Sex in Parthenogenetic Planarians: Phylogenetic Relic or Evolutionary Resurrection?

D’Souza, Thomas G.; Michiels, Nico K.

doi:10.1007/978-90-481-2770-2_18

Cited by 15 publications

(19 citation statements)

References 72 publications

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“…Second, hermaphrodites can combine the production of parthenogenetic eggs and sperm, which then can be used to trigger parthenogenetic reproduction in either other conspecifics (e.g. sperm-trading planarians [42]) or themselves (self-compatibility commonly evolves in pseudogamous plants [53]). Interestingly, the former category frees the parthenogens from the constraint of having to coexist with the parental sexual species, which can be ecologically a very difficult form of coexistence [55].…”

Section: (A) a Marginal Habitat?mentioning

confidence: 99%

“…Alternatively, the generation of new asexual genotypes can still be ongoing, for instance via mutation [64], continuing hybridization of, or with, the sexual parents [65], contagious asexuality via endosymbiont transmission [66] or rare crossings with sexuals (e.g. [42] in hermaphrodite flatworms; [67] in Daphnia and [68] in Artemia owing to rare parthenogenetic sons), or forms of 'parasex' [69] such as horizontal gene transfer between individuals (bdelloid rotifers, see [70]) or introgression of environmental DNA (anhydrobiotic rotifers or tardigrades [71]). …”

Section: (A) a Marginal Habitat?mentioning

confidence: 99%

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What does the geography of parthenogenesis teach us about sex?

Tilquin

Kokko

2016

Phil. Trans. R. Soc. B

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One contribution of 15 to a theme issue 'Weird sex: the underappreciated diversity of sexual reproduction'. Theory predicts that sexual reproduction is difficult to maintain if asexuality is an option, yet sex is very common. To understand why, it is important to pay attention to repeatably occurring conditions that favour transitions to, or persistence of, asexuality. Geographic parthenogenesis is a term that has been applied to describe a large variety of patterns where sexual and related asexual forms differ in their geographic distribution. Often asexuality is stated to occur in a habitat that is, in some sense, marginal, but the interpretation differs across studies: parthenogens might not only predominate near the margin of the sexuals' distribution, but might also extend far beyond the sexual range; they may be disproportionately found in newly colonizable areas (e.g. areas previously glaciated), or in habitats where abiotic selection pressures are relatively stronger than biotic ones (e.g. cold, dry). Here, we review the various patterns proposed in the literature, the hypotheses put forward to explain them, and the assumptions they rely on. Surprisingly, few mathematical models consider geographic parthenogenesis as their focal question, but all models for the evolution of sex could be evaluated in this framework if the (often ecological) causal factors vary predictably with geography. We also recommend broadening the taxa studied beyond the traditional favourites.This article is part of the themed issue 'Weird sex: the underappreciated diversity of sexual reproduction'.

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Section: (A) a Marginal Habitat?mentioning

confidence: 99%

Section: (A) a Marginal Habitat?mentioning

confidence: 99%

What does the geography of parthenogenesis teach us about sex?

Tilquin

Kokko

2016

Phil. Trans. R. Soc. B

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“…It should be noted that occurrence of S. polychroa in North America is the result of human‐mediated dispersal (Ball, ; Benazzi & Benazzi‐Lentati, ). The species S. mediterranea is a model organism in regeneration research (Reddien & Alvarado, ; Rink, ) with a fully sequenced genome (Robb, Ross, & Alvarado, ; Grohme et al, ), while S. polychroa has been used as a model organism in studies on embryogenesis (Cardona, Hartenstein, & Romero, ; Monjo & Romero, ) and reproduction (D'Souza & Michiels, ; Pongratz, Storhas, Carranza, & Michiels, ). In comparison with these two model species, S. lugubris and S. nova are poorly studied.…”

Section: Introductionmentioning

confidence: 99%

Diversification and biogeographic history of the Western Palearctic freshwater flatworm genusSchmidtea(Tricladida: Dugesiidae), with a redescription ofSchmidtea nova

