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Is inbreeding an issue in parthenogenic species?


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Parthenogenic species are all females, and they make "clones" of themselves, right? Normal species are males and females, and they need to mate to make babies. Males and females can come from different gene pools, so there is genetic diversity in their species. But parthenogenic species do not have any genetic diversity, because they do not mate to make babies, they just make "clones" of themselves, right? So i could theoretically start a colony of parthenogenic roaches with only one specimen, and have no problem with inbreeding or any genetic problems caused by inbreeding, right?

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with parthogenic species, its impossible to have ANY inbreeding at all. Every single parthogenic roach that was ever made anywhere is an exact copy of the maturnal mother. Yes, you can start with only one specimen and get a culure going like that.

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You won't have inbreeding due to the fact that they aren't exchanging genetic material, but there'll still be a chance of mutations. Many mutations will have no effect, but the individuals carrying these mutations will pass them on to their offspring. If by chance you end up with only mutants, you may see further mutations that have some effect.

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It is my understanding that obligate asexual organisms are generally less adaptable to new environments. While they may have new mutations, if there is no gene transfer (conjugation in bacteria, sexual reproduction, etc) then new mutations never have the opportunity to get shuffled and recombined into potentially useful combinations.

So, I would expect parthenogenic organisms to be fit for their environment, but genetically less able to cope with change.

Comparing 2 hypothetical broods of \the same species in a sort of thought experiment. Assuming a carrying capacity of some very small number of organisms (let's say 2, to be extreme) and assuming that genders are a non issue (so the species is not tragically doomed if two of the same gender are in the same generation). Finally, assume that each population was founded by a single gravid female.

100 generations later:

The gene pool of the parthenogenic species should be essentially identical to the founding female. No significant loss or gain of genetic information (ignoring the small rate of mutation)

The gene pool of the sexual species will be greatly degraded, as each generation will lose some measurable amount of genetic info (imagine a family with 2 children- is EVERY gene present in each of the parents present in the children generation- NO). You would be left with a very homozygous population. While selective pressure could/would have generally preserved the positive traits, in such a small population random chance events could remove a positive gene from the population at regular intervals.

So, back to the initial posting...

If one had to start a colony with a single gravid female, a parthenogenic species should not have significant genetic impacts from that. If one had to start with a single gravid female of a sexual species, it would be on utmost importance to keep as many of the first few generations of individuals alive as possible to preserve all of the genetic variability of the mother, and to maintain the colony at a level where statistically each of the genes (all of the variation) would be present in various individuals of each generation. What that magically number of individuals is, I have no idea, but for myself, I would err on the side of more offspring, at least in the first several generations.

Speaking entirely theoretically...

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Plants can help with this topic.

Many plants are self fertile, yes pollen is male part but it's from the same plant. When you grow seed you get tiny differences from the parent in offspring which gives you diversity.

Even in plant clones, sometimes a plant will get a mutation and develop variegated leaves, those are green leaves with splashes or white or yellow on them. You can grow a fully variegated plant from that one leaf.

Ever seen those colorful grafted cactus? In red,pink, orange,etc... Well they develop new tiny cactus offsets on the bodies that are clones of the parent, but sometimes those clones present new mutations from previous Parents, like my purple cactus developed 1 pink offset out of many purple, meaning somewhere in lineage was a pink parent in the line. This is how new diversity comes to populations that don't have genetic diversity. Like Galapagos animals.

My point is you might get some mutations but the species won't suffer from inbreeding if you keep isolating any you might be able to get new looking roach population. I know some parthenogenic species on rare occasions can produce a male and mate sexually, be on the lookout for this too.

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Thanks for the info keith! The reason I brought this up is kyle is selling a really cool parthenogenic species ( polyphaga saussurei ), a starter colony 6 nymphs for $50, or 1 nymph for $10. I wanted to see if I could start a colony with only one or two individuals. Thank you, all of you! :)

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Actually, I used to live in Florida, and there were many surinam roaches in my backyard. Now that I think of it, I caught one, and kept it as a pet. I remember one day I looked in the container to find a bunch of nymphs crawling around. Unfortunately, I had to get rid of them when I moved to idaho.

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There are actually two major forms of parthenogenesis.

  • "Apomictic parthenogenesis" is essentially cloning. Unless a mutation occurs, all offspring are identical to their mother.
  • "Automictic parthenogensis," on the other hand, is not true cloning. Often, this happens when two haploid egg cells combine to form a viable embryo. It is basically self-fertilization (extreme inbreeding), although no sperm cells are involved. In many species (usually those that also use sexual reproduction), offspring produced in this way are much weaker.

I'm not sure which type parthenogenetic cockroaches would use, but I hope that helps a bit. It might be worth mentioning that some termite and preying mantis species (both close relatives of cockroaches) are known to use the second - automictic parthenogenesis.

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Something else interesting to mention, while we're on this subject, is that obligately parthenogenetic species usually do not last very long on an evolutionary time scale. The "Red Queen" hypothesis suggests that this is mainly because asexual organisms (at least, multicellular ones) cannot adapt quickly enough to changing pathogens/parasites. There are other explanations, but I think that this one makes the most sense.

Of course, there are exceptions. Darwinulid ostracods, bdelloid rotifers, and oribatid mites have all reproduced exclusively through parthenogenesis for tens of millions of years.

Anyway, this subject is particularly intriguing to me, as you can probably tell. :)

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We will all probably be dead by the time the surinam roach goes extinct, lol! And it is indeed a very interesting subject. :)

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We will all probably be dead by the time the surinam roach goes extinct, lol! And it is indeed a very interesting subject. :)

Agreed. I think that, one day, a pathogen will finally catch up with them, but I expect that it will be long after humanity has gone extinct. They are tough little roaches. :)

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