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Darwinism explains beetles’ same sex behaviour?


From Eurekalert:

The frequent occurrence of same-sex behaviors in beetles of one sex could be explained by genes that are favored by natural selection when expressed in the opposite sex, according to a study published in the open access journal BMC Evolutionary Biology.

The study by researchers from Uppsala University, Sweden sheds new light on same-sex sexual behavior in the animal kingdom through examination of the seed beetle, Callosobruchus maculatus, a common beetle found in bean stores across the world.

The scientists showed that when a particular sex had been bred for increased SSB, siblings of the opposite sex enjoyed an increase in reproductive performance. They also showed changes in traits such as mobility and sex recognition after selective breeding on SSB, providing evidence for genetic links between SSB and these traits across the sexes, according to the researchers.

Dr David Berger, lead author of the research paper, said: “Our findings show that studying the genetic links between different characteristics in males and females can hold major clues to how genetic conflicts between the sexes shape the evolution of traits, and same-sex sexual behaviors are just one example of this. The genetic mechanism explaining the occurrence of SSB that we demonstrate in these beetles could apply equally well in very different animals.More.

So same-sex behaviour in cowpea weevils actually helps increase their numbers? That sounds counterintuitive.

If one could induce same-sex behaviour in all of the beetles, we would see many fewer of them, no?

Also, why would it apply “equally well in very different animals”? If it did, should we not look first in other groups of beetles?

Rob Sheldon wrote to say,

It’s politically motivated research, which is to say, undoubtedly wrong.

The theory is that reproductive advantage for female beetles, say, a gene that makes it produce more pheromes and attract more males, will also be expressed in males. So the benefit to females turns out to make males more “gay” and suppress their reproduction. Hence the gene helps one sex but hurts the other, causing a genetic “war”.

There are just so many things wrong with this study, I don’t know where to start. To begin with, reproduction takes two to tango, and this supposed “war” will perhaps change the ratios of M/F but says nothing about the success of this species, which is what Darwinism is all about. E.g., we are applying Darwinism where it manifestly doesn’t work.

Furthermore, the sex ratios are not a genetic war, they are dictated more by environment. This has almost nothing to do with genes.

Third, the beetles may not even be using the X/Y sex chromosomes that people have, so whatever is going on in beetle genetics may have nothing to do with humans.

Now that he mentions it, sex in insects seems often to be determined very differently than in, say, mammals:

Sex determination refers to the developmental programme that commits the embryo to either the male or the female pathway. The animal kingdom possesses a wealth of mechanisms via which gender is decided, all of which are represented among the insects. This manuscript focuses on a number of insects for which genetic and molecular data regarding sex determination mechanisms are available. The sex determination genetic cascade of Drosophila melanogaster is first discussed, followed by an analysis of the sex determination genes of other dipteran and non-dipteran insects. Representative examples of sex determination mechanisms that differ in their primary signal are also described. Finally, some evolutionary aspects of these mechanisms are discussed.

File:A small cup of coffee.JPG Oh well, if it can be called evolution, it will make sense to lots of people, no matter what.

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Its not same sex attraction if they will go both ways. Do these bugs REJECT the opposite sex.? will they reject breeding with the opposite? Not just liking both or mixed up! no creatures in the animal kingdom are ever homosexual. They never reject the opposite sex. tIndeed all easily are bi sexual. They don't care. only humans care because of relationship to each other is based on identity and not mere sexual fun or need to reproduce. just as in the animal kingdom NEVER do creatures judge the opposite sex by looks. They never care about beauty ideas in the opposite sex. Only people do. again because its about identity. Robert Byers
If one could induce same-sex behaviour in all of the beetles, we would see many fewer of them, no?
Possibly, possibly not. It would partially depend on whether males will only try to mate with a single sex: if they are willing to mate with both, and mate several times, then the cost of an incorrect mating might be low enough that it can be offset by the advantages. Whether it is or not I don't know: one would have to do the maths. I'm not sure what Rob Sheldon was trying to say - the paper is nothing to do with sex ratios (as it happens this species does have an X/Y sex determination system). I can't see how it would affect sex ratios if the determination is genetic. And if it was environmental you would need a gene by environment interaction to get a change in sex ratio as a response to genetic changes. Bob O'H

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