Leria

Sluys

Riutort

2018

J Zool Syst Evol Res

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The freshwater flatworm genus Schmidtea is endemic in the Western Palearctic region, where it is represented by only four species, thus contrasting with the high species diversity of the closely related genus Dugesia within Europe. Although containing an important model species in developmental and regeneration research, viz. Schmidtea mediterranea, no evolutionary studies on the genus Schmidtea have been undertaken. For the first time, we present a well‐resolved molecular phylogenetic tree of the four species of the genus, inferred on the basis of two molecular markers, and provide also the first detailed morphological account of Schmidtea nova. The phylogenetic tree generated corroborates an earlier speciation hypothesis based on karyological data and points to chromosomal rearrangements as the main drivers of speciation in this genus. The high genetic divergence between the four species, in combination with previous dating studies and their current geographic distribution, suggests that Schmidtea could have originated in Laurasia but lost most of its diversity during the Oligocene. Thus, its present distribution pattern may be the result of the expansion of three of its four relictual species over Europe, probably after the Pleistocene glaciations. Our detailed morphological study of S. nova revealed that it shows a number of remarkable features: interconnected testis follicles, parovaria, an ejaculatory duct exiting into the primary as well as the secondary seminal vesicle by means of a nipple, and the wall of the distal section of the ejaculatory duct being sclerotic or chitinized.

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“…The resulting offspring will be a polyploid F1 hybrid with an unchanged degree of polyploidy. Accordingly, there may be a cycle involving triploids and tetraploids or sex without any change in ploidy level [D'Souza and Michiels, 2009]. …”

Section: A Premeiotic Doubling Of the Chromosome Number Ismentioning

confidence: 99%

“…The process can be 'leaky', and so fertilization occurs in some cases [D'Souza and Michiels, 2009] with entire genomes or subgenomic amounts of paternal DNA contributing to the offspring (overview in vertebrates: Lamatsch and Stöck [2009]). This process is mostly referred to as gynogenesis ('female birth') or 'sperm-dependent parthenogenesis' [Beukeboom and Vrijenhoek, 1998].…”

mentioning

confidence: 99%

Meiosis and Its Deviations in Polyploid Animals

Stenberg¹,

Saura²

2013

Cytogenet Genome Res

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We review the different modes of meiosis and its deviations encountered in polyploid animals. Bisexual reproduction involving normal meiosis occurs in some allopolyploid frogs with variable degrees of polyploidy. Aberrant modes of bisexual reproduction include gynogenesis, where a sperm stimulates the egg to develop. The sperm may enter the egg but there is no fertilization and syngamy. In hybridogenesis, a genome is eliminated to produce haploid or diploid eggs or sperm. Ploidy can be elevated by fertilization with a haploid sperm in meiotic hybridogenesis, which elevates the ploidy of hybrid offspring such that they produce diploid gametes. Polyploids are then produced in the next generation. In kleptogenesis, females acquire full or partial genomes from their partners. In pre-equalizing hybrid meiosis, one genome is transmitted in the Mendelian fashion, while the other is transmitted clonally. Parthenogenetic animals have a very wide range of mechanisms for restoring or maintaining the mother's ploidy level, including gamete duplication, terminal fusion, central fusion, fusion of the first polar nucleus with the product of the first division, and premeiotic duplication followed by a normal meiosis. In apomictic parthenogenesis, meiosis is replaced by what is effectively mitotic cell division. The above modes have different evolutionary consequences, which are discussed. See also the sister article by Grandont et al. in this themed issue.

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Sex in Parthenogenetic Planarians: Phylogenetic Relic or Evolutionary Resurrection?

Cited by 15 publications

References 72 publications

What does the geography of parthenogenesis teach us about sex?

What does the geography of parthenogenesis teach us about sex?

Diversification and biogeographic history of the Western Palearctic freshwater flatworm genusSchmidtea(Tricladida: Dugesiidae), with a redescription ofSchmidtea nova

Meiosis and Its Deviations in Polyploid Animals

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