Dissertation Research: Reaction Norms of Ontogenetic Trajectories in Lobelia

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Ontogeny and genetic variation are two topics that are thought to be crucial for our understanding of patterns and processes of evolutionary change. Although the basic concepts for the study of developmental systems and the reaction of norms of genotypes to the environments had been formulated during the first half of this century, only recently have they become a central focus of experimental and theoretical work. The developmental aspect focuses on the concept of ontogenetic trajectories, which describes the change in phenotype during growth. The environmental variation, which elicits a genotype-specific response called phenotypic plasticity, is described by a function that relates environments and phenotypes through the genotype: i.e., the reaction norm. The aim of this proposal is to couple the developmental and environmental aspects in a study of genetic variability in two species, Lobelia cardinalis and Lobelia siphilitica (Lobeliaceae). The research project is divided into two distinct experiments: (I) Experiment I is a description of the plasticity for ontogenetic trajectories to different level of shading in the genotypes samples from two populations for each species. The objective is to gain information about 1) genetic variation for reaction norms across development and 2) how environmental changes can modify the developmental trajectory. (II) Experiment II is an artificial selection experiment which - based on the information obtained from Experiment I - will test the ability of the genetic systems of Lobelia spp. to respond to selection on additive genetic variance of their reaction norms. A proximal objective of this type of research is to obtain reliable models of phenotypic evolution, using some of the parameter values from actual experiments. Attempts in this sense have already been published, but focused only on the ontogenetic component of variation. A more comprehensive model is desirable, which includes environmental variation and is consistent with our general understanding of biological complexity and with actual experimental possibilities. The ultimate goal is to gain a basic understanding and a general phenomenological description of the ways in which phenotypic novelties can arise and eventually be fixed during macroevolution. These notions, together with the parallel increase in our knowledge of the physiological and molecular basis of such phenomena, would eventually lead us to less vague statements about how population biology and molecular genetics can be coupled for a more complete understanding of evolutionary phenomena.