Relations between the Yellowhammer (<Emphasis Type="Italic">Emberiza citrinella</Emphasis>) and the Pine Bunting (<Emphasis Type="Italic">Emberiza leucocephalos</Emphasis>) in the Forested Steppe of the Trans-Urals

We studied the phenotypic composition of the populations and variability of songs in two bunting species in three localities on the western border of the sympatry zone: in the southern part of Tyumen’ oblast and in the center and southern of Kurgan oblast. Over the last several decades, the zone of contact of the studied species has expanded significantly. The pine bunting started breeding regularly in the area at the end of the 20th century, and at present it is considered a common species comparable in abundance to the yellowhammer. The share of phenotypic hybrids varies from 25 to 50% reaching its maximum at the boundary of the pine bunting’s nesting range. East of this boundary, the hybridization level is reduced, this being seen in a sharp decrease in the share of “leucocephala hybrids.” An analysis of the phenotypic variability of the hybrids shows that they can be divided into two groups similar in coloration to the parental species. The study results let us presume that the hybridization is limited and hybrids return mostly to backcrossing with the parental species. This presumption also finds support in an analysis of the song structure: the yellowhammer and the pine bunting have songs of different, easily distinguishable dialects.     

Mitochondrial introgression and replacement between yellowhammers (Emberiza citrinella) and pine buntings (Emberiza leucocephalos) (Aves: Passeriformes)

In studies of phylogeography and taxonomy, strong emphasis is usually placed on the study of mitochondrial (mt)DNA. In the present study, we present a remarkable case in which highly phenotypically divergent species have almost no divergence in mtDNA. Yellowhammers ( Emberiza citrinella Linnaeus) and pine buntings ( Emberiza leucocephalos S. G. Gmelin) differ noticeably in appearance and song but hybridize in some areas of contact. They share a variety of closely-related mtDNA haplotypes, with little divergence in frequencies, indicating a mitochondrial divergence time sometime during or after the last major glacial period. By contrast, nuclear DNA (amplified fragment length polymorphism markers and CHD1Z gene sequences) differs more strongly between the species, and these differences can be used to identify intermediate genetic signatures of hybrids. The combined amount of mitochondrial diversity within yellowhammers and pine buntings is very low compared to other Emberiza species pairs, whereas the level of variation at the nuclear gene CHD1Z is comparable to that within other species pairs. Although it is difficult to completely reject the possibility that the two species split extremely recently and experienced rapid nuclear and phenotypic differentiation, we argue that the evidence better supports another possibility: the two species are older and mtDNA has recently introgressed between them, most likely as a result of a selective sweep. Mismatches between mitochondrial and nuclear phylogeographic patterns may occur more commonly than previously considered, and could have important implications for the fields of phylogeography and taxonomy.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 98 , 422–438.     

Ten new microsatellite loci for the yellowhammer (Emberiza citrinella) and their cross‐species applicability among related taxa

We describe isolation and characterization of the first microsatellite loci specifically developed for a very common European passerine bird, the yellowhammer Emberiza citrinella. Nine out of our 10 loci are polymorphic within the species E. citrinella. Number of alleles ranged from two to 21 per locus and observed heterozygosity between 0.20 and 0.91. Four primer pairs also yielded reproducible results in other species of Emberizidae. These loci comprise a set of molecular markers for various applications, from moderately polymorphic loci suitable for population studies to highly polymorphic loci for pedigree analysis in Emberizidae.     

The phylogenetic affinities of the Socotra Bunting Emberiza socotrana

The monophyly of the African ‘brown bunting’ complex was corroborated by a recent molecular study. However, the little-known Socotran endemic Emberiza socotrana, which is morphologically similar to the other taxa in this complex, was not included. Here we present a hypothesis of the phylogenetic relationships of the Socotra Bunting based on one mitochondrial gene and one nuclear intron. We found the Socotra Bunting to be deeply nested within the African ‘brown bunting’ complex and, although morphologically most similar to E. capensis, it proved to be more closely related to the E. striolata/sahari and E. tahapisi/goslingi species groups. The phylogenetic uniqueness of the Socotra Bunting underpins once more the evolutionary importance of the Endemic Bird Area of Socotra, which is often considered the ‘Galápagos of the Indian Ocean’.     

