Sympatric speciation by allochrony in a seabird

doi:10.1073/pnas.0700446104

Sympatric speciation by allochrony in a seabird

*Department of Biology, Queen's University, Kingston, ON, Canada K7L 3N6;
^‡Departament Biologia Animal, Universitat de Barcelona, Avenue Diagonal 645, 08028 Barcelona, Spain;
^§Royal Society for the Protection of Birds, U.K. Headquarters, The Lodge, Sandy, Bedforshire SG19 2DL, United Kingdom;
^¶Department of Oceanography and Fisheries, University of Azores, 9901-862 Horta, Portugal; and
^‖Institute of Biomedical and Life Sciences, Graham Kerr Building, University of Glasgow, Glasgow G12 8QQ, United Kingdom

Edited by Douglas J. Futuyma, Stony Brook University, Stony Brook, NY, and approved October 2, 2007 (received for review January 17, 2007)

Abstract

The importance of sympatric speciation (the evolution of reproductive isolation between codistributed populations) in generating biodiversity is highly controversial. Whereas potential examples of sympatric speciation exist for plants, insects, and fishes, most theoretical models suggest that it requires conditions that are probably not common in nature, and only two possible cases have been described for tetrapods. One mechanism by which it could occur is through allochronic isolation—separation of populations by breeding time. Oceanodroma castro (the Madeiran or band-rumped storm-petrel) is a small seabird that nests on tropical and subtropical islands throughout the Atlantic and Pacific Oceans. In at least five archipelagos, different individuals breed on the same islands in different seasons. We compared variation in five microsatellite loci and the mitochondrial control region among 562 O. castro from throughout the species' range. We found that sympatric seasonal populations differ genetically within all five archipelagos and have ceased to exchange genes in two. Population and gene trees all indicate that seasonal populations within four of the archipelagos are more closely related to each other than to populations from the same season from other archipelagos; divergence of the fifth sympatric pair is too ancient for reliable inference. Thus, seasonal populations appear to have arisen sympatrically at least four times. This is the first evidence for sympatric speciation by allochrony in a tetrapod, and adds to growing indications that population differentiation and speciation can occur without geographic barriers to gene flow.

Footnotes

^†To whom correspondence should be addressed. E-mail: vlf{at}queensu.ca
Author contributions: V.L.F., A.L.S., E.G.-D., R.W.F., J.G.-S., and L.R.M. designed research; A.L.S., E.G.-D., M.B., R.W.F., J.G.-S., and L.R.M. performed research; V.L.F. analyzed data; and V.L.F. wrote the paper.
↵**Deceased December 11, 1999.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
Data deposition: The mitochondrial sequences reported in this paper have been deposited in the GenBank database (accession nos. AY600297, AY771004, AY771005, DQ178703–DQ178869, and EU252035–EU252071).
This article contains supporting information online at www.pnas.org/cgi/content/full/0700446104/DC1.