The first record of a female hybrid between the Common Nightingale (Luscinia megarhynchos) and the Thrush Nightingale (Luscinia luscinia) in nature
Abstract
Understanding the mechanisms causing reproductive isolation between incipient species can give important insights into the process of species origin. Here, we describe a record of a hybrid female between two closely related bird species, the Common Nightingale and the Thrush Nightingale.
These species are separated by incomplete prezygotic isolation and the occurrence of fertile hybrid males in nature has been documented before. Our record represents the first genetically confirmed evidence of hybrid females in nature.
Although the hybrid was captured in the peak of the breeding season, it did not show any sign of reproductive activity, suggesting that it was sterile. This suggests that hybrid female sterility plays an important role in reproductive isolation in nightingales.
Unexpectedly, the hybrid female had highly developed fat reserves and was in the process of moulting. This unusual moult pattern could contribute to lower fitness of hybrid females and thus to speciation in nightingales.