Ecological effects of invasive alien species on native communities, with particular emphasis on the interactions between aphids and ladybirds Pavel Kindlmann • Olga M. C. C. Ameixa • Antony F. G. Dixon Received: 8 April 2011 / Accepted: 30 May 2011 Ó International Organization for Biological Control (IOBC) 2011 Abstract The ecological effects of introduced spe- cies on native organisms can sometimes, but not always be significant. The risks associated with invasive alien pests are difficult to quantify. This paper concentrates on the ecological effects of invasive insect predators that feed on pest insects, because the former may potentially affect the biological control of the latter. The literature indi- cates that invasive predatory insects generally are resistant to changes in environmental conditions, long-lived and voracious with a high reproductive rate, high dispersal ability, able to spread very rapidly across landscapes and exhibit phenotypic plasticity. Their colonization of patches of prey may induce native predators to leave, but the evidence that invaders negatively affect the abundance of the native species is scarce and not persuasive. Insect predators do not substantially affect the abundance of their prey, if the ratio of generation time of the predator to that of the prey is large (the generation time ratio hypothesis), therefore the effect of an invasion by long-lived alien predators on systems consisting of long-lived native predators and short-lived prey on the abundance of the prey is hard to detect. Keywords Invasive alien species Á Predators Á Insect pests Á Ecological effects Á Intraguild predation Introduction The ecological effects of introduced species on native organisms can sometimes but not always be signif- icant (Vitousek et al. 1996). For example, Nedve ˇd et al. (2011) report that invasive spiders pose little threat to biodiversity. The risks associated with invasive alien pests (e.g., of widespread establish- ment or ecological effect) are difficult to quantify, as they involve interactions between factors operating across a range of spatial and temporal scales, such as the population dynamics of an invader, environmen- tal conditions in the invaded region and the status of potential dispersal pathways (Barney and Whitlow 2008). Handling Editor: Helen Roy P. Kindlmann Á O. M. C. C. Ameixa (&) Á A. F. G. Dixon Department of Biodiversity Research, Global Change Research Centre AS CR, Na sa ´dka ´ch 7, C ˇ eske ´ Bude ˇjovice, Czech Republic e-mail: olgameixa@portugalmail.pt P. Kindlmann Institute for Environmental Studies, Charles University, Benatska 2, Prague, Czech Republic O. M. C. C. Ameixa Faculty of Sciences, University of South Bohemia, Branis ˇovska ´ 31, C ˇ eske ´ Bude ˇjovice, Czech Republic A. F. G. Dixon School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, UK 123 BioControl (2011) 56:469–476 DOI 10.1007/s10526-011-9384-4