key: cord-0821645-brjcfut9
authors: Pârâu, Liviu G.; Wink, Michael
title: Common patterns in the molecular phylogeography of western palearctic birds: a comprehensive review
date: 2021-05-13
journal: J Ornithol
DOI: 10.1007/s10336-021-01893-x
sha: d34d21cbda2af2509e0b4d5aa71748e3819e322e
doc_id: 821645
cord_uid: brjcfut9

A plethora of studies have offered crucial insights in the phylogeographic status of Western Palearctic bird species. However, an overview integrating all this information and analyzing the combined results is still missing. In this study, we compiled all published peer-reviewed and grey literature available on the phylogeography of Western Palearctic bird species. Our literature review indicates a total number of 198 studies, with the overwhelming majority published as journal articles (n = 186). In total, these literature items offer information on 145 bird species. 85 of these species are characterized by low genetic differentiation, 46 species indicate genetic variation but no geographic structuring i.e. panmixia, while 14 species show geographically distinct lineages and haplotypes. Majority of bird species inhabiting the Western Palearctic display genetic admixture. The glaciation cycles in the past few million years were pivotal factors in shaping this situation: during warm periods many species expanded their distribution range to the north over wide areas of Eurasia; whereas, during ice ages most areas were no longer suitable and species retreated to refugia, where lineages mixed. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10336-021-01893-x.

Past climatic events are embedded in the DNA of organisms (Hewitt 2000) . Across the paleogeographic areas of the world, local fauna shares molecular evidence indicating how they responded to the major successions of cold and warm periods (Webb and Bartlein 1992) . In the past three decades, the emergence of fine-tuned molecular techniques triggered a renaissance in zoology. Based on DNA sequencing, scientists were finally able to decipher the chronological and spatial evolution of species and subspecies (Hewitt 1999) . With the possibility of assessing the progress of a species in both time and space, the field of phylogeography emerged (Avise et al. 1987) . This served as an unprecedented opportunity and soon after the first studies began to appear (Cwynar and MacDonald 1987; Martin and Simon 1990; Reeb and Avise 1990; Nevo and Beiles 1992; Prinsloo and Robinson 1992; Quinn 1992; Melnick et al. 1993) . Initial studies had a limited focus, dealing with small sample sizes and generally employed a single molecular marker, most often a mitochondrial DNA (hereafter mtDNA) gene. Moreover, in the first few years, both software and statistical techniques were a crude limitation to data analysis (Edwards and Bensch 2009) .

As advanced DNA sequencing techniques became widely available, phylogeography became more popular, and the field entered a period of formidable growth (Hickerson et al. 2010) , with thousands of studies currently being available. One would expect that a considerable amount of work would also have been done in bringing together and interpreting this colossal volume of data. However, such reviews are very scarce, and they generally have a wide focus, from assessing the hypotheses behind the genetic lineages, to number of papers and species. To date, review articles have included the status of phylogeographic research for oceanic habitats at global level (Bowen et al. 2016) , or for archipelagos (Shaw and Gillespie 2016) . Reviews are also available for research on continental areas (Riddle 2016) , or studies dealing exclusively with the Southern hemisphere (Beheregaray 2008). One review examined exclusively the terrestrial taxa in the Aegean archipelago and surrounding regions (Poulakakis et al. 2015) . Among all the vertebrates which became a research focus in phylogeography, birds proved to be the most iconic (Weiss and Ferrand 2007) .

Numerous avian species had their phylogeography revealed. In Eurasia, the bird families which received most attention are the raptors, especially the Accipitridae, the crows (Corvidae), flycatchers and wheatears (both in Muscicapidae), as well as species from Phasianidae and the waders (Scolopacidae). To date, surprisingly few review and comparative studies have focused on birds. The first, authored by Robert M. Zink (Zink 1996) , analyzed mtDNA geographic patterns of five North American bird species, to determine that their absence of genetic structure is linked to recent population expansion. The second, a book section in 1997, written by the same author (Zink 1997) , offers an improved version of the first review, with more species included, which overall indicates the same population genetic structure. The third, in 1998, written by John C. Avise and DeEtte Walker (Avise and Walker 1998), compares 63 species from a phylogeographic and speciation perspective, confirming that the Pleistocene had a decisive effect on avian speciation. The fourth, as a chapter in the PhD thesis of Alexandra Pavlova (Pavlova 2004) , has compared phylogeographic information of 28 Eurasian bird species, concluding that the South contains regions with higher genetic diversity and phylogeographic endemism, with the overall genetic structure being shaped by the post-Pleistocene recolonization of Eurasia. In 2009, a review focused on the phylogeography of birds from the Australo-Papuan region, indicated extensive paraphyly among birds in Australia (Joseph and Omland 2009) . Following the chronological order, the next review brings into attention the horizontal and elevational phylogeographical patterns of Himalayan and Southeast Asian birds (Päckert et al. 2012) . The seventh study collected phylogeographic data for 210 bird species in the New World, to reveal that species from lower latitudes have higher genetic diversity (Smith et al. 2017 ). The most recent study, authored by Alexey P. Kryukov (Kryukov 2019) has an exclusive focus on Palearctic corvid species and reviews published data on the natural hybrid zones between crow species.

To the best of our knowledge, no study aimed specifically at deciphering the avian phylogeography of the Western Palearctic has been published. This region has received extensive attention, triggered both by the geographic composition e.g. various islands promoting endemism, as well as the density of research groups and availability of funding. In this study, we compiled a comprehensive body of published scientific literature with a clear focus on phylogeography of bird species inhabiting the Western Palearctic.

Between November 2018 and June 2020, we conducted an extensive search for relevant literature on: (1) ISI Web of knowledge, (2) Google Scholar, (3) Research Gate and (4) Google. We used the following keywords: "phylogeography" AND ("bird" OR "avian") AND ("Western Palearctic" OR "Europe"). Our initial searches were made using English, French, Spanish, German and Russian, which are recognized as some of the most used languages for scientific publishing in our target region (Ammon 2001; Ammon and McConnell 2002) . However, as we only found proper results in English, we excluded the other languages from further searches. Moreover, we considered both peer-reviewed and grey literature. We extracted additional papers from the references of the articles revealed by our systematic review, when the title or citation context indicated a bird phylogeography investigation. This study is limited to the area of the Western Palearctic, as presented in Shirihai & Svensson (Shirihai and Svensson 2018) , consisting of Europe, North Africa, the Middle East and Asia Minor, the Cape Verde, Azores and Canary Islands, Madeira, Jan Mayen, Svalbard and Iceland. As the Eastern limit, we expanded until the Caspian Sea and the Ural Mountains. For taxonomy, we followed the IOC World Bird List (Gill et al. 2020) .

