Energy allocation in desert winter annuals: test of the r- and k- selection theory

TitleEnergy allocation in desert winter annuals: test of the r- and k- selection theory
Publication TypeThesis
Year of Publication1978
AuthorsDePree E
Number of Pages77
Date Published1978
UniversityNew Mexico State University
CityLas Cruces, New Mexico
Thesis TypeM.S. Thesispp
Call Number00494
Keywordsannual plant, reproduction, dissertation, dissertations, reproduction, annual plants, selection theory,annual plants, theses, thesis
AbstractPopulations of three winter annuals were sampled in two or more of the U.S. southwestern deserts: Mojave, Sonoran, and Chihuahuan. These deserts represent different levels of environmental predictability as defined by rainfall patterns. The Mojave has the most winter rainfall and the Chihuahuan has the least winter rainfall, with the Sonoran intermediate. Collections of approximately 30 individuals of each species took place in a number of sites where the species occurred in each desert. Sites varied greatly in topography and soils. The purpose of this study was to determine if reproductive allocation varied between populations within and between deserts as predicted by the concept of r-K selection. For each species, large variations in reproductive allocation were found between populations sampled within a desert. The differences between sites could be paritally expelained by the difference in the topography and soils of the colleciton sites. No consistent differences were found in reproductive, vegetative or root allocation between populations of different deserts, relative to r- and K-selection theory. Dewert annuals appear to ahve adapted to unpredicatble rainfall patterns by methods different than simply increasing reproductive allocation, indicating that not all adjustments in life-history strategies cna be explained by invoking the r- and K-selection theory.