Cottonwood hybrid zones as centres of abundance for gall aphids in western North America

Importance of relative habitat size

Kevin D. Floate, Gregory D. Martinsen, Thomas G Whitham

Research output: Contribution to journalArticle

26 Citations (Scopus)

Abstract

1. In western North America, populations of the leaf-galling aphid Pemphigus betae are concentrated in natural zones of overlap and hybridization between species of cottonwoods (Populus). Averaged over seven drainages in four American states and one Canadian province, P. betae galls were 28-fold more abundant in hybrid zones than in adjacent pure zones of the narrowleaf host species. 2. The strength of this pattern is impressive in that it occurred in all of the river drainages surveyed and spanned a north south gradient of 1600 km (15 latitude). Furthermore, this pattern was not restricted to one species-pair of cottonwoods, but occurred in zones of narrowleaf x Fremont, narrowleaf x Eastern, and narrowleaf x balsam x Eastern cottonwood. 3. The concentration of galls in the hybrid zone was not influenced by the absolute size of the hybrid zone. However, there was a significant inverse relationship (P = 0.02) between relative gall density and the relative size of the hybrid zone. All else being equal, small hybrid zones supported higher concentrations of aphids than large hybrid zones. Three hypotheses, 'hybrid zones as aphid sinks', 'hybrid zones as aphid sources' and an 'introgression' hypothesis, are proposed which may explain this regional pattern. 4. Riparian cottonwood forests shelter a rich diversity of animal and plant species that is threatened by habitat loss through anthropogenic activities. If the concentration of P. betae in cottonwood hybrid zones is a pattern common to other hybridizing plants and their dependent species, preserving these relatively small areas could have it disproportionately positive role in preserving biodiversity.

Original languageEnglish (US)
Pages (from-to)179-188
Number of pages10
JournalJournal of Animal Ecology
Volume66
Issue number2
StatePublished - Mar 1997

Fingerprint

hybrid zone
gall
galls
aphid
Aphidoidea
Pemphigus betae
habitat
habitats
drainage
Populus deltoides subsp. deltoides
North America
riparian forest
regional pattern
introgression
habitat loss
Populus
habitat destruction
shelter
anthropogenic activities
human activity

Keywords

  • bioconservation
  • hybrid zones
  • Pemphigus betae
  • Populus
  • riparian forests

ASJC Scopus subject areas

  • Animal Science and Zoology
  • Ecology

Cite this

Cottonwood hybrid zones as centres of abundance for gall aphids in western North America : Importance of relative habitat size. / Floate, Kevin D.; Martinsen, Gregory D.; Whitham, Thomas G.

In: Journal of Animal Ecology, Vol. 66, No. 2, 03.1997, p. 179-188.

Research output: Contribution to journalArticle

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