Cytotaxonomic Studies of Louisiana Irises

Randolph, L. F.; Mitra, Jyotirmay; Nelson, Ira S.

doi:10.1086/336137

Cited by 22 publications

(18 citation statements)

References 3 publications

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“…The number of linkage groups is one more than the number determined cytologically by Randolph et al (1961). The number of framework markers for each linkage group ranges from two to 10, and linkage groups vary in length from 0 to 166 Kosambi cM.…”

Section: Genotyping and Linkage Mapping For Bcib And Bcifmentioning

confidence: 98%

Loci Affecting Long-Term Hybrid Survivorship in Louisiana Irises: Implications for Reproductive Isolation and Introgression

2005

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Abstract. Iris fulva and I. brevicaulis are long-lived plant species known to hybridize where they coexist in nature. Year-to-year survival contributes significantly to overall fitness for both species and their hybrid derivatives, and differences in hybrid survivability may have important consequences to interspecific gene flow in nature. We examined the genetic architecture of long-term survivorship of reciprocal backcross I. fulva ϫ I. brevicaulis hybrids in a commongarden, greenhouse environment. Differences in mortality were found between the two backcross (BC 1 ) hybrid classes, with hybrids crossed toward I. fulva (BCIF) revealing twice the mortality of those hybrids backcrossed toward I. brevicaulis (BCIB). Using genomic scans on two separate genetic linkage maps derived from the reciprocal hybrid populations, we found that hybrid survivorship is influenced by several genetic regions. Multiple interval mapping (MIM) revealed four quantitative trait loci (QTLs) in BCIF hybrids that were significantly associated with survivorship. Introgressed I. brevicaulis DNA increased survivorship at three of the four QTLs. For the fourth QTL, introgressed I. brevicaulis DNA was associated with decreased survivorship. No QTLs were detected in BCIB hybrids; however, single-marker analysis revealed five unlinked loci that were significantly associated with survivorship. At all five markers, survivorship was positively associated with introgressed I. fulva DNA. The present findings have important implications for the evolutionary dynamics of naturally occurring hybrid zones. Regions of the genome that increase survivorship when in a heterozygous (i.e., hybrid) state should have an increased likelihood of passing across species boundaries, whereas those that decrease survivorship will be less likely to introgress.

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Section: Genotyping and Linkage Mapping For Bcib And Bcifmentioning

confidence: 98%

Loci Affecting Long-Term Hybrid Survivorship in Louisiana Irises: Implications for Reproductive Isolation and Introgression

2005

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“…Randolph (1966) first described this new species and hypothesized a homoploid hybrid origin based on cytological (Randolph et al, 1961) and morphological data (Randolph, 1966). Randolph (1966) suggested that I. nelsonii was derived from hybridization between two widespread species of Louisiana Iris (I. fulva and I. hexagona) and possibly a third widespread species (I. brevicaulis).…”

Section: Introductionmentioning

confidence: 99%

Genomic collinearity and the genetic architecture of floral differences between the homoploid hybrid species Iris nelsonii and one of its progenitors, Iris hexagona

Taylor

Rojas

et al. 2012

Heredity

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Hybrid speciation represents a relatively rapid form of diversification. Early models of homoploid hybrid speciation suggested that reproductive isolation between the hybrid species and progenitors primarily resulted from karyotypic differences between the species. However, genic incompatibilities and ecological divergence may also be responsible for isolation. Iris nelsonii is an example of a homoploid hybrid species that is likely isolated from its progenitors primarily by strong prezygotic isolation, including habitat divergence, floral isolation and post-pollination prezygotic barriers. Here, we used linkage mapping and quantitative trait locus (QTL) mapping approaches to investigate genomic collinearity and the genetic architecture of floral differences between I. nelsonii and one of its progenitor species I. hexagona. The linkage map produced from this cross is highly collinear with another linkage map produced between I. fulva and I. brevicaulis (the two other species shown to have contributed to the genomic makeup of I. nelsonii), suggesting that karyotypic differences do not contribute substantially to isolation in this homoploid hybrid species. Similar to other studies of the genetic architecture of floral characteristics, at least one QTL was found that explained 420% variance in each color trait, while minor QTLs were detected for each morphological trait. These QTLs will serve as hypotheses for regions under selection by pollinators.

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“…Chromosomal markers were also identified for I. nelsonii and were compared to the unique marker chromosomes of I. fulva, I. hexagona and I. brevicaulis (Randolph eta!., 1961). Their analysis indicated that I. nelsonii possessed at least one of the marker chromosomes characteristic of I. fu!va and a marker chromosome similar to one found in I. hexagona, but with a different centromere position (Randolph et a!., 1961 or all of the allozyme markers were also present in contemporary hybrid populations. Allele frequencies present in I. nelsonii largely reflect those of I. fulva.…”

Section: Introductionmentioning

confidence: 99%

“…Second, since this species apparently occupies a habitat that is unique in comparison to I. fulva, I. hexagona and I. brevicaulis (i.e., heavily shaded areas with deep water), an ecological separation between I. ne!sonii and the parental species may also have assisted in its stabilization. Finally, I. hexagona, I. fulva, I. brevicaulis and I. nelsonii each are characterized by unique marker chromosomes (Randolph et a!., 1961) indicating that I. nelsonii may be a hybrid derivative that is stable with regard to a "hybrid" chromosomal complement. Multiple avenues for the stabilization of hybrid derivatives should enhance the likelihood of hybrid speciation and would be possible whenever there is any combination of asexual and sexual reproduction, chromosomal differentiation and available ecological niches for hybrid derivatives to invade.…”

Section: Introductionmentioning

confidence: 99%

Allozyme variation in Louisiana irises: a test for introgression and hybrid speciation

1990

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Cytotaxonomic Studies of Louisiana Irises

Cited by 22 publications

References 3 publications

Loci Affecting Long-Term Hybrid Survivorship in Louisiana Irises: Implications for Reproductive Isolation and Introgression

Loci Affecting Long-Term Hybrid Survivorship in Louisiana Irises: Implications for Reproductive Isolation and Introgression

Genomic collinearity and the genetic architecture of floral differences between the homoploid hybrid species Iris nelsonii and one of its progenitors, Iris hexagona

Allozyme variation in Louisiana irises: a test for introgression and hybrid speciation

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