Phylogenetic relationships in Pterodroma petrels are obscured by recent secondary contact and hybridization.

Ruth M Brown,Carl G Jones,Leandro Bugoni,Chris G Faulkes,William C Jordan,Richard A Nichols,Vikash Tatayah,Ricardo L Palma

doi:10.1371/journal.pone.0020350

Abstract

The classification of petrels (Pterodroma spp.) from Round Island, near Mauritius in the Indian Ocean, has confounded researchers since their discovery in 1948. In this study we investigate the relationships between Round Island petrels and their closest relatives using evidence from mitochondrial DNA sequence data and ectoparasites. Far from providing clear delimitation of species boundaries, our results reveal that hybridization among species on Round Island has led to genetic leakage between populations from different ocean basins. The most common species on the island, Pterodroma arminjoniana, appears to be hybridizing with two rarer species (P. heraldica and P. neglecta), subverting the reproductive isolation of all three and allowing gene flow. P. heraldica and P. neglecta breed sympatrically in the Pacific Ocean, where P. arminjoniana is absent, but no record of hybridization between these two exists and they remain phenotypically distinct. The breakdown of species boundaries in Round Island petrels followed environmental change (deforestation and changes in species composition due to hunting) within their overlapping ranges. Such multi-species interactions have implications not only for conservation, but also for our understanding of the processes of evolutionary diversification and speciation.

Highlights

Molecular phylogenies are commonly used to disentangle relationships among taxa that have proven difficult to classify by other means
The gadfly petrels (Pterodroma spp.) provide an excellent example; the taxonomic treatment of this group has provoked considerable debate among researchers and is frequently revised, with traditional classification methods based on phenotype, anatomy and calls often proving insufficient to differentiate species
Molecular phylogenetic analysis provides a logical alternative, and molecular methods have already proven useful in determining the identity of some disputed Pterodroma species [1]

Summary

Introduction

Molecular phylogenies are commonly used to disentangle relationships among taxa that have proven difficult to classify by other means. In this study we focus on petrels which breed at Round Island (22 km NE of Mauritius in the Indian Ocean) and their relationship to congeners that breed worldwide. Since their discovery in 1948 [2], the origin and classification of Round Island petrels has been uncertain. The aim of this investigation is to clarify the taxonomic treatment of Pterodroma on Round Island, and to determine the relationships between these birds and a number of closely related species, whose taxonomy is controversial

Objectives

Methods

Results

Conclusion