0
$\begingroup$

I think having some fairly complex life forms in world's biosphere being asexual for a long time would add a lot in terms of mystique and spur lore engagement. I was intrigued by some discussion on this article concerning the evolution of sexual reproduction. One segment in particular:

Furthermore, even though asexual lineages do arise, they rarely persist for long periods of evolutionary time. Among flowering plants, for example, predominantly asexual lineages have arisen over 300 times, yet none of these lineages is very old.

It seems that currently, we see little to no examples in nature for asexual lineages to persist for long periods of time (in terms of geological/evolutionary time scales). While there are several facets to this question, I will narrow the scope to the issue of diversity/lack-there-of.

The Red Queen hypothesis asserts that when a species' genomic make-up remains unchanged for too long, it imposes a extinction risk factor on itself -- the rest of the biological world is evolving and eventually some mutations elevate competitive norms.

Below is a diagram that illustrates the concept (as well as the adversity an asexual lineages in trees, plants, more complex life)

enter image description here

Question

How can an asexual lineage of trees/flowers/similarly complex life forms continue to reproduce and stay "competitive" for millions of years?

Further clarifications

  • Microbes are out of scope
  • Trying to avoid too many double-digit-sigma events (not asking them to be mass-extinction proof or anything, but also not assuming they can have the perfect random mutation at each juncture)
$\endgroup$
4
  • $\begingroup$ worldbuilding.stackexchange.com/q/189285/30492 this asked the same question $\endgroup$
    – L.Dutch
    Nov 3 '20 at 3:46
  • $\begingroup$ @L.Dutch-ReinstateMonica That's informative, but would like to keep the focus on plants and not microbes. Thought I was clear on that, but I can make it more explicit to be safe. Thanks nonetheless $\endgroup$ Nov 3 '20 at 3:48
  • $\begingroup$ The question asks about humans, not microbes. $\endgroup$
    – L.Dutch
    Nov 3 '20 at 3:52
  • $\begingroup$ @L.Dutch-ReinstateMonica True. But, again if my focus is on plants, I guess the jury is still out. Different evolutionary niche / food chain constituent than humans. Broad brush inferences may not be that helpful in such cases. Thanks for the clarification though. $\endgroup$ Nov 3 '20 at 4:01
1
$\begingroup$

Reusing part of my answer:

Since you are not interested in just random mutations, which can still happen nonetheless, you are looking into

A plasmid is a small, extrachromosomal DNA molecule within a cell that is physically separated from chromosomal DNA and can replicate independently. They are most commonly found as small circular, double-stranded DNA molecules in bacteria; however, plasmids are sometimes present in archaea and eukaryotic organisms. In nature, plasmids often carry genes that benefit the survival of the organism and confer selective advantage.

some classes of plasmids encode the conjugative "sex" pilus necessary for their own transfer.

Your plants can use a similar mechanism: though they reproduce asexually (thus not using two gametes), they can still exchange genetic materials with other specimens. They will use the modified genetic code resulting from the exchange to produce their offspring.

The genetic material can be exchanged in a similar way to the pollen emission.

$\endgroup$
1
$\begingroup$

1. Sexual reproduction is rare across the board.

Asexual creatures are not in competition with similar sexual creatures. Just about everything is asexual.

2. Asexual creatures are optimal for their environments.
There is really no room for improvement. Current asexual creatures are so well adapted to their circumstances that any change in the genome is a change for the worse. To make this work, the environment itself must be stable as well.

  1. Creatures have hypermutable subsets of cells that can be used to adapt while leaving the overall genome stable. We humans do this. Our immune cells can undergo somatic hypermutation - VDJ recombination - to allow accomodation of new antigens in the environment without shuffling the entire genome. https://en.wikipedia.org/wiki/V(D)J_recombination

This sort of intraorganismal somatic recombination allows for a lot of the genomic benefit of sex without the risk to a genome which is successful over the long term. Perhaps your creatures do this for cells other than just their immune cells. I have wondered if long lived plants like trees have some system like this to contend on the fly with parasites that have generation times many orders of magnitude faster.

$\endgroup$

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .