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160 results for “introgressive hybridization”
Data from: Invasion facilitates hybridization with introgression in the Rattus rattus species complex
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Data from: Introgression across hybrid zones is not mediated by Large X-effects in green toads with undifferentiated sex chromosomes
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Data from: Asymmetric introgression in a spotted salamander hybrid zone
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Data from: Widespread hybridization and bidirectional introgression in sympatric species of coral reef fish
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Data from: Introgressive hybridization and natural selection in Darwin's finches
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Maintaining genetic integrity with high promiscuity: Frequent hybridization with low introgression in multiple hybrid zones of Melocactus(Cactaceae)
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Data from: Spontaneous hybridization and introgression between walleye (Sander vitreus) and sauger (S. canadensis) in two large reservoirs: insights from genotyping-by-sequencing
<p>Anthropogenic activities may facilitate undesirable hybridization and genomic introgression between fish species. Walleye (<i>Sander vitreus</i>) and sauger (<i>Sander canadensis</i>) are economically valuable freshwater species that can spontaneously hybridize in areas of sympatry. Levels of genomic introgression between walleye and sauger may be increased by modifications to waterbodies (e.g., reservoir development) and inadvertent propagation of hybrids in stocking programs. We used genotyping by sequencing (GBS) to examine 217 fish from two large reservoirs with mixed populations of walleye and sauger in Saskatchewan, Canada (Lake Diefenbaker, Tobin Lake). Analyses with 20,038 (r90) and 478 (r100) SNPs clearly resolved walleye and sauger, and classified hybrids with high confidence. F<sub>1</sub>, F<sub>2</sub>, and multi-generation hybrids were detected in Lake Diefenbaker, indicating potentially high levels of genomic introgression. In contrast, only F<sub>1</sub> hybrids were detected in Tobin Lake. Field classification of fish was unreliable; 7% of fish were misidentified based on broad species categories. Important for activities such as brood stock selection, 12/173 (7%) fish field-identified as pure walleye, and 1/24 (4%) identified as pure sauger were actually hybrids. In addition, 2/15 (13%) field-identified hybrids were actually pure walleye or sauger. We conclude that hybridization and introgression are occurring in Saskatchewan reservoirs, and that caution is warranted when using these populations in stocking programs. GBS offers a powerful and flexible tool for examining hybridization without pre-identification of informative loci, eliminating some of the key challenges associated with other marker types.</p>
Data from: Differential introgression and the maintenance of species boundaries in an advanced generation avian hybrid zone
Background: Evolutionary processes, including selection and differential fitness, shape the introgression of genetic material across a hybrid zone, resulting in the exchange of some genes but not others. Differential introgression of molecular or phenotypic markers can thus provide insight into factors contributing to reproductive isolation. We characterized patterns of genetic variation across a hybrid zone between two tidal marsh birds, Saltmarsh (Ammodramus caudacutus) and Nelson's (A. nelsoni) sparrows (n = 286), and compared patterns of introgression among multiple genetic markers and phenotypic traits. Results: Geographic and genomic cline analyses revealed variable patterns of introgression among marker types. Most markers exhibited gradual clines and indicated that introgression exceeds the spatial extent of the previously documented hybrid zone. We found steeper clines, indicating strong selection for loci associated with traits related to tidal marsh adaptations, including for a marker linked to a gene region associated with metabolic functions, including an osmotic regulatory pathway, as well as for a marker related to melanin-based pigmentation, supporting an adaptive role of darker plumage (salt marsh melanism) in tidal marshes. Narrow clines at mitochondrial and sex-linked markers also offer support for Haldane's rule. We detected patterns of asymmetrical introgression toward A. caudacutus, which may be driven by differences in mating strategy or differences in population density between the two species. Conclusions: Our findings offer insight into the dynamics of a hybrid zone traversing a unique environmental gradient and provide evidence for a role of ecological divergence in the maintenance of pure species boundaries despite ongoing gene flow.
