Data from: Outstanding intraindividual genetic diversity in fissiparous planarians (Dugesia, Platyhelminthes) with facultative sex

Background: Predicted genetic consequences of asexuality include high
intraindividual genetic diversity (i.e., the Meselson effect) and
accumulation of deleterious mutations (i.e., Muller’s Ratchet), among
others. These consequences have been largely studied in parthenogenetic
organisms, but studies on fissiparous species are scarce. Differing from
parthenogens, fissiparous organisms inherit part of the soma of the
progenitor, including somatic mutations. Thus, in the long term,
fissiparous reproduction may also result in genetic mosaicism, besides the
presence of the Meselson effect and Muller’s Ratchet. Dugesiidae
planarians show outstanding regeneration capabilities, allowing them to
naturally reproduce by fission, either strictly or combined with sex
(facultative). Therefore, they are an ideal model to analyze the genetic
footprint of fissiparous reproduction, both when it is alternated with sex
and when it is the only mode of reproduction. Results: In the present
study, we generate and analyze intraindividual cloned data of a nuclear
and a mitochondrial gene of sexual, fissiparous and facultative wild
populations of the species Dugesia subtentaculata. We find that most
individuals, independently of their reproductive strategy, are mosaics.
However, the intraindividual haplotype and nucleotide diversity of
fissiparous and facultative individuals is significantly higher than in
sexual individuals, with no signs of Muller’s Ratchet. Finally, we also
find that this high intraindividual genetic diversity of fissiparous and
facultative individuals is composed by different combinations of ancestral
and derived haplotypes of the species. Conclusions: The intraindividual
analyses of genetic diversity point out that fissiparous reproduction
leaves a very special genetic footprint in individuals, characterized by
mosaicism combined with the Meselson effect (named in the present study as
the mosaic Meselson effect). Interestingly, the different intraindividual
combinations of ancestral and derivate genetic diversity indicate that
haplotypes generated during periods of fissiparous reproduction can be
also transmitted to the progeny through sexual events, resulting in
offspring showing a wide range of genetic diversity and putatively
allowing purifying selection to act at both intraindividual and individual
level. Further investigations, using Dugesia planarians as model
organisms, would be of great value to delve into this new model of genetic
evolution by the combination of fission and sex.