EAPSI:The Evolution and Development of Extreme Weapons: Have Weapons Reached their Limit?

O'Brien Devin M, Missoula MT

Investigators

Abstract

Animal weapons represent some of the world's most incredible morphology. Traits such as the massive antlers of elk, or the incredible tusks of elephants, occur in thousands of animal species. But despite this diversity of form, one thing remains constant across these traits: those individuals with the largest weapons win the most fights and, as a result, are expected to have the highest reproductive success. This should lead to strong directional selection for large weapons. However, when biologists go out in the wild and quantify how selection is acting on these weapons, this is not what they find. Instead, animal weapons are often characterized by weak net selection for large weapons. Contrary to what is expected, males with the largest weapons do not have the highest mating success. Why? In this award, potential limits to extreme weapons are explored through analyses of metabolism, biomechanics, and developmental mechanisms of exaggerated growth in frog-legged beetles. This work will be conducted in collaboration with Dr. Teruyuki Niimi at the National Institute for Basic Biology in Okazaki, Japan, one of the leading researchers in the field of exaggerated growth and animal weapons. This work will help advance understanding of a fundamantal puzzle in evolutionary developmental biology and enhance communication of basic science in public outreach on this strangely beautiful species in collaboration with a local children's museum. Using the non-model system, frog legged beetles, two potential limits to extreme weapons will be examined. These are the metabolic costs associated with large, muscle filled weapons, and the biomechanical limits weapons experience as they get very large. These factors will be measured directly in the field to determine how they can curb the reproductive benefits associated with bearing large weapons. This work will be paired with genetic analyses focusing on the developmental basis of extreme growth in animal weapons. RNA knockdowns will be performed on candidate growth pathways to elucidate how exaggerated weapons develop and to gain a better understanding of potential targets of selection in extreme weapon systems. This NSF EAPSI award supports the research of a U.S. graduate student and is funded in collaboration with the Japan Society for the Promotion of Science.