Evol Ecol Res 3: 199–207 (2001)     Full PDF if your library subscribes.

Is selection ready when opportunity knocks?

Ian M. Ferguson and Daphne J. Fairbairn

Department of Biology, Concordia University, 1455 de Maisonneuve Boulevard, Montreal, Quebec H3G 1M8, Canada

Author to whom all correspondence should be addressed.
e-mail: ian@vax2.concordia.ca


The opportunity for selection, I, defined as the variance in relative fitness, has been called an estimate of the ‘total amount of selection’. However, while a non-zero I is a necessary condition for selection, it is not a sufficient one. We investigated the relationship between I and the magnitude of standardized linear and non-linear selection gradients for body size in the waterstrider Aquarius remigis, measured over three episodes of selection. Male I exceeded female I for daily reproductive success, but the difference was not statistically significant and had little impact on net adult I. Linear selection gradients were only weakly correlated with I, while non-linear gradients were uncorrelated with I. Partitioning I among the three episodes of selection revealed that variance in net adult fitness was largely generated by variance in pre-reproductive survival. The patterns of selection across the adult life stage suggested by analysis of the opportunity for selection differed qualitatively and quantitatively from those revealed by selection gradient analysis. In particular, the former identified pre-reproductive survival as the key component of net adult fitness, even though there is little selection on total length in this life stage. We conclude that I is a useful adjunct to selection gradient analyses, but is perhaps most useful in the analysis of life-history evolution where the traits themselves are direct estimates of fitness.

Keywords: Aquarius remigis, fitness, Gerridae, opportunity for selection, partitioning, selection gradient.

IF you are connected using the IP of a subscribing institution (library, laboratory, etc.)
or through its VPN.


        © 2001 Ian M. Ferguson. All EER articles are copyrighted by their authors. All authors endorse, permit and license Evolutionary Ecology Ltd. to grant its subscribing institutions/libraries the copying privileges specified below without additional consideration or payment to them or to Evolutionary Ecology, Ltd. These endorsements, in writing, are on file in the office of Evolutionary Ecology, Ltd. Consult authors for permission to use any portion of their work in derivative works, compilations or to distribute their work in any commercial manner.

       Subscribing institutions/libraries may grant individuals the privilege of making a single copy of an EER article for non-commercial educational or non-commercial research purposes. Subscribing institutions/libraries may also use articles for non-commercial educational purposes by making any number of copies for course packs or course reserve collections. Subscribing institutions/libraries may also loan single copies of articles to non-commercial libraries for educational purposes.

       All copies of abstracts and articles must preserve their copyright notice without modification.