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Differences between the 7-spot and 2-spot ladybird beetles (Coccinellidae) in their toxic effects on a bird predator |
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| Authors: | NICOLA M MARPLES PAUL M BRAKEFIELD RICHARD J COWIE |
| Institution: | Department of Zoology, University College Cardiff, Cardiff, Wales;*Department of Zoology, University College Cardiff, Cardiff, Wales, Section of Evolutionary Biology, Department of Population Biology, University of Leiden, Leiden, The Netherlands |
| Abstract: | Abstract. 1. Experiments with nestling blue tits Parus caeruleus L. examined the effects of feeding them 7-spot ladybird Coccinella septempunctata (L.), 2-spot ladybird Adalia bipunctata (L.) or controls Tenebrio sp. 2. A feeding rate of 51/3 7-spot ladybirds per day 'killed' nestlings within 2 days. Three of six nestlings fed at half this rate survived 4 days. In contrast, all experimental birds survived sixty-four 2-spot ladybirds fed over 4 days (equivalent by weight to the high 7-spot diet). 3. Nestlings fed 7-spot ladybirds also grew more slowly than birds fed 2-spot ladybirds. The latter birds showed no difference in weight gain from the controls although they begged more strongly for food. 4. Cadavers of birds fed 7-spot ladybirds showed evidence of severe liver damage. 5. The results indicate a substantial difference between the ladybird species in their toxicity to nestling blue tits. They support the hypothesis that 2-spot ladybirds are largely-edible, polymorphic Batesian mimics of well-protected, monomorphic species such as the 7-spot ladybird. |
| Keywords: | Coccinellidae Adalia bipunctata Coccinella septempunctata Parus caeruleus toxicity mimicry selection alkaloids liver |