The papers revealed by our on-line searches were further filtered according to the following criteria: (i) to focus on naturally occurring species in the Western Palearctic and (ii) to have samples originating from at least three geographically distinct populations. These facts were obtained upon reading the abstract plus materials and methods section. We later extracted information on the phylogeographic status of the studied species and assigned it one of the three categories: (i) panmixia, when the haplotypes are randomly distributed across the sampled area and no structure can be observed; (ii) low differentiation, if a certain degree of geographic delimitation of the haplotypes occur yet the lineage sorting is incomplete (e.g. Western vs. Eastern European haploclades, continental Europe vs. UK lineages) or (iii) geographically distinct lineages, for cases where certain haplotypes can be safely attributed to a geographic area and monophyletic groups are present (e.g. haplotypes found exclusively in one mountain range).

In addition, for each bird species, we noted the type of molecular technique (markers) used for obtaining the data and the migratory status of the respective species. The later information was retrieved from the IUCN Red List (IUCN 2019). We used the program R (R Core Team 2019) for data visualization.

To offer a better visualization of the phylogeographic differences among the three defined categories, we selected one species for each category, constructed its haplotype network and positioned all three networks side by side. We chose the European Turtle Dove (Streptopelia turtur) to illustrate panmixia, the European Green Woodpecker (Picus viridis) for low geographic differentiation and the African Blue Tit (Cyanistes teneriffae) as model for the geographically distinct lineages category. Complete details on the GenBank sequences used for the visualization are found in Table S4 . Mainly, the sequences are derived from the following studies: (Calderón et al. 2016) for the dove, (Perktas et al. 2011) for the woodpecker and (Dietzen et al. 2008) for the tit. After downloading the sequences from GenBank, we grouped all files belonging to one species into a fasta file, using MEGA X . We further assessed the number of haplotypes in DNA SP (Rozas et al. 2017) and finally employed the PopArt software (Leigh and Bryant 2015) to create the networks.

In total, 145 bird species from the Western Palearctic have been the target of phylogeographic studies (Tables 1, 2, 3,  Table S1 ). A number of 198 literature items (Table S2) , including 186 peer-reviewed articles, one preprint, four PhD theses and one Master thesis, four articles in conference proceedings, and two book chapters matched our literature selection criteria. The year of publication ranges from 1993 until 2020. The Western Capercaillie (Tetrao urogallus) has been the focus of ten publications, which makes it the most investigated species in our dataset.

In terms of molecular markers, for the majority of bird species (132 out of 145) the choice has been mtDNA ( Fig. 1) , which is also one of the three markers used since the first studies in 1993. Secondly, microsatellites have been used for 36 species and nuclear DNA sequences (hereafter nuDNA) for 36 as well. Seven studies have employed sex chromosomes and a further seven studies used next-generation DNA sequencing (hereafter NGS). In the NGS category we included research with whole-genome sequencing, ddRAD sequencing and SNPs. One study (Resano-Mayor et al. 2017 ) has used hydrogen isotopes in combination with mtDNA. Furthermore, one study (Lagerholm et al. 2017) employed ancient DNA extracted from fossil bones. For each marker, the above-mentioned values consist of both the occasions where the respective marker has been applied alone or in combination with another marker.

Across the Western Palearctic, 85 avian species show signs of low genetic differentiation (Fig. 2) , while 46 are genetically diverse but do not show a geographic structuring-indicating panmixia, and the remaining 14 species display geographically distinct lineages. Regarding the migratory behavior of the species comprising each category, we observed that the majority of the birds with low genetic differentiation and panmixia are migratory, while the species showing geographically distinct lineages are mainly resident and/or inhabitants of Oceanic islands (Fig. 2) .

Our haplotype network comparison revealed substantial differences among the three selected species. To visualize the situation for birds with panmixia, we chose the European Turtle Dove (Streptopelia turtur). For species with low geographic differentiation, we selected the European Green Woodpecker (Picus viridis). We chose the African Blue Tit (Cyanistes teneriffae), as a model for the geographically distinct lineages category. Figure 3 (and in higher quality as figure S3) contains our visual comparison, which points to the differences in the distribution of haplotypes, among the three species. For the European Turtle Dove, all seven countries share haplotypes, regardless of the distance in between e.g. UK and Bulgaria. The network for the European Green Woodpecker indicates that several haplotypes are shared among the various populations, but some countries have specific haplotypes e.g. Italy, Turkey, Greece. It should be mentioned, that the Iberian population of the Green Woodpecker was found to be genetically different and has been consequently split as a new species Picus sharpei (Perktas et al. 2011; Pons et al. 2011) . For the African Blue Tit, which is found in the Canary Islands, plus in Morocco, Algeria, Tunisia and Libya, the haplotype distribution is very clear. Majority of the islands in the Canary archipelago have distinct haplotypes, which are not found on the other islands. On the African continent, Libya has its own haplotypes, while Moroccan birds appear to be sharing some genetic background with birds from Fuerteventura.

Complete details on the GenBank sequences used for the visualization are found in Table S4 .

Substantial research has been carried out to understand the phylogeographic history of Western Palearctic avifauna, resulting in 145 bird species being studied. This represents roughly 20% of the 720 bird species found in the region (Shirihai and Svensson 2018) . Our review indicates that majority of the species are characterized by similar patterns of genetic variation and admixture. This situation is inextricably connected to the climatic past of the Western Palearctic (Lisiecki and Raymo 2007) , with the evidence being encrypted in the DNA of the species inhabiting this region (Taberlet et al. 1998; Weiss and Ferrand 2007) . The periods mainly responsible for shaping the genetic background for the current avifauna are the Pleistocene and Pliocene (Rand 1948; Avise and Walker 1998; Zink et al. 2004) . During these two eras, the climate oscillated between glaciations and warm cycles, accompanied by shifts in the composition of the vegetation (Frenzel et al. 1992) . In turn, these oscillations led to massive bird population crashes at the arrival of each glaciation, or great population expansions, when the ice sheet retreated (Hewitt 1999 ). Subsequently, these demographic processes triggered population admixture both in the refugia (see Fig. 4 ) and at the contact zones (during population expansion times). As a result, the overwhelming majority of bird species in our dataset (i.e. 131 out of 145, or 90.3%) are characterized by high levels of genetic admixture, with either complete panmixia or low differentiation among various breeding populations. Furthermore, the majority (i.e. 97 out of 131, or 74%) of species with genetic admixture are migrants or partial migrants (see Fig. 2 ). This suggests that the legacy of migration, which is strongly connected to the population expansion history in the Pleistocene and Pliocene (Bell 2000), had a central contribution to the species' current genetic structure.

