Species life history traits, metapopulation theory, and niche theory: Predictors of reserve success for rare plants

Understanding the relative importance of habitat quality and spatial structure is a key component of understanding plant distributions and developing successful reserves for rare plants. Studies to date have had mixed results, with some supporting niche-based models, where resource partitioning shapes plant distributions, and others supporting metapopulation-based models, where habitat area and isolation shape plant distributions. I hypothesize that the relative importance of habitat quality and spatial structure for plants varies based on species specific traits such as longevity and dispersal mode. In a metapopulation model, species with a very high patch colonization rate (i.e., long-distance dispersers) or a very low patch extinction rate (i.e., long-lived individuals) would be less sensitive to the effects of spatial habitat configuration, and therefore would more likely be niche-limited. Species with poor colonization or high extinction rates would be spatially limited by dispersal or recruitment. Over a three-year period, we assessed the effects of habitat quality and spatial configuration on populations of four co-occurring rare plants in the Pine Hill Reserve System in El Dorado County, California, a network of nine reserves of varying size and isolation. Preliminary results show that spatial habitat configuration has the greatest effect on the population distribution and success of a poor disperser (gravity dispersed), while habitat quality is more important for a good disperser (wind dispersed). These results indicate that individual life-history traits may be important determinants of plant species success in a fragmented landscape.