Next week's lab meeting:
September 1st 2015, I am organizing the lab meeting at 10.00 in Argumentet.
Fika will be provided as usual. All are welcome!
Persistent directional selection on body size and a resolution to the paradox of stasis
Njal Rollinson & Locke Rowe
ABSTRACTDirectional selection on size is common but often fails to result in micro-evolution in thewild. Similarly, macro-evolutionary rates in size are low relative to the observed strength ofselection in nature. We show that many estimates of selection on size have been measured onjuveniles, not adults. Further, parents influence juvenile size by adjusting investment peroffspring. In light of these observations, we help resolve this paradox by suggesting that theobserved upward selection on size is balanced by selection against investment per offspring,resulting in little or no net selection gradient. We find that trade-offs between fecundity andjuvenile size are common, consistent with the notion of selection against investment peroffspring. We also find that median directional selection on size is positive for juveniles butno net directional selection exists for adult size. This is expected because parent-offspringconflict exists over size, and juvenile size is more strongly affected by investment peroffspring than adult size. These findings provide qualitative support for the hypothesis thatupward selection on size is balanced by selection against investment per offspring, whereparent-offspring conflict over size is embodied in the opposing signs of the two selectiongradients.