Nature press release:
Evolution: Placenta evolution increases fish promiscuity
DOI: 10.1038/nature13451
The evolution of placentas in certain species of fish helps the females to
keep their options open when picking a mate while allowing males more
chances of opportunistic mating, a study in this week’s Nature shows. The
findings may advance our knowledge of the evolution of reproductive traits
in other animals that evolved placentas.
Among animal species that lay
eggs for external fertilization, females select mates based on courtship and
display traits that may give an indication of the male quality, but risk mating
with genetically inferior males masquerading as suitable mates. The
evolution of the placenta reduces the risks of wasting costly eggs and is
thought to reduce mate selection occurring before copulation — instead, it
is assumed that the female relies on post-fertilization cues that influence
maternal investment in their embryos.
To investigate changes in sexual
selection linked to placenta evolution, Bart Pollux and colleagues study
Poeciliidae — a family of fish that includes guppies and their relatives in
which placentas have repeatedly evolved or been lost. They show that the
evolution of the placenta is associated with large mixed-paternity litters
resulting from females mating with multiple males. Males become less
showy as they do not need to attract a mate; moreover, males become
smaller and have longer genitalia that allow them to be sneaky or coercive
with copulation, thereby circumventing female choice.
These adaptions
increase male reproductive success and decrease the female’s risk of
putting all of her eggs in a genetically inferior basket.
CONTACT B. J A. Pollux (University of California, Riverside, USA) Tel:
+31 (0) 317 486083; E-mail: b.pollux@gmail.com
Link to the scientific paper: http://dx.doi.org/10.1038/nature13451