Mating-call variation across a narrow hybrid zone between Crinia laevis and C. victoriana (Anura : Leptodactylidae)

1973 ◽  
Vol 21 (2) ◽  
pp. 277 ◽  
Author(s):  
MJ Littlejohn ◽  
GF Watson
Keyword(s):  
Gene Flow ◽  
Hybrid Zone ◽  
Mating Call ◽  
Parental Taxon

A transect was established across the eastern extreme of the zone of interaction between the two closely related, parapatric taxa, Crinia laevis and C, victoriana. In this area the range of C. laevis extends as a narrow salient surrounded by the range of C. victoviana. Analyses of mating-call recordings obtained at six localities along the transect suggest that the interaction may be described as a hybrid zone in which the recombination products are fitter than individuals of either parental taxon. In spite of the possibility of reduced conspecific gene flow to individuals of C. laevis at the interface, no indications of reduction of hybridization through reinforcing selection were detected. Because the hybrid zone now separates individuals of each taxon, the two taxa are prevented from directly interacting.

Assessment of gene flow across a hybrid zone in red-tailed chipmunks (Tamias ruficaudus)

2009 ◽  
Vol 18 (14) ◽  
pp. 3097-3109 ◽  
Author(s):  
SARAH HIRD ◽  
JACK SULLIVAN
Keyword(s):  
Gene Flow ◽  
Hybrid Zone

scholarly journals Morphometric Variation as an Indicator of Genetic Interactions Between Black-Capped and Carolina Chickadees at a Contact Zone in the Appalachian Mountains

The Auk ◽  
2000 ◽  
Vol 117 (2) ◽  
pp. 427-444 ◽  
Author(s):  
Gene D. Sattler ◽  
Michael J. Braun
Keyword(s):  
Genetic Variation ◽  
Gene Flow ◽  
Genetic Markers ◽  
Hybrid Zone ◽  
Morphological Variation ◽  
Genetic Data ◽  
Mixed Ancestry ◽  
Morphometric Variation ◽  
Average Gene ◽  
Hybridization And Introgression

AbstractWe studied hybridization and introgression between Black-capped (Poecile atricapillus) and Carolina (P. carolinensis) chickadees along two transects in the Appalachians using four genetic markers and multivariate analysis of morphology. Genetic data revealed that at least 58% of the birds in the center of each transect were of mixed ancestry and that recombinant genotypes predominated among hybrids, demonstrating that hybridization is frequent and that many hybrids are fertile. Genetic clines generally were steep and coincident in position, but introgression was evident well beyond the range interface. Introgression was higher at the one autosomal locus surveyed than in mitochondrial DNA or in two sex-linked markers, suggesting that the hybrid zone is a conduit for gene flow between the two forms at some loci. On a broad scale, morphometric variation was concordant with genetic variation. Clines in morphological variation based on principal components (PC) scores were steep and coincident with genetic clines. Also, a strong correlation within a population between PC scores and an individual's genetic makeup suggested that a large amount of morphological variation was genetically determined. However, morphological analysis indicated that hybrids were uncommon on one transect, whereas genetic data clearly showed that they were common on both. In addition, patterns of morphological variation were equivocal regarding introgression across the hybrid zone. Thus, genetic data provided a complementary and more detailed assessment of hybridization, largely due to the discrete nature of genetic variation. Genetic markers are useful in understanding hybridization and introgression, but diagnostic markers may underestimate average gene flow if selection against hybrids maintains steep clines at diagnostic loci. To gain a clearer picture of the genome-wide effects of hybridization, a much larger number of loci must be assayed, including non-diagnostic ones.

Cytonuclear Theory for Haplodiploid Species and X-Linked Genes. II. Stepping-Stone Models of Gene Flow and Application to a Fire Ant Hybrid Zone

Evolution ◽  
1998 ◽  
Vol 52 (5) ◽  
pp. 1423 ◽  
Author(s):  
Michael A. D. Goodisman ◽  
D. DeWayne Shoemaker ◽  
Marjorie A. Asmussen
Keyword(s):  
Gene Flow ◽  
Hybrid Zone ◽  
Fire Ant ◽  
Stepping Stone ◽  
Stepping Stone Models

scholarly journals The role of hybridization during ecological divergence of southwestern white pine (Pinus strobiformis) and limber pine (P. flexilis)

