Hybridization with a common relative - the threat or chance for the protected bird species?

Background

Species are assumed to be reproductively isolated from other taxa, what believed to be a principal rule in biological species concept. However, observations of individuals with characters intermediate between two species suggested that mating of distinct taxa is possible and could lead to development of a new type organism called ‘hybrids’. Currently, thanks to increasing number of observations and studies, it is known that hybrids are common in the animal kingdom, and that hybridization is crucial for biology, evolution, ecology and conservation of species. In birds, misallies occur quite often - they have been documented in the case of approx. one fifth of studied species. Woodpeckers are no exception, but hybrids are known mainly for the American genera. In Eurasia, the most commonly observed hybrids are in the so-called pied woodpeckers (genus Dendrocopos), and in Europe two species are known to hybridize - the Syrian Woodpecker (D. syriacus) and the Great spotted Woodpecker (D. major). The Syrian woodpecker spread from its native range in the Middle East to the Balkans and Central-Eastern Europe since end of XIX century, becoming there fully synantropic. In Europe Syrian woodpeckers met Great spotted woodpeckers which are widespread in any wooded areas. This opens opportunity for interspecific mating. This pair of species is especially interesting for studying hybridization in birds, as the taxa met very recently (in evolutionary timescale) in artificial conditions (synantropic), and their crosses are viable and fertile. Interspecific mating between these two species probably have some evolutionary consequences as recent studies indicate that some urban populations include approx. 20% of hybrids, including backcrosses in further generations. Moreover, hybridization could be a threat for Syrian woodpecker populations, at least in the verge of this species range ,where these birds are rare. It is important to highlight that Syrian woodpecker is rare and specially protected in EU (it is a species protected by the Birds Directive of the EU with Natura 2000 areas have been created for its protection).

Aims

The major goal of the project is to use information about the structure of sympatric populations of Syrian and Great spotted woodpeckers to assess the impact of interspecific mating and hybridization on the conservation of Syrian woodpecker as a species of special concern in the EU.

For this purpose, it is intended to test specific hypotheses with are focused on the prediction that the extent of interspecific pairing and hybridization is a result of current parental species distribution and environmental constraints like the availability of suitable habitats and species selection to various landscape types.

It is planned to examine the span of interspecific mating and hybrid occurrence in various scales: European (across Syrian woodpecker sympatric range with great-spotted woodpecker in Europe), regional (examination along urban-rural gradient in Central Europe) and local (details about ecology, hybrid share in populations and reproduction success for selected populations like the best known area of hybridization in southern Poland).

woodpecker hybrids

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