Dr. Kristina Hufford

Scientists have long recognized the role of islands as natural laboratories for ecology and evolution (Darwin 1859). The distribution of populations within and among islands and their mainland counterparts provides a unique opportunity to evaluate ecological and evolutionary process that cause the adaptation of organisms to their environment. In particular, the isolation of oceanic islands results in two features of insular ecosystems that differ from the mainland: 1) a decreased overall number of species, and 2) an increased number of endemic species (Simberloff 1974). These features are explained by the biased arrival on islands of organisms with the ability to disperse long distances, and by the diversification of successful immigrants into ecological niches that were unavailable on the mainland (Carlquist 1974; Simberloff 1974).

Studies of island biodiversity and the adaptive radiation of island organisms have traditionally focused on large groups of taxa such as the Hawaiian silversword alliance (28 species in three genera; Carlquist 1970). Many of these studies include endemic plants in efforts to examine speciation resulting from the adaptive specialization of mainland organisms to island habitats (e.g. Ranker et al. 2000). However, the adaptive evolution of organisms on islands may occur at a much more subtle level – within a single species common to both island and mainland sites. The adaptive evolution within populations of a single species results in different races called ‘ecotypes’ and the formation of ecotypes is more likely in common, widespread species than in rare or endemic species (Turresson 1936; Krebs 1994).

Considerable evidence suggests that plants are adapted to local environmental conditions (Bradshaw et al. 1984). Examples include metal tolerance of plants that grow on mine tailings and herbicide resistance in weedy plants (Linhart and Grant 1996). Given the geographic isolation of island populations, it is likely these populations have diverged from one another over time (due to barriers to interpopulation gene flow). If differences in the genetic structure and genetic composition of plant populations are the result of adaptation to local environments, then genetic variation among populations may be correlated with the ecological characteristics of their habitats.

I propose to examine the ecological and genetic variation of populations of three native grass species on Santa Catalina Island (Nassella pulchra, Elymus glaucus, and Bromus carinatus). I will compare data collected on Catalina with data from the Channel Islands National Park and representative mainland sites in Santa Barbara County. A unique combination of genetic analyses and ecological field studies will allow me to address several questions concerning ecotypic variation of plants distributed between island and mainland habitats. Namely, do island populations of these species resemble mainland populations, or do they represent unique genetic resources? If populations are genetically differentiated, are populations on the same island more similar than on different islands? Similarly, are island populations more similar to each other than mainland populations? Are populations on different islands more distinct from each other than mainland populations separated by similar distances due to stronger dispersal barriers between islands? Does genetic variation correlate with ecological variables such as climate, soil characteristics and rainfall? Finally, can I detect a genetic basis for morphological variation among populations in a common garden study? These data will contribute to knowledge of the genetic diversity of these native grasses, as well as contribute to efforts in grassland restoration (Hufford and Mazer 2003).