To better underline this situation, we also indicate that in our dataset, 12 out of the 14 species with geographically distinct genetic lineages are resident, which brings further evidence that movement patterns plays an important role in shaping genetic diversity. Our results, in conjunction with previous research, indicate that most of the migrants from warm areas are genetically mixed, while species better adapted to cold climates show less admixture. This implies that species like the Hazel Grouse, Western Capercaillie, and ptarmigans could have spent some of the ice ages in small mountain refugia, inside the ice sheet (Lagerholm et al. 2017 ) (see Fig. 4 ). From a different perspective, some steppe species (Garcia et al. 2011 ) had their maximum distribution during the glaciations, when much of today's central and Southern Europe had scarce vegetation and resembled a steppe formation (Frenzel et al. 1992) . Similarly, the genus Prunella has been shown to have colonized new areas mainly during the glacial periods (Liu et al. 2017) . Regarding the migratory movements of birds in the past 50,000 years, a recent study proposed that Old World species had relatively short movements (Somveille et al. 2020) . In comparison, the same simulation-based study shows that birds in the New World were already doing transcontinental migrations. Overall, this brings further evidence that, in the past thousands of years, migratory behavior had an important role in shaping today's genetic background of bird species. Additional factors like the time of glacial isolation, habitat selection, variation of the ecological niche through time (Eyres et al. 2021) , geographical barriers and hybridization have also been crucial in species' phylogeographical structure (Avise 2000).

In the dataset we compiled, several bird species show two main mtDNA haploclades. The Eurasian Collared Dove (Bagi et al. 2018), Common Redstart (Hogner et al. 2012) and Red-backed Shrike (Pârâu et al. 2019 ) are characterized by two main haplotype clades, with no geographic structure. However, the Little Owl (Pellegrino et al. 2014 ) and Great Reed Warbler (Hansson et al. 2008) , also with two main mtDNA groups, display Western and Eastern European specific haploclades. In addition, species like the Skylark and Great Grey Shrike (Olsson et al. 2010) which are spread across the entire Palearctic also show two divergent clades: Western Palearctic versus East Asian individuals. Previous research on the North American continent has revealed a similar situation for the Snow Goose (Quinn 1992) and Common Raven (Webb et al. 2011) , which show two haploclades, with a relatively clear geographic structure. The most plausible explanation for the occurrence of two or more haploclades are the glacial refugia (Weiss and Ferrand 2007) . The thousand years spent in these Southern refugia e.g. Iberian Peninsula or the Balkans in Europe, have acted as a selective force on genetic lineages. During the cyclical back-and-forth population expansion processes associated with ice ages, only certain populations survived, became in contact, and interbred. Although in the past 12 thousand years there was no ice age in the Western Palearctic and birds from different refugia freely mixed, the genetic legacy of the cold ages is still deeply rooted in the DNA. Furthermore, several species still have refugia-specific haplotypes, like in the case of the Rook (Corvus frugilegus) (Salinas et al. 2021 ). However, in terms of species with several haploclades or sister species sharing haplotypes, hybridization and introgression of gene flow also represent a valuable explanation. Avian hybridization has long been a point of interest for ornithologists and geneticists, as evidence for active speciation, or in simple terms-seeing in real-time how a species is borne (McCarthy 2006; Ottenburghs et al. 2015) . Hybridization is known to occur in 9% of the bird species (Grant and Grant 1992) . In these cases, genetic material from one species is incorporated into another, potentially enforcing speciation (Rheindt and Edwards 2011; Ottenburghs et al. 2017) . In Europe, the classic example is the Italian Sparrow (Passer italiae), which still shares mtDNA haplotypes with its parent species, the Spanish Sparrow (Passer hispaniolensis) and the House Sparrow (Passer domesticus), representing an admixture of both genetic and phenotypic factors (Hermansen et al. 2011; Trier et al. 2014; Saetre et al. 2017) . The dawn of the genomic era already provides strong molecular evidence into the complexity of genomic regions directly responsible for speciation, and promising a much better understanding in the years to come (Joseph 2018) .

The Western Palearctic also includes a series of oceanic islands situated at low latitudes i.e. Macaronesia, which experienced different climate conditions during the Pliocene and Pleistocene (Webb and Bartlein 1992) . These oceanic islands, which were not connected by land bridges with the continent were not affected by glaciations, which represents the triggering factor for genetic admixture in the avifauna of continental Western Palearctic (Wink 2018a). This circumstance of continental bird species being characterized by genetic admixture does not represent a special feature of the Western Palearctic avifauna, but rather the general situation for birds in the Northern temperate areas. Research on the North American continent has revealed similar patterns in several bird species (Zink 1996; Avise and Walker 1998; Dohms 2016) , with most populations sharing haplotypes and only a handful of examples for geographically distinct genetic lineages.

