However, in the UV-range, visible to birds, the male is much more colourful. A look at the monogamous mating system again reveals that all is not what it seems: in every second nest are chicks not related to the care-giving father.
Blue tit - is it a male or a female?
Dr. R. Höling
Are all eggs in the nest of these blue tits from one father? Emmi Schlicht
An already mated male can increase the number of his offspring by siring extra-pair offspring. Emmi Schlicht and Bart Kempenaers of the Max Planck Institute for Ornithology in Seewiesen investigated if this could be the driving force behind the evolution of sexual dimorphism. However, effects of extra-pair paternity are limited, cuckoldry can even reduce the intensity of sexual selection.
In many species males and females look very different. Male deer wear impressive antlers and the magnificent plumage of a male peacock is impressive not only to the hen. In our backyard we can identify the male in chaffinches or house sparrows easily from the distinctive colouration of breast and crown. Why do these differences exist? For deer and peacock the answer is straightforward, at least in principle: a well-endowed male can better defend the females on his territory, or attract more females in the first place. For these animals sexual dimorphism has evolved, because such traits help males to obtain additional offspring. For females sexual selection is weaker as they cannot increase their number of offspring by outcompeting other females.
However, many bird species pose a challenge for this explanation by evolutionary biologists. Most bird species are socially monogamous, in permanent relationships with a partner of the other sex. Both parents have to work hard to raise their offspring. So why do males in monogamous species have more colourful plumage than females, if the number of offspring for both parents is decided by the clutch size of the female?
Paternity analyses have long revealed that not all offspring are related to the male that feeds them. Therefore, a monogamous male can have additional offspring if he succeeds in siring additional eggs in the nest of other females. Is extra-pair mating the key to sexual dimorphism?A study on blue tits has tackled this question at its basis. Emmi Schlicht and Bart Kempenaers of the Max Planck Institute for Ornithology in Seewiesen have used data from six years of field research to examine the mating system of blue tits. The result: social relationships are the ones that count, whereas extra-pair liaisons are of advantage but do not strongly enhance sexual selection.
„Male blue tits have most of their descendants with their social partner, some of them can even form pair bonds with two females“ says Bart Kempenaers, the senior author. „A few additional eggs due to an extra-pair mating cannot compete with that“. Selection will thus optimize the traits of these males to secure social success and only to a lesser extent to win additional offspring with extra-pair matings.Interestingly, the scientists found an unexpected effect of extra-pair activity. In a sibship- analysis they estimated that there are up to 24 additional males per year that sire offspring, but do not breed in the nestboxes on the study site. If these unknown males really did not have an own nest, the offspring in other broods were their only descendants. That means that for these unpaired males, the offspring produced by extra-pair matings are essential. “In this case extra-pair matings actually reduce the differences between males in their reproductive success”, says Emmi Schlicht, first author of the study. “That makes a selection of „the best“ less effective and hinders a fast evolution of traits in males that increase their mating success”. Infidelity can even slow evolution of sexual dimorphism. (ES/ SSP)
Dr. Sabine Spehn | Max-Planck-Institut
Fingerprint' technique spots frog populations at risk from pollution
27.03.2017 | Lancaster University
Parallel computation provides deeper insight into brain function
27.03.2017 | Okinawa Institute of Science and Technology (OIST) Graduate University
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
27.03.2017 | Earth Sciences
27.03.2017 | Life Sciences
27.03.2017 | Life Sciences