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

了解栖息地碎片化的生态影响对于保护生物多样性至关重要。红冠麻雀在较大的生境斑块中相对常见，但在加州南部人工改造的较小斑块中不常见。这项保护和恢复生物学研究中要检验的假设是，红冠麻雀罕见的小碎片可以归因于一个或多个人口、行为、群落或生态系统水平的变化，这些变化是栖息地碎片化的结果。这一假设将通过对沿海鼠尾草灌丛的配对地块、相对较小的斑块和嵌入较大未开发区域的斑块进行比较研究来解决。相关的人口统计参数将在每个补丁中进行测量。将测量资源丰度和枯竭率。这项研究试图在整个生态条件变化的背景下解释单一物种的景观规模分布。这项研究是在物种和空间尺度上进行的，与在快速变化的景观中切实保护生物多样性直接相关。人们早就知道，近亲交配，即密切相关的个体的交配，对个体后代和整个种群都不健康。理论研究确凿地证明了这一点，家畜交配也是如此，近亲交配的牛、狗或马比近亲交配的动物健康或健康状况差得多。此外，近亲交配会导致种群失去遗传变异，这意味着它在遗传上适应不断变化的环境的能力可能会受到损害。今天，保护生物学家经常负责管理当地物种的小而受威胁的种群，这些种群可能容易受到近亲繁殖和由此导致的遗传变异的丧失。不幸的是，人们对野生动物的遗传变异和适合度(寿命、抗病能力、繁殖成功)之间的关系知之甚少。为了分析这个问题，索尔博士将研究一种特别适合这项研究的动物的自然种群--口袋地鼠--一种在加州各地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，一些地鼠的遗传变异水平异常高，而另一些地鼠的遗传变异水平极低。但这些遗传差异会影响健康吗？动物的生理活力将通过两种方式来衡量--正常活动期间的代谢率(穴居)和通过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存活和繁殖最好。然后，他将确定最适合的动物是不是在其种群中具有最大遗传变异的动物，或者来自遗传可变种群的动物通常比来自较少变异种群的动物最适合。最后，他将评估哪些基因变异的测量在这些比较中最有信息量。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.