A List of Species with Nucellar and Integumentary Embryony

Naumova, Tamara N.

doi:10.1201/9781351069755-6

Cited by 23 publications

(41 citation statements)

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“…The species with apomixis appear polyphyletically within the phylogeny of the genus (Hoffmann & al., 2013). Likewise, the species of Euonymus with adventitious embryony appear scattered over the phylogeny (Naumova, 1992;. All these examples exhibit (i) a high level of facultative sexuality, (ii) a low degree of morphological differentiation of sexual and apomictic cytotypes, and (iii) mostly non-hybrid, multiple origins.…”

Section: From Theory To Practice: Species Delimitationmentioning

confidence: 99%

The classification of asexual organisms: Old myths, new facts, and a novel pluralistic approach

Hörandl

2018

TAXON

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Organisms reproducing via asexuality harbor a great diversity of lineages, morphotypes and ecotypes. However, classification of asexual taxa does not fit into contemporary species concepts, and hence the diversity of apomictic plant complexes is not well reflected in taxonomy. Plants reproducing via apomixis (i.e., asexual seed formation = agamospermy) exemplify the theoretical and practical problems of classification. Obligately asexual organisms do not form reproductive communities, but they do constitute ancestor-descendant lineages. From the conceptual side, evolutionary lineage concepts would fit best for species delimitation. Recent research showed that these lineages are not necessarily threatened by rapid extinction and do have persistence in time and space. Facultative sexuality and low levels of residual recombination counteract the accumulation of deleterious mutations due to the lack of recombination (Muller's ratchet). Apomictic lineages do have adaptive potential, which is demonstrated by the ability to occupy large distribution areas and to experience ecological niche shifts. The challenge for classification of asexual lineages, however, is to find operational criteria for species delimitation. Current practices of species delimitation can be grouped into four main principles: (1) the sexuals-first principle means that obligate sexual progenitor species are classified separately from their apomictic derivatives.(2) The all-in-one principle merges sexual progenitors and highly facultative apomictic derivatives into one species, whereby the apomicts often represent autopolyploids without differentiated phenotypes. (3) The cluster concept applies to allopolyploid complexes with facultative apomixis and a huge diversity of genotypes and morphotypes; here the main genetic clusters are treated as species. (4) Almost obligate apomictic lineages are being classified as agamospecies. The four principles reflect quite well evolutionary traits and diversity of lineages. Finally, a recommendation for a workflow is given, following this gradient from obligate sexuality to obligate apomixis.

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Section: From Theory To Practice: Species Delimitationmentioning

confidence: 99%

The classification of asexual organisms: Old myths, new facts, and a novel pluralistic approach

Hörandl

2018

TAXON

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“…In this study, in one of the heteroploid crosses using tetraploid plants with a high genome base (x = 9.25 to 7.50/2C pg; Caperta & al., 2017) polyembryony is found. Polyembryonic species generally are associated with high x-values (Naumova, 1993;Carman, 1997). Interestingly, a common origin of apomixis and tetraspory has been hypothesized based on the identification of similar cytological characteristics during ovule development (Carman & al., 1997;Peel & al., 1997a, b).…”

Section: Discussionmentioning

confidence: 99%

Limonium homoploid and heteroploid intra‐ and interspecific crosses unveil seed anomalies and neopolyploidy related to sexual and/or apomictic reproduction

