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      Cytotype stability, facultative apomixis and geographical parthenogenesis in Ranunculus kuepferi (Ranunculaceae)

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          Abstract

          Background and Aims

          Asexual organisms are more widespread in previously glaciated areas than their sexual relatives (‘geographical parthenogenesis’). In plants, this pattern is probably dependent on reproductive isolation and stability of cytotypes within their respective distribution areas. Both partial apomixis and introgressive hybridization potentially destabilize the spatial separation of sexual and apomictic populations. The wide distribution of apomicts may be further enhanced by uniparental reproduction which is advantageous for colonization. These factors are studied in the alpine species Ranunculus kuepferi.

          Methods

          Geographical distribution, diversity and mode of reproduction of cytotypes were assessed using flow cytometry and flow cytometric seed screening on samples from 59 natural populations of Ranunculus kuepferi. Seed set of cytotypes was compared in the wild.

          Key Results

          Diploid sexuals are confined to the south-western parts of the Alps, while tetraploid apomicts dominate in previously glaciated and in geographically isolated areas despite a significantly lower fertility. Other cytotypes (3 x, 5 x and 6 x) occur mainly in the sympatric zone, but without establishing populations. The tetraploids are predominantly apomictic, but also show a partial apomixis via an uncoupling of apomeiosis and parthenogenesis in the seed material. Both pseudogamy and autonomous endosperm formation are observed which may enhance uniparental reproduction.

          Conclusions

          Diploids occupy a glacial relic area and resist introgression of apomixis, probably because of a significantly higher seed set. Among the polyploids, only apomictic tetraploids form stable populations; the other cytotypes arising from partial apomixis fail to establish, probably because of minority cytotype disadvantages. Tetraploid apomicts colonize previously devastated and also distant areas via long-distance dispersal, confirming Baker's law of an advantage of uniparental reproduction. It is concluded that stability of cytotypes and of modes of reproduction are important factors for establishing a pattern of geographical parthenogenesis.

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          Most cited references 97

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          A new evolutionary law

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            Molecular evidence for glacial refugia of mountain plants in the European Alps.

            Many mountain ranges have been strongly glaciated during the Quaternary ice ages, and the locations of glacial refugia of mountain plants have been debated for a long time. A series of detailed molecular studies, investigating intraspecific genetic variation of mountain plants in the European Alps, now allows for a first synopsis. A comparison of the phylogeographic patterns with geological and palaeoenvironmental data demonstrates that glacial refugia were located along the southwestern, southern, eastern and northern border of the Alps. Additional glacial refugia were present in central Alpine areas, where high-elevation plants survived the last glaciation on ice-free mountain tops. The observed intraspecific phylogeographies suggest general patterns of glacial survival, which conform to well-known centres of Alpine species diversity and endemism. This implies that evolutionary or biogeographic processes induced by climatic fluctuations act on gene and species diversity in a similar way.
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              Destabilizing Hybridization, General-Purpose Genotypes and Geographic Parthenogenesis

               Michael Lynch (1984)
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                Author and article information

                Journal
                Ann Bot
                annbot
                annbot
                Annals of Botany
                Oxford University Press
                0305-7364
                1095-8290
                March 2010
                24 January 2010
                24 January 2010
                : 105
                : 3
                : 457-470
                Affiliations
                Department of Systematic and Evolutionary Botany, Faculty Centre for Biodiversity, simpleUniversity of Vienna , Rennweg 14, 1030 Vienna, Austria
                Author notes
                [* ]For correspondence. E-mail elvira.hoerandl@ 123456univie.ac.at
                Article
                mcp304
                10.1093/aob/mcp304
                2826254
                20100695
                © The Author 2010. Published by Oxford University Press on behalf of the Annals of Botany Company

                This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( http://creativecommons.org/licenses/by-nc/2.5/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

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