Beetle study explains how parental care influences evolution
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A group of researchers has demonstrated that the progress of species can be determined, both at the individual and population level, by collective dynamics. A fundamental role is played by the attention from the parents or their absence
The parental care they are an example of parental investment in favoring the survival and expansion of one’s genetic heritage in a population.
From the point of view of the “selfish gene”, that is, it is a way in which the replicative efficacy of a certain genome is increased, by increasing the number of copies it will leave in the population, not through a greater number of replicative cycles – that is, by increasing the progeny beyond belief – but by increasing the probability that one’s progeny, by becoming an adult, can in turn multiply.
In addition, for those species like ours that also transmit a culture, and not just genes, taking care of the children for a sufficiently long time serves to transmit additional information useful for survival with respect to that encoded in the genes and that obtainable from each individual directly from the environment.
However, a new study, published for now in the form of a preprint, illustrates a further, interesting consequence connected to the practice of parental care. Contrary to the effects which have just been mentioned, which increase the fitness of an individual (or rather of a couple of individuals, in the case of sexual reproduction) by increasing the chances of survival and replication of their offspring, in the work just published they show effects of different types, which affect the fitness of an entire population, and therefore of the species as a whole, increasing the reserves of genetic variability available to cope with environmental changes.
Researchers have been experimenting with a particular type of beetles (Nicrophorus vespilloides). These beetles seek out the corpses of small animals such as mice or birds. In the presence of a corpse, a male and female form a pair, fighting each other’s conspecifics and gradually burying their prey. They then remove feathers or fur and intestines, then coat the corpse with antimicrobial fluids to form a nest. Then they lay eggs. Unusual among beetles, the parents may stay and care for the young. Not only do they protect them from predators, but they also feed the larvae, which are able to request food with stereotyped movements, i.e. by lifting the anterior half of the body.
The researchers created four groups of 60-80 beetles each in the laboratory. In two, the parents were removed after spawning; in the other two, the parents remained with their offspring throughout their time. Populations were allowed to evolve over 30 generations, and the entire genome of some larvae was sequenced in each generation.
Populations without parental care have evolved rapidlyFor example, their jaws have become larger to help the larvae penetrate the carrion available to them, and individuals have become more cooperative with their siblings for the same reason.
Interestingly, however, was the finding of a much higher mutation rate in parental care populations, which did not evolve specific traits, compared to those deprived of parental care. While the latter have specialized in the new condition, much more genetic variability has remained in the former; even some lethal recessive mutations have been maintained, ie which killed the carriers in double copy.
This result implies that the lower environmental pressure, due to the protection offered by the parents, allows the survival of a greater number of genetic traits in a population (including some negative ones); since, in general, genetic variability in a population means a greater possibility of adaptation in the event of new environmental pressures, the demonstration of a long-hypothesized but never proven role of parental care in favoring the adaptability of a species emerges through the study promoting individual genetic variability in component populations.
In the case studied, moreover, it is also observed how the harsher environment experienced by individuals without parental care has imposed a strong directional selection with consequent rapid adaptation and reduction of genetic variability in the population. Among the genetic adaptations observed in populations without parental care, we note in particular a set of effects on genes that control social behavior: the loss of parental care, that is, favors the emergence of a new social trait, the increased congregation among individuals of the same offspring, which partially balances the negative effects in terms of malnutrition and exposure to the dangers due to the absence of the parents.
These results indicate that, downstream of the well-established genetic effect in determining an individual’s social traits, there is also an inverse effect at the population level, in which social traits such as parental care (or lack thereof) determine both the overall genetic variability of a population and the selection of compensatory genetic traits, which then, in turn, can again manifest themselves in the form of social adaptations of behavior.
Thus, genes and behaviors chase and influence each other, determining a continuous adaptive chase to increase the survival and well-being of populations, demonstrating how social traits are also part of our extended phenotype and influence the Darwinian selection of genes more suitable.
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