Abstract
Oscillations of periods with low and high temperatures during the Quaternary in the northern hemisphere have influenced the genetic composition of birds of the Palearctic. During the last glaciation, ending about 12,000 years ago, a wide area of the northern Palearctic was under lasting ice and, consequently, breeding sites for most bird species were not available. At the same time, a high diversity of habitats was accessible in the subtropical and tropical zones providing breeding grounds and refugia for birds. As a result of long-term climatic oscillations, the migration systems of birds developed. When populations of birds concentrated in refugia during ice ages, genetic differentiation and gene flow between populations from distinct areas was favored. In the present study, we explored the current genetic status of populations of the migratory European bee-eater. We included samples from the entire Palearctic-African distribution range and analyzed them via mitochondrial and nuclear DNA markers. DNA data indicated high genetic connectivity and panmixia between populations from Europe, Asia and Africa. Negative outcomes of Fu’s Fs and Tajima’s D tests point to recent expansion events of the European bee-eater. Speciation of Merops apiaster started during the Pliocene around three million years ago (Mya), with the establishment of haplotype lineages dated to the Middle Pleistocene period circa 0.7 Mya. M. apiaster, which breed in Southern Africa are not distinguished from their European counterparts, indicating a recent separation event. The diversification process of the European bee-eater was influenced by climatic variation during the late Tertiary and Quaternary. Bee-eaters must have repeatedly retracted to refugia in the Mediterranean and subtropical Africa and Asia during ice ages and expanded northwards during warm periods. These processes favored genetic differentiation and repeated lineage mixings, leading to a genetic panmixia, which we still observe today.
Highlights
Abiotic and biotic conditions have an important influence on the genetic structure of resident and long-distance migratory birds
When differentiated lineages meet in refugia, lineages can mix, leading to genetic panmixia
All the samples were deposited in the bird tissue collection of the Institute of Pharmacy and Molecular Biotechnology (IPMB) or loaned by the following collections and researchers: Claire Spottiswood; Field Museum of Natural History, USA (FMNH); Louisiana State University Museum of Natural History, USA (LSUMNS); Natural History Museum of Denmark, Copenhagen, Denmark (ZMUC); Zoological Museum of Bashkir University, Russia (ZMBU); Zoological Museum of Belarusian University, Azerbaijan
Summary
Abiotic and biotic conditions have an important influence on the genetic structure of resident and long-distance migratory birds. When physical and/or ecological barriers limit gene flow between populations, phylogeographic differentiation can occur. Gene flow will take place between populations. When differentiated lineages meet in refugia, lineages can mix, leading to genetic panmixia. These scenarios have been observed in phylogeographic studies of several migratory. Philopatry, habitat fragmentation, specific migratory flyways, and climatic conditions can influence the speciation of migratory taxa by limiting gene flow between populations and promoting genetic divergence [4]. Species with differing migratory routes and destinations are usually genetically distinct, while species with similar breeding and wintering areas show weak genetic structure [2,5]
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