Population decline but increased distribution of an invasive ant genotype on a Pacific atoll
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ORIGINAL PAPER
Population decline but increased distribution of an invasive ant genotype on a Pacific atoll M. A. M. Gruber • A. R. Burne • K. L. Abbott R. J. Pierce • P. J. Lester
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Received: 11 March 2012 / Accepted: 21 August 2012 / Published online: 29 August 2012 Ó Springer Science+Business Media B.V. 2012
Abstract Populations of invasive species are often studied when their effects are perceived as a problem. Yet observing the dynamics of populations over longer time periods can highlight changes in effects on invaded communities, and assist with management decisions. In this study we revisit an invasion of the yellow crazy ant (Anoplolepis gracilipes) in the Tokelau archipelago to determine if the distribution and abundance of the ant has changed *7 years after surveys completed in 2004. We were particularly interested in whether populations of a previously identified invasive haplotype (D) had increased in distribution and abundance, as this haplotype was implicated in negative effects on resident ant communities. Indeed, haplotype D populations have become more widespread since the initial survey, more likely owing to new introductions or movement by humans, rather than intrinsic characteristics of the haplotype. We also found that despite no significant change in the abundance of A. gracilipes overall, haplotype D
populations have declined in abundance. Residents of the Tokelau atolls no longer consider the ant to be a pest as they did 7 years ago, when populations of this ant interfered with their food production and many other aspects of daily life. We observed no significant differences between A. gracilipes invaded and uninvaded communities, which suggests that the ant is at a level of abundance below which significant negative ecological effects may occur. Population declines of invasive species are not infrequent, and understanding these population dynamics, particularly the underlying mechanisms promoting population declines or stabilisation, should be a high priority for invasion ecology. Keywords Haplotype Abundance Population dynamics Pacific Anoplolepis gracilipes
Introduction M. A. M. Gruber (&) A. R. Burne P. J. Lester School of Biological Sciences, Victoria University of Wellington, PO Box 600, Wellington 6140, New Zealand e-mail: [email protected] K. L. Abbott Monash University, Melbourne, VIC 3800, Australia R. J. Pierce Eco Oceania Pty Ltd, 165 Stoney Creek Road, Speewah, QLD 4881, Australia
Populations of invasive species are often sampled, and their effects described, when they are perceived as a problem (Strayer et al. 2006). These populations attract attention because of their high densities and negative effects on biodiversity and human populations. Invading populations are less often re-examined after long intervening periods (Strayer et al. 2006). It is often expected that invading populations that are already present in high numbers would persist and
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spread if left unchecked. Indeed, many studies have found that invading populations become more a
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