Patterns of at-sea behaviour at a hybrid zone between two threatened seabirds

Rhiannon E Austin,Clara Péron,Russell B Wynn,Ana Rodríguez,Lavinia Suberg,Clive Trueman,David Grémillet,Tim Guilford,Louise Maurice,Stephen C Votier,Miguel Mcminn,Meritxell Genovart,Jason Newton

doi:10.1038/s41598-019-51188-8

Abstract

Patterns of behavioural variation and migratory connectivity are important characteristics of populations, particularly at the edges of species distributions, where processes involved in influencing evolutionary trajectories, such as divergence, mutual persistence, and natural hybridization, can occur. Here, we focused on two closely related seabird species that breed in the Mediterranean: Balearic shearwaters (Puffinus mauretanicus) and Yelkouan shearwaters (Puffinus yelkouan). Genetic and phenotypic evidence of hybridization between the two species on Menorca (the eastern and westernmost island in the breeding ranges of the two shearwaters, respectively) has provided important insights into relationships between these recently diverged species. Nevertheless, levels of behavioural and ecological differentiation amongst these populations remain largely unknown. Using geolocation and stable isotopes, we compared the at-sea movement behaviour of birds from the Menorcan ‘hybrid’ population with the nearest neighbouring populations of Balearic and Yelkouan shearwaters. The Menorcan population displayed a suite of behavioural features intermediate to those seen in the two species (including migration strategies, breeding season movements and limited data on phenology). Our findings provide new evidence to support suggestions that the Menorcan population is admixed, and indicate a role of non-breeding behaviours in the evolutionary trajectories of Puffinus shearwaters in the Mediterranean.

Highlights

Behavioural and ecological processes can be central to understanding patterns of evolutionary differentiation amongst animal populations[1,2,3,4], in wide-ranging marine vertebrates, such as seabirds, unconstrained by the physical barriers to gene flow that promote species divergence in other taxa[5]
We explore the spatio-temporal patterns of seasonal movement behaviour and habitat use in two closely related shearwater species from the Mediterranean Sea, the Balearic shearwater Puffinus mauretanicus and the Yelkouan shearwater P. yelkouan, at breeding colonies close to a presumed contact zone, and in a third, probable hybrid population breeding in that zone
We focus on behavioural and ecological differentiation between the Menorcan population, a Balearic shearwater population from neighbouring Mallorca Island, and one of the nearest Yelkouan shearwater populations on the French Mediterranean coast (Port Cros and Porquerolles Islands)[35], to improve understanding of the evolutionary processes acting on these species

Summary

Introduction

Behavioural and ecological processes can be central to understanding patterns of evolutionary differentiation amongst animal populations[1,2,3,4], in wide-ranging marine vertebrates, such as seabirds, unconstrained by the physical barriers to gene flow that promote species divergence in other taxa[5] Factors such as non-breeding segregation[5], habitat specialization[6,7], natal philopatry[8] and mate preference[9] can all play a role in promoting genetic isolation in this group. Our results provide new behavioural and ecological insights into Menorcan shearwaters of relevance to this population’s taxonomic status, and highlight the potential role of at-sea behaviours in the differentiation of closely related seabird populations

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