Item

Abstract

The Asian lady beetle Harmonia axyridis originates from Asia and has
established invasive populations worldwide. Recent population genetic studies trace
their invasion routes and demonstrate that bottlenecks in population size have reduced
their genetic diversity. Consequently, phenotypical differences are highlighted between
native and invasive populations. Among phenotypical traits, cuticular hydrocarbons
(CHCs) might reflect the geographical origin of a lady beetle, especially because of their
genetic basis. The present study investigates whether (i) the CHC profiles qualitatively
and quantitatively differ between females of H. axyridis from native and invasive
populations and (ii) males discriminate females from native and invasive populations
using CHC profiles. CHCs are solvent-extracted before being quantified and identified
by gas chromatography and mass spectrometry. In total, 17 CHCs are detected from
female elytra, including six alkanes, three polyunsaturated and eight monounsaturated
alkenes. The total quantity of CHCs differs among the populations, with lady beetles
from Tai’an (China) displaying higher CHC concentrations than lady beetles from
Gembloux (Belgium) and from Beijing (China) populations. Multivariate analyses
detect differences in CHC qualitative profiles, with females from Tai’an being different
from the two other populations. Finally, behavioural assays show that females originating
from the native Tai’an population are less preferred by males, whereas females
from the invasive population are mounted more often. The behavioural assays suggest
that CHCs are not involved in discrimination of mating partners based on their origin.