A molecular phylogeny of the nightjars (Aves: Caprimulgidae) suggests extensive conservation of primitive morphological traits across multiple lineages

Abstract

We report a molecular re-assessment of the classification of the nightjars which draws conclusions that are strongly at odds with the traditional, morphology-based classifications. We used maximum likelihood and Bayesian methods to compare the cytochrome b gene for 14 species from seven of the 15 genera of the Caprimulgidae and partial cytochrome b sequence data was available for a further seven species including three further genera. We found that within the Caprimulgidae there were four geographically isolated clades with bootstrap support greater than 70%. One of these clades contained just Chordeiles species, the remaining three clades each contained a mixture of genera including Caprimulgus sp. A clade of exclusively South American nightjars included the genera Caprimulgus, Uropsalis, Eleopthreptus and Hydropsalis. A clade of African and Eurasian birds included Caprimulgus and Macrodipteryx. Phalaenoptilus nuttallii and Caprimulgus vociferous formed a clade of North American birds. Two ecological factors appear to make morphological classification potentially misleading: first, the apparent retention of primitive anti-predator and foraging-related traits across genetically divergent groups; second, rapid divergence in other traits, especially those related to mating, which generate high levels of morphological divergence between species that are genetically very similar. The cytochrome b data suggests that the genus Caprimulgus is not monophyletic and is restricted to Africa and Eurasia and that Caprimulgus species from outside this area have been misclassified as a consequence of retention of primitive adaptations for crepuscular/nocturnal living. Some other genera also appear to have little support from the cytochrome b data.