Comparative and phylogenetic analysis of the echo clicks and social vocalizations of swiftlets (Aves: Apodidae)
Several swiftlet species echolocate to navigate in the darkness of their nesting caves. We investigated whether swiftlets’ echo clicks and social vocalizations differed among species and whether they could be used in phylogenetic inference. We incorporated echo clicks of eight swiftlet species and social vocalizations of 27 echolocating and nonecholocating swifts and swiftlets. Characters in the frequency and time domain were used and analysed using nonparametric multivariate analysis of variance and stepwise discriminant analysis. We performed maximum parsimony analyses and character mapping to investigate phylogenetic signal and evolutionary patterns of swiftlet vocalizations. Echo clicks were species-specific. As well as in navigation, they may be used in recognition of conspecifics. Social vocalizations were species-specific also. However, the vocalizations contained no phylogenetic interpretable information. Maximum parsimony trees of echo clicks and of social vocalizations were almost completely unresolved. Moreover, resolved branches showed no congruence to a DNA-based tree that had been obtained previously. Mapping of the vocalization characters on the DNA-based tree revealed no consistent phylogenetic patterns. © 2006 The Linnean Society of London, Biological Journal of the Linnean Society, 2006, 88, 631–643.
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