About horns

Gentlemen, coleopterists, please clarify the following question. In different subfamilies of scarabaeidae, and even in lucanids, there are very similar morphotypes of the male's prehensile apparatus: one horn on the head, and one or more horns on the pronotum opposing it. Is this horniness a sign of an ancestral form for all these groups, which was later lost by many, or is it a convergent similarity?

Uv. Eno, don't swear like that, please ))

This post was edited by koty - 01.11.2016 13: 20

What exactly did you see as an expletive? While waiting for an answer, I will probably correct the bourgeois "gentlemen", after which a comma was accidentally placed, introducing some ambiguity, to the proletarian "comrades"

This post was edited INO-01.11.2016 17: 30

What exactly did you see as an expletive? While waiting for an answer, I will probably correct the bourgeois "gentlemen", after which a comma was accidentally placed, introducing some ambiguity, to the proletarian "comrades"

Yes, I was just joking)) in the sense of coleopterologists, morphotypes, ancestral, convergent, etc...

And on the merits of the question, what do you think/know?

RAPID ANTAGONISTIC COEVOLUTION BETWEEN PRIMARY AND SECONDARY SEXUAL CHARACTERS IN HORNED BEETLES
Harald F. Parzer and Armin P. Moczek
here is a more concise note on this topic:
On the origin and evolutionary diversification of beetle horns
Douglas J. Emlen, Laura Corley Lavine, and Ben Ewen-Campen

Thank you, but could you briefly answer the question in your own words?

in short, I think this is a convergent similarity, but you can understand in each case by comparing how they use these horns - that is, maybe the whole family is characterized by some kind of pose in the mating game that contributed to the appearance of such horns.

These horns are not used for mating games, but for fights between males. The shape is quite consistent with the function: the protrusions on the head and on the reconnection form prehensile pincers, the hinge in which is the connection of the head with the chest. With these ticks, the beetles grab their opponents, tear them off the substrate and throw them from the tree to the ground. But if this is purely a convergence, then it is strange why such horns are found only in scarabaeids and phylogenetically close to them lucanids, while in other beetles they do not occur. There must be something that unites them in addition to ethology, perhaps the "horned" genes inherited from a common ancestor, but inactivated in many of his descendants. Then the mutation occurs again-the genes are activated again and horns appear again. And those orders of beetles that do not have these genes because of their origin from other ancestors, obviously, it was much more difficult to acquire such a device from scratch, and many of them took alternative paths. For example, in males of many hornless animals (who have lost their horns?) lucanides for grabbing rivals hypertrophied the mandibles, and the same thing happened in some cerambycids, the latter ticks of the first type have never possessed. Obviously, there is already convergence in its purest form. Somehow, this is how I think purely speculatively.

These horns are not used for mating games, but for fights between males.

well mating games are right here

With these ticks, the beetles grab their opponents, tear them off the substrate and throw them from the tree to the ground.

here I am not sure that everyone with horns does such things - especially dung beetles, who just try to hide in the manure or grass. and the horns are not the same as those of the hercules beetle, but still not bad.

But if this is purely a convergence, then it is strange why such horns are found only in scarabaeids and phylogenetically close to them lucanids, while in other beetles they do not occur.

well, that's why I think that there is a certain preadaptation here. but in what form:[quote=ENO, 22.11.2016 00: 35]

Well, they hide in manure, as I understand it, from predators (including collectors) and not from male rivals. Here you immediately need to compare which dung beetles have pronounced horns, and it is their behavior that you should observe more closely. At the same time, take into account that their activity is mainly nocturnal, and any light can frighten. It seems to me that, for example, copras still use their horns. In any case,of all the horned beetles whose behavior I had the opportunity to closely observe (including tropical bronzes), there was not one that shirked the use of horns for their intended purpose. I think that as soon as the horns lose their functionality, they begin to reduce, because without them it is much more convenient to rummage in the substrate. It is not for nothing that females of almost any species have horns of this type. Although, of course, I do not exclude the existence of beetle species with non-functional horns, which simply have not yet managed to lose them.

no, well, I started talking about manure to the fact that it's not on trees and they have no place to throw each other off, besides, just on that day when I wrote the message, I saw a bunch of these same dung beetles, including srogami and flying in the brightest sunlight.
of course, there may be species that have not lost their horns, but dung beetles often have an interesting phenomenon of male dimorphism and positive allometry of horns and body - that is, inside many species there are both hornless and horned forms

This is typical not only for dung beetles, but also for almost all horned beetles in general (including those horned with mandibles). And here it is not only and not so much in genetics, but in the conditions of development of the larva and pupa. If there is not enough food or space, then small males with very modest horns are obtained. They are naturally unable to fight on equal terms with their more horned cousins, but they still have a chance to find a lone female and fertilize her while the others are not around. But I have not seen horned dung flies flying in the daytime, apparently, this is not our fauna.

Well, it is obvious that roka can be used not only to drop from a tree, but also on the ground to turn the opponent over or just drive away, pushing like a bulldozer. On trees, their effectiveness is simply maximized, so this mechanism reaches the greatest development, mainly in tree beetles.