When They Become British Stick Insects Stop Bonking

And quite right too, none of that bringing your filthy foreign habits over here. A particular species of stick insect immigrated with some plants perhaps a century ago. And since then they seem to have gone off bonking and now reproduce asexually:

A New Zealand stick insect that migrated to the UK more than seven decades ago has given up having sex and become asexual, prompting biologists to wonder about the use of sex at all – especially in Britain. The Clitarchus hookeri* is native to New Zealand but migrated to the UK some time between 1910 and 1935, catching a ride on shiploads of New Zealand plants that were transported to the subtropical Tresco Abbey Garden on the Scilly Isles islands off the coast of Cornwall.

Biologists from Massey University in New Zealand’s North Island have discovered that some time in the last 100 years the Scilly isles population of Clitarchus hookeri gave up having sex and start to reproduce asexually. The local population of Scilly Isles stick insects is now entirely female.

Well, OK, so that’s fine. Insects will do as insects do, foreigners as foreigners. What does worry though is that the biologist seems not to grasp the basics of his own subject:

Morgan-Richards said the research presented several avenues for further study – including why sex remained useful for species at all, when from an evolutionary perspective females save time and energy by reproducing alone.

Yes, we even know what this is:

“It is a difficult road to get back into sexuality, but the fact it is almost universal shows that there must be an evolutionary advantage to having males and females produce offspring,” said Prof Steve Trewick of Massey.

Indeed so and again we know what this is.

Asexual reproduction – cloning – is just great in a stable environment. It is indeed more efficient in those energy terms – just think of all the energy not expended on dating.

By analogy, planning works in a stable economy too. If we’ve a static set of technologies, a static set of consumer desires, then sure, the bureaucracy will indeed zero in – barring public choice theory – on efficient methods of using the one to sate the others. But as that experiment called the 20th century showed us, neither capability nor desire stays static. Therefore we need the chaos of the market economy to do that sorting and efficiency drive for us.

And so it is for sex and evolution. That clone that is the commercial banana does just fine in that stable environment. Then some bug mutates – the bug is evolving even if the banana isn’t – and the entire crop of all the world’s bananas is at risk. As happened to the Gros Michel and is to the Cavendish. And as will happen to the asexual stick insects at some point.

We need the mixing of the genes in order to preserve their existence over the longer term. For no other reason that everything else is doing the mixing therefore the insect has to too.

Or, as the standard evolution story puts it, it’s the environment that determines suitability and that environment is constantly changing. Therefore so does suitability and sex is the answer to that.

*There are very British fnarr fnarr jokes to make about the name of this species but we’ll leave those to the reader.

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Quentin Vole

I’d question whether sexual reproduction is ‘almost universal’*. There are many species that reproduce entirely asexually (or almost so), including very successful ones.

* unless we’re talking about a specific phylum, such as chordata.