Survival of Hybrids in a Mosaic Hybrid Zone

Howard, Daniel J.; Waring, Gwendolyn L.; Tibbets, C. Alana; Gregory, Pamela G.

doi:10.1111/j.1558-5646.1993.tb01234.x

Cited by 48 publications

(41 citation statements)

References 29 publications

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“…In recent years, new techniques have been developed to take advantage ofgenetic data from hybrid populations (Asmussen et al 1987;Nason et al 1992). The application of techniques for the analysis of genetic variation and associations among loci have allowed researchers to make inferences about the processes responsible for patterns ofhybridization and the persistence of hybrid zones (Forbes and Allendorf 1991;Paige et al 1991;Scribner and Avise Harrison 1985;Kocher and Sage 1986;Howard et al 1993) and ofcontrolled matings (Semlitsch and Reyer 1992;Scribner 1993) have been used in some systems, but this approach has not been widely taken. With the range of analytical tools now available, a thorough examination of the genetic structure of different life-cycle stages in hybrid populations could yield a more detailed understanding of the processes contributing to the maintenance and structuring ofhybrid zones.…”

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confidence: 99%

Assortative Mating and Natural Selection in an Iris Hybrid Zone

Cruzan¹,

Arnold²

1994

Evolution

138

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The phenology of different genotypes and the distribution of genetic variation among flowering plants and their progeny were examined to assess the levels of assortative mating and selection in a hybrid population of Iris. This study and a previous survey ofRAPD nuclear markers and chloroplast markers indicate that the population consists ofparental genotypes and recombinant hybrid genotypes that are similar to the parental species (I.fulva and I. brevicaulis), although lacking intermediate genotypes. Early in the season only I. fulva genotypes produced flowers, but as flowering in these plants decreased, the hybrid genotypes and I. brevicaulis genotypes began flowering, resulting in a 24-d period of coincidental flowering. The genotypic distribution of seeds produced during the period of flowering overlap contained a high frequency of intermediate genotypes that were not present in the adult generation. The degree of effective assortative mating was examined by comparing the observed progeny genotypic distributions with expected distributions from a mixed-mating model. The model included selfing and random outcrossing to the nearest plants that had pollen-bearing flowers on the day the recipient flower was receptive. The observed genotypic distribution of progeny from plants with I. brevicaulis chloroplast DNA (cpDNA) was not significantly different from the expected distribution. For I. fulva genotypes, however, there were higher than expected frequencies in the extreme genotypic classes, although intermediate genotypes were absent, indicating that these plants were preferentially mating with similar genotypes. Compared with the extreme genotypes, a larger proportion of the intermediate seed progeny produced were aborted, indicating that intermediate genotypes have lower viability. On the basis of the observed progeny genotypes and genetic disequilibria estimates for the adults and the progeny, there appears to be a pattern of effective asymmetrical mating in this population. This asymmetry is most likely due to pollen-style interactions that reduce the fertilization ability of genetically dissimilar pollen, or preferential abortion of genetically intermediate zygotes by I. fulva-like genotypes. The lack of any apparent discrimination by I. brevicaulis-like genotypes creates a directional exchange of nuclear genetic elements that will have implications for introgression and the evolution of hybrid genotypes.

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confidence: 99%

Assortative Mating and Natural Selection in an Iris Hybrid Zone

Cruzan¹,

Arnold²

1994

Evolution

138

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“…In mosaic hybrid zones, ecological segregation limits the potential for hybridizing species to interact (Howard 1986;Howard et al 1993). For example, in south-eastern Canada, the distribution of eastern wolves, coyotes, gray wolves, and their hybrids has been attributed to affinities for different habitat conditions (Sears et al 2003;Benson et al 2012Benson et al , 2014, which may limit intermixing (Wilson et al 2009;Rutledge et al 2010a).…”

Section: Mechanisms Of Isolationmentioning

confidence: 99%

Describing a developing hybrid zone between red wolves and coyotes in eastern North Carolina, USA

Bohling

Dellinger

McVey

et al. 2016

Evolutionary Applications

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When hybridizing species come into contact, understanding the processes that regulate their interactions can help predict the future outcome of the system. This is especially relevant in conservation situations where human activities can influence hybridization dynamics. We investigated a developing hybrid zone between red wolves and coyotes in North Carolina, USA to elucidate patterns of hybridization in a system heavily managed for preservation of the red wolf genome. Using noninvasive genetic sampling of scat, we surveyed a 2880 km2 region adjacent to the Red Wolf Experimental Population Area (RWEPA). We combined microsatellite genotypes collected from this survey with those from companion studies conducted both within and outside the RWEPA to describe the gradient of red wolf ancestry. A total of 311 individuals were genotyped at 17 loci and red wolf ancestry decreased along an east–west gradient across the RWEPA. No red wolves were found outside the RWEPA, yet half of individuals found within this area were coyotes. Hybrids composed only 4% of individuals within this landscape despite co‐occurrence of the two species throughout the RWEPA. The low proportion of hybrids suggests that a combination of active management and natural isolating mechanisms may be limiting intermixing within this hybrid system.

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“…The approach was pioneered by Szymura and Barton (1986) as a complementary alternative to geographic cline analysis, where genetic data are evaluated against spatial coordinates or distance. Geographic cline analysis is not always appropriate, for example, in mosaic hybrid zones where hybridizing taxa segregate by habitat at a finer grain than their overlapping geographic ranges (Harrison and Rand 1989;Howard et al 1993), broadly admixed populations such as humans in North America (Parra et al 1998), captive livestock herds (Musani et al 2006), introduced species (Hansen et al 2001;Fitzpatrick and Shaffer 2007b), or other dynamic hybrid zones with patchy introgression (Machol an et al 2011).…”

Section: Introductionmentioning

confidence: 99%

Alternative forms for genomic clines

Fitzpatrick

2013

Ecology and Evolution

113

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Understanding factors regulating hybrid fitness and gene exchange is a major research challenge for evolutionary biology. Genomic cline analysis has been used to evaluate alternative patterns of introgression, but only two models have been used widely and the approach has generally lacked a hypothesis testing framework for distinguishing effects of selection and drift. I propose two alternative cline models, implement multivariate outlier detection to identify markers associated with hybrid fitness, and simulate hybrid zone dynamics to evaluate the signatures of different modes of selection. Analysis of simulated data shows that previous approaches are prone to false positives (multinomial regression) or relatively insensitive to outlier loci affected by selection (Barton's concordance). The new, theory-based logit-logistic cline model is generally best at detecting loci affecting hybrid fitness. Although some generalizations can be made about different modes of selection, there is no one-to-one correspondence between pattern and process. These new methods will enhance our ability to extract important information about the genetics of reproductive isolation and hybrid fitness. However, much remains to be done to relate statistical patterns to particular evolutionary processes. The methods described here are implemented in a freely available package “HIest” for the R statistical software (CRAN; http://cran.r-project.org/).

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Survival of Hybrids in a Mosaic Hybrid Zone

Cited by 48 publications

References 29 publications

Assortative Mating and Natural Selection in an Iris Hybrid Zone

Assortative Mating and Natural Selection in an Iris Hybrid Zone

Describing a developing hybrid zone between red wolves and coyotes in eastern North Carolina, USA

Alternative forms for genomic clines

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