Genome Biology and the Evolution of Cell-Size Diversity

Cell size is highly variable among different species across the Tree of Life. For decades, biologists have generated hypotheses to explain this variation, in many cases, drawing on the correlations that exist among cell size, genome size, nucleus size, and various physio-logical and developmental parameters. In recent years, our understanding of the molecular processes that generate variation in genome size over evolutionary time, as well as the processes that maintain homeostasis in cell size over ontogenetic time, has increased dra-matically. The goal of this article is to highlight how information from these fields can be integrated to generate new hypotheses to explain cell-size diversity. Evolutionary biologists have been interested inthe diversity of genome sizes among species for decades. Across the Tree of Life, the size of the genome is correlated with many other features, for example, the size of the nucleus, the size of the cell, the rate of metabolism, and the rate of development (Gregory 2005a,b). Much of the previous work aimed at understanding the evo