[1] San Francisco State Univ, Dept Biol, 1600 Holloway Ave, San Francisco, CA 94132 USA
[2] Stanford Univ, Dept Biol, Palo Alto, CA 94304 USA
[3] Univ Calif Davis, Sch Vet Med, Dept Pathol Microbiol & Immunol, Davis, CA 95616 USA
[4] Calif Acad Sci, Inst Biodivers Sci & Sustainabil, San Francisco, CA 94118 USA