2017 ◽  
Author(s):  
Mitra Menon ◽  
Justin C. Bagley ◽  
Christopher Friedline ◽  
Amy V. Whipple ◽  
Anna W. Schoettle ◽  
...  
Keyword(s):  
Gene Flow ◽  
Hybrid Zone ◽  
Ecological Niche Modeling ◽  
Life History Strategies ◽  
Species Boundaries ◽  
Disruptive Selection ◽  
Hybrid Index ◽  
Extrinsic Factors ◽  
Intrinsic Factors ◽  
Demographic Modeling

AbstractInteractions between extrinsic factors, such as disruptive selection, and intrinsic factors, such as genetic incompatibilities among loci, can contribute to the maintenance of species boundaries. The relative roles of these factors in the establishment of reproductive isolation can be examined using species pairs characterized by gene flow throughout their divergence history. We investigated the process of speciation and the maintenance of species boundaries between Pinus strobiformis and P.flexilis. Utilizing ecological niche modeling, demographic modeling, and genomic cline analyses, we illustrated a history of divergence with continuous gene flow between these species. We found an abundance of advanced generation hybrids and a lack of loci exhibiting large allele frequency differences across the hybrid zone. Additionally, we found evidence for climate-associated variation in the hybrid index and niche divergence between parental species and the hybrid zone. Our results are consistent with extrinsic factors, such as climate, being an important isolating mechanism for these species. A buildup of intrinsic incompatibilities and of co-adapted gene complexes is also apparent in our results, although these appear to be in the earliest stages of development. This supports previous work in coniferous species demonstrating the importance of extrinsic factors in creating and enforcing species boundaries. Overall, we lend support to the hypothesis that varying strengths and directions of selection pressures across the long lifespans of conifers, in combination with their life history strategies, delay the evolution of strong intrinsic incompatibilities.

scholarly journals Estimates of selection and gene flow from measures of cline width and linkage disequilibrium in heliconius hybrid zones.

Genetics ◽  
1990 ◽  
Vol 124 (4) ◽  
pp. 921-936 ◽  
Author(s):  
J Mallet ◽  
N Barton ◽  
G Lamas ◽  
J Santisteban ◽  
M Muedas ◽  
...  
Keyword(s):  
Gene Flow ◽  
Hybrid Zone ◽  
Color Pattern ◽  
Butterfly Species ◽  
Hybrid Zones ◽  
Square Root ◽  
Color Patterns ◽  
Long Distance ◽  
Locus Selection ◽  
Cline Width

Abstract Hybrid zones can yield estimates of natural selection and gene flow. The width of a cline in gene frequency is approximately proportional to gene flow (sigma) divided by the square root of per-locus selection (square root of s). Gene flow also causes gametic correlations (linkage disequilibria) between genes that differ across hybrid zones. Correlations are stronger when the hybrid zone is narrow, and rise to a maximum roughly equal to s. Thus cline width and gametic correlations combine to give estimates of gene flow and selection. These indirect measures of sigma and s are especially useful because they can be made from collections, and require no field experiments. The method was applied to hybrid zones between color pattern races in a pair of Peruvian Heliconius butterfly species. The species are Müllerian mimics of one another, and both show the same changes in warning color pattern across their respective hybrid zones. The expectations of cline width and gametic correlation were generated using simulations of clines stabilized by strong frequency-dependent selection. In the hybrid zone in Heliconius erato, clines at three major color pattern loci were between 8.5 and 10.2 km wide, and the pairwise gametic correlations peaked at R approximately 0.35. These measures suggest that s approximately 0.23 per locus, and that sigma approximately 2.6 km. In erato, the shapes of the clines agreed with that expected on the basis of dominance. Heliconius melpomene has a nearly coincident hybrid zone. In this species, cline widths at four major color pattern loci varied between 11.7 and 13.4 km. Pairwise gametic correlations peaked near R approximately 1.00 for tightly linked genes, and at R approximately 0.40 for unlinked genes, giving s approximately 0.25 per locus and sigma approximately 3.7 km. In melpomene, cline shapes did not perfectly fit theoretical shapes based on dominance; this deviation might be explained by long-distance migration and/or strong epistasis. Compared with erato, sample sizes in melpomene are lower and the genetics of its color patterns are less well understood. In spite of these problems, selection and gene flow are clearly of the same order of magnitude in the two species. The relatively high per locus selection coefficients agree with "major gene" theories for the evolution of Müllerian mimicry, but the genetic architecture of the color patterns does not. These results show that the genetics and evolution of mimicry are still only sketchily understood.

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