Signs Of Introgression Research Articles

No evidence for hybridization in Calanus: Reply to the comment by Parent et al.

No evidence for hybridization in <i>Calanus</i>: Reply to the comment by Parent et al.

Identification and taxonomy of Betula (Betulaceae) in Great Britain and Ireland

Floras and identification guides typically do not list the full range of identification features that discriminate between Betula pendula Roth and B. pubescens Ehrh., and some accounts contain errors. Discriminatory identification features are described and illustrated. Introgression from the diploid, B. pendula into B. pubescens is widespread. It also occurs from B. nana L. into B. pubescens, but obviously introgressed examples of the latter are probably rare. Betula pubescens presents the greatest unresolved identification difficulties. Trees identified as B. pubescens subsp. celtiberica (Rothm. &amp; Vasc.) Rivas Mart., particularly in Wales, may be part of the variation within British B. pubescens, due to introgression from B. pendula. The most widespread of the small-leaved forms of B. pubescens is correctly named var. fragrans Ashburner &amp; McAll. Several misapplied names have been given to this taxon, most recently subsp. tortuosa (Ledeb.) Nyman, which does not occur in Europe. Not all small-leaved B. pubescens are var. fragrans; some examples show clear signs of introgression from B. nana, and may be referable to the northern var. pumila (L.) Govaerts.

Western Kingbird (Tyrannus verticalis) with bill deformity in Memphis, Tennessee, USA

Bill deformities have been documented in many avian species across the globe and can be caused by environmental or genetic conditions that may also reflect ecosystem health. We describe the first case of bill deformity in the genus Tyrannus, in a young male Western Kingbird (Tyrannus verticalis) that fledged from a nest in an industrial park in Memphis, Tennessee, USA. The upper mandible of the bill was curved to the left and below the plane of the normal lower mandible making it unlikely that the individual would be able to forage normally and survive to adulthood. Genetic testing for evidence of hybridization with Scissor-tailed Flycatchers (T. forficatus) showed no sign of introgression, and it is unclear what caused the deformity.

Genomic consequences of human-mediated translocations in margin populations of an endangered amphibian.

Due to their isolated and often fragmented nature, range margin populations are especially vulnerable to rapid environmental change. To maintain genetic diversity and adaptive potential, gene flow from disjunct populations might therefore be crucial to their survival. Translocations are often proposed as a mitigation strategy to increase genetic diversity in threatened populations. However, this also includes the risk of losing locally adapted alleles through genetic swamping. Human‐mediated translocations of southern lineage specimens into northern German populations of the endangered European fire‐bellied toad (Bombina bombina) provide an unexpected experimental set‐up to test the genetic consequences of an intraspecific introgression from central population individuals into populations at the species range margin. Here, we utilize complete mitochondrial genomes and transcriptome nuclear data to reveal the full genetic extent of this translocation and the consequences it may have for these populations. We uncover signs of introgression in four out of the five northern populations investigated, including a number of introgressed alleles ubiquitous in all recipient populations, suggesting a possible adaptive advantage. Introgressed alleles dominate at the MTCH2 locus, associated with obesity/fat tissue in humans, and the DSP locus, essential for the proper development of epidermal skin in amphibians. Furthermore, we found loci where local alleles were retained in the introgressed populations, suggesting their relevance for local adaptation. Finally, comparisons of genetic diversity between introgressed and nonintrogressed northern German populations revealed an increase in genetic diversity in all German individuals belonging to introgressed populations, supporting the idea of a beneficial transfer of genetic variation from Austria into North Germany.

Absence of genetic introgression between Elymus ciliaris and E. pendulinus (Triticeae: Poaceae) as shown by endosperm protein SDS-electrophoresis in connection with hypotheses of E. amurensis origin

The StY-genome group of Elymus species is of special interest, most of its species ranges extending to Russia from southern frontier territories, mainly from China. The ranges of Elymus pendulinus , E. ciliaris and E. amurensis within Russia overlap in the southern part of the Russian Far East only. Elymus ciliaris is considered by Russian taxonomists to be phylogenetically close to E. pendulinus, while hybridization of these species gave rise to the independent species E. amurensis. Moreover, in China, E. amurensis is recognized as a variety of E. ciliaris. Endosperm protein polymorphism was studied by SDS-electrophoresis for the purpose to reveal species specificity in E. pendulinus, E. ciliaris, and E. amurensis from a number of localities in the Primorskii Krai. Accessions of species from places of their joint occurrence were analyzed to detect identical polypeptide components which could have appeared due to genetic introgression. Nevertheless, both electrophoretic images visual analyses and construction the dendrograms of populations with various similarity coefficients revealed a high species specificity of E. ciliaris и E. pendulinus but no signs of introgression in spite of the fact that the two species often grow in common ecotopes and even form sterile hybrids. No indications of the origin of E. amurensis from the highly distinct species E. ciliaris and E. pendulinus were found either. The necessity of biosystematic and experimental methods for confirmation of the origin and taxonomic rank of new and many recognized species in the genus Elymus is shown.