Absence of Mate Guarding in the Yellowhammer (Emberiza citrinella)?

The mate guarding behaviour of male yellowhammer (Emberiza citrinella) was studied with special reference to the effects of age, body size (tarsus length) and coloration of males. Measurements of intra-pair distance do at the most provide evidence for relatively lax mate guarding. On the other hand, patterns of male song activity and inter-male aggression were more in agreement with the predictions of the mate guarding hypothesis. The reasons for the comparatively low mate guarding intensity in the yellowhammer may be that males do not need to guard their mates intensely. Age differences were found in song and aggressive activity, older males singing and fighting the most. Size had no effect on guarding behaviour. Coloration was correlated with inter-male aggressiveness and conflict initiation propensity. Less colourful males fought the most in the pre-fertile period of their mates, whereas colourful and old males fought the most during the fertile period. This suggests that coloration may be an indicator of individual fighting and guarding ability.     

The Causes and Evolutionary Consequences of Mixed Singing in Two Hybridizing Songbird Species (Luscinia spp.)

Bird song plays an important role in the establishment and maintenance of prezygotic reproductive barriers. When two closely related species come into secondary contact, song convergence caused by acquisition of heterospecific songs into the birds’ repertoires is often observed. The proximate mechanisms responsible for such mixed singing, and its effect on the speciation process, are poorly understood. We used a combination of genetic and bioacoustic analyses to test whether mixed singing observed in the secondary contact zone of two passerine birds, the Thrush Nightingale (Luscinia luscinia) and the Common Nightingale (L. megarhynchos), is caused by introgressive hybridization. We analysed song recordings of both species from allopatric and sympatric populations together with genotype data from one mitochondrial and seven nuclear loci. Semi-automated comparisons of our recordings with an extensive catalogue of Common Nightingale song types confirmed that most of the analysed sympatric Thrush Nightingale males were ‘mixed singers’ that use heterospecific song types in their repertoires. None of these ‘mixed singers’ possessed any alleles introgressed from the Common Nightingale, suggesting that they were not backcross hybrids. We also analysed songs of five individuals with intermediate phenotype, which were identified as F₁ hybrids between the Thrush Nightingale female and the Common Nightingale male by genetic analysis. Songs of three of these hybrids corresponded to the paternal species (Common Nightingale) but the remaining two sung a mixed song. Our results suggest that although hybridization might increase the tendency for learning songs from both parental species, interspecific cultural transmission is the major proximate mechanism explaining the occurrence of mixed singers among the sympatric Thrush Nightingales. We also provide evidence that mixed singing does not substantially increase the rate of interspecific hybridization and discuss the possible adaptive value of this phenomenon in nightingales.     

Neighbour-stranger song discrimination in territorial ortolan bunting Emberiza hortulana males

Neighbour-stranger discrimination has been demonstrated in many species, but the mechanisms employed in discrimination vary. We tested whether an oscine bird with small repertoire size, the ortolan bunting Emberiza hortulana , discriminated between songs of neighbours and strangers. We performed playback experiments to measure response of males to a repeated single example of a single song type derived from a repertoire of a neighbour or stranger. Thirteen males were tested twice each, and in both cases songs were broadcast from the territory boundary shared by the subject male and the neighbour. Subjects responded more aggressively to songs of strangers than neighbours, i.e. they approached the loudspeaker faster and came closer and did more flights during the playback of stranger song. We found no significant differences in vocal response between treatments. We conclude that ortolan bunting can discriminate between songs of neighbours and strangers. This study provides experimental evidence for ortolan buntings in neighbour-stranger discrimination. It also demonstrates that a single example of song is enough to discriminate between neighbours and strangers. We discuss which song characteristics are the possible acoustic basis for discrimination in the studied species.     

