RAPID: Reproductive Behavior of an Unlikely Colonist

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Volcanic eruptions are one of the most dramatic natural events on Earth. In 2018, the eruption of Kilauea captured the attention of the world as lava poured over vast areas of the Big Island of Hawaii and created brand new, barren land as it cooled. The first organisms to colonize new habitats are often able to disperse long distances and breed quickly. However, the first organism to colonize after a lava flow in Hawaii is the poorly studied lava cricket, Caconemobius fori. This cricket is an unlikely first colonist for several reasons. First, these crickets don't have wings, which means that they cannot fly to travel long distances but instead walk. This also means that they cannot sing to find mates like most other cricket species. Second, little is known about the mating behavior of the lava cricket, but in its close relatives, the female chews on the leg of the male and consumes his blood. In a hot, dry environment like a lava field, this loss of fluid could be very costly for males. The recent eruption of the Kilauea volcano provides an unprecedented opportunity to investigate the potentially unusual behaviors of these crickets, and how, or if, they overcome these challenges to succeed as first colonists. The investigators will conduct behavioral studies to understand how the crickets find each other despite not being able to sing, and will characterize the mating behaviors and reproductive success of the crickets. Investigators will interact with visitors and personnel at Volcanoes National Park, develop materials for the visitors center at the park, and develop a short film about the focal species to share findings about this unique species with the general public. Volcanic eruptions are dramatic and environmentally devastating. The 2018 eruption of Kilauea on the Island of Hawaii covered almost 14 square miles of land and left continuous areas of barren lava in its wake. Despite the desolation of the habitat, it is colonized within several months following lava cooling. Surprisingly, the first multicellular colonist of lava flows in Hawaii is not a plant or generalist invertebrate, but is the cricket, Caconemobius forii, a potentially highly specialized species. Generally, first colonizers of new habitat are thought to be 'weedy' species capable of dispersing long distances and breeding profusely. Yet the lava cricket, C. fori, challenges these assumptions. These crickets lack wings, rendering them dispersal limited and unable to call to locate mates like most other cricket species. Furthermore, closely related species show high levels of mating failure and male investment - while mating, females chew on the tibial spur of males and drink the hemolymph. Given the extreme heat and dry condition of lava flows, this should be very costly for males. The aims of this study are to (1) conduct field surveys to clarify C. fori habitat use of lava flows of different ages; (2) test whether C. fori uses olfactory cues for mate localization, and (3) characterize their reproductive behavior and success. The results of this study will provide insight to the characteristics of first colonists, and advance our understanding of animal communication and reproduction in extreme environments.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.