ABSTRACT The biodiversity of the Neotropics is considerable, but it is likely underestimated owing to gaps in sampling effort and a focus on using morphological features of animals to determine species differences rather than divergence in their mating signals and behavior. Recent multi-trait analyses incorporating morphological, plumage, and vocal data have allowed for more accurate quantification of tropical biodiversity. We present a comprehensive study of morphological features, plumage, and vocalizations of the Neotropical resident Rufous-capped Warbler (Basileuterus rufifrons). This species' taxonomic status is controversial because the B. r. salvini subspecies is intermediate in plumage coloration between the neighboring B. r. delattrii and B. r. rufifrons subspecies. Using morphological and spectral plumage measurements of field and museum specimens, as well as analyses of vocalizations from field recordings and sound libraries, we compared phenotypes of all 8 currently recognized Rufous-capped Warbler subspecies, with an emphasis on delattrii, rufifrons, and salvini. We found that delattrii and rufifrons differ significantly in morphology and plumage, and that salvini is similar to rufifrons in morphology and some plumage features. Vocalizations fall into 2 distinct groups, delattrii and rufifrons-salvini, which differ in multiple spectro-temporal characteristics with no overlap between them, even among individuals in the delattrii–rufifrons zone of sympatry. Our results therefore suggest that Rufous-capped Warblers comprise 2 distinct groups: Rufous-capped Warblers (B. r. rufifrons and salvini as well as B. r. caudatus, dugesi, and jouyi) and Chestnut-capped Warblers (B. r. delattrii as well as B. r. actuosus and mesochrysus). Future genomic analysis of samples from multiple sites in Mexico and Central America will further refine our assessment of range-wide phenotypic and genetic divergence in this species complex. LAY SUMMARY The taxonomy of Rufous-capped Warblers is controversial: 8 subspecies exhibit divergent plumage color and songs and consequently they are sometimes treated as 2 separate species. Using field data, museum specimens, and sound archives, we compared the body size, plumage color, and songs of all 8 Rufous-capped Warbler subspecies Seven of 8 subspecies comprised 2 groups with different color, songs, and body size: the northern, white-bellied rufifrons group and the southern, yellow-bellied delattrii group. The eighth subspecies, salvini, showed similarity to the rufifrons group, rather than being intermediate between the 2 groups as described in previous studies. We found that Rufous-capped Warblers comprise 2 separate groups, which improves our knowledge of Neotropical avian biodiversity.

中文翻译：

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羽毛、声音和形态的差异表明红冠莺（Basileuterus rufifrons）的物种形成

摘要 新热带地区的生物多样性是相当可观的，但由于采样工作的差距以及侧重于利用动物的形态特征来确定物种差异而不是交配信号和行为的差异，它可能被低估了。最近结合形态、羽毛和声音数据的多性状分析可以更准确地量化热带生物多样性。我们对新热带居民红冠莺 (Basileuterus rufifrons) 的形态特征、羽毛和发声进行了全面研究。该物种的分类地位存在争议，因为 B. r. Salvini 亚种的羽毛颜色介于相邻的 B. r. 之间。delattrii 和 B. r. rufirons 亚种。使用野外和博物馆标本的形态和光谱羽毛测量，以及野外录音和声音库中的发声分析，我们比较了目前公认的所有 8 种红褐色冠莺亚种的表型，重点是 delattrii、rufifrons 和 salvini。我们发现 delattrii 和 rufifrons 在形态和羽毛上有显着差异，salvini 在形态和一些羽毛特征上与 rufifrons 相似。发声分为 2 个不同的组，delattrii 和 rufifrons-salvini，它们在多个光谱时间特征上不同，它们之间没有重叠，即使在 delattrii-rufifrons 同情区的个体之间也是如此。因此，我们的结果表明，红褐色冠莺包括 2 个不同的群体：红褐色冠莺（B. r. rufifrons 和 salvini 以及 B. 河 caudatus、dugesi 和 jouyi）和栗冠莺（B. r. delattrii 以及 B. r. actuosus 和 mesochrysus）。未来对来自墨西哥和中美洲多个地点的样本进行基因组分析，将进一步完善我们对该物种复合体的广泛表型和遗传差异的评估。LAY 总结 红冠莺的分类是有争议的：8 个亚种表现出不同的羽毛颜色和歌曲，因此它们有时被视为 2 个独立的物种。使用野外数据、博物馆标本和声音档案，我们比较了所有 8 个红冠莺亚种的体型、羽毛颜色和鸣叫声，8 个亚种中有 7 个亚种包括 2 个不同颜色、鸣叫和体型大小的组：北方、白腹 rufifrons 组和南部的黄腹 delattrii 组。第八亚种，Salvini 显示出与 rufifrons 组的相似性，而不是像之前的研究中描述的那样介于 2 个组之间。我们发现红顶莺包括 2 个独立的群体，这提高了我们对新热带鸟类生物多样性的了解。