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.
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