Phonological-dependent territorial responses in yellowhammers (Emberiza citrinella)

In songbirds, males sing to attract potential mate and to defend their territory. Information about the sender such as its sex, its motivational state, its strength or identity can be encoded through subtle modifications in songs. In this study, we investigated whether territorial responses of yellowhammer males may be affected by modifications of song syntax and phonology. Yellowhammer song is mainly composed of three elements among which the last one is a long and low frequency note that is supposed to be the main component used by males to assess their potential rival. We carried out field experiments and played back either fully natural songs or partly natural and partly artificial songs to test this hypothesis. We identified that phonology rather than syntax modifications altered territorial responses. Our results also suggest that the phonology of the first song element plays a critical role in driving territorial responses.     

芦鹀种群中的文化、遗传和形态进化的同时比较

我们比较了芦 (Emberizaschoeniclus)两个亚种组 ,即北部的薄喙亚种组和南部的厚喙亚种组的 10个种群中的文化、遗传和形态变异。使用了四个不同的变异标记物 ,其中两个用来测量文化分化 ,一个用来测量遗传分化 ,即微卫星等位基因的频次 ,一个用来测量种群的形态分化 ,即喙的高度。将遗传分化作为进化时间的尺度 ,我们计算了亚种组间和组内分化指标与所估计的进化率之间的相关性 ,发现只有文化定量指标和遗传分化与种群的形态分化相关 ,而两个文化分化指标之间没有关系 ,文化分化与遗传分化之间也没有关系。使用文化 -定量分化指标 ,发现亚种组间的文化进化率高于亚种内的文化进化率 ,提示鸣唱在防止杂交方面只有微弱的、也许是次要的作用。鸣唱定量特征的变异与微卫星频次相同 ,实际上在自然界中更可能是遗传决定的 ,这可以解释由于分析两个文化变异指标所得出的结果的不一致性。鸣唱的声学特性可能由于栖息地的差异或形态上的限制而发生了演变 ,而文化传播单位 (Meme)的特性可能由于学习鸣唱和文化传播而受到了影响     

Variability of response of the corn bunting,Emberiza calandra,to songs of different dialects

Experiments on the corn bunting were carried out in two localities of different dialects. In the center of the territory of each bird, we played two natural songs: either one local song and one song of the foreign dialect or two local songs coming from a neighbor and from a non-neighboring individual. The following results were obtained: (1) The behavioral responses are always more intense to the local song than to the song of a foreign dialect. Thus, the behavior of the corn bunting is similar to that of species with dialects studied up to now. (2) Eighty percent of the birds tested with the song of the foreign dialect react weakly or not at all. This peculiarity, which is specific to the corn bunting, suggests limited possibilities of generalization in this species. (3) The behavioral responses to the songs of a neighbor and of a non-neighboring individual of the same locality, are aggressive and of the same intensity. This means that the song of a neighbor, emitted from a different place than usual, is perceived by the bird as a threat to its territory.     

Characterization of a contemporaneous hybrid zone between two darter species (Etheostoma bison and E. caeruleum) in the Buffalo River System

Hybrid zones have long intrigued evolutionary biologists and provide a natural laboratory to explore the evolution of reproductive isolation (speciation). Molecular characterization of hybrid zone dynamics can provide insight into the strength of reproductive isolation as well as the underlying evolutionary processes shaping gene flow. Approximately one-third of darter species naturally hybridize making this species-rich North American freshwater teleost fish clade an ideal system to investigate the extent and direction of hybridization. The objective of this study was to use diagnostic microsatellite markers to calculate genetic hybrid index scores of two syntopic, but distantly related darter species, Etheostoma bison and Etheostoma caeruleum. A combination of hybrid index scores, assignment tests, and mitochondrial haplotype profiles uncovered mixed ancestry in approximately 6 % of sampled adult individuals, supporting contemporaneous hybridization that was previously undocumented in E. bison. Moreover, hybrids were not limited to the F₁ generation, but encompassed the entire suite of hybrid categories (F₁, F₂ and backcross hybrids). The low number of hybrids assigned to each hybrid category represents a bimodal hybrid zone, suggesting reproductive isolation is strong (but incomplete) and also advocates for the ability of hybrids to produce second-generation hybrids and backcross into both parental species, mediating introgression across species boundaries. To this end, cytonuclear profiles of the sampled parental species and hybrids were consistent with bidirectional gene flow, although there was an overall trend of asymmetric hybridization between E. caeruleum females and E. bison males. The spatiotemporal variation in hybridization rates and resulting cytonuclear patterns expanded on in this study provide a comparative genetic framework on which future studies can begin to elucidate the underlying processes that not only generate a mosaic hybrid zone, but maintain the distinctness of species in the face of gene flow.     

