Observations of viviparous petsilia have helped biologists to prove that the sexual preferences of females completely determine in which direction the evolution of their species will go. The scientists' findings were published in the journal Nature Communications.
The development of almost all multicellular living things is governed by two factors - natural and sexual selection. In the first case, evolution is conducted by changing environmental conditions, and in the second - intraspecific competition for the opportunity to continue the genus.
As a rule, the brightest individuals win this struggle, which leads to the appearance of such useless ornaments as peacock tails or rooster combs, which most often do not help, but interfere with survival.
The reasons for the existence of sexual selection are still a matter of controversy among scientists. Some biologists believe that it helps populations to be prepared for abrupt changes in conditions. Others believe that such competition protects species from degeneration and keeps them competitive in an evolutionary arms race.
In the past, as Reznik notes, scientists believed that sexual selection works quite simply - females choose the male that is most interesting to them and mate only with him, which pushes the entire species towards acquiring their distinctive features. In other words, sexual selection should be the main driving force behind evolution.
Recently, these classic Darwinian notions have been shaken as biologists have discovered that females of most animal species mate not once, but several times in a single breeding season.
This, as many evolutionists have suggested, should ease the pressure of sexual selection on males or eliminate it altogether. Others, on the other hand, believe that the loving nature of females should enhance sexual selection, forcing males to compete in how many gametes they can produce and how often they can have sexual intercourse.
Reznik and his colleagues have figured out the reason for this behavior of females, and have proven that they continue to play a leading role in the evolution of species by studying breeding strategies and observing the behavior of several dozen species of platies.
Promotional video:
These fish, as evolutionists have noticed, can be divided into two broad categories based on how their males look. Some species have rather ordinary-looking representatives of the stronger sex, while in others they look very bright and actively compete for the attention of females.
When Reznik saw bright male platies in the store, he drew attention to an interesting fact - they all belonged to those species of fish that do not have a placenta, but bear offspring in the womb. Nondescript suitors almost always belonged to the number of "placental" species.
This observation gave him the idea that such a coincidence was not accidental and was due to how the choice of females influenced the evolution of these species. To test this idea, he acquired several dozen platies, and also analyzed the genomes of almost two hundred of these fish and the records of naturalists about their mating traditions.
Such a comparative analysis not only confirmed Reznik's suspicions, but also revealed several interesting features of evolution that scientists had not previously suspected. For example, it turned out that the absence of a placenta doubled the rate of evolution and the formation of new species.
The ways for this can be very different - the female's organism can independently "select" higher-quality genetic material even before fertilization or kill insufficiently high-quality embryos after it. All this, as biologists have found, greatly influenced the appearance of males, the speed and general nature of the evolution of platies.
Interestingly, the doubled rate of evolution in those fish species whose females did not have a placenta completely contradict the well-established theories about the principles of the formation of new species, as well as observations of how this process proceeds among mammals.
Why this is so, scientists have yet to find out, but Reznik and his colleagues believe that this is due to the fact that other groups of scientists studied not the formation of new species, but the process of their separation after separation from the common tree of evolution. They plan to test this by studying similar relationships among other viviparous fish.