Collaborative Research: Phenotypic and lineage diversification after key innovation(s): multiple evolutionary pathways to air-breathing in labyrinth fishes and their allies

Some anatomical structures or behaviors can be game-changing at evolutionary scales for certain groups of organisms. Such traits, called “key innovations”, radically alter how an organism interacts with its environment, and may confer competitive advantages. Examples are innovations that enable avoiding competition or predation with other species, or allowing access to new habitats and resources. A potential key innovation for some fishes is the ability to breathe atmospheric air with a unique air-breathing organ. These air-breathing organs have evolved several times in fishes such as bettas, gouramis, and snakeheads, and may have been the key to their success in spreading across the world millions of years ago and again during more recent biological invasions (e.g., snakeheads). This project will examine whether air-breathing structures are key innovations and then answer how these structures alter intrinsic (anatomical) or extrinsic (ecological) evolutionary dynamics. This project will use high resolution micro-computed tomographic imaging (microCT), coupled with contrast-staining and histology to provide insight into the diversity of air-breathing organs across the Anabantaria (gouramis, snakeheads, spiny and swamp eels). Using a phylogenetic comparative framework, the research team will assess the homology of different air-breathing structures across anabantarians. Three-D geometric morphometrics will be used to capture skull shape diversity in these fishes, air-breathing and non-air-breathing species alike. Finally, the research team will test whether air-breathing structures are key innovations and then answer how these structures alter evolutionary dynamics, either by (1) providing new opportunities for continental invasions, (2) facilitating body shape diversification, or (3) by changing the fundamentals of how the skull, which houses the air-breathing organ, adapts to changing roles. For the Broader Impacts of this study, the research team at University of Louisville will partner with colleagues at the University of Michigan Museum of Natural History for outreach and training. The University of Louisville research team, PI, post docs and students, will partner with the Louisville Zoo community programs office to build on existing programs. 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.