Repeated evolution of eye regression and loss: phylogenomics of scallops and relatives (Bivalvia: Pectinoidea)

Iowa State University, Ames IA

Investigators

Abstract

Eyes in their many different forms have evolved numerous times in animals. However, eyes are energetically expensive to produce, use, and maintain. As a result, animals that live in dim light environments tend to have eyes that maximize the ability to capture light at the expense of generating clear images. Thus, different light environments produce selective pressures that are predicted to affect eye number, form, and performance. The project will test hypotheses of how the transition into dim or totally dark marine environments may be related to eye regression and loss. To address these fundamental questions in sensory biology, the project will collect and analyze genetic, morphological, and ecological data under an evolutionary framework. Broader societal impacts include addressing goals of the Next Generation Science Standards (NGSS) by incorporating molecular concepts in the teaching of evolution while using the eye as an approachable example. Novel curriculum on evolution at the high school level will be created through a collaboration with two educators immersed in the research project. Lesson plans will be publicly available via websites (e.g., National Science Teaching Association) and pedagogical data will be published in peer-reviewed journals. To expand training opportunities, the team will develop a workshop on teaching evolution for 12 additional high school teachers in Year 3. Workshop impact will be assessed with pre- to post- surveys. The work also will directly support the cross disciplinary training of postdoctoral researchers and undergraduate students. Participation of underrepresented groups in STEM is a priority. Understanding visual system diversity requires determining ecological and evolutionary mechanisms responsible for functional and morphological changes. Scallops and relatives (Pectinoidea) have tens to hundreds of eyes on a single animal and broad bathymetric distributions spanning the taxonomic and ecomorphological diversity of the clade. The proposed work will use the Pectinoidea to understand eye evolution in association with functional and ecological changes that may drive eye regression and loss, such as oceanic depth. Harnessing the true potential of pectinoideans for macroevolutionary research is contingent on the resolution of a robust time-calibrated phylogeny and anatomical knowledge for the poorly studied taxa. This work will address three central questions: 1) What are morphological and functional changes of eyes among deep- and shallow- dwelling species? 2) When and how many times have eyes been regressed or completely lost among pectinoidean taxa? 3) Could the invasion of dim light or aphotic zones be related to eye regression and loss? The project will infer the phylogenomics of Pectinoidea using an anchored hybrid enrichment approach to understand the tempo and mode of eye evolution and regression. The project will 1) provide extended taxon sampling, a time-calibrated phylogeny, and taxonomic revision; 2) address major gaps in knowledge of the factors and forces that have contributed to the evolution and diversification of visual systems; 3) inform a broader understanding of evolutionary processes underlying new traits; and 4) generate new genetic resources for bivalves, an understudied, but phenotypically diverse, group. All materials will be archived through publicly accessible repositories. 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.