Conceição

Róis

Caperta

2018

TAXON

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Apomixis is a form of asexual reproduction that consists in cloning through seeds. In Limonium (Plumbaginaceae) species present a pollen-stigma dimorphism linked to a sporophytic self-incompatibility system associated with sexual and/ or apomictic reproductive modes. Previous work in other genera suggests that the emergence of apomixis is associated with hybridization and/or polyploidy. In this study, our goal was to test the ability of diploid and tetraploid species to hybridize and to evaluate the variate outcomes from these crosses. To achieve this, sexual diploid (L. nydeggeri, L. ovalifolium) and facultative apomict tetraploid (L. binervosum, L. dodartii) plants from cultivated material, previously cytogenetically and reproductively characterized, were used for experimental intra-and interspecific crosses. Genome sizes, ploidy levels and morphology were examined in the resulting progenies. Results showed a high production of viable seeds in particular in plants from tetraploid × diploid (heteroploid) crosses. In these crosses, some seedlings exhibited pleiocotyly (tricotyl, tetracotyl), while others showed polyembryony. In both homoploid (diploid × diploid) and heteroploid (tetraploid × diploid) crosses, most of the offspring plants were morphologically and in their ploidy similar to the female receiver, although some morphological abnormalities were found. Molecular progeny tests using the nrDNA ITS1-ITS2 sequence demonstrated an astounding range of diploid offspring plants originated from diploid × diploid crosses that were either genetically similar or distinct from parental plants. Although in intraspecific crosses most of the resulting progeny was diploid, one triploid plant was formed. Moreover, in homoploid interspecific crosses, neopolyploids (two tetraploid plants) were produced. Progeny plants from heteroploid crosses always showed nrDNA ITS1-ITS2 sequences identical to the parental plant used as female receiver. In conclusion, diploid homoploid crosses presented genetically diverse offspring arising from sexual reproduction. By contrast, heteroploid crosses generated clonal, maternal (apomictic) offspring. (Tables S1-S3, Fig. S1) and DNA sequence alignments (used to compare parental and progeny plants of nine homoploid and/or interploid crosses) are available from https://doi. Supplementary Material The Electronic Supplement

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“…Chromosome counts show that Nigritella comprise both diploid taxa with the somatic number 2n = 2x = 40, and a series of polyploid taxa with chromosome numbers ranging from 2n = 60 to 2n = 100. Embryological studies have revealed that all diploids are sexual, and that all polyploids in central Europe agree with the Scandinavian N. nigra (Afzelius 1928(Afzelius , 1932 in being apomicts that reproduce by adventitious embryony (nucellar embryony, Teppner 1996; for general aspects see Naumova 1993). Molecular studies based on allozymes (Hedrén et al 2000) and AFLPs (Ståhlberg 1999) corroborated many of the taxonomic conclusions drawn in previous studies and confirmed the patterns of genetic variation expected from breeding systems.…”

Section: Introductionmentioning

confidence: 91%

Evolution and systematics of polyploid Nigritella (Orchidaceae)

Hedrén

Lorenz²,

Teppner³

et al. 2018

Nordic Journal of Botany

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Members of the orchid genus Nigritella are widespread in European mountains, but species circumscriptions and evolutionary patterns in the genus are subjects to conflicting opinions. We analyzed a representative material of Nigritella for differentiation at nuclear and plastid marker loci. In agreement with predictions from embryological studies, diploid members of Nigritella are sexual and mostly out‐crossing, whereas triploid, tetraploid and pentaploid members are apomicts. The diploid taxa were poorly differentiated in the investigated molecular markers, except for the western N. gabasiana, which was separated in plastid haplotypes. Polyploid Nigritella aggregate into three groups and within each of these groups apomictic polyploids have given rise to new species. Within the N. nigra group, the tetraploid N. nigra subsp. austriaca is somewhat differentiated from the triploid subsp. nigra at nuclear as well as plastid loci. Fusion of an unreduced egg cell from subsp. nigra with a haploid microgamete from Gymnadenia conopsea gave rise to Gymnigritella runei. Within the N. widderi group, N. archiducis‐joannis is poorly separated from N. widderi in molecular markers, and the pentaploid N. buschmanniae has evolved by fusion of an unreduced egg cell from N. widderi with a haploid microgamete from a diploid Nigritella. Within the N. miniata group, N. stiriaca is somewhat differentiated from N. miniata at nuclear loci, but no other segregates of N. miniata are supported at species level. Polyploid Nigritella species accumulate genetic diversity by somatic mutations. In the widespread N. nigra subsp. austriaca and N. miniata this diversity is correlated to geography. Although some polyploids may be of recent origins, each polyploid contain genetic markers no longer encountered in diploid members of the genus. According to plastid marker data, Nigritella and Gymnadenia may constitute monophyletic sister genera.

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A List of Species with Nucellar and Integumentary Embryony

Cited by 23 publications

References 0 publications

The classification of asexual organisms: Old myths, new facts, and a novel pluralistic approach

The classification of asexual organisms: Old myths, new facts, and a novel pluralistic approach

Limonium homoploid and heteroploid intra‐ and interspecific crosses unveil seed anomalies and neopolyploidy related to sexual and/or apomictic reproduction

Evolution and systematics of polyploid Nigritella (Orchidaceae)

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