Song repertoires and seasonal song in the yellowhammer, Emberiza citrinella

Songs were recorded from male yellowhammers, Emberiza citrinella, in England and West Germany. Sonagraphic analysis revealed three major types of song structure in both populations. Most males had a repertoire of two distinct song types, and sharing between individuals was extremely rare. Most song is produced late in the breeding season, and playback experiments confirmed that it is correlated with an increase in territorial aggression at this time. Some speculations are advanced concerning the origins and functions of song repertoires in the yellowhammer.     

Ameiurus melas (black bullhead): morphological characteristics of new introduced species and its comparison with Ameiurus nebulosus (brown bullhead)

In the present study we examined and compared external morphology as well as osteological characters of two species of the genus Ameiurus (Teleostei, Ictaluridae): the black bullhead (Ameiurus melas) and brown bullhead (Ameiurus nebulosus), two catfish species that are invasive to Europe. In total 83 (53 and 30) individuals were captured in the Czech Republic and the Slovak Republic and further analysed. For genetic screening of both Ameiurus species were chosen three DNA regions: part of nuclear Recombination activating gene 1 (RAG-1), mitochondrial gene for cytochrome b (cyt b) and mitochondrial sequence which includes 12S and 16S ribosomal RNA genes. The results presented in this paper concern specific osteological characteristics (original scheme of pectoral spine and pectoral girdle) used for the determination purposes and also verification that mathematical multivariate methods for external morphology analysis can be used for the determination of Ameiurus species. The summary of 80 out of 83 fish (96.4 %) was correctly classified using the discriminant analysis.     

Evolution of arid zone birds in Australia: leapfrog distribution patterns and mesic-arid connections in quail-thrush (Cinclosoma, Cinclosomatidae)

The quail-thrush, Cinclosoma, include between five and seven species distributed broadly across arid and semi-arid inland Australia, mesic forests of south-eastern Australia and New Guinea. It has been suggested that the arid zone species of quail-thrush arose from forest ancestors as Australia changed from a warm wet climate to a cooler drier climate since the late-Miocene. We generated multilocus (mitochondrial ND2 and eight nuclear loci) gene and species trees with complete taxon sampling of Cinclosoma to investigate evolutionary relationships and species status of some taxa. Topologies reconstructed in congruent, highly-resolved gene trees and species trees that supported the recognition of seven species. Ancestral state reconstruction and divergence time estimates suggest that arid-adapted taxa radiated in parallel with a drying climate and changing habitat. A ‘leapfrog’ distribution in phenotypes of arid zone taxa was likely a result of ancestral retention of inconspicuous (or camouflaged) plumage patterns. A specimen-based report from 1968 of hybridization between non-sister taxa Cinclosoma castanotum and Cinclosoma marginatum was verified using molecular analysis on specimens collected at the same locality 40 years later. We discuss the implications of hybridization to the evolution of this species group.     