Data from: Parallel plumage color evolution and introgressive hybridization in wheatears
Genetic and phenotypic mosaics, in which various phenotypes and different genomic regions show discordant patterns of species or population divergence, offer unique opportunities to study the role of ancestral and introgressed genetic variation in phenotypic evolution. Here, we investigated the evolution of discordant phenotypic and genetic divergence in a monophyletic clade of four songbird taxa – pied wheatear (O. pleschanka), Cyprus wheatear (O. cypriaca), and western and eastern subspecies of black-eared wheatear (O. h. hispanica and O. h. melanoleuca). Phenotypically, black back and neck-sides distinguish pied and Cyprus wheatears from the white-backed/necked black-eared wheatears. Meanwhile, mitochondrial variation only distinguishes western black-eared wheatear. In the absence of nuclear genetic data, and given frequent hybridization among eastern black-eared and pied wheatear, it remains unclear whether introgression is responsible for discordance between mitochondrial divergence patterns and phenotypic similarities, or whether plumage coloration evolved in parallel. Multispecies coalescent analyses of about 20'000 SNPs obtained from RAD data mapped to a draft genome assembly resolve the species tree, provide evidence for the parallel evolution of color phenotypes, and establish western and eastern black-eared wheatears as independent taxa that should be recognized as full species. The presence of the entire admixture spectrum in the Iranian hybrid zone and the detection of footprints of introgression from pied into eastern black-eared wheatear beyond the hybrid zone despite strong geographic structure of ancestry proportions furthermore suggest a potential role for introgression in parallel plumage color evolution. Our results support the importance of standing heterospecific and/or ancestral variation in phenotypic evolution.
Restricted X chromosome introgression and support for Haldane's rule in hybridizing damselflies
<p>Contemporary hybrid zones act as natural laboratories for the investigation of species boundaries and allow to shed light on the little understood roles of sex chromosomes in species divergence. Sex chromosomes are considered to function as a hotspot of genetic divergence between species; indicated by less genomic introgression compared to autosomes during hybridisation. Moreover, they are thought to contribute to Haldane's rule which states that hybrids of the heterogametic sex are more likely to be inviable or sterile. To test these hypotheses, we used contemporary hybrid zones of <i>Ischnura elegans</i>, a damselfly species that has been expanding its range into the northern and western regions of Spain, leading to chronic hybridization with its sister species <i>Ischnura graellsii</i>. We analysed genome-wide SNPs in the Spanish <i>I. elegans</i> and <i>I. graellsii</i> hybrid zone and found (i) that the X chromosome shows less genomic introgression compared to autosomes and (ii) that males are underrepresented among admixed individuals as predicted by Haldane's rule. This is the first study in Odonata that suggests a role of the X chromosome in reproductive isolation. Moreover, our data adds to the few studies on species with X0 sex determination system and contradicts the hypothesis that the absence of a Y chromosome causes exceptions to Haldane's rule.</p>
Genome assembly of a commercial tomato hybrid (Funtelle) for haplotyping an introgression that confers TMV resistance
<p>Plant crop genome assemblies facilitate the characterization of genetically diverse cultivated and wild germplasm. </p> <p>The cultivated tomato (Solanum lycopersicum) has been improved through the introgression of genetic material from related wild species, including genetic resistance to pandemic strains of Tobacco Mosaic virus (TMV) and tomato mosaic virus (ToMV) originating from Solanum peruvianum. The exact size and the structure of the introgression from Solanum peruvianum containing the TMV/ToMV resistance gene (Tm-2^2 gene) has remained unknown, although it was known to include at least half of the physical length of chromosome 9.<br> <br> We selected a commercial cultivated tomato cultivar called Funtelle, which contains the Tm-2^2 resistance introgression in a hemizygous state, and generated Oxford Nanopore sequencing reads. Using Flye, a genome assembly tool, we assembled the reads. The assembled DNA sequences (contigs) from the Flye assembly are made available here. Subsequently, as described in detail in the associated manuscript, we made use of the assembled contigs for comprehensive haplotyping of the chromosome 9 introgression region in this commercial hybrid.<br> <br> The raw Oxford Nanopore sequencing reads of the Funtelle variety are available via the European Nucleotide Archive under project number PRJEB44956.</p>
