Long-tailed tit, or polovniki avoid mating with parents and children, because they learn their voice. This mechanism helps to reduce the risk of inbreeding in terms when related birds settle together and occasionally help each other raise offspring, say the authors publishing in the journal PNAS. Meanwhile, no protection against mating between brothers and sisters in this species does not exist — possibly because the risk of such events is much lower.
Inbreeding results in offspring that suffer from health problems and has a low breeding success. Biologists call this phenomenon of inbreeding depression and is associated with the fact that interbreeding of close relatives increases the risk of homozygous individuals, in the phenotype which are manifested harmful mutations.
It is not surprising that most organisms have learned to avoid inbreeding. For example, many birds, this problem is solved very simply: young individuals settle upon a vast territory, where they are unlikely to have another meeting with the parents or the siblings. However, in some species, social structure is too complex, so such passive protection was effective.
A classic example of the kind of long-tailed tit (Aegithalos caudatus). These small insectivorous birds inhabiting the North of Eurasia, does not belong to the family of the true Tits (Paridae), so many bird watchers prefer to use national name — polovniki. In addition to the breeding pair in rearing offspring in this species, often involves the so-called helpers — birds of the neighbouring land who have lost a partner or the clutch and try to compensate this by helping related individuals.
Young polovniki often settle near their place of birth, that is, next to relatives. This increases the likelihood that they will become helpers, but also increases the risk of inbreeding. A team of ornithologists headed by Amy Lidell (Amy E. Leedale) from the University of Cambridge wondered whether polovniki avoid inbreeding, and if so — how they do it. To find out, they carefully studied the population of this species, which inhabits the surrounding area of the British city of Sheffield.
First the researchers estimated how dangerous inbreeding of long-tailed Tits. Comparing the extent of homozygosity 17 genetic markers with multiple indicators of adaptation of individuals, they came to the conclusion that inbreeding can negatively affect overall health and reduce the success of hatching eggs. Thus, Polonicum advantageous to avoid inbreeding.
Further analysis showed that although the members of this species often live surrounded by relatives, they are rarely associated with them to form pairs. Of the 609 couples the monitoring that was conducted from 1994 to 2016, only one consisted of first-order relatives (parents and children) and two of the relatives of the second order (brothers and sisters). Genetic analysis and mathematical modeling have confirmed the low level of interbreeding between parents and children. However, they also showed that brothers and sisters mate among themselves more often: the signs were observed in 15% of couples, which corresponds to a random choice. According to researchers, social structure of long-tailed Tits make the most likely pairing between parents and children and between brothers and sisters. That is why a special mechanism, which would avoid mating with relatives of the second order, has not appeared.
The watchers knowthat polovniki are able to distinguish relatives of the first order according to the votes of the parents and the children they have high similarity, which is laid in the early stages of life. This mechanism allows potential sponsors to find out their parental couple and join her for rearing. The authors of the study speculated that he used to avoid inbreeding. To test this hypothesis, they analyzed the characteristic of long-tailed Tits “ringing” signals — calls. It turned out that breeding pairs calls partners differ much stronger than the calls of males and females that have each other relatives of the first order. According to the researchers, this means that polovniki avoid partners whose voices are similar to their own. This mechanism also helps them to avoid mating between parents and children.
The need to know each other by voice not only allows you to choose the right partner, but also increases the efficiency of hunting. For example, as shown by a recent study bats skladchatogo Pallas (Molossus molossus) mark their echolocation signals, which allows individuals from one group not to scatter too far and hunt together.
Sergey Knee High