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

CRB：产生景观水平模式的局部机制：破碎的沿海鼠尾草灌木栖息地对红冠麻雀的相对栖息地适宜性

• 批准号: 9424559
• 负责人: Douglas Bolger
• 金额: $ 14.98万
• 依托单位: Dartmouth College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1995
• 资助国家: 美国
• 起止时间: 1995-09-15 至 1999-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9424559&HistoricalAwards=false
• 关键词: CRB; Local; Mechanisms; Generate; Landscape

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.

了解栖息地破碎化的生态效应对保护生物多样性至关重要。红冠麻雀在大型栖息地斑块中相对常见，但在南加州人类改造景观的小斑块中并不常见。在这项保护和恢复生物学研究中需要验证的假设是，红冠麻雀在小片段中的稀缺性可归因于栖息地破碎化导致的一种或多种人口统计学、行为、社区或生态系统水平的变化。这一假设将通过在相对较小的斑块和嵌入较大未开发地区的斑块中对沿海鼠尾草灌丛的匹配地块进行比较研究来解决。将在每个补丁中测量相关的人口统计参数。将测量资源的丰度和枯竭率。本研究试图在一系列变化的生态条件下解释单一物种的景观尺度分布。这项研究是在一个物种和空间尺度上进行的，这与在快速变化的景观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。理论研究确凿地证明了这一点，家养动物的交配也证明了这一点，近亲繁殖的牛、狗或马的健康状况远不如近亲繁殖的动物。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损。今天，自然保护生物学家通常负责管理本地物种的小的、受威胁的种群，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，在野外，人们对遗传变异和适应性（寿命、抗病能力、繁殖成功率）之间的关系知之甚少。为了分析这个问题，Soule博士将研究一种自然存在的动物种群，这种动物特别适合于这项研究——口袋地鼠——一种在加州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。但是这些基因差异会影响健康吗？动物的生理活力将通过两种方式来衡量——正常活动（挖洞）时的代谢率和确定哪种动物最有效地吸收和利用食物。Soule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种群中遗传变异最多的动物，还是来自遗传变异较小的种群的动物通常最适合。最后，他将评估哪些基因变异的测量在这些比较中提供了最多的信息。从长远来看，这种类型的研究将有助于确定如何最好地测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。