4 - Genetic Variation in the Response of Plant Populations to Elevated CO2 in a Nutrient-Poor, Calcareous Grassland

Abstract

This chapter proposes that the response of ecosystems to global change, in particular increasing CO2, depends mainly on the extent to which plant species adjust to new conditions by plasticity or evolutionary change, which in turn depends on genetic variation. The chapter suggests that both in models and in experiments, there are implicit misconceptions about the nature of ecosystems because they are thought to contain assemblages of species, or of individuals of species that have only mean properties. Variation within species is assumed to be negligible, interactions among species are rarely taken into account, and evolution is not allowed. Variation in natural populations is caused by several factors, including plastic response to variations in environmental conditions, genetic differences among individuals, and developmental noise. Phenotypic plasticity is an environmentally induced phenotypic change that occurs within an organism's lifetime. The existence of large genetic variations within populations in ecologically relevant characters demonstrates that species cannot be considered as constants in ecosystem studies and global-change models. Therefore, characters measured at the level of the individual may be more promising indicators of an ecosystem change than higher level characters.