Cannibalism in invasive, native and biocontrol populations of the harlequin ladybird
1 INRA, UMR, 1062, CBGP Montpellier, France
2 INRA, UMR 1355 Institut Sophia Agrobiotech, F-06903 Sophia Antipolis, France
3 Université de Nice-Sophia Antipolis, UMR Institut Sophia Agrobiotech, F-06903 Sophia Antipolis, France
4 CNRS, UMR 7254 Institut Sophia Agrobiotech, F-06903 Sophia Antipolis, France
5 V.N. Sukachev Institute of Forest, Siberian Branch of Russian Academy of Sciences, Akademgorodok 50/28, Krasnoyarsk 660036, Russia
6 Evolutionary Biology Group, School of Biological, Biomedical and Environmental Sciences, University of Hull, Cottingham Road, Kingston-Upon-Hull HU6 7RX UK
7 Department of Crop Protection, Ghent University, Coupure Links 653, B-9000 Ghent, Belgium
BMC Evolutionary Biology 2014, 14:15 doi:10.1186/1471-2148-14-15Published: 5 February 2014
Cannibalism is widespread in both vertebrates and invertebrates but its extent is variable between and within species. Cannibalism depends on population density and nutritional conditions, and could be beneficial during colonisation of new environments. Empirical studies are needed to determine whether this trait might facilitate invasion of a new area in natural systems. We investigated whether the propensity for cannibalism in H. axyridis differs both between native and invasive populations and between invasive populations from the core and from the front of the invasive area in Western Europe. We also compared the propensity for cannibalism of these natural populations with that of laboratory-reared biocontrol populations. We measured the cannibalism rates of eggs by first instar larvae and adult females at two different individual densities of ladybirds from three types of population (invasive, native and biocontrol), in laboratory-controlled conditions.
Cannibalism was significantly greater in larvae from invasive populations compared to native or biocontrol populations, but there was no difference in cannibalism rates between populations from the core or front of the invaded range. Cannibalism was significantly lower in larvae from biocontrol populations compared to wild (invasive and native) populations. No differences in cannibalism rates of adult females were found between any populations. While high population density significantly increased cannibalism in both larvae and adults, the norm of reaction of cannibalism to individual density did not change significantly during the invasion and/or laboratory rearing processes.
This study is the first to provide evidence for a higher propensity for cannibalism in invasive populations compared to native ones. Our experiments also shed light on the difference in cannibalism evolution with respect to life stages. However, we are still at an early stage in understanding the underlying mechanisms and several different research perspectives are needed to determine whether the higher propensity for cannibalism is a general feature of the invasion process.