For avian species in areas not affected by glaciations in the past few million years e.g. tropical areas and oceanic islands (see above), genetic structure and differentiation is, in many species, distinct. For example, the gnatcatchers and gnatwrens (Polioptilidae), pectoral sparrows (Arremon taciturnus), tyrant-manakins (Pipridae) and the Straightbilled Hermit (Phaethornis bourcieri) from South America show very distinct genetic groups, with almost no gene flow (Araújo- Silva et al. 2017; Capurucho et al. 2018; de Melo et al. 2018 de Melo et al. ,2020 Smith et al. 2018) . A similar situation has been described for the Wedge-billed Woodcreeper (Fernandes et al. 2013) , the Southern Chestnut-tailed Antbird (Sciaphylax hemimelaena) (Fernandes et al. 2012) , both Spotted and Spot-backed Antbirds (Hylophylax naevioides/ naevius) (Fernandes et al. 2014 ) and lowland antpittas (Grallariidae) (Carneiro et al. 2018) . The consensus of the above-mentioned research is that genetic diversification in South American bird species was mainly triggered by the consolidation of Amazonian rivers and drainage system, which acted as dispersal barriers (Haffer 1969; Silva et al. 2019) . These geological events took place during the Miocene and Pliocene (Rull 2011) , which gave several million years of additional speciation for neotropical birds, in comparison to the birds from the Western Palearctic. Furthermore, the South American continent had a less fluctuating climate during these eras, a crucial factor contributing to species delimitation. A recent study indicated similar effects of the major geological events in the past million years on local birds phylogeography in Australia (Dolman and Joseph 2015) . For the African continent, both river barriers and large vegetation shifts promoted bird speciation (Voelker et al. 2010 (Voelker et al. , 2013 . In regard to other fauna and flora taxa inhabiting the Western Palearctic, certain degrees of genetic variation can be observed and very often, individuals can be linked to certain populations or geographic areas. This is illustrated by recent studies on Brown Hares (Lepus europaeus) (Minoudi et al. 2018) , Stone Martins (Martes foina) (Tsoupas et al. 2019) , plus Balkan Mole (Talpa stankovici) and European Mole (Talpa europaea) (Tryfonopoulos et al. 2010) , which revealed that populations from the Balkans have region specific haplotypes. However, the Wild Cat (Felis silvestris) only shows five main geographic groups across the whole of Europe, with some populations hybridizing with domestic cats (Mattucci et al. 2016) . Similarly, the European Roe Deers (Capreolus capreolus) and European Wild Boars (Sus scrofa) are characterized by a three clade pattern (Scandura et al. 2008; Sommer et al. 2009 ). Overall, the carnivores tend to exhibit region specific lineages, as has been shown in the Golden Jackals (Canis aureus) (Rutkowski et al. 2015) , the Brown Bears (Ursus arctos) (Swenson et al. 2011 ) and the Grey Wolves (Canis lupus) (Pilot et al. 2010) . Smaller mammals, such as the Field Vole (Microtus agrestis) and the Wood Mouse (Apodemus sylvaticus) equally show geographically specific clades across Europe (Jaarola and Searle 2002; Michaux et al. 2003) . Reptiles and amphibians, which show very limited mobility, are defined by even more distinct genetic lineages (Joger et al. 2010) , as indicated by the Tree Frogs (Hyla arborea) (Dufresnes et al. 2019) , the Blotched Snakes (Elaphe sauromates) (Jablonski et al. 2019), the Grass Snakes (Natrix natrix) (Kindler et al. 2017 ) and the Ocellated Skinks (Chalcides ocellatus) (Kornilios et al. 2010) , to name just a few. Several studies in plants have also revealed comparable genetic differentiation (see ivy Hedera sp. (Grivet and Petit 2002) and numerous tree species (Petit et al. 2005) ). One study based on mtDNA indicates that the European Stag Beetle (Lucanus cervus) has two main lineages, one restricted to the Balkan peninsula, while the second one is widely distributed in Europe (Cox et al. 2019) . For the European Stone Crayfish (Austropotamobius torrentium), several region specific lineages were also uncovered by sequencing the mtDNA (Pârvulescu et al. 2019) .

The above examples offer evidence that a species' phylogeographic status is shaped by a combination of factors, including its locomotive capacities, fidelity to both breeding and migratory areas, as well as the age of the respective species. Furthermore, the current genetic population structure of a species is just a temporary step in its evolution (Avise 2000) . To illustrate, species that are characterized by panmixia in present might be undergoing an active process of speciation and lineage sorting, such as the Great Tit (Parus major), which has been shown to have differentiating genomic elements in peripheral populations (Spurgin et al. 2019) .

To conclude, genetic admixture in Western Palearctic birds (except the birds from the Macaronesia islands) represents a result of past climatic events, which occurred during the Pleistocene and Pliocene, as well as the high vagility of birds (unparalleled by other taxa), which helped to achieve such high gene flow.

To date, the majority (i.e. 132 out of 198) of avian phylogeographic studies have employed nucleotide sequences of mtDNA as a molecular marker. In avian and other taxa population history, mtDNA has been a pivotal method which helped the field of phylogeography flourish (Avise 2004; Beheregaray 2008). It has been primarily used in initial surveys of population demography and biography, due to its low cost and efficiency (Mindell 1997) . However, mtDNA does have limitations, as it is non-recombinant and maternally inherited (Krebs et al. 2018 ). These shortcomings have ignited a number of debates (Hebert et al. 2003; Ballard and Whitlock 2004; Hurst and Jiggins 2005; Edwards and Bensch 2009 ), but we consider that the advantages easily overcome the drawbacks (Rubinoff and Holland 2005; Sequeira et al. 2008; Zink and Barrowclough 2008) . To bring further support for mtDNA, we argue that in our dataset, two different studies on the Saker Falcon (Falco cherrug), one employing mtDNA (Nittinger et al. 2007 ) and the more recent one, using SNPs (Zhan et al. 2015) , produced the same phylogeography for the species. Similarly, two studies on the Eurasian Curlew (Numenius arquata), one using nuclear and mitochondrial DNA (Rodrigues et al. 2019) , and one with NGS (Tan et al. 2019) , yielded comparable results.

After mtDNA, microsatellites and nuDNA are the most commonly used markers. With the accompanying benefits of these two last markers (Avise 2004), the main restrain is that the focus is on a small strain of DNA.

Concerning the low scale usage of NGS (seven out of 198) across the studies included in our review, this is a relatively novel technology (see Fig. 1 ) and we argue that the costs still represent an impediment for many research groups. Although the sequencing costs are dropping fast, harnessing and affording high-quality computational analyses represents the major drawback. Unfortunately, bioinformatic expert support is still a luxury for many bird research labs.

As a final regard, we envision mtDNA will continue to provide robust first phylogeographic assessments for many years to come and we expect an increase in studies based on NGS data.

Until present, the bulk of animal phylogeography research has been dominated by mtDNA (Emerson and Hewitt 2005; Avise et al. 2016) . With the advent of sequencing techniques, coupled with a decrease in running costs, we expect that the era of big "omics" data will revolutionize the phylogeographic research. However, regarding the later costs, the expenses for computational analyses, computer clusters and human bioinformatic resources are increasing (Muir et al. 2016) . Whole-genome sequencing will challenge the present image offered by mtDNA (Kraus and Wink 2015; Ottenburghs et al. 2019) and we anticipate that a number of species currently characterized by panmixia will reveal a certain degree of differentiation. Furthermore, the maturation of phylogeography will benefit not only from developments in DNA sequencing techniques, but also from the advancement of theory and statistical analyses in this field (Stiller and Zhang 2019) .

Finally, bird populations are very dynamic and their distribution in space and time are affected by multiple factors such as climate, availability of habitat and food but also, in the past hundred years, anthropogenic threats. This complex network of factors has a fundamental influence on shaping their future phylogeography . With climate change, unprecedented human-driven alteration of the environment and overall decrease of food stocks (e.g. insects), genetic consequences on bird populations might not be that far away.