Data from: Genotyping-in-Thousands by Sequencing panel development and application for high-resolution monitoring of introgressive hybridization within sockeye salmon
<p>Stocking programs have been widely implemented to re-establish extirpated fish species to their historical ranges; when employed in species with complex life histories, such management activities should include careful consideration of resulting hybridization dynamics with resident stocks and corresponding outcomes on recovery initiatives. Genetic monitoring can be instrumental for quantifying the extent of introgression over time, however, conventional markers typically have limited power for the identification of advanced hybrid classes, especially at the intra-specific level. Here, we demonstrate a workflow for developing, evaluating, and deploying a Genotyping-in-Thousands by Sequencing (GT-seq) SNP panel with the power to detect advanced hybrid classes to assess the extent and trajectory of intra-specific hybridization, using the sockeye salmon (<em>Oncorhynchus nerka)</em> stocking program in Skaha Lake, British Columbia, as a case study. Previous analyses detected significant levels of hybridization between the anadromous (sockeye) and freshwater resident (kokanee) forms of <em>O. nerka</em>, but were restricted to assigning individuals to pure-stock or "hybrid". Simulation analyses indicated our GT-seq panel had high accuracy, efficiency and power (> 94.5%) of assignment to pure-stock sockeye salmon/kokanee, F<sub>1</sub>, F<sub>2</sub>, and B<sub>2</sub> backcross-sockeye/kokanee. Re-analysis of 2016/2017 spawners previously analyzed using TaqMan<span> </span>assays and otolith microchemistry revealed shifts in assignment of some hybrids to adjacent pure-stock or B<sub>2</sub>-backcross classes, while new assignment of 2019 spawners revealed hybrids comprised 31% of the population, ~74% of which were B<sub>2</sub>-backcross or F<sub>2</sub>. Overall, the GT-seq panel development workflow presented here could be applied to virtually any system where genetic stock identification and intra-specific hybridization are important management parameters.</p>
Figure 5 from: Espinasa L, Robinson J, Soares D, Hoese G, Toulkeridis T, Toomey III R (2018) Troglomorphic features of Astroblepus pholeter, a cavefish from Ecuador, and possible introgressive hybridization. Subterranean Biology 27: 17-29. https://doi.org/10.3897/subtbiol.27.27098
Figure 5 Specimens collected in 1962 (A modified from Collette 1962) and 2011 (B Modified from Soares and Niemiller 2013) had proportionally longer pectoral fins and maxillary barbels than specimens observed in the field in 2015 (C). Images have been scaled to the same body size (blue arrow). Notice that length of appendages in C–D (red arrows) are progressively smaller than in B and A (red plus yellow and green arrows).
Figure 1 from: Espinasa L, Robinson J, Soares D, Hoese G, Toulkeridis T, Toomey III R (2018) Troglomorphic features of Astroblepus pholeter, a cavefish from Ecuador, and possible introgressive hybridization. Subterranean Biology 27: 17-29. https://doi.org/10.3897/subtbiol.27.27098
Figure 1 Specimens collected in 1962 (holotype, and paratypes of A.pholeter from left to right) 2011, 2015 and 2018. Notice that there is a progressive reduction in the expression of troglomorphic features. After 2011 the skin was distinctly more pigmented and the barbels and fins were shorter. Eyes are also embedded under a thinner dermal layer of skin. In 2011 the population was highly variable.
Figure 3 from: Espinasa L, Robinson J, Soares D, Hoese G, Toulkeridis T, Toomey III R (2018) Troglomorphic features of Astroblepus pholeter, a cavefish from Ecuador, and possible introgressive hybridization. Subterranean Biology 27: 17-29. https://doi.org/10.3897/subtbiol.27.27098
Figure 3 AChaetostomamicrops (Surface catfish) BAstroblepuspholeter (Cave catfish). Both species inhabit the same river drainage.
