Sexy sons thanks to mom

Sep 29, 2011
A Zebra Finch male is displaying his color ornaments. Credit: Image courtesy of UZH

It is not the superior genes of the father, but the mother's resource investment in the eggs that makes Zebra Finch males particularly attractive. A Swiss-Australian research team lead by evolutionary ecologists at the University of Zurich has challenged the theory that females mate with superior males to obtain good genes for their offspring.

In Zebra Finches, as in most other , both parents contribute to offspring rearing. The of a female, however, is not always the biological father of the young. If the opportunity arises, females will choose to pair with partners other than their primary mate – with the interesting result that the offspring of different fathers have different qualities. And, as evolutionary ecologists from the University of Zurich and biologists from Macquarie University in Sydney have discovered, offspring sired by an extra-pair partner develop larger color ornaments and are more attractive to females than their social half-brothers.

Up to now, the quality differences between social and extra-pair offspring have generally been assumed to reflect the genetic superiority of the extra-pair male. Indeed, are believed to engage in extra-pair copulation with genetically superior males to obtain better genes for their offspring. Now, Barbara Tschirren, professor for evolutionary ecology at the University of Zurich, and her team have challenged the idea of the exceptional male. In a study published in Proceedings of the Royal Society the researchers demonstrate that -- despite the observed quality differences -- the fathers of attractive sons are neither better looking nor genetically superior.

According to the study, attractive sons are not the result of exceptional ; rather, their enhanced ornamentation is due to the mother's investment in the . Tschirren was able to demonstrate that maternal resource investment decreases steadily over the course of the laying sequence of a , with eggs laid early in a clutch being larger and containing more nutrients and hormones. Favoring early eggs and the first hatchlings is a worthwhile investment for the mother as these offspring have a demonstrably higher chance of survival. "It appears that there is strong competition among males to fertilize these valuable eggs early in a female's laying sequence," explains lead author Barbara Tschirren. "They try to exploit the female's egg investment bias to ensure a head start for their own ." She hypothesizes that sperm competition might decide the battle, with males with faster sperm being able to fertilize the most valuable eggs.

Explore further: Male monkey filmed caring for dying mate (w/ Video)

Provided by University of Zurich

4 /5 (4 votes)

Related Stories

Study fuels debate about why female birds seek extra mates

Apr 30, 2009

When female birds mate with males other than their social partners and have broods of mixed paternity, the offspring sired by these "extra-pair" fathers may often get a head start in life, according to a new report published ...

Attractive dads have more grandchildren

Jul 15, 2011

(PhysOrg.com) -- A study of zebra finches has shown that males' attractiveness influences the number and size of eggs their daughters produce – not genetically but through the effect of their attractiveness on their ...

The cost of keeping eggs fresh for mother cockroaches

Feb 26, 2007

One of the defining differences between the sexes is in the size of their gametes. Males make many tiny sperm while females make only a few large eggs. This suggests that sperm are cheap while eggs are expensive. ...

Infidelity pays off for female Gouldian finches

Aug 23, 2010

(PhysOrg.com) -- Females in socially monogamous bird species such as finches often engage in sexual activities with birds outside the pair bond. This is known to benefit males if they produce more offspring, ...

Recommended for you

Male monkey filmed caring for dying mate (w/ Video)

Apr 18, 2014

(Phys.org) —The incident was captured by Dr Bruna Bezerra and colleagues in the Atlantic Forest in the Northeast of Brazil.  Dr Bezerra is a Research Associate at the University of Bristol and a Professor ...

Orchid named after UC Riverside researcher

Apr 17, 2014

One day about eight years ago, Katia Silvera, a postdoctoral scholar at the University of California, Riverside, and her father were on a field trip in a mountainous area in central Panama when they stumbled ...

In sex-reversed cave insects, females have the penises

Apr 17, 2014

Researchers reporting in the Cell Press journal Current Biology on April 17 have discovered little-known cave insects with rather novel sex lives. The Brazilian insects, which represent four distinct but re ...

Fear of the cuckoo mafia

Apr 17, 2014

If a restaurant owner fails to pay the protection money demanded of him, he can expect his premises to be trashed. Warnings like these are seldom required, however, as fear of the consequences is enough to ...

User comments : 0

More news stories

Meth mouth menace

Something was up in Idaho. While visiting a friend in Athol, a small town north of Coeur d'Alene, Jennifer Towers, director of research affairs at the Tufts University School of Dental Medicine, noticed ...