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Are sexual or asexual events determining the genetic structure of populations in the liverwort Mannia fragrans?


Hock, Z; Szövényi, P; Schneller, J J; Urmi, E; Tóth, Z (2008). Are sexual or asexual events determining the genetic structure of populations in the liverwort Mannia fragrans? Journal of Bryology, 30(1):66-73.

Abstract

Reproductive ecological traits such as success of fertilization, partitioning of sexes, the relative success of sexual versus asexual reproduction and dispersal distances are likely to considerably influence genetic structure within and among plant populations. In the liverwort Mannia fragrans both sexual and asexual reproduction can be frequently observed: sporophytes are produced abundantly every year and asexual propagation by fragmentation of thalli is also common. The aim of this study was to use ecological and molecular methods (ISSR markers) to separate the role of sexual and asexual components in shaping the partitioning of genetic variability within and among populations. In addition to genetic analyses conducted seasonally, sex expression and fertilization rates, sex ratios, regeneration from vegetative fragments and outcrossing was estimated in 3 populations of the species. Sex expression rates were high and, in spite of strongly female biased sex ratios, high fertilization rates were detected. However, capacity for regeneration from fragments was also high. Despite frequent spore production genetic diversity was low within populations. This is probably the result of the predominance of asexual reproduction s. 1. including crossing between genetically identical plants. Although recombination and mutation occasionally generates new haplotypes, these have little chance to spread because of the large spores mainly falling into their own patch, where chances for germination are low. Due to small size and isolation of the populations, genetic drift is likely to eliminate these haplotypes. Remote populations differed significantly, each being dominated by a few clones, reflecting negligible gene flow among them. Differences among individual populations can partly be related to differences in their reproductive behaviour and degree of isolation.

Abstract

Reproductive ecological traits such as success of fertilization, partitioning of sexes, the relative success of sexual versus asexual reproduction and dispersal distances are likely to considerably influence genetic structure within and among plant populations. In the liverwort Mannia fragrans both sexual and asexual reproduction can be frequently observed: sporophytes are produced abundantly every year and asexual propagation by fragmentation of thalli is also common. The aim of this study was to use ecological and molecular methods (ISSR markers) to separate the role of sexual and asexual components in shaping the partitioning of genetic variability within and among populations. In addition to genetic analyses conducted seasonally, sex expression and fertilization rates, sex ratios, regeneration from vegetative fragments and outcrossing was estimated in 3 populations of the species. Sex expression rates were high and, in spite of strongly female biased sex ratios, high fertilization rates were detected. However, capacity for regeneration from fragments was also high. Despite frequent spore production genetic diversity was low within populations. This is probably the result of the predominance of asexual reproduction s. 1. including crossing between genetically identical plants. Although recombination and mutation occasionally generates new haplotypes, these have little chance to spread because of the large spores mainly falling into their own patch, where chances for germination are low. Due to small size and isolation of the populations, genetic drift is likely to eliminate these haplotypes. Remote populations differed significantly, each being dominated by a few clones, reflecting negligible gene flow among them. Differences among individual populations can partly be related to differences in their reproductive behaviour and degree of isolation.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Systematic and Evolutionary Botany
Dewey Decimal Classification:580 Plants (Botany)
Uncontrolled Keywords:Clonal propagation, fertilization rate, genetic variability, sex expression, sex ratio, spore size
Language:English
Date:2008
Deposited On:28 Jan 2009 18:22
Last Modified:06 Dec 2017 17:27
Publisher:Maney Publishing
ISSN:0373-6687
Publisher DOI:https://doi.org/10.1179/174328208X282120

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