencing of invertebrate and fish gut contents that coral associates have much more specialized feeding behaviors than initially thought.
I am expanding this research looking at the context-dependency of predator-prey interactions in a project in collaboration with Friederike Clever and Richard Preziosi at Manchester Metropolitan University.
Field manipulation of predatory fish to understand how they affect decapod symbionts and the host coral (Stier and Leray, 2014). Photo credit (fish): Thomas Vignaud
Hawkfish feeding on a coral crab. Because trophic interactions are difficult to quantify on coral reef ecosystems, we often need to rely on indirect experimental and molecular approaches.
Laboratory experiments showed that the more decapod symbionts a coral hosts, the better. They help keep corals healthy by removing sediments that would otherwise kill polyps (Stier et al. 2012)
SELECTED PUBLICATIONS ON THIS TOPIC
Leray M, Alldredge AL, Yang JY, Meyer CP, Holbrook SJ, Schmitt RJ, Knowlton N, Brooks AJ. 2019. Dietary partitioning promotes the coexistence of planktivorous species on coral reefs. Molecular ecology In press
Galtier d'Auriac I, Quinn RA, Maughan H, Nothias LF, Little M, Kapono CA, Cobian A, Reyes BT, Green K, Quistad SD, Leray M, Smith JE, Dorrestein PC, Rohwer F, Deheyn DD, Hartmann AC. 2018. Before platelets: the production of platelet-activating factor during growth and stress in a basal marine organism. Proceedings of the Royal Society B: Biological Sciences285, 20181307
Rouzé H, Leray M, Magalon H, Penin L, Gélin P, Knowlton N, Fauvelot C. 2017. Molecular characterization reveals the complexity of previously overlooked coral-exosymbiont interactions and the implications for coral-guild ecology. Scientific Report 7,44923
Leray M, Meyer CP, Mills SC. 2015. Metabarcoding dietary analysis of coral dwelling predatory fish demonstrates the minor contribution of coral mutualists to their highly partitioned, generalist diet. PeerJ3,e1047
Stier AC, Leray M. 2014. Predators alter community organization of coral reef cryptofauna and reduce abundance of coral mutualists. Coral Reefs33,181-191
Leray M, Beraud M, Anker A, Chancerelle Y, Mills S. 2012. Acanthaster planci outbreak, decline in coral health, coral size structure modification and consequences for obligate decapod assemblages. PLoS One7,e35456
Stier AC, Gil MA, McKeon CS, Lemer S, Leray M, Mills SC, Osenberg CW. 2012. Housekeeping mutualisms, do more symbionts facilitate host performance? PLoS One7,e32079