Two sibling species sympatrically breeding: a new conservation concern for the critically endangered Balearic shearwater

Abstract

Two Puffinus shearwater species are endemic to the Mediterranean region: the Yelkouan shearwater P. yelkouan breeding in the central and eastern, and the critically endangered Balearic shearwater P. mauretanicus in the western, exclusively breeding at the Balearic archipelago. All individuals caught in Minorca, a Balearic breeding site, showed phenotypic traits of Yelkouan shearwaters. Ten birds from that colony were sampled and genetically analysed. A fragment of 857 base pairs of the cytochrome b was sequenced and compared to published sequences of both species obtained from GenBank. A NeighborJoining (NJ) reconstruction distinguished two clades with high bootstrap support, showing that both species bred sympatrically in that colony. This result was unexpected since shearwaters do not usually form mixed colonies. New conservation concerns arise also from our study: at first, breeding population of Yelkouan shearwaters is even smaller than previously thought; additionally, other potential threats emerge, such as hybridization and ecological competition.

Comparing Multiple Criteria for Species Identification in Two Recently Diverged Seabirds

“…Indeed, the bycatch bird ringed in Menorca was assigned as YS by plumage colouration, biometry, genetic and isotopic criteria and clustered with (1) birds of known YS species and; (2) the majority of reference sequences of BS from Menorca. This is in line with other studies suggesting that at least part of the population breeding in Menorca actually belong to YS species [86] .…”

Genetic and Phenotypic Differentiation between the Critically Endangered Balearic Shearwater and Neighboring Colonies of Its Sibling Species

“…The aim of this study was to analyze variation in genetic and phenotypic characters in a critically endangered seabird, the Balearic shearwater Puffinus mauretanicus, and compare it to its closest sibling species, the Yelkouan shearwater P. yelkouan, with which it is thought to hybridize (Genovart et al 2005). The taxonomy of this group is much debated and has undergone changes in recent years (Austin 1996); although the Balearic shearwater was once considered to be a subspecies of the Yelkouan shearwater (Sibley and Monroe 1990;Yésou et al 1990), they are now considered to be different young species that are separable by morphometrics and coloration (Walker et al 1990;Heidrich et al 1998;Sangster et al 2002;Ruiz and Martí 2004).…”

Genetic Divergence and Hybrid Speciation

“…Such interspecific hybridization may have important evolutionary consequences depending on the frequency of intermating and the fitness of the resulting hybrid progeny (Barton and Hewitt 1985; Burke and Arnold 2001). For example, if hybrids are viable and fertile, and if there are repeated opportunities for hybridization, extensive gene flow may result in the extinction of one of the hybridizing taxa via genetic assimilation (e.g., Haddon 1984; Ayres et al 2004; Konishi and Takata 2004; Rosenfield et al 2004; Genovart et al 2005), or even the merging of the two taxa into a single evolutionary lineage (e.g., Echelle and Connor 1989; Hegde et al 2006; Taylor et al 2006). In contrast, persistent gene flow accompanied by reduced hybrid fitness can result in a stable hybrid zone, allowing for genetic exchange in certain genomic regions (including the possible introgression of beneficial alleles), but preventing the merging of the taxa (Barton and Hewitt 1985).…”