| Summary: | Spéciation in birds is generally accepted to follow the allopatric mode suggested by Mayr. Current research on spécia tion seems to be centered around two “ levels ”. At the first, called 11 genetical ” level, one uses the techniques of electropho resis to analyze phenotypic variability due to isoenzymes repre senting alleles of gene loci. The second level is “ ecological ” and its practitioners employ museum specimens as basic material, as well as a variety of field techniques, which include experimen tal playback of tape recordings of songs or other vocalizations, analysis of reproductive isolating mechanisms, and measures of niche breadth or niche overlap. In the present paper comments are made on certain unsolved problems in bird spéciation in the Middle East, especially Iran. These remarks focus on the eco logical level of spéciation studies. Spéciation is less well analyzed and understood in Eurasian birds than in birds from the Nearctic, Neotropical, Ethiopian, or Australian Regions. In the twenties and thirties many significant papers were published on spéciation phenomena of Eurasian birds (geographical variation, hybridization, secondary contacts, etc.). A rather small number of similar studies have been undertaken more recently within the framework of modern spéciation theory, in spite of the broad background provided by a few early zoogeo- graphic syntheses, such as Stegmann’s, and in spite of the detailed distributional and taxonomic data available in the more recent systematic revisions of Vaurie. This state of affairs may be due, first to the emphasis, in taxonomic publications, on the assignment of taxa to either spe cies or subspecies, and second, to the masking of actual evolutio nary problems by the use of formal taxonomic nomenclature. All concerned biologists would benefit if taxonomists would make their evolutionary findings more widely available to others. This paper has been written in the hope that it might contribute to a better dialogue between taxonomists and ecologists. Questions are presented on three levels : (1) intraspecific variability (polymorphism), especially plumage color polymorphism, and spéciation, (2) hybridization between morphologically differentiated populations having reached, or close to reaching, the status of species, and coming together in secondary contact zones, and (3) geographical and ecological overlap, including character displacement, of differentiated taxa in zones of secondary contact. The following taxa are discussed : (1) Polymorphism : Buteo rufinus, Oenanthe hispanica, O. pleschanka, and O. xanthoprymna. (2) Hybridization in secondary contact zones : Corvus corone, Oenanthe hispanica X O. pleschanka, O. xanthoprymna, and Emberiza melanocephala X E. bruniceps. (3) Secondary contacts with or without overlap : Buteo buteo and B. rufinus (overlap), Falco peregrinus and F. pelegrinoides (overlap ?), Merops spp. (overlaps), Hirundo rupestris and H. obsoleta (overlap), Corvus corvus and C. ruficol lis (no overlap ?), Sitta neumayer and S. tephronota (overlap, non overlap, and character displacement), Turdoides caudatus and T. altirostris (overlap, character displacement ?), Phylloscopus neglectus and Phylloscopus spp. (systematic position, overlap ?), Rhodopechys spp. (partial overlaps, secondary contacts), and Emberiza hortulana and E. buchanani (overlap ?). Basic taxonomic work permits workers to detect problems of evolutionary interest in cases such of those reviewed here. In order to solve these problems, however, it is necessary to carry out programs of field work carefully designed to yield data per tinent to the solution of these problems. Field techniques of ecologists have much to offer. The collecting of fresh series of museum material from areas of hybridization or contact is indis pensable, and must be carried out together with the ecological work. Both local institutions (universities and museums) and western research centers will benefit from mutual associations on such projects. It is necessary to emphasize that these projects have more than intrinsic ecological or evolutionary importance. They also have a large potential interest for the teaching of bio logical disciplines. In Iran and other countries the textbooks in use could be illustrated with examples drawn not only from North America or Western Europe, but also from fascinating examples from the local environment. Finally, one may envision to set aside certain areas of evolutionary interest, such as one or more regions where hybridization takes place, as examples of “ natural laboratories ” where conservation measures may be of as much value for the future as the preservation of entire ecosystems.
|
|---|