And then there were the frogs. Very, very small frogs.*

[bending_sickle]

They had such a tiny life cycle it still had trainer wheels on it.*

capn_mactastic asks biology questions about parthenogenesis, thelytoky and hybridogenesis. The Biologist in me cannot let such a challenge go. My first reply:


How likely is it that a species would reproduce by both hybridogenesis and automictic thelytoky?

Well, odds are it does happen, but I can't find any references to the fact. The closest I could find was an insect that uses both hybridogenesis and androgenesis (which is, unless I'm completely confused, the male-equivalent of thelytoky, in that the embryo contains only paternal chromosomes.

Thinking about it, though, it's probably really uncommon. I mean, hybridization doesn't give you a species per say, rather a reproducing hybrid sustained by back-crossing with either original species. (Simple-looking diagram confuses me!) But for it to reproduce by thelytoky, it's parent species would need to have this too, right? I mean, it couldn't evolve this trick because it's a new-formed species every time (sort of). Also, scholar.google gives me nothing besides that bug.


But in evolutionary terms why would a species fall back on hybridogenesis if they could go all the way (especially since "daddy's" genes get dumped by the next generation?)*

...wait. A species can't fall back on hybridogenesis, because this is just getting it on with another species to get a hybrid (which is capable of mating with one of the parent species to get more hybrids). So whatever evolutionary advantages there are in hybridization are lost to the parent species, because they'll never get those good genes into their own genes. It's like throwing genes out the window - sure, you'll end up with a pool outside your window, and occasionally people will come into your house with buckets for more water for their pool, but do they ever give you water? Hell no. (My visual mind, let me show you it.)

You can have parthenogenesis and normal reproduction, though, which is excellent for colonizer species. From wiki: this gives an advantage to colonization of islands, where a single female could theoretically have male offspring asexually, then switch to sexual reproduction with them to maintain higher level of genetic diversity than asexual reproduction alone can generate.[13]

* Species do go all the way with it. Then there's the mess of New Mexico whiptails, which result from hybridization going really well, creating a species which reproduces by parthenogenesis. Conceivably, when the species was evolving from hyrbid into proper partheno-species, it used both tactics. The result is female-only species with multiple lineages (from different historic hybridization events) with with low genetic diversity within lineages, but high diversity between.

Wiki: "Parthenogenesis has been studied extensively in the New Mexico whiptail (genus Cnemidophorus), of which 15 species reproduce exclusively by parthenogenesis. [...] All these asexual species appear to have arisen through the hybridization of two or three of the sexual species in the genus leading to polyploid individuals. [...] Because multiple hybridization events can occur, individual parthenogenetic whiptail species can consist of multiple independent asexual lineages. Within lineages, there is very little genetic diversity, but different lineages may have quite different genotypes."

Aaaaand further questions bring us my reply, part two. Posted here because it's huge.


...could the offspring of species A and species B (where A = parthenogenic and B = donor species) mate with either species? Or do they have to go back to A and produce more A babies? So A + B = AB, can AB + B = AB? Or can it only be AB + A = A. (obviously AB + B = BB is not an option with this method)

Parthenogenesis: Asexual reproduction. May be the normal means of reproduction, or the “Heya, good conditions! Moar babies!” means of reproductions.

Species C (parthenogenetic) x Species D (normal) -> Only if parthenogenetic = hybridogenetic, as basic parthenogenesis is completely asexual, while hybridogenesis uses a donor Species.


Hybridogenesis: A hemiclonal type of (not-really asexual) parthenogenesis.

How it works: (See also diagram.)

Speciea A and B are normal, Hybrid (Species) AB is hybridogenetic.


Our peeps for the day:

Poeciliopsis monacha x lucida: Fishies!
Female Species A(monarcha) x Male Species B (lucida) = Female Hybrid AB (Gamete A)
Hybrid AB x Male Species B = Hybrid AB

Rana escuelenta: Frogies!
Male Species A (lessonae) x Female Species B = Female and Male Hybrid AB
Common: Female Hybrid AB x Male Species A = Hybrid Species AB
Suspected (rare): Male Hybrid AB x Female Species B = Hybrid AB


Species A x Species B = Hybrid AB
This step may sex-specific, in that only Female A x Male B may result in hybrid offspring, either due to the actual genetics or more commonly to the selective behaviour of the male/female pair. (e.g. Males of Species B prefer large females, and lo and behold, Species A females are huge. No self-respecting Species A Male would mate with a dinky little Species B Female.

