Role of abiotic factors in governing susceptibility to invasion: A test with argentine ants

David A. Holway, Andrew V. Suarez, Ted J. Case

Research output: Contribution to journalArticlepeer-review

Abstract

Hypotheses concerning community-level vulnerability to invasion often emphasize biotic interactions but fail to consider fine-scale variation in the physical environment. In this study, the interplay between interspecific competition and abiotic factors is examined with respect to whether scrub habitats in southern California become invaded by the Argentine ant (Linepithema humile). Argentine ants penetrate further into and attain higher abundances in mesic scrub fragments than they do in xeric scrub fragments. Probably as a result, native ant richness is lower in small (<30 ha), mesic fragments than in either small, xeric fragments or in small plots in unfragmented areas. Compared to six species of native ants, Argentine ants ranked lowest in their ability to tolerate high temperatures in the laboratory with 100% of field-collected workers dying after 60 min of exposure to temperatures ≥46°C. Field data corroborate these results; mean temperatures at which colonies of Argentine ants attained maximum abundance at baits (34.0°C) and abandoned baits (41.6°C) were both lower than for the native ant Dorymyrmex insanus. Laboratory studies further revealed that low levels of soil moisture depress mean worker survival in experimental colonies of Argentine ants. In a factorial laboratory experiment that varied both physical conditions and interspecific competition, Argentine ants exhibited greater worker activity and survival under warm, moist conditions than under hot, dry conditions, whereas the presence of a competitor, Forelius mccooki, had no significant effect. Experimental colonies of F. mccooki, in contrast, were more active under hot, dry conditions than under warm, moist conditions and exhibited reduced activity in the presence of L. humile irrespective of physical conditions. Taken together, these experimental data demonstrate how the abiotic environment impinges on both colony-level activity and colony growth in the Argentine ant and provide a general explanation for the patterns observed at the community level. A key consequence of the condition-specific nature of the competitive asymmetry between Argentine ants and native ants is that community-level vulnerability to invasion appears to depend primarily on the suitability of the physical environment from the perspective of L. humile.

Original languageEnglish (US)
Pages (from-to)1610-1619
Number of pages10
JournalEcology
Volume83
Issue number6
DOIs
StatePublished - Jun 1 2002
Externally publishedYes

Keywords

  • Abiotic factors
  • Biological invasions
  • Competitive exclusion
  • Condition-specific competition
  • Habitat fragmentation
  • Interspecific competition
  • Linepithema humile

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics

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