Life as a female moth is hard. Sitting alone in the dark, you are listening to the ultrasonic sounds of the night. Is this the attractive call of a male moth? If so, go ahead and make some love. But be careful. Bats are out there. You can hear their ultrasonic sounds which they use for echolocation. So you should be sure that the singing male moth is worth the risk. Is it the Romeo of your dreams or just a little wimp? The answer lies in the song, the environment temperature and your perception. The lesser wax moth (Achroia grisella) belongs to the group of insects which choose their partner mainly by their acoustic performance, like you know it from crickets and grasshoppers. A healthy male moth is supposed to produce louder songs with higher frequencies, compared to his old/weak rivals. However, there is the problem of the environmental temperature which can make the process of finding a partner a little bit more tricky. As cold blooded animals, the muscle performance of the male (and so its song quality) is enhanced with increasing temperatures. Therefore, in grasshoppers, not only the male song changes with increasing temperature but also the preferred song of the female is temperature dependent. This temperature coupling of “producer” and “receiver” ensures that the female is able to identify the males of the right species at different temperatures. (Here I would like to refer to the great work of my former colleague F.A. Römschied https://elifesciences.org/articles/02078 ). But is this temperature coupling, which can be found in many different acoustic species, really the result of the evolutionary need to find the right partner or is it just a lucky coincidence, that the female perception changes with temperature? This is the question of a paper from Greefield and Medlock in 2007. They point out that temperature coupling just makes sense when you (1) have a narrow range of “attractive songs” for females which selects against faster and slower rates and you (2) have other acoustic species around, which you have to distinguish. Therefore, in their paper, they focus on the lesser wax moth, which does not fulfill these criteria. Female moth prefer any songs above a certain frequency and their habitat is lacking any other acoustic species (besides the bats with low frequency sounds). Moreover, the female acceptance threshold for acceptance is much lower than the male song rates. Therefore, temperature effects on male song rates does not conflict with the moth concept of “the fastest and loudest song is the most attractive one”. Nevertheless, male song rate and female acceptance threshold do exhibit parallel increases with elevated temperature. But why, when there is no evolutionary benefit? Greefield and Medlock show that male and female thermal effects are genetically correlated. Of course that genetic coupling could be there, because evolution selected for parallel temperature effects in female and male. However, as evolutionary benefit of thermal coupling is hard to explain in this case, it could also be, that the thermal coupling is just a coincidence because the same genes can control different properties in different tissues like the song production with the wings in the male and the song perception in the female. So the main message of the paper is, that when there is thermal coupling between the sexes, you should not automatically assume that it is based on an evolutionary need to adapt sound and sound preference but it could also just be that sound production and sound perception are two temperature dependent processes which are controlled by the same genes.
0 Kommentare
Hinterlasse eine Antwort. |
IdeaI love to increase my general science knowledge by reading papers from different fields of science. Here I share some of them. Archiv
März 2018
Kategorien
Alle
|