Diploid Amazon mollies (Poecilia formosa) show a higher fitness than triploids in clonal competition experiments

Abstract

The gynogenetic livebearing Amazon molly (Poecilia formosa) is a sexual parasite that exploits males of closely related species for sperm. This is needed as physiological stimulus for embryo development; however, none of the male's genes are normally incorporated into the genome of the gynogenetic offspring. Mostly diploid individuals were reported from the natural habitats in North-Eastern Mexico and South-Eastern Texas but stable populations of triploids have been reported from the Río Soto la Marina drainage and in the Río Guayalejo in North-Eastern Mexico. Triploidy is the result of defects in the mechanisms that normally clear the host sperm from the ameiotic diploid egg. Triploids also reproduce gynogenetically and their frequencies fluctuate markedly between years, seasons, and localities. To understand the dynamics of this mating system, it is important to understand the relative reproductive success of triploids and diploids. We hypothesize that triploids should have a selective advantage over diploids due to heterosis and/or gene redundancy based on the additional genetic material from the sexual host. However, clonal competition Electronic Supplementary Material The online version of this article (experiments revealed a clear reproductive advantage of diploids competing with triploids. This result contradicts not only our hypothesis but also the stable co-existence of diploids and triploids in natural habitats. Frequency dependent selection, niche partitioning and environmental heterogeneity are discussed as possible explanations.

The epidermal structure of Carassius gibelio: a link with ploidy status in spawning and postspawning periods

“…Considering the polyploid complexes in fish species, it was shown that different environmental factors are disadvantageous for triploid maintenance and survival, e.g. triploids appear to be less sensitive to environmental cues associated with food deprivation and show a lower fitness than diploids (Lamatsch et al , 2009; Tobler et al , 2010). Moreover, asexual triploid forms are more susceptible to pathogen or parasite infection due to lower immune activity than diploid forms (Hakoyama et al , 2001; Mee & Rowe, 2006).…”

The occurrence of spermatozoa in the ovary of the gynogenetic viviparous teleost Poeciliaformosa (POECILIIDAE)

“…This mode of parthenogenesis corresponds to gynogenesis; that is, parthenogenetic development is initiated by spermatozoa from another species. However, the genetic content of the spermatozoa is excluded from the developing embryo (Hubbs and Hubbs, 1932;Schartl et al, 1995;Lampert and Schartl, 2008;Lamatsch et al, 2009). These parthenoform species have been defined as sexual parasites that exploit males of closely related species (Schartl et al, 1995;Turner et al, 1980).…”

Differential survival among genotypes of Daphnia pulex differing in reproductive mode, ploidy level, and geographic origin

“…*indicate probability less than 0.05 polyploids formation (Dufresne and Hebert 1995;Weider and Hobaek 2003). It is also possible that polyploid organisms are forced to colonize new areas if they do not compete well with their diploid ancestors (Lamatsch et al 2008).…”