I came here to say this; there are many species of Eukaryotes that seem to reproduce exclusively asexually. I know Malmesbury said not to mention Fungi, but I’m a mycologist so it’s what I do. The lesson there seems to be the asexuality evolves fairly easily from sexuality, and is adaptive when you have a good genome which is well adapted to a relatively stable environment. But it’s also kind of a dead end; you don’t usually see large groups of related species which are all asexual (with the possible exception of Glomeromycota, although their genomes suggest they are in fact getting some action). Instead, the closest relatives of asexual species are often sexual species. I believe the same is also observed in plants.
The n°1 reason why I said not mention fungi is that I’m absolutely not a mycologist and I wouldn’t be able to talk about them. So I greatly appreciate that you do it!
Typically, I had never heard of glomeromycota, despite them apparently being involved in symbiosis with 80% of plants. I like to think that I have a decent understanding of the living world, and then I’m constantly reminded that I don’t, and probably nobody does...
My understanding is pretty much what you said—when the going is good, then go asexual (e.g. strawberry runners, grasses or Asian knotweed), but also try for seeds, There are a couple of species of plants that have lost the ability for sexual reproduction, but I can’t recall them right now. That being said, various plants used by humans can be pretty much exclusively reproduced asexually and so have lost the ability for sexual reproduction, specifically because they have very stable environments. The obvious examples are seedless fruits (bananas, grapes), but ginger and garlic are interesting plants that have been propagated from cuttings or bulbs for thousands of years and so lost the ability to produce seeds (with the normal caveats).
Aphids are also an interesting example, where the previous year’s eggs hatch in the spring as females, which then clone themselves as fast as possible—when there’s too many of them they will create clones with wings, and when autumn comes around, they will create male clones to then go through the normal sexual reproductive route. Which is also an example of the stable/unstable environment issues you mentioned.
I came here to say this; there are many species of Eukaryotes that seem to reproduce exclusively asexually. I know Malmesbury said not to mention Fungi, but I’m a mycologist so it’s what I do. The lesson there seems to be the asexuality evolves fairly easily from sexuality, and is adaptive when you have a good genome which is well adapted to a relatively stable environment. But it’s also kind of a dead end; you don’t usually see large groups of related species which are all asexual (with the possible exception of Glomeromycota, although their genomes suggest they are in fact getting some action). Instead, the closest relatives of asexual species are often sexual species. I believe the same is also observed in plants.
The n°1 reason why I said not mention fungi is that I’m absolutely not a mycologist and I wouldn’t be able to talk about them. So I greatly appreciate that you do it! Typically, I had never heard of glomeromycota, despite them apparently being involved in symbiosis with 80% of plants. I like to think that I have a decent understanding of the living world, and then I’m constantly reminded that I don’t, and probably nobody does...
My understanding is pretty much what you said—when the going is good, then go asexual (e.g. strawberry runners, grasses or Asian knotweed), but also try for seeds, There are a couple of species of plants that have lost the ability for sexual reproduction, but I can’t recall them right now. That being said, various plants used by humans can be pretty much exclusively reproduced asexually and so have lost the ability for sexual reproduction, specifically because they have very stable environments. The obvious examples are seedless fruits (bananas, grapes), but ginger and garlic are interesting plants that have been propagated from cuttings or bulbs for thousands of years and so lost the ability to produce seeds (with the normal caveats).
Aphids are also an interesting example, where the previous year’s eggs hatch in the spring as females, which then clone themselves as fast as possible—when there’s too many of them they will create clones with wings, and when autumn comes around, they will create male clones to then go through the normal sexual reproductive route. Which is also an example of the stable/unstable environment issues you mentioned.