Coevolution is used to describe evolutionary changes in which two or more interacting species reciprocally alter each other’s evolution. Studies of coevolution in species interactions can provide insight into the fundamental processes generating and maintaining biodiversity, including genetic and phenotypic diversity within and between species; however, we still understand very little about how coevolution works in diverse multi-species interactions, or about the relative importance for trait evolution of diverse biotic and abiotic sources of selection.

Interactions between coniferous plants and their associated microbes provide a good model system for experiments  exploring the nature of selection in multispecies interactions and the relative importance of biotic versus abiotic sources of selection, as conifers interact with a suite of belowground microorganisms including mutualistic ectomycorrhizal fungi.


Edge of the Monterey pine forest in Cambria, CA.

To investigate possible sources of selection for multispecies interactions, we used the Monterey pine system. Monterey pine (Pinus radiata) is a locally dominant conifer, the native range of which consists of small isolated populations spanning a broad latitudinal gradient. Post-Pleistocene native populations of Monterey pine are restricted to a small set of geographically separated sites along the west coast of California (USA) and two islands off Baja California (Mexico). These populations are sufficiently isolated by distance such that each population should represent a unique evolutionary history, and provide an opportunity to study how geographically isolated, diverse interactions evolve amid limited gene flow among populations.In order to more directly isolate the effect of phenotypic variation in influencing plant fitness, we conducted a common garden experiment in which seedlings from Monterey pine phenotypes representing a suite of possible plant traits were grown in a single location, minimizing the contribution of environmental variation for altering plant fitness.

This work is ongoing.

Collaborators: Jason Hoeksema (University of Mississippi)

Relevant Links:

UC Santa Barbara’s Kenneth S. Norris Rancho Marino Reserve