Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

The evolutionary consequences of infidelity

02.04.2013
Male and female blue tits are hard to distinguish for the human observer.

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)

Original publication:
Emmi Schlicht and Bart Kempenaers: Effects of social and extra-pair mating on sexual selection in blue tits (Cyanistes caeruleus). Evolution. Published online on 22 March 2013

Contact:
Emmi Schlicht
Max Planck Institute for Ornithology (MPIO), Seewiesen
Department Behavioural Ecology and Evolutionary Genetics
schlicht@orn.mpg.de
Phone +49 8157 932 349

Prof. Dr. Bart Kempenaers
MPIO Seewiesen, Department Behavioural Ecology and Evolutionary Genetics
b.kempenaers@orn.mpg.de
Phone +49 8157 932 232

Dr. Sabine Spehn
MPIO Seewiesen, Public Relations
pr_seewiesen@orn.mpg.de
Phone +49 8157 932 421

Dr. Sabine Spehn | Max-Planck-Institut
Further information:
http://www.orn.mpg.de

More articles from Life Sciences:

nachricht Two Group A Streptococcus genes linked to 'flesh-eating' bacterial infections
25.09.2017 | University of Maryland

nachricht Rainbow colors reveal cell history: Uncovering β-cell heterogeneity
22.09.2017 | DFG-Forschungszentrum für Regenerative Therapien TU Dresden

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: LaserTAB: More efficient and precise contacts thanks to human-robot collaboration

At the productronica trade fair in Munich this November, the Fraunhofer Institute for Laser Technology ILT will be presenting Laser-Based Tape-Automated Bonding, LaserTAB for short. The experts from Aachen will be demonstrating how new battery cells and power electronics can be micro-welded more efficiently and precisely than ever before thanks to new optics and robot support.

Fraunhofer ILT from Aachen relies on a clever combination of robotics and a laser scanner with new optics as well as process monitoring, which it has developed...

Im Focus: The pyrenoid is a carbon-fixing liquid droplet

Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.

A warming planet

Im Focus: Highly precise wiring in the Cerebral Cortex

Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.

The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...

Im Focus: Tiny lasers from a gallery of whispers

New technique promises tunable laser devices

Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...

Im Focus: Ultrafast snapshots of relaxing electrons in solids

Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!

When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

I-ESA 2018 – Call for Papers

12.09.2017 | Event News

EMBO at Basel Life, a new conference on current and emerging life science research

06.09.2017 | Event News

 
Latest News

LaserTAB: More efficient and precise contacts thanks to human-robot collaboration

25.09.2017 | Trade Fair News

Highest-energy cosmic rays have extragalactic origin

25.09.2017 | Physics and Astronomy

Two Group A Streptococcus genes linked to 'flesh-eating' bacterial infections

25.09.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>