Patterns and processes in the phylogenetic structure of tropical reef fish assemblages

Duration: 6 months starting in January/February 2015 (circa 540 euros per month)

Supervisors: Fabien Leprieur ([email protected] ; http://fableprieur.weebly.com, Associate Professor) and Théo Gaboriau ([email protected], Ph.D. student), UMR MARBEC, University of Montpellier (http://www.umr-marbec.fr/fr/)

Determining why some species coexist while others do not in ecological communities is a challenging and central goal in ecology (Webb et al. 2002). This is best exemplified by the recent development of methods to integrate phylogenetic information into community ecology (i.e. the field of ‘phylogenetic community ecology’) that allows simultaneously addressing questions about how species assemble in space and time and what processes impact assemblage membership (Cavender-Bares et al. 2009). The use of phylogenetic relatedness in community ecology is based on the assumption that potential species ecological differences are proportional to the amount of time since they diverged from a common ancestor, hence assuming homogeneous rates of trait evolution across the phylogenetic tree (Webb et al. 2002). Thus, an assemblage where species are phylogenetically less related than expected by chance (over-dispersion) is commonly interpreted as a consequence of interspecific competition, because ecologically similar species cannot co-occur and exclude each other (MacArthur and Levins 1967). In contrast, an assemblage composed of species that are more phylogenetically related than expected by chance (clustering) is commonly attributed to environmental filtering, because specific environmental conditions allow only species with a certain set of traits to persist (Webb et al. 2002). When assemblage structure does not differ from that expected by chance (based on a null model), studies commonly concluded that neutral processes (e.g. related to dispersal limitation) predominated. However, phylogenetic distances between species may be not a relevant proxy of their ecological distances if species traits are not phylogenetically conserved (i.e. trait lability resulting from convergent evolution), which may blur the interpretation of the role of environmental filtering vs. competition in shaping assemblage structure (Swenson and Enquist 2009). Then, spatial differences in assemblage structure and composition can be explained not solely by ecological processes but also by historical and evolutionary processes (Cavender- Bares et al. 2009).
For this project, the student will combine phylogenetic and trait-based approaches to evaluate the role of historical/evolutionary, neutral and ecological processes in structuring tropical reef fish assemblages at different spatial scales using reef fish traits coupled to resolved phylogenies. All these analyses will be performed using R and related packages such as PICANTE, APE.

This project is part of the research program REEFISH funded by the French National Agency, in close collaboration with the the group of Landscape Ecology at ETH Zurich (www.ethz.ch) and WSL Birmensdorf (www.wsl.ch) led by Prof. Loïc Pellissier.

References
Cavender-Bares, J., K. H. Kozak, P. V. A. Fine, and S. W. Kembel. (2009). The merging of community ecology andphylogenetic biology. Ecology Letters 12, 693–715.
MacArthur, R. and Levins, R. (1967). The Limiting Similarity, Convergence, and Divergence of Coexisting Species. The American Naturalist, 101, 377-385.
Swenson, N.G., and Enquist, B.J. (2009). Opposing assembly mechanisms in a Neotropical dry forest: implications for phylogenetic and functional community ecology. Ecology, 90, 2161-2170.
Webb C.O., Ackerly D.D., McPeek M.A., Donoghue M.J. (2002) Phylogenies and community ecology. Annual Review of Ecology and Systematics, 33, 475-505

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