After 30 years of studies in phylogeography, we have a good understanding of avian population history in the Western Palearctic, based on the 145 species whose genetic background has been elucidated. The majority of them show high levels of genetic admixture, whereas the species inhabiting the oceanic islands (i.e. Macaronesia) are resident and developed distinct genetic lineages. The panmixia is the legacy of the Pleistocene and Pliocene climatic fluctuations, which forced the birds to cyclically retreat in refugia only to subsequently expand and recolonize higher latitudes, after the ice sheet retreat. These events caused population admixture, both in the refugia and at the contact zones, during population expansion. The bulk of the avian phylogeographic information comes from nucleotide sequences of mtDNA, which, with few limitations, has proven to be a robust and trustworthy molecular marker. With the current dawn of big genomic data in bird research, which offers a much higher resolution than previous studies, we envision a steep increase of NGSdriven phylogeography studies. These new studies have both the power to offer initial population structure surveys and, most important, to challenge previous views based on other markers. Nonetheless, the utility of mtDNA when used with due understanding and in conjunction with NGS is clearly (Perktas et al. 2011) for the woodpecker (ND2 sequences) and Dietzen et al. 2008 (Dietzen et al. 2008 for the tit (Cytb sequences). This figure is available in higher quality as Figure S3 ◂ Fig. 4 Visualization of the Western Palearctic during glaciation, with blue areas depicting possible alpine refugia, while the red ones indicate Southern refugia very high. We, therefore, urge our peers not to forget mtDNA completely, which has been a great companion in the past 30 years.

The online version contains supplementary material available at https:// doi. org/ 10. 1007/ s10336-021-01893-x.

We would like to express our sincere gratitude to Carina Carneiro de Melo Moura, who offered great support and valuable ideas at an incipient stage of the study. We further thank Erjia Wang, Roberto Carlos Frias-Soler, Hedwig Sauer-Gürth, Beate Waibel and Ivan Starikov for burgeoning discussions on the topic of phylogeography and for useful ideas to improve this review. We also acknowledge Petra Fellhauer for technical support. Alexandru Tomazatos provided constructive comments on an earlier draft of the manuscript. Kylynn Clare kindly helped with proofreading and English grammar corrections. We acknowledge the help of Franz Bairlein, Jan T. Lifjeld, Per Alström and one anonymous reviewer for their contribution to the peer-review of this work. Mare Haider, Pelin and Irmgard Yildiz, Philipp Scheffzek, Dietlinde Schiebel and Markus Schirmer provided logistical support at the initial stage of the study. LP would like to dedicate this article to his esteemed ornithology mentor, Prof. Eugen Petrescu from Danube Delta-Romania, who triggered his passion and curiosity on bird science, providing constant guidance in the past 19 years.

Authors' contributions LP and MW conceived the study. LP collected and analyzed the data, and wrote the manuscript. MW provided regular intellectual input, reviewed drafts of the paper and approved the final manuscript. 

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Mitochondrial phylogeography of the genus Eremophila confirms underestimated species diversity in the Palearctic

Densely sampled phylogenetic analyses of the Lesser Short-toed Lark (Alaudala rufescens)-Sand Lark (A. raytal) species complex (Aves, Passeriformes) reveal cryptic diversity

IOC World Bird List v10

Phylogeography, genetic structure and diversity in the endangered bearded vulture (Gypaetus barbatus, L.) as revealed by mitochondrial DNA

Phylogeography of the Calonectris shearwaters using molecular and morphometric data

Evidence from DNA nucleotide sequences and ISSR profiles indicates paraphyly in subspecies of the Southern Grey Shrike (Lanius meridionalis)

Hybridization of bird species

Phylogeography of the common ivy (Hedera sp.) in Europe: genetic differentiation through space and time

Columba palumbus Cyt b-like Numt sequence: comparison with functional homologue and the use of universal primers

History of the Crested Lark in the Mediterranean region as revealed by mtDNA sequences and morphology

Shallow genetic population structure in an expanding migratory bird with high breeding site fidelity, the Western Eurasian Crane Grus grus grus

Speciation in amazonian forest birds

Postglacial colonisation patterns and the role of isolation and expansion in driving diversification in a passerine bird

Phylogeographic patterns in widespread corvid birds

Discordance between genomic divergence and phenotypic variation in a rapidly evolving avian genus (Motacilla)

Phylogeographic analysis and genetic cluster recognition for the conservation of Ural Owls (Strix uralensis) in Europe

Biological identifications through DNA barcodes

Hybrid speciation in sparrows I: phenotypic intermediacy, genetic admixture and barriers to gene flow

Genetic differences among Iberian White-Throated Dipper Cinclus cinclus populations based on the cytochrome b sequence

Is isolation by distance the cause of the genetic structure of the Iberian whitethroated dipper populations?

Post-glacial re-colonization of European biota

The genetic legacy of the Quaternary ice ages

Phylogeography's past, present, and future: 10 years after Avise

Genetic variability in European black grouse (Tetrao tetrix)

Phylogeography of the Black-tailed Godwit Limosa limosa: substructuring revealed by mtDNA control region sequences

Deep sympatric mitochondrial divergence without reproductive isolation in the Common redstart Phoenicurus phoenicurus

Mitochondrial DNA and nuclear microsatellites reveal high diversity and genetic structure in an avian top predator, the White-tailed sea eagle, in central Europe

Genetic structure of Eurasian and North American mallard ducks based on mtDNA data

Evidence of a highly complex phylogeographic structure on a specialist river bird species, the Dipper (Cinclus cinclus)

Recent allopatric divergence and niche evolution in a widespread Palearctic bird, the Common rosefinch (Carpodacus erythrinus)

Multilocus coalescence analyses support a mtDNA-based phylogeographic history for a widespread Palearctic passerine bird, Sitta europaea

Problems with mitochondrial DNA as a marker in population, phylogeographic and phylogenetic studies: The effects of inherited symbionts

A multi-gene approach reveals a complex evolutionary history in the Cyanistes species group

Genetic, morphological, and acoustic evidence reveals lack of diversification in the colonization process in an island bird

Acoustic, genetic, and morphological analyses of the Canarian common chaffinch complex Fringilla coelebs ssp. reveals cryptic diversification

Maternal genetic structure reveals an incipient differentiation in the Canary Islands Chiffchaff Phylloscopus canariensis

The IUCN Red List of Threatened Species. Version 2019-2

Phylogeography of Field voles (Microtus agrestis) in Eurasia inferred from mitochondrial DNA sequences

