Rapid loss of flight in the Aldabra whitethroated rail (1 Viewer)

[Fred Ruhe]

Janske van de Crommenacker, Nancy Bunbury, Hazel A. Jackson, Lisa J. Nupen, Ross Wanless, Frauke Fleischer-Dogley, Jim J. Groombridge, Ben H. Warren, 2019

Rapid loss of flight in the Aldabra whitethroated rail

PLoS ONE 14(12): e0226064. https://doi.org/10.1371/journal.
pone.0226064

Free pdf: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0226064&type=printable

Abstract:

Flight loss has evolved independently in numerous island bird lineages worldwide, and particularly in rails (Rallidae). The Aldabra white-throated rail (Dryolimnas [cuvieri] aldabranus) is the last surviving flightless bird in the western Indian Ocean, and the only living flightless subspecies within Dryolimnas cuvieri, which is otherwise volant across its extant range. Such a difference in flight capacity among populations of a single species is unusual, and could be due to rapid evolution of flight loss, or greater evolutionary divergence than can readily be detected by traditional taxonomic approaches. Here we used genetic and morphological analyses to investigate evolutionary trajectories of living and extinct Dryolimnas cuvieri subspecies. Our data places D. [c.] aldabranus among the most rapid documented avian flight loss cases (within an estimated maximum of 80,000–130,000 years). However, the unusual intraspecific variability in flight capacity within D. cuvieri is best explained by levels of genetic divergence, which exceed those documented between other volant taxa versus flightless close relatives, all of which have full species status. Our results also support consideration of Dryolimnas [cuvieri] aldabranus as sufficiently evolutionary distinct from D. c. cuvieri to warrant management as an evolutionary significant unit. Trait variability among closely related lineages should be considered when assessing conservation status, particularly for traits known to influence vulnerability to extinction (e.g. flightlessness).

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Fred

 

[Fred Ruhe]

Bayesian analysis (Yule speciation prior, 30 million generations) of concatenated Cytb and CR mtDNA data from contemporary and museum (indicated with ^) specimens of D. c. cuvieri from Madagascar, D. c. abbotti from Assumption, and D. [c.] aldabranus from Aldabra (different islands; indicated with colours, and Native North (N) and South (S) Aldabra islands are indicated with the black encircled letters). Bayesian branch support values (>75%) are indicated. Error bars display the 95% higher posterior density and time on the x-axis is given in millions of years before the present. († = population now extinct, Mlb� = Picard population recently introduced from Malabar). Although the analysis with the Yule speciation prior was illustrated here because of the interspecific nature of our deeper-level sampling (see [57] for discussion), the equivalent analyses with Coalescent-Inversegamma and Coalescent-Uniform speciation priors are illustrated in S3 Appendix. Furthermore, to magnify nodes and confidence intervals of interest for our focus, we excluded the outgroups from this figure. The full tree (Yule speciation prior) including the outgroups can also be found in S3 Appendix.

Fred