title: Individual fluctuations in toxin levels affect breeding site fidelity in a chemically defended amphibian.
abstract: Behaviours that influence habitat selection strongly determine species movement patterns. One component of animal behaviour that largely influences movement patterns and habitat choice is site fidelity. California newts (family Salamandridae) demonstrate remarkable site fidelity, typically homing to the same pool of a stream each breeding season. Individuals often occupy a specific pool throughout the breeding season, but some males shift among breeding pools, altering their set of potential mates, competitors, and predators. In this study, we measured dermal concentrations of the chemical defence compound tetrodotoxin (TTX) in recaptured male California newts (Taricha torosa) over five breeding seasons to evaluate whether relative TTX concentrations are associated with breeding site fidelity in the field. Our five years of field sampling indicates that TTX concentrations of individuals and group means fluctuate tremendously, implying that TTX is not a stable phenotypic trait. Despite such fluctuations, we found that an individual's relative TTX concentration explains fidelity to a breeding pool and suggests that newts may be able to assess both their own concentrations of TTX and that of conspecifics to make decisions about remaining in or abandoning a breeding pool. These results provide us a novel dimension to chemical defence phenotypes in nature and their ecological consequences, potentially requiring a re-evaluation of the coevolutionary dynamics of predation pressure on toxin-laden organisms.
authors.affiliation: Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA 90095, USA UCLA La Kretz Center for California Conservation Science, Institute of the Environment and Sustainability, Los Angeles, CA 90095, USA garyb@ucla.edu.
authors.forename: Gary M
authors.initials: GM
authors.lastname: Bucciarelli
authors.affiliation: Natural Science Division, Pepperdine University, 24255 Pacific Coast Highway, Malibu, CA 90263, USA.
authors.forename: David B
authors.initials: DB
authors.lastname: Green
authors.affiliation: Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA 90095, USA UCLA La Kretz Center for California Conservation Science, Institute of the Environment and Sustainability, Los Angeles, CA 90095, USA.
authors.forename: H Bradley
authors.initials: HB
authors.lastname: Shaffer
authors.affiliation: Natural Science Division, Pepperdine University, 24255 Pacific Coast Highway, Malibu, CA 90263, USA.
authors.forename: Lee B
authors.initials: LB
authors.lastname: Kats
mesh_terms: D000818:Animals; D002140:California; D017753:Ecosystem; D008297:Male; D012098:Reproduction; D012455:Salamandridae / Q000502:physiology*; D013779:Tetrodotoxin / Q000378:metabolism*
chemical_list: D013779:Tetrodotoxin
keywords: Santa Monica Mountains; Taricha; coevolution; newts; site fidelity; tetrodotoxin