Hybrid AB is (nearly) always female and produces only female gametes*. Its gametes have only Species A genome. Reproductively-speaking, Hybrid AB is essentially a Species A.
* True in Poeciliopsis, but Hybrid Rana escuelenta has both male and females.

a) Hybrid AB x Species B = Gamete A x Gamete B = Mating successful.
In some species, Species B prefers Hybrid AB over Species B, which sucks for them, evolutionarily-speaking.
There is suggestion that male hybrids of R. escuelenta - offspring of Male Species A x Female Species B - have bred with Females Species A, so breeding back to donor Species isn’t limited to the original sex of the parent (in this case, a Female Species B).

New Hybrid AB then creates A gametes, mates with a B, and so on.

b) Hybrid AB x Hybrid AB = Nothing at all.
In the case of Rana escuelenta, where you can have Male Hybrid AB, you could conceivably have Hybrid AB x Hybrid AB = Species A, as both parents use maternal DNA only (from the same species).

c) Hybrid AB x Species A = Gamete A x Gamete A = Theoretical mating successful.
If behavioural preferences don’t prevent Hybrid AB x Species A, then we’d get a gamete A x gamete A cross, which would give us a Species A offspring. There is, however, evidence of Species’s sex preference (e.g. Poeciliopsis monacha x lucida), although this is not always a strict preference (e.g. Rana escuelenta, from Rana ridibunda and Rana lessonae, see here)

Curiously, the hybrid species R. escuelenta has both males and females (although males have reduced fertility and contribiute little to the maintenance of their population).

Conclusion:

Hybrid AB x Species B = Gamete A x Gamete B = Mating successful. Hybrid AB x Species A = Gamete A x Gamete A = Theoretical mating successful depending upon behavioural preferences.
Hybrid AB x Hybrid AB = Nothing at all if Hybrid AB can only be of one sex.
If Hybrid AB can be two sexes, maternal DNA would still be used (e.g. Hybrid AB x Hybrid AB = AA Gamete Combination = Species A). This assumes no behavioural preferences of (AB x A) over (AB x AB). (This is totally conjecture.)


… if a species can reproduce through true parthenogenesis, would the ability to reproduce by hybridogenesis be useful anymore?

The important thing to remember is that, while related, these two are different mechanisms and can’t be switched interchangeably. For example, parthenogenesis, the true asexual "virgin birth" kind, occurs in a normal species, while hybridogenesis occurs in a hybrid "species".

If the hybrid species were to evolved "virgin birth" parthenogenesis, cutting out the middle-man, it wouldn’t have to depend on finding its donor species (although they’d have to coexist in the first place, else no hybrid), but it wouldn’t gain much, and lose more. (The really winning evolutionary trick is getting normal sexual reproduction between hybrids and becoming a fully independent species.)

But hybridogenesis results in a higher genetic diversity than parthenogenesis, which, being truly asexual, is basically cloning oneself. Hybridogenesis results in a population of hybrids with different lineages (from different parent). Within a lineage, genetic diversity is low, but between the, that’s where evolution has more of a hand. Less chance of being totally wiped out as a species (lineages might suffer). Parthenogenesis, in general, is a really sucky move as the single form of reproduction, but excellent if you’re all alone in the environment and aren’t squicked by incest.

This was one part fascinating and two parts confusing. I hope I haven't screwed it up.


* Wings, TPratchett

Comments

[capn-mactastic.livejournal.com]

I iz pest right?

OMG thankyou for all of this. I feel so guilty. But expect an acknowledgement when this fic finally goes up ;)

So, the way I'm reading this *drags you back out from wherever you've run and hid*:

It's NOT possible for a species to have the capability to reproduce by parthenogenesis, hybridogenesis and sexually, depending on what options were open to the individual at the time. i.e. nobody suitable, okay, virgin birth it is; Not the same species but will do the job - produce a fertile hybrid that will only pass on mum's genes; same species available - sex.

Is that right?