Causas e consequências de uma falta de coevolução em mimetismo mülleriano

Causes and consequences of a lack of coevolution in Müllerian mimicry

JAMES MALLET
Galton Laboratory, Department of Biology, University College London, 4 Stephenson Way, London NW1 2HE, England

(http://abacus.gene.uel.ac.uk/jim/)

Received 9 June 2000; accepted 27 November 2000

Co-ordinating editor: C. Rowe

We are rarely able in such investigations to arrive at entirely satisfactory conclusions owing to lack of adequate material and data, and I fear the present e€ort is no exception. The results may, however, serve to indicate the directions in which future workers ¼ may hope to obtain more de®nite results (Eltringham, 1916).

Abstract. Müllerian mimicry, in which both partners are unpalatable to predators, is often used as an example of a coevolved mutualism. However, it is theoretically possible that some Müllerian mimics are parasitic if a weakly defended mimic benefits at the expense of a more highly defended model, a phenomenon known as `quasi-Batesian mimicry'. The theory expounded by Müller and extended here for unequal unpalatability, on the other hand, suggests that quasi-Batesian mimicry should be rare in comparison with classical, or mutualistic Müllerian mimicry. Evolutionarily, quasi-Batesian mimicry has consequences similar to classical Batesian mimicry, including unilateral `advergence' of the mimic to the model, and diversifying frequency-dependent selection on the mimic which may lead to mimetic polymorphism. In this paper, theory and empirical evidence for mutual benefit and coevolution in Müllerian mimicry are reviewed. I use examples from well-known insect Müllerian mimicry complexes: the Limenitis±Danaus (Nymphalidae) system in North America, the Bombus±Psithyrus (Apidae) system in the north temperate zone, and the Heliconius± Laparus (Nymphalidae) system in tropical America. These give abundant evidence for unilateral advergence, and no convincing evidence, to my knowledge, for coevolved mutual convergence. Furthermore, mimetic polymorphisms are not uncommon. Yet classical mutualistic Müllerian mimicry, coupled with spatial (and possibly temporal) variation in model abundances convincingly explain these apparent anomalies without recourse to a quasi-Batesian explanation. Nevertheless, the case against classical Müllerian mimicry is not totally disproved, and should be investigated further. I hope that this tentative analysis of actual mimicry rings may encourage others to look for evidence of coevolution and quasi-Batesian e€fects in a variety of other Müllerian mimicry systems.

Key words: advertising coloration, aposematism, Batesian mimicry, mimicry, mutualism, signalling, warning colour

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