This theory fails to account for the children being identical to one of the parents. If a (2n) cell was formed and then underwent meiosis to turn into (1n), some DNA would be exchanged.
Nice to see this translated (I'm a bio undergrad). I'll try to answer questions on what I think.
>do the differnt yukkuri types act like sex, or like different 'breeds' of plants? The yukkuri in a sense act more like different breeds of plants.
>Are all yukkuris, regardless of their filling, completely inter-breedable? From what I gather, as long as all yukkuri are part of the same species, then yes. I would imagine that mating is limited by physical means though.
>This theory fails to account for the children being identical to one of the parents. If all the information that gives a yukkuri its "supertype" (Reimu, Marisa, etc.) is stored on one gene (which can only be swapped as a whole), then this theory wouldn't be violated.
I would also hypothesize on the following as well: Yukkuris are probably hermaphrodites; they exhibit male and female parts. They share one common gene for this. Based on the fact that one tendril is created for any one mating session, one egg is released at a time per session. As haploid beings in the majority of their life cycle, there is no such thing as a "recessive trait". Thus it is only possible for a yukkuri to receive a "Yukkurisa gene" and not another. This means that crossbreeds are impossible, except in chimeras. As haploids, this also means that a yukkuri pair will yield a unique tendril, except in mutations. Possible different genes could be "Fruit-bearing", "Body type", etc. Mendelian genetics apply for the tendrils.
Yukkuris actually are hermaphrodites. Quote from Yukkuri Wiki: "The Peni Peni is an extremely vulnerable organ, and as such it is only deployed during copulation. The rest of time it's stored inside the body in an inverted form (like a glove flipped inside-out), in this state it serves as Mamu Mamu."
I should also note that another possibility for non-crossover yukkuris is if: 1) There are genes that code for different aspects (ex. Hat, hair colour, eye colour) 2) These genes are linked and can be defined as a haplotype, a collection of alleles. (Ex. Marisa haplotype = Wizard hat + yellow hair + etc.) 3) There are internal mechanisms that prevent the recombination of the alleles in the haplotype.
Should a gene recombination happen, which results in an accesory swap, and the outcome is the death of the recombined koyukkuris, as shown in this picture:
That means that selection pressure favours yukkuri that don't undergo gene recombination. This allows regulator genes that inhibit/prevent gene swapping of the haplotype to be passed on, and regulators that permit recombination to be weeded out. This would explain why yukkuri can only give birth to certain haplotypes. Evolution by means of natural selection (selection of course being the other yukkuri killing off the crossbreeds).
I should further expand on my opinion on diploid/haploid.
I think this "yukkuri-haploid tendril-diploid" theory actually answers and unifies a lot of things yukkuri. It would be difficult to apply a fully diploid theory to yukkuris based on birth patterns. If a diploid system were to occur, Mendelian genetics apply, and I'd run into problems if a "Reimu allele" and a "Marisa allele" were to pair up. The only explanation I can come up with for a diploid theory with birth patterns is that all heterozygotes fail to develop at all. This theory is still consistent with tendril patterns; tendrils would merely be an extension of the parent, and it'd be possible for a tendril to yield more than two types of yukkuri under this.
With haploid, this isn't a problem if yukkuri can only carry one allele for each gene. It would be impossible for a yukkuri to carry a "Reimu allele" and a "Marisa allele" like this. Tendrils are considered seperate entities dependent on the parent in this theory, which explains the "multiple tendrils kill the parent effect". It would be impossible for a tendril to yield more than two types of yukkuri under this.