CRB: Local Mechanisms that Generate Landscape-level Patterns: Relative Habitat Suitability of Fragmented Coastal Sage Scrub Habitat for the Rufous-crowned Sparrow

了解生境破碎化的生态影响对于保护生物多样性至关重要。 棕冠麻雀在大的栖息地斑块中相对常见，但在南加州的人类改造景观中较小的斑块中不常见。 在这项保护和恢复生物学研究中要检验的假设是，棕冠麻雀在小片段中的稀有性可归因于一个或多个人口，行为，社区或生态系统水平的变化，这些变化是栖息地破碎化的结果。 这一假设将通过比较研究，在匹配的地块的沿海鼠尾草灌丛在相对较小的补丁和补丁嵌入在一个较大的未开发地区。 将在每个贴剂中测量相关人口统计学参数。 将测量资源丰度和枯竭率。 本研究试图在一整套不断变化的生态条件下解释单个物种的生态尺度分布。 这项研究是在一个物种和一个空间尺度上进行的，这与在一个迅速变化的环境中实际保护生物多样性直接相关。长期以来，人们都知道近亲繁殖，即近亲交配，对个体后代和整个种群都是不健康的。 理论研究得出结论，家养动物交配也是如此，近亲繁殖的牛、狗或马比远系繁殖的动物健康或适应性差得多。 此外，近亲繁殖导致种群失去遗传变异，这意味着其遗传适应不断变化的环境的能力可能会受到损害。 今天，保护生物学家通常负责管理小的、受威胁的本地物种种群，这些物种可能容易受到近亲繁殖的影响，从而导致遗传变异的丧失。 不幸的是，人们对野生环境中遗传变异与健康（长寿、抗病、繁殖成功）的关系知之甚少。 为了分析这个问题，Soule博士将研究一种特别适合这项研究的自然发生的动物种群-囊地鼠--在整个加州很常见的小型穴居啮齿动物。 早期对不同地鼠种群的研究表明，有些种群具有异常高的遗传变异水平，而有些种群的遗传变异水平极低。 但这些基因差异会影响健康吗？ 动物的生理活力将以两种方式测量-正常活动（挖洞）期间的代谢率和确定哪些动物最有效地吸收和利用食物。 索尔博士还将确定哪些动物在自然界中生存和繁殖得最好。 然后，他将确定最适合的动物是否是在其种群中具有最多遗传变异的动物，或者来自遗传变异种群的动物是否通常比来自较少变异种群的动物更适合。 最后，他将评估哪些遗传变异的测量在这些比较中最具信息性。 从长远来看，这类研究将有助于确定如何最好地衡量受威胁物种的遗传变异，以及遗传变异是否是生存或整体健康的重要因素。

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.