Phylogeography of the Temminck’s Stint (Calidris temminckii): historical vicariance but little present genetic structure in a regionally endangered Palearctic wader

AbstractAim We study the population differentiation and phylogeography of the Temminck’s Stint (Calidris temminckii). Specifically, we seek signs of past and present population size changes and dispersal events and evaluate management and conservation unit status of the populations. We also study the possibility of introgression as the origin of two mitochondrial DNA (mtDNA) lineages found and estimate the divergence time of the lineages.Location Northern Eurasia.Methods We analysed 583 bp of mtDNA control region domains I and II and 11 microsatellite loci from 13 localities throughout the breeding range. In addition, we used mitochondrial cytochrome c oxidase subunit I (COI), a barcoding gene, to search for signs of introgression.Results More population differentiation was found from microsatellites than from mtDNA, although differentiation was weak in both markers. Signs of past population growth were observed, in addition to more recent decline in some areas. Both control region and COI sequences revealed two maternal lineages coexisting in Fennoscandia and in north‐west Siberia. No signs of introgression were detected. Lineage divergence time was estimated to have occurred during the glacial periods of Pleistocene.Main conclusions Slight differences in mtDNA and microsatellite differentiation and diversity may reflect different features – such as the mutation rate and effective population size – of the markers used, or female‐biased dispersal pattern and high male site‐fidelity of the species. The coexistence of the two mitochondrial lineages is most likely a consequence of post‐glacial mixing of two refugial Pleistocene populations. Based on genetic information alone, global conservation concerns are not imminent. However, fast decline of a marginal Bothnian Bay population and the smallness and remoteness of a Central Yakutian population warrant conservation actions.

Hybridization and introgression across different ploidy levels in the Neotropical orchidsEpidendrum fulgensandE. puniceoluteum(Orchidaceae)

The hypothesis of gene flow between species with large differences in chromosome numbers has rarely been tested in the wild, mainly because species of different ploidy are commonly assumed to be reproductively isolated from each other because of instantaneous and strong postzygotic barriers. In this study, a broad-scale survey of molecular variation was carried out between two orchid species with different ploidy levels: Epidendrum fulgens (2n = 2x = 24 chromosomes) and Epidendrum puniceoluteum (2n = 4x = 52 chromosomes). To test the strength of their reproductive barriers, we investigated the distribution of genetic variation in sympatric and allopatric populations of these two species and conducted crossing experiments. Nuclear and plastid microsatellite loci were used to genotype 463 individuals from eight populations across the geographical range of both species along the Brazilian coastal plain. All six sympatric populations analysed presented hybrid zones, indicating that hybridization between E. fulgens and E. puniceoluteum is a common phenomenon. Bayesian assignment analysis detected the presence of F(1) and F(2) individuals and also signs of introgression, demonstrating a high potential for interspecific gene flow. Introgression occurs preferentially from E. fulgens to E. puniceoluteum. Pure parental individuals of both species display strong genotype-habitat associations, indicating that environment-dependent selection could be acting in all hybrid zones. This study suggests that hybridization and introgression are evolutionary processes playing a role in the diversification of Epidendrum and indicates the importance of investigations of hybrid zones in understanding reproductive barriers and speciation processes in Neotropical orchid species.

The Bosmina kessleri-like morphotype of Eubosmina in Lake Muskoka, Ontario, Canada, as putative interspecific hybrids

Like Bythotrephes, Bosmina (Eubosmina) coregoni coregoni Baird appears to have invaded North America from Eurasia, since there are no records from before 1965. All previously known North American populations have a well-rounded ventrocaudal corner of the carapace, suggesting that the founding race is one of the rotunda type, the most common eubosminid in European lakes. In Lake Muskoka, immediately to the east of Georgian Bay, Ontario, eubosminids were found that shared features of B. (E.) longicornis kessleri Ulianine. In contrast to other North America populations of B.(E. )c. coregoni, these specimens have a short, broadly based mucro. Morphological features suggest that these are interspecific F1-hybrids between B. (E.) longispina Leydig and B. (E.) coregoni, without any signs of introgression.