How Many Kinds of Birds Are There and Why Does It Matter?
George F. Barrowclough , Joel Cracraft, John Klicka, Robert M. Zink
Published: November 23, 2016 http://dx.doi.org/10.1371/journal.pone.0166307
Source/Fonte: Wendy Paulson
Estimates of global species diversity have varied widely, primarily based on variation in the numbers derived from different inventory methods of arthropods and other small invertebrates. Within vertebrates, current diversity metrics for fishes, amphibians, and reptiles are known to be poor estimators, whereas those for birds and mammals are often assumed to be relatively well established. We show that avian evolutionary diversity is significantly underestimated due to a taxonomic tradition not found in most other taxonomic groups. Using a sample of 200 species taken from a list of 9159 biological species determined primarily by morphological criteria, we applied a diagnostic, evolutionary species concept to a morphological and distributional data set that resulted in an estimate of 18,043 species of birds worldwide, with a 95% confidence interval of 15,845 to 20,470. In a second, independent analysis, we examined intraspecific genetic data from 437 traditional avian species, finding an average of 2.4 evolutionary units per species, which can be considered proxies for phylogenetic species. Comparing recent lists of species to that used in this study (based primarily on morphology) revealed that taxonomic changes in the past 25 years have led to an increase of only 9%, well below what our results predict. Therefore, our molecular and morphological results suggest that the current taxonomy of birds understimates avian species diversity by at least a factor of two. We suggest that a revised taxonomy that better captures avian species diversity will enhance the quantification and analysis of global patterns of diversity and distribution, as well as provide a more appropriate framework for understanding the evolutionary history of birds.
Citation: Barrowclough GF, Cracraft J, Klicka J, Zink RM (2016) How Many Kinds of Birds Are There and Why Does It Matter? PLoS ONE 11(11): e0166307.
Editor: Andy J. Green, Consejo Superior de Investigaciones Cientificas, SPAIN
Received: May 11, 2016; Accepted: October 23, 2016; Published: November 23, 2016
Copyright: © 2016 Barrowclough et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Data Availability: All relevant data are within the paper and its Supporting Information files.
Funding: This paper received support from the U.S. National Science Foundation awards 1241066 and 1146423 (J.C.) and DEB 0815057 (J.K.).
Competing interests: The authors have declared that no competing interests exist.
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