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in Chen, White, Benson, et al., 2019.
DOI: 10.3390/d11090143
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Abstract
Strisores is a clade of neoavian birds that include diurnal aerial specialists such as swifts and hummingbirds, as well as several predominantly nocturnal lineages such as nightjars and potoos. Despite the use of genome-scale molecular datasets, the phylogenetic interrelationships among major strisorean groups remain controversial. Given the availability of next-generation sequence data for Strisores and the clade’s rich fossil record, we reassessed the phylogeny of Strisores by incorporating a large-scale sequence dataset with anatomical data from living and fossil strisoreans within a Bayesian total-evidence framework. Combined analyses of molecular and morphological data resulted in a phylogenetic topology for Strisores that is congruent with the findings of two recent molecular phylogenomic studies, supporting nightjars (Caprimulgidae) as the extant sister group of the remainder of Strisores. This total-evidence framework allowed us to identify morphological synapomorphies for strisorean clades previously recovered using molecular-only datasets. However, a combined analysis of molecular and morphological data highlighted strong signal conflict between sequence and anatomical data in Strisores. Furthermore, simultaneous analysis of molecular and morphological data recovered differing placements for some fossil taxa compared with analyses of morphological data under a molecular scaffold, highlighting the importance of analytical decisions when conducting morphological phylogenetic analyses of taxa with molecular phylogenetic data. We suggest that multiple strisorean lineages have experienced convergent evolution across the skeleton, obfuscating the phylogenetic position of certain fossils, and that many distinctive specializations of strisorean subclades were acquired early in their evolutionary history. Despite this apparent complexity in the evolutionary history of Strisores, our results provide fossil support for aerial foraging as the ancestral ecological strategy of Strisores, as implied by recent phylogenetic topologies derived from molecular data.
Keywords: Strisores; avian; phylogeny; evolution; morphology; total-evidence
Conclusions:
The present work represents one of the most comprehensive studies on strisorean phylogeny to date in terms of character sampling, combining a genome-scale molecular dataset and a large sample of fossil taxa in an attempt to resolve the internal relationships of this enigmatic clade of birds. The preferred topology found in this study places Caprimulgidae, (Steatornithidae + Nyctibiidae), and Podargidae as successively closer relatives of Daedalornithes, which is congruent with the results of some other recent phylogenomic analyses of Strisores. We also identified possible morphological synapomorphies that unite strisorean clades recovered using molecular data and potential fossil evidence that may support aerial foraging as the ancestral ecology of Strisores, as implied by molecular topologies. Contrary to expectations, however, combining morphological and molecular datasets did not increase confidence in any specific phylogenetic topology, despite the inclusion of a phylogenetically diverse range of well-known fossil taxa. We attribute this surprising result to high levels of morphological homoplasy in Strisores, early morphological diversification possibly obscuring ancestral morphologies in known fossil strisoreans, and the relatively small size of existing morphological matrices pertaining to strisoreans. Further refinement of phylogenomic methods may also advance future estimates of strisorean phylogeny. Our findings suggest that improved understanding of morphological evolution in strisoreans will be contingent on the discovery of even older fossil taxa that retain more plesiomorphic morphologies, as well as more comprehensive character sampling in morphological datasets.
Albert Chen, Noor D. White, Roger B.J. Benson, Michael J. Braun and Daniel J. Field. 2019. Total-Evidence Framework Reveals Complex Morphological Evolution in Nightbirds (Strisores). Diversity. 11(9); 143. DOI: 10.3390/d11090143
