Friday, April 29, 2011

Ecological interactions and evolutionary relatedness: contrary effects of conserved niches

ResearchBlogging.orgOver the past several years a multitude of papers linking patterns of evolutionary relatedness to community structure and species coexistence. Much of this work has looked at co-occurrence patterns and looked for non-random patterns of relatedness. The key explanations of patterns has been that communities comprised of more distantly-related species is thought to be structured by competitive interactions, excluding close relatives. Alternatively, communities comprised of species that are closely related, are thought to share some key feature that allows them to persist in a particular set of environmental conditions or stress. This whole area of research is completely predicated on close relatives having more similar niche requirements then two distant relatives. This predication is seldom tested.In a recent paper in the Proceedings of the National Academy of Science, Jean Burns and Sharon Strauss examine the ecological similarity among 32 plant species and tested if evolutionary relationships offered insight into these similarities. The ecological aspects they examined were germination and early survival rates as well as interaction strengths among species. To assess how these were influenced by evolutionary relatedness, they planted each species in the presence of one of four other species varying in time since divergence from a common ancestor, creating a gradient of relatedness for each species. They found that germination and early survival decreased with increasing evolutionary distance. This surprising result means that species germinating near close relatives do better early on then if they are near distant relatives. The explanation could be that they share many of their biotic and abiotic requirements, and these conserved traits influence early success.

Conversely, when they examined interaction strengths over a longer period (measured as relative individual biomass with and without a competitor), they found that negative interactions were stronger among close relatives.

These two results reveal how evolutionary history can offer insight into ecological interactions, and that the mutually exclusive models of competitive exclusion versus environmental filtering do not capture the full and subtle influence of conserved ecologies. Evolutionarily conserved traits can explain both correlated environmental responses and competitive interactions.

Burns, J., & Strauss, S. (2011). More closely related species are more ecologically similar in an experimental test Proceedings of the National Academy of Sciences, 108 (13), 5302-5307 DOI: 10.1073/pnas.1013003108


Ted Hart said...

I think this is an interesting result, and I wonder how it fits in with the body of work on genotypic diversity. Especially when we begin to think of genotypic diversity within species as just the logical extension of phylogenetic diversity. Of course this begs the question if we might expect fundamentally different types of responses when we consider communities with different phylogenetic diversities (PD) and within species genetic diversities or if genetic diversity (GD) is truly a logical extension of phylogenetic diversity. More simply, how do PD and GD interact to structure communities, if at all? I'm not really qualified to answer the question, but it seems like something worth exploring by someone.

I worked on a paper with some colleagues where we found positive frequency dependence when grasses were planted with clonal neighbors, similar to what Burns and Strauss found for the potting soil result. Ours was a field study as well. Here is our paper:

Thanks for brining attention to the article.

Essy said...

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