Adaptive Evolution of Nearctic Deepwater Fish Vision: Implications for Assessing Functional Variation for...

Area of Science:

• Evolutionary biology
• Molecular biology
• Ecology

Background:

• Intraspecific functional variation is key for species adaptation to environmental changes.
• Visual opsin variation often reflects ecological niches but is understudied regarding intraspecific differences and recent environmental impacts.
• Postglacial lakes offer insights into rapid environmental change and functional evolution.

Purpose of the Study:

• To investigate molecular adaptation in vision within two deep-lake specialist fish lineages: ciscoes and deepwater sculpin.
• To explore depth-related functional variation in rhodopsin and its evolutionary convergence.
• To assess the implications of intraspecific functional variation for conservation and Indigenous communities.

Main Methods:

• In vitro characterization of rhodopsin spectral sensitivity.
• Analysis of depth-related variation in rhodopsin alleles in ciscoes and deepwater sculpin.
• Development and application of a metabarcoding approach in collaboration with the Saugeen Ojibway Nation.

Main Results:

• Convergent evolution of depth-related rhodopsin variation was observed in both fish lineages.
• Deepwater rhodopsin alleles exhibited blue-shifts in spectral sensitivity compared to other alleles.
• Blue-shifted rhodopsin alleles were found in deep, clear postglacial lakes with blue-light-enriched underwater environments.

Conclusions:

• Remarkably rapid and convergent visual adaptation, including intraspecific functional variation in rhodopsin, has occurred.
• Intraspecific functional variation in rhodopsin has significant implications for the conservation of culturally and commercially important fish species.
• A collaborative metabarcoding approach efficiently recovers the ecological distribution of functionally relevant variation, bridging protein function studies and large-scale surveys.