Dissertation Research: Hybridization between the Western Gull (Larus occidentalis) and the Glaucous-winged Gull (L. glaucescens)

加州大学伯克利分校的博士生道格拉斯·贝尔在内德·约翰逊博士的指导下，正在进行一项雄心勃勃的研究，研究西部和格劳克斯的地理变异。翼鸥以及两者之间的混合区。西鸥是一种重要的沿海物种，范围从巴哈半岛北部沿太平洋海岸到华盛顿州南部，在那里它让位于向北延伸到最西部阿留申群岛的格劳斯翼鸥；杂交种群分布在俄勒冈州北部到华盛顿州。虽然海鸥物种(属)之间的杂交经常被引用为物种形成过程的一个例子，但海鸥之间杂交的实际范围、性质和起源却鲜为人知。贝尔建议解决三个概念上的焦点：1)亲本物种的地理变异，2)杂交区的类型(杂交区是否稳定，杂交种是否是对照选择的，杂交种是否在生态上处于中间重叠的区域被选择？)，以及3)历史背景下杂交区的起源。这项研究将涉及野外工作，收集标本，收集关于杂交和非杂交配对繁殖成功的数据，关于分类交配和发声的数据，并对行为进行野外观察。将根据羽毛颜色变化和其他“软”部分颜色变化(虹膜颜色、腿部颜色等)的混合指数得分、骨骼测量的统计分析和分子水平来描述地理差异的特征。对亲缘关系如此密切，以至于它们仍然杂交(尽管基础有限)的物种的研究，为剖析导致物种起源的遗传学和进化过程提供了机会。

Douglas Bell, a doctoral student working under the direction of Dr. Ned Johnson at the University of California..Berkeley, is working on an ambitious study of geographic variation in the Western and Glaucous.winged Gulls and a hybrid zone between the two. The Western Gull is an important coastal species ranging from the Baja Peninsula north along the Pacific coast to southern Washington where it gives way to the Glaucous.winged Gull which ranges northward to the western most Aleutian Islands; the hybrid populations occur from northern Oregon through Washington. Although hybridization among gull species (genus >Larus>) is often cited as an example of the process of species formation, the actual extent, nature and origin of hybridization among the gulls is poorly known. Bell proposes to address three conceptual foci: 1) geographical variation in the parental species, 2) the type of hybrid zone (is the hybrid zone stable, are hybrids selected against, are hybrids favored by selection in an ecologically intermediate area of overlap?), and 3) the origin of the hybrid zone in a historical context. The study will involve field work to collect specimens, to collect data on reproductive success in hybrid and non.hybrid pairings, on assortative mating and on vocalizations, and to make field observations on behavior. Characterizations of geographic variation will be made on hybrid index scores based on plumage color variation and other "soft" part color variation (iris color, leg color, etc.), on statistical analysis of skeletal measurements and at the molecular level. The study of species that are so closely related that they still hybridize (albeit on a limited basis) provide opportunities for dissecting the genetics and evolutionary processes that lead to the origin of species.