The biogeography of Elaphe sauromates (Pallas, 1814), with a description of a new Rat snake species

Relict populations and endemic clades in Palaearctic reptiles: evolutionary history and implications for conservation

Phylogeography and the role of hybridization in speciation. In: Tietze DT (ed) Bird species: how they arise, modify and vanish

Phylogeography: its development and impact in Australo-Papuan ornithology with special reference to paraphyly in Australian birds

Unravelling population processes over the Late Pleistocene driving contemporary genetic divergence in Palearctic Buzzards

Significant Asia-Europe divergence in the Middle spotted woodpecker

Hybridization patterns in two contact zones of grass snakes reveal a new Central European snake species

Temporal landscape genetic data indicate an ongoing disruption of gene flow in a relict bird species

Genetic similarity among Eurasian subspecies of Boreal owls Aegolius funereus

Genetic differentiation and polymorphism of the Volga population of the Imperial Eagle (Aquila heliaca, Falconiformes, Accipitridae) according to a mitochondrial DNA analysis

Phylogeography of the ocellated skink Chalcides ocellatus (Squamata, Scincidae), with the use of mtDNA sequences: a hitch-hiker's guide to the Mediterranean

Avian genomics: fledging into the wild!

Lewin's genes XII

Phylogeography and hybridization of corvid birds in the Palearctic Region

Deep phylogeographic breaks in Magpie Pica pica across the Holarctic: concordance with bioacoustics and phenotypes

Phylogeography of the mallard Anas platyrhynchos from Eurasia inferred from sequencing of the mtDNA control region

Holarctic phylogeographic structure of Eurasian wigeon

A review of phylogeography: biotic and abiotic factors

MEGA X: molecular evolutionary genetics analysis across computing platforms

Mitochondrial phylogenetics of the goshawk Accipiter [gentilis] superspecies

The colonization history and present-day population structure of the European great tit (Parus major major)

Phylogeography of a Palaearctic sedentary passerine, the willow tit

Glacial history and colonization of Europe by the Blue tit Parus caeruleus

Colonisation and diversification of the blue tits (Parus caeruleus teneriffae-group) in the Canary Islands

Population decline is accompanied by loss of genetic diversity in the Lesser Grey Shrike Lanius minor

Range shifts or extinction? Ancient DNA and distribution modelling reveal past and future responses to climate warming in cold-adapted birds

Genetic structure and phylogeography of a European flagship species, the White-tailed sea eagle Haliaeetus albicilla

Phylogeography of the White-throated dipper Cinclus cinclus in Europe

Population structure of Purple Sandpipers (Calidris maritima) as revealed by mitochondrial DNA and microsatellites

Geographic patterns of genetic differentiation and plumage colour variation are different in the Pied flycatcher (Ficedula hypoleuca)

POPART: Full-feature software for haplotype network construction

Shaped by uneven Pleistocene climate: mitochondrial phylogeographic pattern and population history of White wagtail Motacilla alba (Aves: Passeriformes)

Phylogeography and colonization history of Lesser Black-backed Gulls (Larus fuscus) as revealed by mtDNA sequences

Genetic differentiation and phylogeography of gulls in the Larus cachinnans-fuscus group (Aves: Charadriiformes)

Species-level divergences in multiple functional traits between the two endemic subspecies of Blue Chaffinches Fringilla teydea in Canary Islands

Plio-Pleistocene climate evolution: trends and transitions in glacial cycle dynamics

Explosive radiation and spatial expansion across the cold environments of the Old World in an avian family

Mitochondrial DNA variation and the phylogeography of the Grey partridge (Perdix perdix) in Europe: from Pleistocene history to present day populations

Lack of genetic structuring and subspecies differentiation in the Capercaillie (Tetrao urogallus) in Finland

Geographical segregation in Dunlin Calidris alpina populations wintering along the East Atlantic migratory flyway-evidence from mitochondrial DNA analysis

Mitochondrial DNA sequence variation and phylogeographical structure of rock partridge (Alectoris graeca) populations

Ecological segregation and population structuring of the Cormorant Phalacrocorax carbo in Europe, in relation to the recent introgression of continental and marine subspecies

Phylogeography and subspecies taxonomy of dunlins (Calidris alpina) in western Palearctic analysed by DNA microsatellites and amplified fragment length polymorphism markers

No phylogeographic structure in the circumpolar Snowy owl (Bubo scandiacus)

Differing levels of among-population divergence in the mitochondrial DNA of periodical cicadas related to historical biogeography

Population genetics after fragmentation: the case of the endangered Spanish imperial eagle (Aquila adalberti)

European wildcat populations are subdivided into five main biogeographic groups: consequences of Pleistocene climate changes or recent anthropogenic fragmentation?

Handbook of avian hybrids of the world

mtDNA diversity in rhesus monkeys reveals overestimates of divergence time and paraphyly with neighboring species

Mitochondrial phylogeography of the woodmouse (Apodemus sylvaticus) in the Western Palearctic region

Avian molecular evolution and systematics

Genetic analyses of brown hare (Lepus europaeus) support limited migration and translocation of Greek populations

Being cosmopolitan: evolutionary history and phylogeography of a specialized raptor, the Osprey Pandion haliaetus

A first assessment of genetic variability in the Eurasian Stone-curlew Burhinus oedicnemus

Multilocus approach reveals an incipient differentiation process in the Stone-curlew, Burhinus oedicnemus around the Mediterranean basin

The genetic structure of the European breeding populations of a declining farmland bird, the Ortolan bunting (Emberiza hortulana), reveals conservation priorities

The real cost of sequencing: scaling computation to keep pace with data generation

Mitochondrial DNA analysis reveals Holarctic homogeneity and a distinct Mediterranean lineage in the Golden eagle (Aquila chrysaetos)

New insights into population structure of the European golden eagle (Aquila chrysaetos) revealed by microsatellite analysis

Natural and anthropogenic influences on the population structure of White-tailed eagles in the Carpathian Basin and central Europe

Phylogeography of a habitat specialist with high dispersal capability: the Savi's Warbler Locustella luscinioides

MtDNA polymorphisms: evolutionary significance in adaptation and speciation of subterranean mole rats

Phylogeography and population structure of the Saker falcon (Falco cherrug) and the influence of hybridization: mitochondrial and microsatellite data

The Lanius excubitor (Aves, Passeriformes) conundrum-Taxonomic dilemma when molecular and non-molecular data tell different stories

