Dataset Information

Species coherence in the face of karyotype diversification in holocentric organisms: the case of a cytogenetically variable sedge (Carex scoparia, Cyperaceae).

ABSTRACT:

Background and aims

The sedge genus Carex, the most diversified angiosperm genus of the northern temperate zone, is renowned for its holocentric chromosomes and karyotype variability. The genus exhibits high variation in chromosome numbers both among and within species. Despite the possibility that this chromosome evolution may play a role in the high species diversity of Carex, population-level patterns of molecular and cytogenetic differentiation in the genus have not been extensively studied.

Methods

Microsatellite variation (11 loci, 461 individuals) and chromosomal diversity (82 individuals) were investigated in 22 Midwestern populations of the North American sedge Carex scoparia and two Northeastern populations.

Key results

Among Midwestern populations, geographic distance is the most important predictor of genetic differentiation. Within populations, inbreeding is high and chromosome variation explains a significant component of genetic differentiation. Infrequent dispersal among populations separated by >100 km explains an important component of molecular genetic and cytogenetic diversity within populations. However, karyotype variation and correlation between genetic and chromosomal variation persist within populations even when putative migrants based on genetic data are excluded.

Conclusions

These findings demonstrate dispersal and genetic connectivity among widespread populations that differ in chromosome numbers, explaining the phenomenon of genetic coherence in this karyotypically diverse sedge species. More generally, the study suggests that traditional sedge taxonomic boundaries demarcate good species even when those species encompass a high range of chromosomal diversity. This finding is important evidence as we work to document the limits and drivers of biodiversity in one of the world's largest angiosperm genera.

SUBMITTER: Escudero M

PROVIDER: S-EPMC3718211 | biostudies-literature | 2013 Aug

REPOSITORIES: biostudies-literature

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Publications

Species coherence in the face of karyotype diversification in holocentric organisms: the case of a cytogenetically variable sedge (Carex scoparia, Cyperaceae).

Escudero Marcial M Weber Jaime A JA Hipp Andrew L AL

Annals of botany 20130530 3

<h4>Background and aims</h4>The sedge genus Carex, the most diversified angiosperm genus of the northern temperate zone, is renowned for its holocentric chromosomes and karyotype variability. The genus exhibits high variation in chromosome numbers both among and within species. Despite the possibility that this chromosome evolution may play a role in the high species diversity of Carex, population-level patterns of molecular and cytogenetic differentiation in the genus have not been extensively ...[more]

PMID: 23723260

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Project description:Background and Aims:Long terminal repeat-retrotransposons (LTR-RTs) comprise a large portion of plant genomes, with massive repeat blocks distributed across the chromosomes. Eleocharis species have holocentric chromosomes, and show a positive correlation between chromosome numbers and the amount of nuclear DNA. To evaluate the role of LTR-RTs in karyotype diversity in members of Eleocharis (subgenus Eleocharis), the occurrence and location of different members of the Copia and Gypsy superfamilies were compared, covering interspecific variations in ploidy levels (considering chromosome numbers), DNA C-values and chromosomal arrangements. Methods:The DNA C-value was estimated by flow cytometry. Genomes of Eleocharis elegans and E. geniculata were partially sequenced using Illumina MiSeq assemblies, which were a source for searching for conserved proteins of LTR-RTs. POL domains were used for recognition, comparing families and for probe production, considering different families of Copia and Gypsy superfamilies. Probes were obtained by PCR and used in fluorescence in situ hybridization (FISH) against chromosomes of seven Eleocharis species. Key Results:A positive correlation between ploidy levels and the amount of nuclear DNA was observed, but with significant variations between samples with the same ploidy levels, associated with repetitive DNA fractions. LTR-RTs were abundant in E. elegans and E. geniculata genomes, with a predominance of Copia Sirevirus and Gypsy Athila/Tat clades. FISH using LTR-RT probes exhibited scattered and clustered signals, but with differences in the chromosomal locations of Copia and Gypsy. The diversity in LTR-RT locations suggests that there is no typical chromosomal distribution pattern for retrotransposons in holocentric chromosomes, except the CRM family with signals distributed along chromatids. Conclusions:These data indicate independent fates for each LTR-RT family, including accumulation between and within chromosomes and genomes. Differential activity and small changes in LTR-RTs suggest a secondary role in nuclear DNA variation, when compared with ploidy changes.

Dataset Information

Species coherence in the face of karyotype diversification in holocentric organisms: the case of a cytogenetically variable sedge (Carex scoparia, Cyperaceae).

Background and aims

Methods

Key results

Conclusions

Publications

Species coherence in the face of karyotype diversification in holocentric organisms: the case of a cytogenetically variable sedge (Carex scoparia, Cyperaceae).

Similar Datasets

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