Animals produce a bewildering diversity of ornaments and weapons that function in male contests over reproductive access to females. Two characteristics are common in the most elaborate of these structures: disproportionate growth yielding exaggerated trait sizes, and growth that is more sensitive to nutrition than is the growth of other, non-sexually-selected, structures (e.g. antlers in moose or elk reach extreme sizes in the largest bulls, and antler growth is especially sensitive to the nutritional state of the animal). Despite intense interest in the evolution of these sexually selected traits, almost nothing is known of the genes or the developmental mechanisms responsible for disproportionate/ exaggerated growth, or of the mechanisms linking nutrition with the amount of trait growth. This proposal addresses a fundamental gap in understanding the evolutionary potential of ornaments and weapons of sexual selection: What are the genes and developmental/ physiological processes that underlie nutrition-dependent expression and exaggerated growth? The premise for this project is that to understand the evolution of these structures requires exploration of the details of how they develop. The long-term goal is to understand how physiology and development interact with the environment to generate diversity in morphological and behavioral phenotypes. The objectives are to identify genes and associated physiological pathways responsible for generating exaggerated weapon growth, and nutrition-dependent phenotypic plasticity. The investigators will (1) test whether the mechanisms generating nutrition-dependent expression are the same as those generating exaggerated growth, and (2) compare these mechanisms for two weapons (horns & mandibles) in three lineages of beetle representing three independent origins of enlarged male weapons (dung beetles, rhinoceros beetles, & stag beetles). The integrative approach utilized will shed light on physiological and developmental pathways involved with nutrition-dependent phenotypic plasticity in animals generally, and will provide one of the most comprehensive studies to date linking variation in male condition with the expression of sexually selected traits - a central tenet of current theories of sexual selection.
A core objective is the cross-training of young scientists in genetics, development, physiology and evolution. The postdoc and students involved with this project will spend extensive periods in all three labs actively learning techniques and interacting and collaborating with all three PIs. The PIs are committed to training undergraduates in all aspects of the research process, and will incorporate innovative teaching methods in science that embrace diversity; the very nature of this system lends itself to learner-centered investigations. The focal species are a fantastic resource for outreach activities and the PIs will use these animals in educational programs designed to enhance STEM learning in K-12 students as well as in informal science education environments, including visiting local school classrooms in both WA and MT, supporting the WSU insect museum, and aiding with a new Montana insect zoo.
