Widespread hybridization between the Greater Spotted Eagle Aquila clanga and the Lesser Spotted Eagle Aquila pomarina (Aves: Accipitriformes) in Europe

Abstract

Hybridization is a significant threat for endangered species and could potentially even lead to their extinction. This concern applies to the globally vulnerable Greater Spotted Eagle Aquila clanga, a species that co-occurs, and potentially interbreeds, with the more common Lesser Spotted Eagle Aquila pomarina in a vast area of Eastern Europe. We applied single nucleotide polymorphism (SNP) and microsatellite markers in order to study hybridization and introgression in 14 European spotted eagle populations. We detected hybridization and/or introgression in all studied sympatric populations. In most regions, hybridization took place prevalently between A. pomarina males and A. clanga females, with introgression to the more common A. pomarina. However, such a pattern was not as obvious in regions where A. clanga is still numerous. In the course of 16 years of genetic monitoring of a mixed population in Estonia, we observed the abandonment of A. clanga breeding territories and the replacement of A. clanga pairs by A. pomarina, whereby on several occasions hybridization was an intermediate step before the disappearance of A. clanga. Although the total number of Estonian A. clanga ¥ A. pomarina pairs was twice as high as that of A. clanga pairs, the number of pairs recorded yearly were approximately equal, which suggests a higher turnover rate in interbreeding pairs. This study shows that interspecific introgressive hybridization occurs rather frequently in a hybrid zone at least 1700-km wide: it poses an additional threat for the vulnerable A. clanga, and may contribute to the extinction of its populations.

The diet of the greater spotted eagle (Aquila clanga) in Belarusian Polesie

“…For detailed information about identification of Greater and lesser spotted eagles and their hybrids see also Bergmanis (1996), Väli & Lõhmus (2004), Dombrovski (2006Dombrovski ( , 2009a, Väli et al (2010a, b).…”

Tests of multiple molecular markers for the identification of Great Spotted and Syrian Woodpeckers and their hybrids

“…The utility of nuclear markers for identification of species and their hybrids has been shown for introns (e.g., Pacheco et al 2002;Nadachowska and Babik 2009), single nucleotide polymorphisms (SNP; e.g., Väli et al 2010;Hohenlohe et al 2011), and microsatellites (e.g., Gay et al 2007;Väli et al 2010). A combined set of nuclear and mitochondrial markers may be the best option for species and their hybrids identification, especially in birds, when hybridizing species diverged recently and share a high proportion of alleles (e.g., Gay et al 2007;Väli et al 2010).…”

Mitochondrial DNA and microsatellite markers evidence a different pattern of hybridization in red-legged partridge (Alectoris rufa) populations from NW Italy

“…In some cases, hybridization occurs naturally due to overlapping habitat and insufficient genetic barriers. This is most frequent in birds (Grant and Grant 1992), e.g., in Scandinavian populations of rock ptarmigan Lagopus mutus and willow ptarmigan Lagopus lagopus (Quintela et al 2010), in Central European populations of greater spotted eagle Aquila clanga and lesser spotted eagle Aquila pomarina (Vali et al 2010), and between house sparrow Passer domesticus and Eurasian tree sparrow Passer montanus in Norway (Solberg et al 2006). Natural hybridization is frequent in Galliformes (McCarthy 2006); indeed, all the native grouse species in Britain can hybridize with at least one other species (Millais 1894).…”