Ecological genetics and the evolution of weeds

Abstract

Evolution results from changes in population genotype. We have two different disciplines dealing with population dynamics, i.e., population genetics and population ecology. Population genetics, starting from the Hardy-Weinberg law relating allelic and genotypic frequencies in a panmictic population (p 2 : 2pq : q 2), aims at understanding the genetic structure of populations. Population ecology or biology, starting from Malthusian theory and the Verhulst-Pearl equation ((d)N/dt = rN(K −N)/K, where N is the number of individuals, r is the intrinsic rate of increase, and K is the carrying capacity of a particular environment), aims at understanding the cause-effect relationships regulating the number of individuals in populations. Although in population genetics the effective number is an important parameter, most of the theories assume density-independence in the relationships considered. On the other hand, in most theories of population biology, the role of genetic variation is not taken into account. These issues have been well discussed by Birch (1960). In this review, we will try to look into the population dynamics of weedy plants from both standpoints collectively.