The Adaptive Significance of an Evolutionary Constraint: from Protein to Organism.

[No authors listed]

UIID-NSF: 972

Abstract

The investigators will determine how the biophysical properties of amino acid mutations in a specific protein influence various levels of biological organization, ultimately affecting the capacity of individuals to live in various communities, and even influencing species interactions at a regional scale. The model system for this research is the interaction between toxic Pacific newts (Taricha) and their resistant predatory garter snakes (Thamnophis). Newts are defended by tetrodotoxin (TTX), one of the most lethal toxins ever discovered. This neurotoxin binds to the outer pore of voltage-gated sodium channels, the proteins responsible for propagating electrical impulses in muscles and nerves, thereby paralyzing muscle and nerve organs. Despite this, multiple garter snake species feast on newts, in large part due to specific changes to the sodium channel protein expressed in muscle. However, these adaptive variants likely bear a high cost; biophysical work on sodium channels suggests that amino acid mutations that reduce TTX binding to the protein are likely to reduce sodium channel function. If this tradeoff scales to the organism, then it may explain why TTX resistant garter snakes are geographically localized, and have not swept across the landscape. Further, this tradeoff may explain why resistance-conferring mutations in snakes represent only a small subset of mutations known to reduce TTX binding to the protein. Nevertheless, the cost of naturally occurring protein variants remains unexplored, as does any relationship between this biophysical tradeoff, tissue function, and organismal performance. Using a truly integrative approach, the investigators will: 1) quantify the apparent tradeoff in this molecular adaptation; 2) determine how resistance to prey toxin and biophysical tradeoffs scale up to the tissue; and 3) determine how tissue resistance and performance in different organs (muscle and nerve) combine to determine the adaptation of the snake. This research will provide a framework for understanding how a tradeoff at the molecular level can influence an individual's response to its environment, ultimately impacting adaptive evolution and species interactions across the landscape. The study provides a tractable model with a clear ecological context to help determine when and why adaptive evolution may be limited, as well as the possible downstream consequences of those constraints on adaptation. The project will lead to training of two graduate students and several undergraduates in a highly integrative investigation where they will participate in molecular data generation, protein analysis, physiological assays, and whole organism performance trials, all in the context of predator-prey coevolution. The research themes of this project will be extended to an outdoor education program for families from Reno, Nevada. This project will sponsor 5 inner-city families to participate in a weekend-long outdoor program where they stay at a field station and explore the biodiversity and ecology of forest ecosystems that exist only 30 minutes from the urban setting in which they live. Applications will be made available to elementary and middle school children engaged in the UNR Mathematics, Engineering, and Science Achievement program (MESA). MESA strives to engage low-income, first-generation students and will be an ideal conduit for identifying students that have interest in science but with financial needs that would otherwise preclude attendance of a program like Family Camp. The PI has chosen a family-based model because he has observed that exposing an individual child to this nature-based experience has a much higher and longer-lasting impact if their immediate family participates as well. This model provides a set of positive, shared family experiences that can be remembered and reinforced, creating a supportive environment as the child continues to develop and explore an interest in science. Such educational opportunities are particularly rare in an EPSCoR state like Nevada but will have significant impact on promoting biodiversity and organismally-based research and education in our community.

Other Details

• Award Instrument: Standard Grant
• Email: [email protected]
• Organization: Board of Regents, NSHE, obo University of Nevada, Reno
• Other Investigators: James Cronin, Normand Leblanc
• Primary Investigator: Chris Feldman
• Program(s): Integrative Ecologi Physiology, EXP PROG TO STIM COMP RES
• Start Date: 04/15/2014