Genetic analysis of sable (<Emphasis Type="Italic">Martes zibellina</Emphasis>) and pine marten (<Emphasis Type="Italic">M. martes</Emphasis>) populations in sympatric part of distribution area in the northern Urals

Analysis of nucleotide sequences of the mitochondrial DNA (mtDNA) control region (495 bp) of sables (Martes zibellina) and pine martens (M. martes) from allopatric parts of the species ranges has shown a considerable interspecific genetic distance (>3%). In sympatric populations of these species in the northern Urals, differences between two species-specific mtDNA lineages are still large; however, classification of each individual nucleotide sequence with one of the two lineages is not correlated with whether the given animal is phenotypically a sable, a pine marten, or a potential hybrid (the so-called “kidas”). This indicates a high degree of reciprocal introgression of the sable and pine marten mtDNA in the northern Urals and suggests that their interspecific hybridization is common in the sympatric zone.     

Genetic studies in the recently divergent Eligmodontia puerulus and E. moreni (Rodentia,Cricetidae, Sigmodontinae) from Puna and Monte deserts of South America

Eligmodontia is a genus of phyllotine rodents adapted to arid environments with seven recognized species. The sister species E. puerulus and E. moreni are distributed in the adjacent highland Puna and lowland Monte deserts respectively, and show remarkable morphological and chromosomal differences. However, analyses of the cytochrome b gene showed important variability, without reciprocal monophyly between them. In order to study the evolutionary processes involved in the diversification of both taxa, we analyzed 1161 bp of the mitochondrial control region and flanking sequences (N = 60), as well as 759 bp of the first exon of the nuclear gene IRBP (N = 14). Individuals of both species from Jujuy, Catamarca and Mendoza Provinces of Argentina were previously karyotyped. Results showed that the mitochondrial sequences present high haplotype and nucleotide diversity within all population, and no haplotype was shared between both species. F_ST indicated that populations of both species were moderately structured. The network was constituted by two major haplogroups, one composed by E. puerulus samples from Jujuy, and the other composed of sequences of all studied populations. The Bayesian analysis showed three clusters, matching the network. Phylogenetic analysis recovered two clades with high support, in coincidence with the network groups. There was only one close join between sequences of both species, corresponding to samples from Catamarca. Thus, mitochondrial data suggested hybridization between both species in Catamarca, with asymmetric introgression. The IRBP showed low variability and, in the phylogenetic analysis, the sequences of E. puerulus form a monophyletic group with intermediate support, whereas those of E. moreni collapse into a basal polytomy. Our data indicated a recent divergence and absence of introgression in the nuclear genomes. The results at the population level with mitochondrial sequences, together with integrative taxonomy at the species level in a biogeographic context, suggest that climatic and geologic changes could have had an important role in the determination of genetic variability patterns observed in these rodents.     

Genetic Evidence of Hybridization between the Endangered Native Species Iguana delicatissima and the Invasive Iguana iguana (Reptilia,Iguanidae) in the Lesser Antilles: Management Implications

The worldwide increase of hybridization in different groups is thought to have become more important with the loss of isolating barriers and the introduction of invasive species. This phenomenon could result in the extinction of endemic species. This study aims at investigating the hybridization dynamics between the endemic and threatened Lesser Antillean iguana (Iguana delicatissima) and the invasive common green iguana (Iguana iguana) in the Lesser Antilles, as well as assessing the impact of interspecific hybridization on the decline of I. delicatissima. 59 I. delicatissima (5 localities), 47 I. iguana (12 localities) and 27 hybrids (5 localities), who were all identified based on morphological characters, have been genotyped at 15 microsatellites markers. We also sequenced hybrids using ND4 mitochondrial loci to further investigate mitochondrial introgression. The genetic clustering of species and hybrid genetic assignment were performed using a comparative approach, through the implementation of a Discriminant Analysis of Principal Component (DAPC) based on statistics, as well as genetic clustering approaches based on the genetic models of several populations (Structure, NewHybrids and HIest), in order to get full characterization of hybridization patterns and introgression dynamics across the islands. The iguanas identified as hybrids in the wild, thanks to morphological analysis, were all genetically F1, F2, or backcrosses. A high proportion of individuals were also the result of a longer-term admixture. The absence of reproductive barriers between species leads to hybridization when species are in contact. Yet morphological and behavioral differences between species could explain why males I. iguana may dominate I. delicatissima, thus resulting in short-term species displacement and extinction by hybridization and recurrent introgression from I. iguana toward I. delicatissima. As a consequence, I. delicatissima gets eliminated through introgression, as observed in recent population history over several islands. These results have profound implications for species management of the endangered I. delicatissima and practical conservation recommendations are being discussed in the light of these findings.     