Figure 4 from: Espinasa L, Robinson J, Soares D, Hoese G, Toulkeridis T, Toomey III R (2018) Troglomorphic features of Astroblepus pholeter, a cavefish from Ecuador, and possible introgressive hybridization. Subterranean Biology 27: 17-29. https://doi.org/10.3897/subtbiol.27.27098
Figure 4 Cross section of the eye from Astroblepuspholeter (A, E–G) and Chaetostomamicrops (B–D). Notice that the pigmented epithelium (G) and iris of A.pholeter (E) are black, implying that they are not albino. Furthermore, A.pholeter eye has retained its lens, optic nerve, and its retina has all the normal layers, as the surface fish eye.
Figure 2 from: Espinasa L, Robinson J, Soares D, Hoese G, Toulkeridis T, Toomey III R (2018) Troglomorphic features of Astroblepus pholeter, a cavefish from Ecuador, and possible introgressive hybridization. Subterranean Biology 27: 17-29. https://doi.org/10.3897/subtbiol.27.27098
Figure 2 A–C Live specimens of cave AstroblepuspholeterD Two different surface Astroblepus sp. from the Apurimac drainage. Notice contrasting coloration between A and B both of which were collected in 2011. Pigmentation level variability within the cave population in 2011 spanned from pinkish-white white (A) to pigmented (B) at levels equivalent to some surface Astroblepus (D). Specimens collected in 2011 had longer fins (A) than those collected in 2015 (C). Notice as well that some surface Astroblepus (bottom one in D) can have small eyes of a size equivalent to cave specimens. A Modified from Haspel et al. (2012)B Modified from the Soares Lab web-page-photo C Specimen collected on 2015 D Modified from Schaefer et al. (2011).
Fig. 2 in Altai Mountains - cradle of hybrids and introgressants: A case study in Veronica subg. Pseudolysimachium (Plantaginaceae)
Fig. 2. Assignments of individuals to K clusters/populations based on Bayesian, multivariate and likelihood approaches as implemented in STRUCTURE, DAPC (in the adegenet package) and IQ-TREE programs respectively. A, Maximum likelihood unrooted tree reconstructed in IQ-TREE, calibrated with 1000 ultrafast bootstrap replicates. The numbers near the nodes represent bootstrap confidence. This analysis was based on 174 putative pure individuals. B, Probability of ancestry of each individual (horizontal axis; total 174 individuals) to each of K = 5 populations (vertical axis). The five populations correspond mostly to the morphotypes hypothesized for putative pure species. C, Discriminant analysis of principal components using the same dataset as in (B). D, Corresponding morphotypes of K = 5. — Photos: P.A. Kosachev.
Data from: Phylogenetic relationships of toads of the Rhinella granulosa group (Anura: Bufonidae): a molecular perspective with comments on hybridization and introgression
The Rhinella granulosa group consists of 13 species of toads distributed throughout open areas of South America and Panama. In this paper we perform a phylogenetic analysis considering all but one species of the group, employing five nuclear and four mitochondrial genes, for up to 7910 bp per specimen. Separate phylogenetic analyses under direct optimization (DO) of nuclear and mitochondrial sequences recovered the R. granulosa group as monophyletic and revealed topological incongruence that can be explained mainly by multiple events of hybridization and introgression, both mitochondrial and nuclear. The DO combined analysis, after the exclusion of putatively introgressed or heterozygous genomes, resulted in a phylogenetic hypothesis for the R. granulosa group in which most of the species are recovered as monophyletic, but with interspecific relationships poorly supported. The optimization of morphological (adult and larval), chromosomal, and behavioural characters resulted in 12 putative phenotypic synapomorphies for this species group and some other synapomorphies for internal clades. Our results indicate the need for additional population genetic studies on R. dorbignyi and R. fernandezae to corroborate the taxonomic status of both taxa. Finally, we discuss biological and genetic characteristics of Bufonidae, as possible explanations for the common occurrence of hybridization and introgression observed in some lineages of this family.
Data from: The genetic architecture of hybrid incompatibilities and their effect on barriers to introgression in secondary contact
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