Searcy William A, Nowicki Stephen, Hughes Melissa, Peters Susan
Department of Biology, University of Miami, Coral Gables, Florida 33124, USA.
Am Nat. 2002 Mar;159(3):221-30. doi: 10.1086/338509.
Whether geographic variation in signals actually affects communication between individuals depends on whether discriminable differences in signals occur over distances that individuals move in their lifetimes. We measure the ability of song sparrows (Melospiza melodia) to discriminate foreign from local songs using foreign songs recorded at a series of increasing distances and compare the results with previous measurements of dispersal distances. We test discrimination in males using playback of songs on territories and measuring approach and in females using playback to estradiol-treated captives and measuring courtship display. Females fail to discriminate against foreign songs recorded at 18 km but do discriminate against foreign songs recorded at 34, 68, 135, and 540 km. Males fail to discriminate against foreign songs recorded at 18, 34, 68, 135, and 270 km but do discriminate against foreign songs from 540 km. Females are more discriminating, but even they do not discriminate at a distance three times the root-mean-square dispersal distance, as estimated from mtDNA variation. We suggest that female preference for local songs benefits females not because it allows them to reject foreign males but because accurate production of local song serves as a test of song-learning ability.
信号中的地理差异是否真的会影响个体之间的交流，取决于在个体一生中移动的距离上，信号是否存在可辨别的差异。我们使用在一系列不断增加的距离处录制的外来歌曲，来测量歌雀（Melospiza melodia）区分外来歌曲和本地歌曲的能力，并将结果与先前测量的扩散距离进行比较。我们通过在领地播放歌曲并测量接近程度来测试雄性的辨别能力，通过向接受雌二醇处理的圈养雌性播放歌曲并测量求偶行为来测试雌性的辨别能力。雌性无法区分在18公里处录制的外来歌曲，但能够区分在34、68、135和540公里处录制的外来歌曲。雄性无法区分在18、34、68、135和270公里处录制的外来歌曲，但能够区分来自540公里处的外来歌曲。雌性更具辨别力，但根据线粒体DNA变异估计，即使是雌性也不会在均方根扩散距离的三倍距离上进行区分。我们认为，雌性对本地歌曲的偏好对雌性有益，不是因为这使它们能够拒绝外来雄性，而是因为准确唱出本地歌曲是对歌曲学习能力的一种考验。