Biogeographical patterns of variation in Western European populations of the great green bush-cricket (Tettigonia viridissima; Orthoptera Tettigoniidae)

The great green bush-cricket, Tettigonia viridissima, is at the northern limits of its geographic distribution in the UK and has suffered a significant reduction in population abundance and range over the last 50 years, now being largely confined to the southern UK. This study uses five characters to investigate differences between UK and mainland Western European populations, questioning the possibility that UK populations might represent a distinct species or sub-species and thus deserve special conservation status. Males of T. viridissima from UK, France and Spain were compared using morphometry, flight, male calling song and analysis of mitochondrial DNA sequences. Results suggest morphological differences between UK population samples and continental Europe with the UK samples showing shorter wing length relative to body length than populations in continental Europe. Morphological differences between French and Spanish populations followed a size cline related to latitude with more southerly populations showing larger features. Analysis of male flight distances and calling song showed significant differences with increased flight distance and minimum stridulation following a southerly latitude which correlates with wing length results. No differences consistent with geographical distributions were found in mitochondrial DNA COI sequence alignments. Morphological differences could be due to developmental differences linked to differing temperature clines or a non-adaptive difference caused by the colonisation history of the species. The consequences of morphometric variation on flight function and stridulation in bush-crickets are discussed.     

Molecular characterization and distribution of Haemoproteus minutus (Haemosporida,Haemoproteidae): A pathogenic avian parasite

Recently, the lineage hTURDUS2 of Haemoproteus minutus (Haemosporida, Haemoproteidae) was reported to cause mortality in captive parrots. This parasite lineage is widespread and prevalent in the blackbird Turdus merula throughout its entire distribution range. Species identity of other closely related lineages recently reported in dead parrots remains unclear, but will be important to determine for a better understanding of the epidemiology of haemoproteosis. Using polymerase chain reaction (PCR)-based and microscopic methods, we analyzed 265 blood samples collected from 52 species of wild birds in Eurasia (23 samples from Kamchatka Peninsula, 73 from Sakhalin Island, 150 from Ekaterinburg and 19 from Irkutsk regions of Russia). Single infections of the lineages hTURDUS2 (hosts are redwing Turdus iliacus and fieldfare Turdus pilaris), hTUPHI1 (song thrush Turdus philomelos) and hTUCHR01 (fieldfare, redwing, song thrush and brown-headed thrush Turdus chysolaus) were detected. We identified species of these haemoproteids based on morphology of their blood stages and conclude that these lineages belong to H. minutus, a widespread parasite of different species of thrushes (genus Turdus), which serve as reservoir hosts of this haemoproteid infection. Phylogenetic analysis shows that the lineages hTURDUS2, hTUCHR01 and hTUPHI1 of H. minutus are closely related to Haemoproteus pallidus (lineages hPFC1 and hCOLL2), Haemoproteus pallidulus (hSYAT03), and Haemoproteus sp. (hMEUND3); genetic distance among their mitochondrial cytochrome b (cyt b) lineages is small (< 1% or < 4 nucleotides). All these blood parasites are different in many morphological characters, but are similar due to one feature, which is the pale staining of their macrogametocytes' cytoplasm with Giemsa. Because of the recent publications about mortality caused by the lineages hTUPHI1 and hTURDUS2 of H. minutus in captive parrots in Europe, H. minutus and the closely related H. pallidus and H. pallidulus are worth more attention as these are possible agents of haemoproteosis in exotic birds. The present study provides barcodes for molecular detection of different lineages of H. minutus, and extends information about the distribution of this blood parasite.