A primary goal of ecology is to understand the processes maintaining species diversity and coexistence in natural communities (also called community assembly). Models of this process suggest that stable coexistence requires competitors to differ in their niches, and that species that are too ecologically similar cannot coexist. Intersecting with this discussion of ecological similarity and coexistence is the degree to which the evolutionary or phylogenetic relatedness between species reflects their ecological similarity, and can thus be used to understand coexistence and community assembly. Several hypotheses to explain community assembly predict a link between ecological similarity and phylogenetic relatedness. Darwin argued that closely related species compete intensely because they have similar morphologies and niches, and thus should not coexist. The proposed study will combine an explicitly experimental field approach across a large diversity of plant species, coupled with extensive observational data, to explore community assembly and the mechanisms underlying species coexistence in a phylogenetic context. Nineteen species of native plants will be placed into the habitats of close and distant relatives and plant performance will be assessed across these habitats both in the presence and absence of herbivores (experimentally manipulated). In addition, species will be planted into sterilized, field-collected soils in the greenhouse and will be inoculated with live or sterilized soil biota communities from these soils. This experiment will indicate the degree to which soil biota collected under relatives influences patterns of competition and coexistence among relatives. Observational data will be collected in the field to document soil biota, soil mineral properties and patterns of coexistence in the field of close and distant relatives, along with functional traits of these species in the field.

Ultimately, the study will contribute to strategies aimed at restoring and maintaining natural communities of high biodiversity, communities that often provide greater ecosystem services than species-poor communities. The data will be made available to other researchers. In addition, these activities will support a public lecture series on current topics in ecology and evolution, as well as train undergraduates, post-doctoral associates and students between undergraduate and graduate schools. A new female Assistant Professor will be supported by the grant and mentored by the PI.

National Science Foundation (NSF)
Division of Environmental Biology (DEB)
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Alan James Tessier
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University of California Davis
United States
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