ИСТИНА

Reinforcement is the process of enhancing reproductive isolation directly controlled by natural selection to cancel maladaptive hybridization between nascent species living together in sympatry. It is significant to check how often this process occurs in nature and how important it is for speciation. Therefore, we studied the character displacement within the breeding area of the Pied Flycatcher (Ficedula hypoleuca) to address this task, because relationships between the Pied Flycatcher and the Collared Flycatcher (F. albicollis) had come to be considered one of the examples of reinforcement. Herewith we checked whether there is a relationship between the mean male breeding plumage colour and the remoteness of the Pied Flycatcher population from the breeding area of the Collared Flycatcher. To do this, we collected all known literature data about the phenotypic structure of the Pied Flycatcher populations. We found information for 41 populations. We also analysed zoological collections from 11 museums. We evaluated the phenotypic structure of another 38 metapopulations. To check whether the distance from the nesting area of the Collared Flycatcher impacted on the phenotypic structure of the Pied Flycatcher, we used a random forest as spatial predictions framework. We showed that the environmental temperature, and not the distance to sympatry, were proven to better describe the geographic pattern of the mean breeding plumage colour of the Pied Flycatcher populations. Therefore, we conclude that ecologically distinct adaptations driven by niche differentiation, but not reinforcement, resulted in the morphological differentiation of the Old World flycatchers (ecological character displacement).