Evolution and genetic basis of locomotor activity patterns among Lake Malawi cichlids: Exploring a novel mechanism of habitat partitioning

University Of Massachusetts Amherst, Amherst MA

Investigators

Abstract

This project investigates a new hypothesis to explain how a high diversity of similar species can coexist in the same environment, that species partition their habitat temporally via divergence in the circadian timing of activity, day vs night. Animals exhibit a range of activity levels and patterns over the course of a day, but how these behaviors are regulated at the genetic level remains poorly understood. Further, closely related species can differ markedly in both levels and patterns of activity, but how variation in these behaviors may facilitate the co-existence of species within a single environment is largely unknown. This project addresses these two knowledge gaps, using cichlid fishes from Lake Malawi, Africa. This cichlid system exhibits unparalleled diversity, with well over 500 species evolving within the last ~1-2 million years. Moreover, Malawi cichlids co-exist in extremely high diversities, with certain localities supporting over 40 species. How this occurs has long fascinated biologists, with most studies focusing on how species partition habitat spatially, for example across different depths. This research has the potential to provide novel insights into how biodiversity is maintained in the Lake Malawi cichlid system, and other groups characterized by high levels of biodiversity, with implications for conservation strategies. More broadly, this project will provide a better understanding of circadian biology, which may provide insights into the linkage between disrupted circadian rhythms in humans and disorders of the brain. Building on past activities, the investigators will deliver summer workshops on evolution to underserved and underrepresented middle school students through partnerships with existing programs in Massachusetts. They will recruit underrepresented high school and undergraduate students into their labs for supervised research. In addition, they will develop and deliver course-based undergraduate research experience laboratories for undergraduates at both institutions to expand access to research. The circadian timing of activity is critical for organismal fitness, and species across the Animal Kingdom exhibit diversity in the timing of activity that ranges from strongly diurnal to strongly nocturnal. While the neural and molecular basis through which animals maintain a 24-hour circadian clock is well-studied, much less is known about how the timing of activity evolves. Identifying the ecological and genetic factors associated with variation in activity patterns would therefore address a critical gap in our knowledge. This project will investigate these open questions by applying high-throughput behavioral analyses in Lake Malawi cichlid fishes – an iconic and powerful model system for ecology and evolutionary research. Malawi cichlids exhibit unparalleled diversity in an array of phenotypes, including behavioral traits. Preliminary data associated with this proposal documented a surprisingly high magnitude of variation in locomotor activity patterns among species, offering a unique opportunity to investigate its evolution and genetic basis. To this end, the investigators will undertake experiments to examine the evolution of activity patterns in an explicit phylogenetic context, assess the degree to which these patterns are modulated by environmental factors including social interactions and food availability, and to characterize the genetic/genomic architecture of locomotor activity. While each experiment will be informative on its own, the combined results will provide key insights into the evolutionary potential of circadian regulation of activity, significantly advancing the field, and establishing a robust foundation for future research. 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.