EUROPEAN JOURNAL OF ENTOMOLOGY

Eur. J. Entomol. 111 (2): 307-311, 2014 | DOI: 10.14411/eje.2014.029

Prevalence of male-killer in a sympatric population of two sibling ladybird species, Harmonia yedoensis and Harmonia axyridis (Coleoptera: Coccinellidae)

Suzuki NORIYUKI¹, Yuichi KAMEDA¹, Naoya OSAWA²

¹ Laboratory of Conservation Biology, Center for Northeast Asian Studies, Tohoku University, 41 Kawauchi, Aoba, Sendai, Miyagi 980-8576, Japan; e-mails: fvgnoriyuki@gmail.com; yuichi.c.kameda@gmail.com

² Laboratory of Forest Ecology, Graduate School of Agriculture, Kyoto University, Kyoto, Japan; e-mail: osawa@kais.kyoto-u.ac.jp

In predatory ladybirds male embryos in clutches of eggs infected with male-killing bacterial endosymbionts do not hatch and are consumed by female hatchlings. Moreover, it is predicted that infection with male-killing bacteria should be prevalent in a ladybird population if the fitness advantage to female ladybirds due to the resulting reallocation of resources is high. We compared male-killer bacterial prevalence in two sibling species of the ladybird genus Harmonia that use different host ranges. Harmonia yedoensis feeds mostly on the highly elusive pine aphid and its hatchlings can greatly enhance their ability to capture prey and thus their survival by consuming un-hatched eggs in the clutch. In contrast, Harmonia axyridis feeds on a wide range of prey and consumption of un-hatched eggs by the hatchlings does not necessarily increase their foraging success. In the study area where these two species of ladybird occur sympatrically 14 of the 22 females of H. yedoensis (64%) laid clutches of eggs of which approximately only a half hatched and did not produce male offspring, whereas only one of 12 of the females of H. axyridis (8%) exhibited symptoms indicating infection with male-killing bacteria. In the H. yedoensis that exhibited symptoms of being infected with male-killing bacteria, the total allocation of resources to each hatchling, which was provided by laying larger eggs and eating the un-hatched eggs in the clutch, was considerable. These results suggest that the difference in the prevalence of infection with male-killing bacteria in these two species of ladybird may reflect differences in the quality of their prey and their foraging behaviour.

Keywords: Coleoptera, Coccinellidae, Harmonia axyridis, H. yedoensis, aphidophagous ladybird, early male-killing, maternal investment, maternally inherited bacteria, sex ratio, sibling cannibalism, sibling species

Received: November 5, 2013; Revised: January 2, 2014; Accepted: January 2, 2014; Prepublished online: March 14, 2014; Published: May 5, 2014  Show citation