Causes and consequences of genome size diversity in animals

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The genomes of animals range >7,000-fold in size, an observation that has remained a central puzzle in genetics for more than 65 years. My lab is at the forefront of research that seeks to catalogue and explain the patterns of genome size diversity across animals. The next 5 years of research in my lab will focus on three complementary areas: 1) Patterns and correlates of genome size diversity across species in several target groups; 2) Tissue-specific modulations of DNA content (endopolyploidy), and 3) Mechanisms of genome size change and transposable element evolution. In the first set of studies, my students and I will use our considerable expertise to greatly expand our knowledge of genome size diversity in molluscs and arachnids, and will provide the very first study of genome sizes in lichens. This will include both broad, discovery-based explorations and focused testing of hypotheses using phylogenetically-informed comparative methods. In the second series of projects, we will investigate the biological significance of endopolyploidy, in which the genome is replicated up to thousands of times within specific tissues. Endopolyploidy appears to be a very widespread phenomenon, but its overall significance remains poorly understood. We will examine the patterns of endopolyploidy in three major case studies from arthropods in order to test ideas regarding the biological relevance of this phenomenon: 1) Silk and venom glands of spiders with varying feeding strategies (e.g., web-weaving vs. active hunting); 2) Nurse cells (trophocytes) found in the ovaries of some insects, which provision the developing eggs with nutrients; and 3) Guts and Malpighian tubules in insects with different diets. Finally, in the third set of projects, we will continue to expand our investigations of the mechanistic bases of genome size change, in particular the role played by transposable elements in affecting total genome size. This area of research uses bioinformatics analyses and survey sequencing using next-generation sequencing technology to determine how transposable element abundance, diversity, and activity are related to genome size variability. The research proposed here will provide opportunities for the training of a number of MSc, PhD, and undergraduate research students, and is expected to be of high impact as it addresses questions of fundamental importance for our understanding of genome form, function, and evolution.