New insights into the intricate taxonomy and phylogeny of the Sylvia curruca complex

Disagreement between morphological and molecular evidence and cryptic divergence: A case for resurrecting Calamoherpe ambigua Brehm 1857

The Avian Hybrids Project: gathering the scientific literature on avian hybridization

Avian introgression in the genomic era

ed) Avian genomics in ecology and evolution

Population differentiation in the redshank (Tringa totanus) as revealed by mitochondrial DNA and amplified fragment length polymorphism markers

Horizontal and elevational phylogeographic patterns of Himalayan and Southeast Asian forest passerines (Aves: Passeriformes)

A revised phylogeny of nuthatches (Aves, Passeriformes, Sitta) reveals insight in intra-and interspecific diversification patterns in the Palearctic

Population history, gene flow, and bottlenecks in island populations of a secondary seed disperser, the Southern grey shrike (Lanius meridionalis koenigi)

High Genetic Diversity among Breeding Red-Backed Shrikes Lanius collurio in the Western Palearctic

A journey on plate tectonics sheds light on European crayfish phylogeography

Genetic differences among mainland and insular forms of the Citril Finch Serinus citrinella

Comparative phylogeography of Eurasian birds. University of Minnesota

Phylogeographic patterns in Motacilla flava and Motacilla citreola: species limits and population history

Evolutionary history, population genetics, and gene flow in the Common rosefinch (Carpodacus erythrinus)

Mitochondrial DNA and plumage evolution in the White wagtail Motacilla alba

Different postpleistocene histories of eurasian parids

Pleistocene evolution of closely related Sand martins Riparia riparia and R. diluta

Phylogeography and Pleistocene refugia of the Little Owl Athene noctua inferred from mtDNA sequence data

Evidence for strong genetic structure in European populations of the Little owl Athene noctua

Where is the line? Phylogeography and secondary contact of western Palearctic coal tits (Periparus ater: Aves, Passeriformes, Paridae)

Historical diversification of migration patterns in a passerine bird

A wide geographical survey of mitochondrial DNA variation in the Great spotted woodpecker complex, Dendrocopos major ( Aves : Picidae )

Phylogeography and species limits in the Green woodpecker complex (Aves: Picidae): multiple Pleistocene refugia and range expansion across Europe and the Near East

Mitochondrial DNA control region diversity in the endangered blue chaffinch, Fringilla teydea

Climate changes and tree phylogeography in the Mediterranean

Phylogeographic history of Grey wolves in Europe

Population subdivision in Europe's great bustard inferred from mitochondrial and nuclear DNA sequence variation

Phylogeography of the Eurasian green woodpecker (Picus viridis)

Genetic variation among Corsican and continental populations of the Eurasian treecreeper (Aves: Certhia familiaris) reveals the existence of a palaeoendemic mitochondrial lineage

The role of western Mediterranean islands in the evolutionary diversification of the Spotted flycatcher Muscicapa striata, a long-distance migratory passerine species

Gene flow and genetic admixture across a secondary contact zone between two divergent lineages of the Eurasian Green Woodpecker Picus viridis

Gene flow and genetic divergence among mainland and insular populations across the south-western range of the Eurasian treecreeper (Certhia familiaris, Aves)

Population structure, diversity, and phylogeography in the near-threatened Eurasian Black Vultures Aegypius monachus (Falconiformes

Europe: insights from microsatellite and mitochondrial DNA variation

A review of phylogeographic analyses of animal taxa from the Aegean and surrounding regions

Geographic mitochondrial DNA variation in the Rock hyrax

Phylogeographical evidence of gene flow among Common Crossbill (Loxia curvirostra, Aves, Fringillidae) populations at the continental level

The genetic legacy of Mother Goose-phylogeographic patterns of lesser snow goose Chen caerulescens caerulescens maternal lineages

R: a language and environment for statistical computing. R Foundation for Statistical Computing

Geographic patterns of mtDNA and Z-linked sequence variation in the Common Chiffchaff and the 'chiffchaff complex

Glaciation, an isolating factor in speciation

Phylogeography of the Rock partridge (Alectoris graeca)

Phylogeography, pre-zygotic isolation and taxonomic status in the endemic Cyprus Wheatear Oenanthe cypriaca

A genetic discontinuity in a continuously distributed species: mitochondrial DNA in the American oyster, Crassostrea virginica

Integrating genetic and stable isotope analyses to infer the population structure of the White-winged Snowfinch Montifringilla nivalis in Western Europe

Genetic introgression: an integral but neglected component of speciation in birds

Comparative phylogeography clarifies the complexity and problems of continental distribution that drove A. R. Wallace to favor islands

Phylogeography and genetic diversity of the Robin (Erithacus rubecula) in the Azores Islands: Evidence of a recent colonisation

Genetic diversity and morphological variation of the Common chaffinch Fringilla coelebs in the Azores

Genetic and morphometric diversity of the goldcrest (Regulus regulus) populations in the Azores

Genetic diversity of the Azores Blackbirds Turdus merula reveals multiple founder events

No genetic differentiation, but less diversity, in the Iberian breeding population of the Eurasian Curlew (Numenius arquata)

Genetic differentiation of an endangered Capercaillie (Tetrao urogallus) population at the Southern edge of the species range

Near panmixia at the distribution-wide scale but evidence of genetic differentiation in a geographically isolated population of the Terek Sandpiper Xenus cinereus

MtDNA genetic diversity and population history of a dwindling raptorial bird, the Red kite (Milvus milvus)

Two sympatric lineages of the Raven Corvus corax jordansi coexist on the Eastern Canary Islands

DNA sequence polymorphism analysis of large data sets

Between two extremes: mitochondrial DNA is neither the panacea nor the nemesis of phylogenetic and taxonomic inference

Neotropical biodiversity: Timing and potential drivers

Colonization history of the high-arctic Pink-footed goose Anser brachyrhynchus

Genetic variability of polish population of the Capercaillie Tetrao urogallus

Population genetics of the Hazel Hen Bonasa bonasia in Poland assessed with noninvasive samples

A European concern? genetic structure and expansion of Golden jackals (Canis aureus) in Europe and the Caucasus

Impacts of forest fragmentation and post-glacial colonization on the distribution of genetic diversity in the Polish population of the Hazel grouse Tetrastes bonasia

Conservation genetics of the Capercaillie in Poland-delineation of conservation units

Conservation genetics of the Black Grouse Tetrao tetrix in Poland -distribution of genetic diversity among the last populations

Rapid polygenic response to secondary contact in a hybrid species

Inference of hazel grouse population structure using multilocus data: a landscape genetic approach

Genetic diversity, differentiation and historical origin of the isolated population of rooks Corvus frugilegus in Iberia

Phylogeography of the Eurasian Willow Tit (Parus montanus) based on DNA sequences of the mitochondrial cytochrome b gene

Integrative taxonomy reveals Europe's rarest songbird species, the Gran Canaria blue chaffinch Fringilla polatzeki

Ancient vs. recent processes as factors shaping the genetic variation of the European wild boar: are the effects of the last glaciation still detectable?

