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Evidence for a monophyletic origin of triploid clones of the Amazon molly, Poecilia formosa

Department of Physiological Chemistry I, University of Wuerzburg, Biozentrum, Am Hubland, 97074 Wuerzburg, Germany.
Evolution (Impact Factor: 4.66). 05/2005; 59(4):881-9. DOI: 10.1554/04-453
Source: PubMed

ABSTRACT Asexual reproduction in vertebrates is rare and generally considered an evolutionary dead end. Asexuality is often associated with polyploidy, and several hypotheses have been put forward to explain this relationship. So far, it remains unclear whether polyploidization in asexual organisms is a frequent or a rare event. Here we present a field study on the gynogenetic Amazon molly, Poecilia formosa. We used multilocus fingerprints and microsatellites to investigate the genetic diversity in 339 diploid and 55 triploid individuals and in 25 P. mexicana, its sexual host. Although multilocus DNA fingerprints found high clonal diversity in triploids, microsatellites revealed only two very similar clones in the triploids. Phylogenetic analysis of microsatellite data provided evidence for a monophyletic origin of the triploid clones of P. formosa. In addition, shared alleles within the triploid clones between the triploid and diploid genotypes and between asexual and sexual lineages indicate a recent origin of triploid clones in Poecilia formosa.

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    • "We used the PopDist software [41] to calculate Tomiuk and Loeschcke’s [42] identity measure (I) between each MLL and its ancestors. This measure is particularly suited for analyses of populations differing in reproductive mode and ploidy since it examines the sharing of alleles rather than gene frequencies and has previously been applied to other asexual complexes including hybrid and polyploid biotypes [5]. The value of I is proportional to the evolutionary time since the divergence of asexual population from its ancestors and therefore it may be used to measure relative ages of observed clonal lineages. "
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    • "This was mirrored in a very high clonal diversity of the triploid form. Similar phenomena have previously been observed in the triploid specimens from Japan (61 clonal lines among 219 specimens, using only three microsatellite loci) (Ohara et al. 2003) and in two other polyploid fish species: Leuciscus alburnoides (Steindachner) (Alves et al. 2001) and P. formosa (Lampert et al. 2005; Schories et al. 2007). These observations are particularly interesting as genotype variability in asexual organisms can be generated only through polyphyletic origin (Vrijenhoek 2006), by mutation, and from incorporation of a sexually produced genome in each generation (Alves et al. 2001). "
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    • "Amazon Mollies are clonal, all female, but require sperm to trigger embryogenesis (Schlupp et al. 1998; Schlupp 2005). Almost all Amazon Mollies are diploid, but occasionally males do make a genetic contribution, either in the form of a whole haploid sperm genome leading to triploids (Lampert et al. 2005) or as microchromosomes (Schartl et al. 1995a). These phenomena contribute to the genetic diversity within the species (Schlupp 2005). "
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