Ed Ricketts Memorial Lecture
George N. Somero
Hopkins Marine Station,
Faunal Changes in Monterey Bay: Is Global Warming Starting to Hurt?
Surveys of marine fauna at Cabrillo Point, near Hopkins Marine Station (HMS), have shown dramatic shifts in species composition over the past 60+ years (Barry et al. 1995, Science 267:672). Abundances of species with southern centers of distribution have increased whereas abundances of northern-occurring species have decreased. Correlated with these faunal changes are increases in water temperature (up to ~2.2 degrees C in maximal summer temperature). To elucidate whether these changes in faunal composition and habitat temperature might be causally linked, scientists at HMS are examining physiological systems that are of importance in establishing thermal tolerance. Data on crustaceans and molluscs suggest that key physiological systems, including heart function in crabs and protein synthetic capacity and ability to mount the heat shock response in molluscs (mussels and snails), may be "living on the edge" of their thermal tolerance ranges. Further increases in habitat temperature, especially in summer maxima, may have pronounced influences on species composition and the costs of living, e.g., energy demands for repair of heat-damaged proteins, of intertidal species.
About George Somero
The 1998 recipient of the Ricketts memorial Lecture Award is Dr. George
N. Somero. George N. Somero received his Ph.D. from Stanford University.
His group studies how changes in protein sequence, and in the intracellular
milieu in which protein function occurs, enable organisms to succeed
in diverse environments.
The abilities of organisms to thrive in environments with different physical and chemical properties depend on adaptive variations in proteins. By comparing homologous proteins from animals adapted to different temperatures, Professor Somero's group has shown that only minor differences in habitat temperature are sufficient to favor evolutionary changes. Comparisons of proteins from closely related congeneric species have shown that minor changes in protein sequence outside of active sites are adequate to effect adaptive change. These comparative studies of protein variants allow deduction of structure-function relationships in proteins (e.g., by revealing the types of amino acid substitutions that alter enzymes' kinetic properties and structural stabilities). Temperature effects on protein expression are also studied, e.g., seasonal shifts in isozyme expression patterns, and both seasonal and daily alterations in expression of heat shock proteins. All of these biochemical and molecular studies are considered in light of the role that adaptation to the environment plays in establishing biogeographical patterning in nature.
Although most emphasis in studies of molecular evolution has been on proteins and nucleic acids, Professor Somero's group has shown that adaptive variation in the "micromolecular" constituents of cells (e.g., protons, inorganic ions, and the low molecular weight organic solutes that comprise the largest share of osmotically active substances) is of great importance in ensuring satisfactory protein structure and function. Their studies of the evolution of the intracellular milieu have explained why many marine organisms contain within their cells unusual organic molecules at high concentrations (e.g., accumulation of urea in sharks and their relatives) and why intracellular pH varies with body temperature.
Professor Somero received a Guggenheim Fellowship and is a member of the National Academy of Sciences and a fellow of the American Association for the Advancement of Science.