Most biologists believe that closely related interbreeding is evolutionarily disadvantageous, since it lowers the genetic diversity of offspring. However, sometimes such crossbreeding can, on the contrary, benefit the population. It is believed that it was the habit of closely related marriages that helped the insane carpenter ant conquer the whole world.
This ant Paratrechina longicornis, which belongs to the Formicidae family (by the way, the well-known red forest ants, Formica rufa, belong to it), is a real disaster for the inhabitants of many tropical and subtropical countries. And not at all because it is poisonous, or bites painfully (as it turned out, these ants are generally harmless to humans), or carries any infections. The fact is that representatives of this species penetrate the walls of houses, settle there and slowly destroy them. In addition, they scurry about everywhere, getting into food, clothes, and even electrical appliances!
And, by the way, why was Paratrechina longicornis nicknamed the “crazy ant”? The fact is that the behavior of workers of this species, collecting food (or, as scientists say, foragers), seemed very strange to zoologists for a long time. Instead of following the forager's trail, finding prey, in orderly rows, they constantly rush from side to side. However, recent studies have explained this strange behavior of the mad ant foragers.
The fact is that the foragers of the mad ant have individual sites for finding food, which only they and no one else hunt. And when one of them discovers a prey, then he begins to randomly run around it, then approaching it, then moving away. By this, he is trying to attract the attention of neighbors so that they come to him and help carry the prey to the anthill. They cannot act in the same way as most other ants, that is, send a scout who will find food and then come running to the anthill for help, marking their way with special "trail pheromones", since they simply do not have them. So you have to arrange dances like those that are arranged by people who meet their relatives at the airport, just in order to attract their attention.
Initially, representatives of the species Paratrechina longicornis lived in the forests of South America, preferring to choose rotting tree trunks for settlement. However, in the 20th century, due to the fact that people began to increasingly penetrate the virgin South American forests, they decided that the wooden walls of a human dwelling are very good in order to build a refuge in them. As a result, the mad ants first conquered the entire New World, and then crossed the oceans on ships and planes and settled in Eurasia, Africa, Australia and Oceania.
Why did these ants manage to spread so widely throughout the world? It is possible that in this they were helped by … incest. Recently, zoologist Morgan Percy of the Free University of Brussels, studying the life of insane ants in laboratory conditions, found that young males and females of this species, when it comes time to leave the anthill and find a mate, do not do it at all. They remain in the nest and mate with each other, that is, figuratively speaking, "indulge in an incestuous relationship." After that, the males die (not at all from shame, it's just that all ants have it), and the fertilized females, attracting some of the workers, establish a new nest not far from the old one (scientists call such a settlement “layering”).
Such behavior of the "newlyweds" Paratrechina longicornis looks even stranger than the mad dances of their foragers. It is no secret that most animals are trying in every possible way to avoid closely related crossings, since they reduce the genetic diversity of the population. And this, in turn, leads to the accumulation of dangerous mutations and a decrease in the ability to adapt to changes in the environment. That is why young males and females in most species of ants during the mating season try to fly away as far as possible from their native nest - there the likelihood of incest is greatly reduced.
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However, oddly enough, this breeding method also has its advantages. It has long been known that up to 80% of young ants can die from predators and accidents during ant summer. And fertilized females are also far from always able to establish a nest in an unfamiliar area - more than two-thirds of them will die without giving rise to a new colony. The mortality rate of newlyweds during intra-nest mating is very low - about five percent. In addition, almost all females immediately organize viable layering colonies.
Dr. Percy believes that it was this kind of incest that helped the insane ant spread so widely across our planet. Indeed, if most of the fertilized females survive, then the total colony population grows rapidly (mainly due to layering). And this, in turn, leads to the expansion of the territory controlled by ants, which provides additional growth in numbers, and so on, like a chain reaction. As a result, the invaders of Paratrechina longicornis successfully drive out many of their neighbors belonging to other species. Because of this, in many countries, nature conservation workers have already declared a real war on this ant (which, however, is still very unsuccessful, because the insane ant turned out to be very resistant to the action of most insecticides).
Photo: AP
Through more detailed genetic studies, scientists also realized that what appears to be incest at first glance is not. After all, the young female of these ants mates sequentially with several males. Their germ cells are stored in special seminal receptacles for the rest of her life. Having studied the genotypes of males, females and working individuals, scientists came to the conclusion that they are all different from each other, since by laying different eggs, the female distributes the genetic material in different ways.
It turned out that when the queen lays eggs, from which the female princesses will appear, only the genetic material of their mother gets into them (that is, these eggs develop without fertilization). The eggs from which the princes are hatched are very diverse, since they contain only the genetic material of their fathers (after fertilization with a sperm, the egg cell's genes degrade). That is, each prince is essentially a clone of his father, and the princess is a mother. Therefore, genetically they cannot be called relatives, and, therefore, there is no incest here.
But all these tricks do not apply to workers, they contain both paternal and maternal genes. So in terms of heredity, non-breeding individuals are the most diverse in the family. This looks quite logical - after all, it is hardworking workers, not idle queens, who must ensure a high degree of adaptability of the entire family to changes in environmental conditions.
True, one of the moments in the personal life of ants is still unclear. If in the first generation closely related crossing does not cause incest, then after a few generations all males and females of a large colony will still be relatives. How do they proceed in this case? Maybe they are still arranging a marriage flight?
Scientists cannot give an answer to this question, since the observed group of ants in the laboratory has been living for a relatively short time and they have not yet faced such a problem. However, it is possible that in nature, insane ants can combine both periods of intra-nest reproduction and periods of out-of-nest mating.
So, as you can see, what is unprofitable under some conditions turns out to be advantageous under others. And even incest can sometimes lead to evolutionary progress …
ANTON EVSEEV