Phylogeography of the House Bunting complex: discordance between species limits and genetic markers

Phylogeography of the European capercaillie (Tetrao urogallus) and its implications for conservation

Capercaillie in the Alps: genetic evidence of metapopulation structure and population decline

From connectivity to isolation: genetic consequences of population fragmentation in capercaillie across Europe

Local differentiation in the presence of gene flow in the citril finch Serinus citrinella

Documenting the advantages and limitations of different classes of molecular markers in a well-established phylogeographic context: Lessons from the Iberian endemic Golden-striped salamander, Chioglossa lusitanica (Caudata: Salamandridae)

A genetic screen of the island races of Wren Troglodytes troglodytes in the Northeast Atlantic

Comparative phylogeography of oceanic archipelagos: hotspots for inferences of evolutionary process

Handbook of western palearctic birds

A dynamic continental moisture gradient drove Amazonian bird diversification

Fine-scale genetic structure in an eastern Alpine black grouse Tetrao tetrix metapopulation

A latitudinal phylogeographic diversity gradient in birds

Species delimitation and biogeography of the gnatcatchers and gnatwrens (Aves: Polioptilidae)

Simulationbased reconstruction of global bird migration over the past 50,000 years

East Asian allopatry and north Eurasian sympatry in Long-tailed Tit lineages despite similar population dynamics during the late Pleistocene

Complete taxon sampling of the avian genus Pica (magpies) reveals ancient relictual populations and synchronous Late-Pleistocene demographic expansion across the Northern Hemisphere

Great journey of Great Tits (Parus major group): Origin, diversification and historical demographics of a broadly distributed bird lineage

Hybridization among Arctic white-headed gulls (Larus spp.) obscures the genetic legacy of the Pleistocene

The Great tit Hap-Map project: a continental-scale analysis of genomic variation in a songbird

Disentangling the complex evolutionary history of the Western Palearctic blue tits (Cyanistes spp. )-phylogenomic analyses suggest radiation by multiple colonization events and subsequent isolation

Comparative phylogenomics, a stepping stone for bird biodiversity studies

Phylogeography and genetic structure of the Canarian common chaffinch (Fringilla coelebs) inferred with mtDNA and microsatellite loci

Genetics and conservation of European brown bears Ursus arctos

Comparative phylogeography and postglacial colonization routes in Europe

Population genomics of two congeneric Palaearctic shorebirds reveals differential impacts of Quaternary climate oscillations across habitats types

Quaternary history of an endemic passerine bird on Corsica Island: glacial refugium and impact of recent forest regression

Population and subspecies differentiation in a high latitude breeding wader, the Common Ringed Plover Charadrius hiaticula

Mitochondrial DNA and microsatellite variation in the Eider duck (Somateria mollissima) indicate stepwise postglacial colonization of Europe and limited current long-distance dispersal

Gene flow in the European coal tit, Periparus ater (Aves: Passeriformes): low among Mediterranean populations but high in a continental contact zone

New data on the distribution and genetic structure of Greek moles of the genus Talpa (Mammalia, Talpidae)

Phylogeography of Martes foina in Greece

The Greater Spotted Eagle Aquila clanga and the lesser spotted eagle A. pomarina: taxonomy, phylogeography and ecology

Genetic structure of Greater Aquila clanga and Lesser Spotted Eagle A. pomarina populations: implications for phylogeography and conservation

The interplay between habitat availability and population differentiation: a case study on genetic and morphological structure in an inland wader (Charadriiformes)

Genetic structure of the Imperial Eagle (Aquila heliaca) population in Slovakia

Pliocene forest dynamics as a primary driver of African bird speciation

River barriers and cryptic biodiversity in an evolutionary museum

Disruptive selection without genome-wide evolution across a migratory divide

Gene flow and genetic drift contribute to high genetic diversity with low phylogeographical structure in European Hoopoes

Phylogeography of the Northern Wheatear Oenanthe oenanthe inferred from genome sequencing data

Can Mitogenomes of the Northern Wheatear (Oenanthe oenanthe) reconstruct its phylogeography and reveal the origin of migrant birds?

Global changes during the last 3 million years: climatic controls and biotic responses

Random interbreeding between cryptic lineages of the Common Raven: evidence for speciation in reverse

Hypervariable-controlregion sequences reveal global population structuring in a longdistance migrant shorebird, the Dunlin (Calidris alpina)

Mitochondrial controlregion sequences in two shorebird species, the Turnstone and the Dunlin, and their utility in population genetic studies

Global mitochondrial DNA phylogeography of Holarctic breeding Dunlins (Calidris alpina)

Conservation genetics and phylogeography of Southern dunlins Calidris alpina schinzii

Taxonomy and genetics: Phylogenetic and phylogeographic relationships

Phylogeny of Falconidae and phylogeography of Peregrine Falcons

Biodiversity on oceanic islands-evolutionary records of past migration events

Phylogeographic relationships of the Lesser Kestrel Falco naumanni in breeding and wintering quarters, inferred from nucleotide sequences of mitochondrial cytochrome b gene

The subspecific origin of the inland breeding colonies of the cormorant Phalacrocorax carbo in Britain

Population genetic structure in the paddyfield warbler

Exonic versus intronic SNPs: contrasting roles in revealing the population genetic differentiation of a widespread bird species

Comparative phylogeography in North American birds

Phylogeographic studies of North American birds

Mitochondrial DNA under siege in avian phylogeography

Phylogeographic patterns in the Great spotted woodpecker Dendrocopos major across Eurasia

Holarctic phylogeography and species limits of three-toed woodpeckers

Recent evolutionary history of the Bluethroat (Luscinia svecica) across Eurasia

The tempo of avian diversification during the Quaternary

Selective neutrality of mitochondrial ND2 sequences, phylogeography and species limits in Sitta europaea

Mitochondrial phylogeographies of five widespread Eurasian bird species

Type specimens matter: new insights on the systematics, taxonomy and nomenclature of the subalpine warbler (Sylvia cantillans) complex

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