Understanding the ecological effects of habitat fragmentation is essential to preserving biodiversity. The Rufous-crowned Sparrow is relatively common in large habitat patches, but uncommon in smaller patches in the human modified landscape of southern California. The hypothesis to be tested in this conservation and restoration biology research is that rarity of the Rufous-crowned Sparrow in small fragments in attributable to one or more demographic, behavioral, community, or ecosystem-level changes which occur as a consequence of habitat fragmentation. This hypothesis will be addressed through comparative studies in matched plots of coastal sage scrub in relatively small patches and in patches embedded in a larger undeveloped area. Relevant demographic parameters will be measured in each patch. Resource abundance and depletion rates will be measured. This study is an attempt to interpret landscape-scale distribution of a single species within the context of an entire suite of changing ecological conditions. The research is being conducted on a species and at a spatial scale that ar e immediately relevant to the practical conservation of biodiversity in a rapidly changing landscapeIt has long been known that inbreeding, the mating of closely related individuals, is unhealthy to both individual offspring and the population as a whole. Theoretical studies show this conclusively, as do domestic animal matings, where inbred cows or dogs or horses are much less healthy, or much less fit, than outbred animals. Further, inbreeding causes a population to lose genetic variation, which means its ability to adapt genetically to a changing environment may be impaired. Today, conservation biologists are often responsible for managing small, threatened populations of native species, which may be susceptible to inbreeding and resultant loss of genetic variation. Unfortunately, little is known about the relationship of genetic variation and fitness ( longevity, disease resistance, reproductive success) in the wild. To analyze this problem Dr. Soule, will study naturally occurring populations of an animal that is particularly well suited for this research - pocket gophers - small, burrowing rodents that are common throughout California. Earlier studies of different gopher popula tions showed that some have unusually high levels of genetic variation, while some have extremely low levels. But do these genetic differences affect fitness? The physiological vigor of animals will be measured in two ways - metabolic rate during normal activity (burrowing) and by determining which animals assimilate and use food most efficiently. Dr. Soule will also determine which animals survive and reproduce best in nature. He will then determine if the animals which are the most fit are the ones which have the most genetic variation within their population, or if animals from genetically variable populations are generally most fit that animals from less variable populations. Finally, he will assess which measurements of genetic variation are most informative in these comparisons. In the long run this type of study will help to determine how best to measure genetic variation in threatened species and whether genetic variation is a significant factor in survival or overall health.
