Eggert Lori S, Terwilliger Lauren A, Woodworth Bethany L, Hart Patrick J, Palmer Danielle, Fleischer Robert C
Center for Conservation and Evolutionary Genetics, National Zoological Park and National Museum of Natural History, Smithsonian Institution, 3001 Connecticut Ave NW, Washington, DC 20008 USA.
BMC Evol Biol. 2008 Nov 14;8:315. doi: 10.1186/1471-2148-8-315.
The Hawaiian honeycreepers (Drepanidinae) are one of the best-known examples of an adaptive radiation, but their persistence today is threatened by the introduction of exotic pathogens and their vector, the mosquito Culex quinquefasciatus. Historically, species such as the amakihi (Hemignathus virens), the apapane (Himatione sanguinea), and the iiwi (Vestiaria coccinea) were found from the coastal lowlands to the high elevation forests, but by the late 1800's they had become extremely rare in habitats below 900 m. Recently, however, populations of amakihi and apapane have been observed in low elevation habitats. We used twelve polymorphic microsatellite loci to investigate patterns of genetic structure, and to infer responses of these species to introduced avian malaria along an elevational gradient on the eastern flanks of Mauna Loa and Kilauea volcanoes on the island of Hawaii.
Our results indicate that amakihi have genetically distinct, spatially structured populations that correspond with altitude. We detected very few apapane and no iiwi in low-elevation habitats, and genetic results reveal only minimal differentiation between populations at different altitudes in either of these species.
Our results suggest that amakihi populations in low elevation habitats have not been recolonized by individuals from mid or high elevation refuges. After generations of strong selection for pathogen resistance, these populations have rebounded and amakihi have become common in regions in which they were previously rare or absent.
夏威夷蜜旋木雀（Drepanidinae）是适应性辐射的最著名例子之一，但如今它们的存续受到外来病原体及其传播媒介——致倦库蚊（Culex quinquefasciatus）的威胁。历史上，诸如绿背拟管舌鸟（Hemignathus virens）、猩红管舌鸟（Himatione sanguinea）和艾氏管舌鸟（Vestiaria coccinea）等物种在从沿海低地到高海拔森林的区域都有发现，但到19世纪后期，它们在海拔900米以下的栖息地变得极为罕见。然而，最近在低海拔栖息地观察到了绿背拟管舌鸟和猩红管舌鸟的种群。我们使用了12个多态微卫星位点来研究遗传结构模式，并推断这些物种对夏威夷岛莫纳罗亚山和基拉韦厄火山东坡沿海拔梯度引入的禽疟的反应。
我们的结果表明，绿背拟管舌鸟具有与海拔高度相对应的遗传上不同的、空间结构化的种群。在低海拔栖息地，我们检测到极少的猩红管舌鸟，未检测到艾氏管舌鸟，并且遗传结果显示这两个物种中不同海拔种群之间仅有极小的分化。
我们的结果表明，低海拔栖息地的绿背拟管舌鸟种群并未被来自中高海拔避难所的个体重新定殖。经过几代对病原体抗性的强烈选择，这些种群已经反弹，绿背拟管舌鸟在它们以前稀少或不存在的地区变得常见。
