title: Insect outbreaks produce distinctive carbon isotope signatures in defensive resins and fossiliferous ambers.
abstract: Despite centuries of research addressing amber and its various inclusions, relatively little is known about the specific events having stimulated the production of geologically relevant volumes of plant resin, ultimately yielding amber deposits. Although numerous hypotheses have invoked the role of insects, to date these have proven difficult to test. Here, we use the current mountain pine beetle outbreak in western Canada as an analogy for the effects of infestation on the stable isotopic composition of carbon in resins. We show that infestation results in a rapid (approx. 1 year) (13)C enrichment of fresh lodgepole pine resins, in a pattern directly comparable with that observed in resins collected from uninfested trees subjected to water stress. Furthermore, resin isotopic values are shown to track both the progression of infestation and instances of recovery. These findings can be extended to fossil resins, including Miocene amber from the Dominican Republic and Late Cretaceous New Jersey amber, revealing similar carbon-isotopic patterns between visually clean ambers and those associated with the attack of wood-boring insects. Plant exudate δ(13)C values constitute a sensitive monitor of ecological stress in both modern and ancient forest ecosystems, and provide considerable insight concerning the genesis of amber in the geological record.
authors.affiliation: Department of Earth and Atmospheric Sciences, University of Alberta, 1-26 Earth Sciences Building, Edmonton, Alberta, Canada. rcm1@ualberta.ca
authors.forename: Ryan C
authors.initials: RC
authors.lastname: McKellar
authors.forename: Alexander P
authors.initials: AP
authors.lastname: Wolfe
authors.forename: Karlis
authors.initials: K
authors.lastname: Muehlenbachs
authors.forename: Ralf
authors.initials: R
authors.lastname: Tappert
authors.forename: Michael S
authors.initials: MS
authors.lastname: Engel
authors.forename: Tao
authors.initials: T
authors.lastname: Cheng
authors.forename: G Arturo
authors.initials: GA
authors.lastname: Sánchez-Azofeifa
mesh_terms: D000416:Alberta; D018647:Amber / Q000737:chemistry*; D000818:Animals; D002247:Carbon Isotopes / Q000032:analysis*; D001517:Coleoptera / Q000033:anatomy & histology* / Q000737:chemistry; D004293:Dominican Republic; D005580:Fossils; D009515:New Jersey; D028223:Pinus / Q000737:chemistry; D011157:Population Dynamics; D012116:Resins, Plant / Q000737:chemistry*
chemical_list: D018647:Amber; D002247:Carbon Isotopes; D012116:Resins, Plant