Evol Ecol Res 7: 421-434 (2005) Full PDF if your library subscribes.
Likelihood models for discriminating alternative phenotypes in morphologically dimorphic species
J. Mark Rowland1* and Clifford R. Qualls2
1Department of Biology and 2Department of Mathematics and Statistics, University of New Mexico, Albuquerque, NM 87131, USA
Author to whom all correspondence should be addressed.
Question: How can we numerically discriminate with explicit confidence the alternative phenotypes in dimorphic species with bimodal threshold traits?
Mathematical method: A bimodal distribution of a dimorphic trait is parameterized by mixture distribution models for normal and gamma distributions. Likelihood ratios of the alternative phenotypes for a given trait size are computed from the mixture models. The likelihood models are tested in several horn-dimorphic beetles and compared with existing piece-wise linear regression methods.
Key assumptions: The bimodal distribution represents a mixture of two discrete distributions. The alternative phenotypes have normal or gamma distributions.
Conclusions: Likelihood methods effectively model the way in which alternative phenotypes are expressed in taxa with bimodal trait size frequency distributions. New likelihood models estimate the probability that a given trait size represents a given phenotype in normal to skewed bimodal frequency distributions. These prove theoretically and empirically superior to linear regression methods. Likelihood methods model the behaviour of threshold mechanisms in natural populations and will enhance exploration of the evolutionary significance of intraspecific conditional phenotypes.
Keywords: alternative tactics, horn dimorphism, intrasexual polyphenism, likelihood models, threshold traits.
DOWNLOAD A FREE, FULL PDF COPY
IF you are connected using the IP of a subscribing institution (library, laboratory, etc.)
or through its VPN.
© 2005 J. Mark Rowland. 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.