Elevated herbivory in plant hybrid zones: Chrysomela confluens, Populus and phenological sinks

K. D. Floate, M. J C Kearsley, Thomas G Whitham

Research output: Contribution to journalArticle

96 Scopus citations


Using Chrysomela confluens (Coleoptera: Chrysomelidae), the authors examined the hypothesis that naturally occurring hybrid zones between two cottonwood species are "sinks' or centers of insect abundance. Over a 3-yr period, 94% of the C. confluens population was restricted to a 13-km hybrid zone, which represents <3% of the cottonwood population. Of several potential mechanisms tested, expanded host phenology in the hybrid zone, relative to pure zones, best explained the distribution of C. confluens which is independent upon newly flushed leaves for optimal growth and reproduction. The hybrid zone is a superior beetle habitat because: 1) early leaf flush in the hybrid zone provides the first source of food for beetles in spring and 2) staggered leaf phenologies in the hybrid zone allow beetles to shift onto newly flushed Fremont trees as foliage of sympatric hybrid and narrowleaf trees declines in quality. This shift by ovipositing females can result in a 600% increase in fecundity relative to nonshifting females. The hybrid zone is a "phenologial sink' that increases beetle fecundity and leads to chronically high herbivory year after year. Because movement from the hybrid zone reduces fecundity, emigration into adjacent pure zones is likely hindered. -from Authors

Original languageEnglish (US)
Pages (from-to)2056-2065
Number of pages10
Issue number7
StatePublished - 1993


ASJC Scopus subject areas

  • Ecology

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