Dataset Information

Epigenetic rather than genetic factors may explain phenotypic divergence between coastal populations of diploid and tetraploid Limonium spp. (Plumbaginaceae) in Portugal.

ABSTRACT:

Background

The genus Limonium Miller comprises annual and perennial halophytes that can produce sexual and/or asexual seeds (apomixis). Genetic and epigenetic (DNA methylation) variation patterns were investigated in populations of three phenotypically similar putative sexual diploid species (L. nydeggeri, L. ovalifolium, L. lanceolatum), one sexual tetraploid species (L. vulgare) and two apomict tetraploid species thought to be related (L. dodartii, L. multiflorum). The extent of morphological differentiation between these species was assessed using ten diagnostic morphometric characters.

Results

A discriminant analysis using the morphometric variables reliably assigns individuals into their respective species groups. We found that only modest genetic and epigenetic differentiation was revealed between species by Methylation Sensitive Amplification Polymorphism (MSAP). However, whilst there was little separation possible between ploidy levels on the basis of genetic profiles, there was clear and pronounced interploidy discrimination on the basis of epigenetic profiles. Here we investigate the relative contribution of genetic and epigenetic factors in explaining the complex phenotypic variability seen in problematic taxonomic groups such as Limonium that operate both apomixis and sexual modes of reproduction.

Conclusions

Our results suggest that epigenetic variation might be one of the drivers of the phenotypic divergence between diploid and tetraploid taxa and discuss that intergenome silencing offers a plausible mechanistic explanation for the observed phenotypic divergence between these microspecies. These results also suggest that epigenetic profiling offer an additional tool to infer ploidy level in stored specimens and that stable epigenetic change may play an important role in apomict evolution and species recognition.

SUBMITTER: Rois AS

PROVIDER: S-EPMC3884021 | biostudies-literature | 2013 Dec

REPOSITORIES: biostudies-literature

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Publications

Epigenetic rather than genetic factors may explain phenotypic divergence between coastal populations of diploid and tetraploid Limonium spp. (Plumbaginaceae) in Portugal.

Róis Ana Sofia AS Rodríguez López Carlos M CM Cortinhas Ana A Erben Matthias M Espírito-Santo Dalila D Wilkinson Michael J MJ Caperta Ana D AD

BMC plant biology 20131206

<h4>Background</h4>The genus Limonium Miller comprises annual and perennial halophytes that can produce sexual and/or asexual seeds (apomixis). Genetic and epigenetic (DNA methylation) variation patterns were investigated in populations of three phenotypically similar putative sexual diploid species (L. nydeggeri, L. ovalifolium, L. lanceolatum), one sexual tetraploid species (L. vulgare) and two apomict tetraploid species thought to be related (L. dodartii, L. multiflorum). The extent of morpho ...[more]

PMID: 24314092

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Project description:The genus Limonium Miller, a complex taxonomic group, comprises annuals and perennials that can produce sexual and/or asexual seeds (apomixis). In this study, we used diverse cytogenetic and cytometric approaches to analyze male sporogenesis and gametogenesis for characterizing male reproductive output on seed production in Limonium ovalifolium and Limonium multiflorum. We showed here that the first species is mostly composed of diploid cytotypes with 2n = 16 chromosomes and the latter species by tetraploid cytotypes with 2n = 32, 34, 35, 36 chromosomes and had a genome roughly twice as big as the former one. In both species, euploid and aneuploid cytotypes with large metacentric chromosomes having decondensed interstitial sites were found within and among populations, possibly involved in chromosomal reconstructions. L. ovalifolium diploids showed regular meiosis resulting in normal tetrads, while diverse chromosome pairing and segregation irregularities leading to the formation of abnormal meiotic products are found in balanced and non-balanced L. multiflorum tetraploids. Before anther dehiscence, the characteristic unicellular, bicellular, or tricellular pollen grains showing the typical Limonium micro- or macro-reticulate exine ornamentation patterns were observed in L. ovalifolium using scanning electron microscopy. Most of these grains were viable and able to produce pollen tubes in vitro. In both balanced and unbalanced L. multiflorum tetraploids, microspores only developed until the "ring-vacuolate stage" with a collapsed morphology without the typical exine patterns, pointing to a sporophytic defect. These microspores were unviable and therefore never germinated in vitro. L. ovalifolium individuals presented larger pollen grains than those of L. multiflorum, indicating that pollen size and ploidy levels are not correlated in the Limonium system. Cytohistological studies in mature seeds from both species revealed that an embryo and a residual endosperm were present in each seed. Flow cytometric seed screens using such mature seeds showed quantitative variations in seeds ploidy level. It is concluded that male function seems to play an important role in the reproduction modes of Limonium diploids and tetraploids.

