During mating, both males and females sometimes evolve creative strategies to pursue their interests. Researchers from Münster (Germany) and Lausanne (Switzerland) have now found out: Male flies manipulate their partners primarily in order to increase their own chances in reproductive competition. The study was published in the journal "PNAS".
The fundamental biological process of reproduction can differ greatly from animal species to species. Both males and females sometimes evolve creative strategies in pursuing their interests in these mating interactions.
This has been studied for quite some time in small species such as the fruit fly Drosophila melanogaster, where the female receives proteins through the male’s seminal fluid – which, after the actual mating, leads to radical changes in her behaviour and in the processes occurring inside her body.
The proteins increase her activity, reduce her sexual receptivity and stimulate her immune system.
It has been known for some time that such processes are not always beneficial for both sexes. Researchers from Münster (Germany) and Lausanne (Switzerland) have now taken a closer look at which mechanisms change evolutionarily if there are no conflicts of interest between the sexes, i.e. competition between males is eliminated.
The result: male flies produce fewer proteins in their seminal fluid, which changes the behaviour of the females. This means that male flies mainly manipulate their partners in order to increase their own chances in reproductive competition – as a side effect, females often have health disadvantages.
“With the current study we confirm a theory that has existed for a long time,” says evolutionary biologist Claudia Fricke, a research group leader at the University of Münster. The study has been published in the journal PNAS (Proceedings of the National Academy of Sciences).
Background and methods:
In order to determine the extent to which the different interests pursued by each sex play a role in the evolution of fruit flies, the researchers arranged for individual pairs of flies to live monogamously over many generations – contrary to their normal mode of reproduction. Only one male and one female mated with each other, ruling out any opportunity for antagonistic interactions among potential partners.
The male only gained as many offspring as the female could lay eggs. In a second group, five males and five females mated freely with one another. This polygamous lifestyle, a perfectly normal one for these insects, naturally created competition – both between males and between females, with the scope for antagonistic interactions. The total population was, however, of equal size in both groups.
After 150 generations and ten years of sexual selection, the researchers compared the behaviour and physiology of the flies in each group. They found that, in the first days after fertilisation, polygamous females laid one-third more eggs than those flies which had mated in an environment containing only one mating partner. Also, the females which had mated with a polygamous male were noticeably more restless – as shown in recordings of movement patterns. Both are factors that are influenced by receipt of these male seminal fluid proteins.
Why is that of advantage to the male? Since female flies are able to store the sperm of several partners and use it for more than a week to fertilise their eggs, the first male the female mates with does everything to ensure that she lays as many eggs as she can as quickly as possible and does not reproduce with others. This early investment is to the detriment of the female, which is discouraged from saving her energy and procreating over a longer time period.
This was also shown in the study: “Females, which had been with polygamous males died twice as frequently – within a few hours of mating – as females in monogamous relationships,” says Laurent Keller from the University of Lausanne, who was involved in the study with his colleague Brian Hollis.
In a further step, the scientists read out the expression of genes of female fruit flies after mating. In the female’s abdomen and brain – i.e. in the structures responsible for reproduction and for any changes in behaviour – the researchers measured the expression of genes important for reproduction. They discovered that these genes are far less expressed in females, which lived monogamously.
This corresponded to what they found in males. Without any competition, the monogamous males had a lower expression of genes coding for male seminal fluid proteins with which females can be manipulated after mating.
In subsequent studies, the researchers hope to identify further genes that play a role in this process in both female and male fruit flies. The general principles of their observation may also be transferable to other insect species with a similar mating system.
The study received financial support from the German Research Foundation, the Swiss National Science Foundation, the European Research Council and the University of Lausanne.
Dr. Claudia Fricke
University of Münster
Institute for Evolution & Biodiversity
Tel: +49 251 83 21042
B. Hollis et al. (2019): Sexual conflict drives male manipulation of female postmating responses in Drosophila melanogaster. PNAS; DOI: 10.1073/pnas.1821386116
Svenja Ronge | idw - Informationsdienst Wissenschaft
A human liver cell atlas
15.07.2019 | Max Planck Institute of Immunobiology and Epigenetics
Researchers reveal mechanisms for regulating temperature sensitivity of soil organic matter decompos
15.07.2019 | Chinese Academy of Sciences Headquarters
For some phenomena in quantum many-body physics several competing theories exist. But which of them describes a quantum phenomenon best? A team of researchers from the Technical University of Munich (TUM) and Harvard University in the United States has now successfully deployed artificial neural networks for image analysis of quantum systems.
Is that a dog or a cat? Such a classification is a prime example of machine learning: artificial neural networks can be trained to analyze images by looking...
An international research group led by scientists from the University of Bayreuth has produced a previously unknown material: Rhenium nitride pernitride. Thanks to combining properties that were previously considered incompatible, it looks set to become highly attractive for technological applications. Indeed, it is a super-hard metallic conductor that can withstand extremely high pressures like a diamond. A process now developed in Bayreuth opens up the possibility of producing rhenium nitride pernitride and other technologically interesting materials in sufficiently large quantity for their properties characterisation. The new findings are presented in "Nature Communications".
The possibility of finding a compound that was metallically conductive, super-hard, and ultra-incompressible was long considered unlikely in science. It was...
An interdisciplinary research team at the Technical University of Munich (TUM) has built platinum nanoparticles for catalysis in fuel cells: The new size-optimized catalysts are twice as good as the best process commercially available today.
Fuel cells may well replace batteries as the power source for electric cars. They consume hydrogen, a gas which could be produced for example using surplus...
The fly agaric with its red hat is perhaps the most evocative of the diverse and variously colored mushroom species. Hitherto, the purpose of these colors was...
Physicists at the Max Planck Institute for Nuclear Physics in Heidelberg report the first result of the new Alphatrap experiment. They measured the bound-electron g-factor of highly charged (boron-like) argon ions with unprecedented precision of 9 digits. In comparison with a new highly accurate quantum electrodynamic calculation they found an excellent agreement on a level of 7 digits. This paves the way for sensitive tests of QED in strong fields like precision measurements of the fine structure constant α as well as the detection of possible signatures of new physics. [Physical Review Letters, 27 June 2019]
Quantum electrodynamics (QED) describes the interaction of charged particles with electromagnetic fields and is the most precisely tested physical theory. It...
24.06.2019 | Event News
29.04.2019 | Event News
17.04.2019 | Event News
15.07.2019 | Life Sciences
15.07.2019 | Power and Electrical Engineering
15.07.2019 | Life Sciences