Does behavior reflect phylogeny in swiftlets (Aves: Apodidae)? A test using cytochrome b mitochondrial DNA sequences.

Swiftlets are small insectivorous birds, many of which nest in caves and are known to echolocate. Due to a lack of distinguishing morphological characters, the taxonomy of swiftlets is primarily based on the presence or absence of echolocating ability, together with nest characters. To test the reliability of these behavioral characters, we constructed an independent phylogeny using cytochrome b mitochondrial DNA sequences from swiftlets and their relatives. This phylogeny is broadly consistent with the higher classification of swifts but does not support the monophyly of swiftlets. Echolocating swiftlets (Aerodramus) and the nonecholocating "giant swiftlet" (Hydrochous gigas) group together, but the remaining nonecholocating swiftlets belonging to Collocalia are not sister taxa to these swiftlets. While echolocation may be a synapomorphy of Aerodramus (perhaps secondarily lost in Hydrochous), no character of Aerodramus nests showed a statistically significant fit to the molecular phylogeny, indicating that nest characters are not phylogenetically reliable in this group. IMAGES:

金丝燕（Swiftlets）是小型食虫鸟类，其中多数营洞穴筑巢，且以具备回声定位能力而广为人知。由于缺乏可资鉴别的形态学特征，金丝燕的分类学研究主要依据回声定位能力的有无及筑巢特征展开。为验证此类行为学特征的可靠性，我们基于金丝燕及其近缘类群的细胞色素b（cytochrome b）线粒体DNA序列构建了独立的系统发育树。该系统发育树与雨燕的高阶分类框架大体吻合，但并不支持金丝燕为单系群。具备回声定位能力的金丝燕属（Aerodramus）与不具备回声定位的“大金丝燕”（Hydrochous gigas）聚为一支，而其余隶属于金丝燕属（Collocalia）的不回声定位金丝燕并未与该类群构成姊妹群。尽管回声定位或为金丝燕属的共有衍征（或许在大金丝燕中发生了次生性丢失），但金丝燕属的所有筑巢特征均未与该分子系统发育树呈现统计学意义上的显著匹配，这表明在该类群中，筑巢特征并不具备系统发育可靠性。
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