Project description:Plumbaginaceae is characterized by a history of multiple taxonomic rearrangements and lacks a broad molecular phylogenetic framework. Limonium is the most species-rich genus of the family with ca. 600 species and cosmopolitan distribution. Its center of diversity is the Mediterranean region, where ca. 70% of all Limonium species are endemic. In this study, we sample 201 Limonium species covering all described infrageneric entities and spanning its wide geographic range, along with 64 species of other Plumbaginaceae genera, representing 23 out of 29 genera of the family. Additionally, 20 species of the sister family Polygonaceae were used as outgroup. Sequences of three chloroplast (trnL-F, matK, and rbcL) and one nuclear (ITS) loci were used to infer the molecular phylogeny employing maximum likelihood and Bayesian analyses. According to our results, within Plumbaginoideae, Plumbago forms a non-monophyletic assemblage, with Plumbago europaea sister to Plumbagella, while the other Plumbago species form a clade sister to Dyerophytum. Within Limonioideae, Ikonnikovia is nested in Goniolimon, rejecting its former segregation as genus distinct from Goniolimon. Limonium is divided into two major clades: Limonium subg. Pteroclados s.l., including L. sect. Pteroclados and L. anthericoides, and L. subg. Limonium. The latter is divided into three well-supported subclades: the monospecific L. sect. Limoniodendron sister to a clade comprising a mostly non-Mediterranean subclade and a Mediterranean subclade. Our results set the foundation for taxonomic proposals on sections and subsections of Limonium, namely: (a) the newly described L. sect. Tenuiramosum, created to assign L. anthericoides at the sectional rank; (b) the more restricted circumscriptions of L. sect. Limonium (= L. sect. Limonium subsect. Genuinae) and L. sect. Sarcophyllum (for the Sudano-Zambezian/Saharo-Arabian clade); (c) the more expanded circumscription of L. sect. Nephrophyllum (including species of the L. bellidifolium complex); and (d) the new combinations for L. sect. Pruinosum and L. sect. Pteroclados subsect. Odontolepideae and subsect. Nobiles.

Project description:Background and aimsLimonium is a well-known example of a group of plants that is taxonomically complex due to certain biological characteristics that hamper species' delineation. The closely related polyploid species Limonium vulgare Mill., L. humile Mill. and L. narbonense Mill. are defined species and can be used for studying patterns of morphological and reproductive variation. The first two taxa are usually found in Atlantic Europe and the third in the Mediterranean region, but a number of intermediate morphological forms may be present alongside typical examples of these species. This study attempts to elucidate morphological, floral and karyological diversity representative of these taxa in the Iberian Peninsula.MethodsThe extent of morphological differentiation was tested through comparison of 197 specimens from both Portugal and Spain using 17 descriptive morphological characters and 19 diagnostic morphometric characters. Analyses of floral morphisms (heterostyly and pollen-stigma dimorphism) and karyological determinations were also conducted.Key results and conclusionsDiscriminant analysis using morphometric variables reliably assigned individuals in natural populations to their respective groups. In addition, the results provide the first direct evidence that L. narbonense and a new species, LIMONIUM MARITIMUM: Caperta, Cortinhas, Paes, Guara, Espírito-Santo and Erben, SP NOV: , related to L. vulgare are present on Portuguese coasts. Most of these species are found together in mixed populations, especially L. vulgare and L. narbonense. It is hypothesized that taxonomic biodiversity found in sites where distinct species co-occur facilitates the evolutionary processes of hybridization, introgression and apomixis. This study therefore contributes to the elucidation of the taxonomic diversity in L. vulgare-related species and may also help in implementing future conservation programmes to maintain the evolutionary processes generating biodiversity.

Dataset Information

Epigenetic rather than genetic factors may explain phenotypic divergence between coastal populations of diploid and tetraploid Limonium spp. (Plumbaginaceae) in Portugal.

Background

Results

Conclusions

Publications

Epigenetic rather than genetic factors may explain phenotypic divergence between coastal populations of diploid and tetraploid Limonium spp. (Plumbaginaceae) in Portugal.

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