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Dryad

Responses of avian predators to polymorphic harlequin ladybird (Harmonia axyridis)

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Dec 18, 2023 version files 64.77 KB

Abstract

Harlequin ladybird (Harmonia axyridis) shows high level of colour polymorphism. Particular forms differ in their colour combination, pattern and abundance.

We tested the willingness of native, wild-caught passerines to attack and eat particular forms. We predicted that those forms that are more abundant in the wild are better protected, as they are more familiar to the predators. We compared the forms novemdecimsignata and spectabilis, which represent 97 % of individuals in the wild population, but importantly differ in their visual appearance (mostly orange vs. mostly black). Further, we examined three intermediate forms: axyridis, which is very scarce in the wild, and two forms not occurring in the wild – originating from laboratory breedings: suturalis and aninkae. As predators, we used great tit (Parus major), which is very aversive towards ladybirds, and tree sparrow (Passer montanus), which is quite willing to attack and even eat ladybirds. We compared their responses to particular ladybird forms, with artificially brown-painted ladybird to test for the effect of visual signal.

We showed that both bird species attacked all forms of ladybird equally and usually very scarcely. The brown-painted novemdecimsignata form was attacked more often, showing that the visual appearance prevents birds from attacking any conspicuous colour combination. Sparrows tended to eat the attacked ladybirds of forms novemdecimsignata, spectabilis and brown painted. Scarce axyridis form and laboratory forms were very well protected from the attack, very likely due to neophobia.