Disentangling the taxonomic status and phylogeographic structure of Marmora\u2019s (Curruca sarda) and Balearic Warbler (Curruca balearica): a genetic multi-marker approach

Davide Nespoli,Andrea Galimberti,Chiara Mengoni,Irene Pellegrino,Mattia Brambilla,Ettore Randi,Gabriel Gargallo,Romolo Caniglia,Fernando Spina,Diego Rubolini,Marco Galaverni,Joseph Sunyer

doi:10.1007/s10336-021-01885-x

Abstract

Marmora’s Warbler (Curruca sarda) and Balearic Warbler (C. balearica) are allopatric sibling species and were recently split mostly based on morphological and ethological characteristics. Here we provide the first phylogenetic and phylogeographic analyses of this species complex to support the taxonomic status of C. sarda and C. balearica in light of integrative taxonomy. We sampled the two taxa in most of their breeding ranges and we sequenced three mitochondrial and one nuclear gene region. All C. balearica individuals had private haplotypes for the four markers and formed monophyletic clades. Genetic distances between the two taxa were comparable with those found between other species belonging to the Curruca genus. Furthermore, most of the genetic variance was expressed at the interspecific level, rather than between different populations within taxa or between individuals within populations. Our results strongly support the current taxonomic status of these two warblers as distinct species.

Highlights

The Mediterranean basin is one of the world’s best explored areas in terms of ornithological research and it is consid‐ ered a main biodiversity hotspot for the Western Palearctic (Myers et al 2000)
We sampled 62 individuals from 27 sites distributed in four different regions (13 individuals from Mallorca, 4 from Elba island, 31 from Sardinia and 14 from Corsica), from which we obtained a total of 191 sequences (Supporting Informa‐ tion Appendix 1)
The amount of divergence between C. sarda and C. balearica is quite high for populations separated by only a few hundreds of kilometres and greater than the diver‐ gence between other sister species within the Curruca genus (e.g. C. crassirostris and C. hortensis; Voelker and Light 2011)

Summary

Introduction

The Mediterranean basin is one of the world’s best explored areas in terms of ornithological research and it is consid‐ ered a main biodiversity hotspot for the Western Palearctic (Myers et al 2000). It acted as a center of origin and diversification for many taxa Since the advent of the Linnean classification, taxonomic research on Mediterranean bird species has usually been based on the analysis of morphological differences among popula‐ tions Such traditional approach might, have led to underestimating the actual degree of diversification occur‐ ring between isolated populations across the Mediterranean region. This divergence can be better evaluated in terms of genetic divergence and the development of reproductive iso‐ lation barriers, which in oscine birds are usually mediated by vocalizations and niche differentiation (Mason et al 2017)

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