Cannibalizing Harmonia axyridis (Coleoptera: Coccinellidae) larvae use endogenous cues to avoid eating relatives

Abstract

Cannibalism is widespread among many different organisms, and can have both negative and positive fitness consequences. Avoiding eating relatives can minimize negative fitness consequences of cannibalism. Such avoidance requires kin discrimination, but evidence for this ability among cannibals is limited with little data that address the cues used in such discrimination. We examined whether larvae of the ladybird beetle Harmonia axyridis avoid eating their relatives. We further manipulated environmental factors to create individuals that had similar or dissimilar rearing environments to begin to test for endogenous versus exogenous recognition cues. In our experiments, third‐instar larvae were much less likely to cannibalize if they were interacting with a relative. Larvae that did cannibalize kin required more encounters, and significantly delayed cannibalism, compared to larvae cannibalizing unrelated individuals. Acquired cues were less important. Even though the different rearing environment resulted in significantly different phenotypic effects, similarity or dissimilarity of rearing environment had no effect on cannibalism, and there was no interaction between environments and relatedness in cannibalism. We suggest that H. axyridis has a well‐developed kin discrimination system, and that kin recognition in this ladybird beetle is based on endogenous rather than exogenous cues. We also argue that these cues reflect either direct or indirect genetic effects on larval phenotypes.

Kin recognition in immatures of Heliconius erato phyllis (Lepidoptera; Nymphalidae)

“…The former found a frequency of 25% for sibling cannibalism and 36% for nonsibling cannibalism, which were not significantly different. As for Joseph et al (1999), they showed that third instar larvae are less prone to cannibalize their siblings than nonsiblings (approximately 1:2). More recently, Michaud (2003) compared the cannibalism of first instar larvae in H. axyridis and found that siblings were less cannibalized than nonsiblings.…”

“…Hare and Eisner (1995) specifically addressed the subject in Utetheisa ornatrix, an arctiid moth, where no recognition was found. More recent papers tested specifically for kin recognition in several different taxa; however the results are conflicting even for the same species, as exemplified by the studies of Osawa (1989) and Joseph et al (1999) both with Harmonia axyridis (Coleoptera). The former found a frequency of 25% for sibling cannibalism and 36% for nonsibling cannibalism, which were not significantly different.…”

Food Relationships

“…However, males ate as many of their own eggs as eggs sired by other males (perhaps because males invest much less energy in eggs and cannot safely distinguish them). Joseph et al (1999) found that third instar Har. axyridis placed together were much less likely to cannibalize siblings than unrelated individuals.…”

Role of surface chemical signals in egg cannibalism and intraguild predation in ladybirds (Coleoptera: Coccinellidae)

“…Although the disadvantages of consuming one's kin has been considered (Osawa 1992;Joseph et al 1999) those associated with eating toxic eggs of other species, although well described (Agarwala & Dixon 1992), has been ignored. The larvae of Adalia bipunctata (L.) and Coccinella septempunctata L., which regularly co-occur in the field, are reluctant to eat conspecific eggs painted with water extracts of whole eggs of the other species, and larvae of C. septempunctata are more likely to develop more slowly and/or die after eating a few eggs of A. bipunctata than 6ice 6ersa (Agarwala & Dixon 1992;Hemptinne et al 2000).…”