DISSERTATION RESEARCH: EVOLUTION, ECOLOGY AND PERSISTENCE IN FRAGMENTED FORESTS: A TALE OF TWO MARTENS (MARTES AMERICANA)

生境破碎化是保护生物学的一个主要问题，因为它的两个主要组成部分，生境丧失和连续生境转变为较小的孤立斑块，威胁着全世界的生物多样性。分散是将居住在孤立栖息地斑块上的动物种群联系起来的主要过程，对于中小型、广泛分布的物种来说，这一过程很难量化。这个项目正在开发一种新的、非侵入性的方法来量化美洲貂（Martes americana）的扩散速度，美洲貂是一种专性森林食肉动物。由于食物中氢、碳和氮的稳定同位素比例被纳入了消费者的组织中，因此食用了同位素富集饵料的貂在其毛发中会有明显的同位素标记。通过将人工富集同位素标记的独特组合应用于不同的森林林分，从毛发陷阱收集的毛发的同位素特征将反映个体起源的森林斑块。在对5只圈养貂的喂养试验中，食用一剂同位素富集的诱饵会在毛发上产生明显的标记。验证在野外使用的马貂同位素标记将允许对这一物种和其他各种物种的扩散速率进行严格的量化。这个项目是一个更大的研究的一部分，该研究评估了进化史和生物体对人类引起的碎片化的反应之间的关系。来自两个不同谱系（美洲貂和caurina貂）的貂是栖息地专家，对森林破碎化很敏感。在更新世，两个貂系在一个连续的东南森林避难所（美洲）和一个冰川破碎的西南避难所（caurina）中进化。目前，这些动物生活在亚历山大群岛和夏洛特女王群岛（海达-瓜伊群岛）的不同岛屿上，这些岛屿的栖息地因工业伐木而受到不同程度的破坏。由于汤加斯国家森林的原始保护区可能不足以维持可生存的种群，因此分散在林分之间对貂的持久性至关重要。因此，在汤加斯国家森林中，在破碎和未破碎的岛屿上，貂的分布创造了一个天然的实验室，来测试貂是否具有更高的分散能力，因此是否比美洲貂更适合在现代破碎的景观中生存。此外，收集到的资料将用于重新设计汤加斯土地管理计划的保护战略。在即将修订的《森林计划》中需要解决的一个重要问题是，是否应该在亚历山大群岛的不同岛屿上实施不同的马丁保护措施。

Habitat fragmentation is a major concern of conservation biology because its two primary components, habitat loss and the conversion of contiguous habitats into smaller isolated patches, threaten biodiversity worldwide. Dispersal, the main process connecting animal populations inhabiting isolated habitat patches, is hard to quantify for small to medium-size, wide-ranging species. This project is developing a novel, noninvasive method for quantifying dispersal rates of American martens (Martes americana), an obligate forest carnivore. Because the ratios of stable isotopes of hydrogen, carbon, and nitrogen of the diet are incorporated into the tissues of consumers, martens that have consumed isotopically enriched baits will have distinct isotopic label in their hairs. By applying unique combinations of artificially enriched isotopic markers to different forest stands, the isotopic signature of hair collected from hair traps, will reflect the forest patch where the individual originated. In feeding trials with five captive martens, consumption of one dose of isotopically enriched baits elicited a distinct label in hair. Validation of the use of isotopic labeling of martens in the field will allow the rigorous quantification of dispersal rates for this and a variety of other species. This project is part of a larger study evaluating the relation between evolutionary history and responses of organisms to human-induced fragmentation. Martens from the two distinct lineages (M. a. americana and M. a. caurina) are habitat specialists and sensitive to forest fragmentation. During the Pleistocene, the two marten lineages evolved in a contiguous southeastern forest refugium (americana) and a glacially fragmented southwestern refugium (caurina). Currently, these animals occur on separate islands in the Alexander and Queen Charlotte (Haida-Gwaii) Archipelagos, which have varying levels of habitat fragmentation from industrial logging. Because old-growth reserves in the Tongass National Forest may not be large enough to maintain viable populations, dispersal among forest stands is vital for persistence of martens. Thus, the distribution of martens in the Tongass National Forest on fragmented and unfragmented islands creates a natural laboratory to test whether caurina martens have higher dispersal capabilities and are therefore better suited to persist in modern-day fragmented landscapes than americana. In addition, information gathered will be applied to the re-designing of the conservation strategy of the Tongass Land Management Plan. An important question to be addressed in the upcoming revision of the Forest Plan is whether different conservation measures for martens should be implemented on different islands of the Alexander Archipelago.