VARIATION IN OFFSPRING SIZE WITH BIRTH ORDER IN PLACENTAL FISH: A ROLE FOR ASYMMETRIC SIBLING COMPETITION?
Article first published online: 20 SEP 2011
© 2011 The Author(s). Evolution © 2011 The Society for the Study of Evolution.
Volume 66, Issue 1, pages 272–279, January 2012
How to Cite
Schrader, M. and Travis, J. (2012), VARIATION IN OFFSPRING SIZE WITH BIRTH ORDER IN PLACENTAL FISH: A ROLE FOR ASYMMETRIC SIBLING COMPETITION?. Evolution, 66: 272–279. doi: 10.1111/j.1558-5646.2011.01422.x
- Issue published online: 3 JAN 2012
- Article first published online: 20 SEP 2011
- Accepted manuscript online: 29 JUL 2011 02:10PM EST
- Received February 26, 2011, Accepted July 15, 2011, Data Archived: Dryad doi:10.5061/dryad.ng20q
- Heterandria formosa;
- size at birth;
- sibling competition;
Asymmetric sibling competition arises when siblings with different competitive abilities share a limited resource. Such competition occurs in species with postnatal parental care and may also occur when mothers provision embryos between fertilization and birth (matrotrophy). We hypothesized that the combination of matrotrophy and the simultaneous provisioning of embryos in different stages of development (superfetation) leads to asymmetric competition between sibling embryos. Moreover, we expect the intensity of this competition to increase with the level of superfetation as high levels of superfetation result in greater temporal overlap between broods. This hypothesis predicts that offspring from early broods, which predominantly compete with less-developed siblings, will be larger at birth than offspring from later broods, which experience competition from more and less-developed siblings. Data on offspring size at birth from two populations of the highly matrotrophic fish, Heterandria formosa, and similar studies of poeciliid fish spanning a range of life histories are consistent with our hypothesis. Together these results suggest that sibling competition is a direct consequence of the evolution of matrotrophy and superfetation in poeciliid fish.