RESEARCH: DIVERSITY AND EVOLUTION OF BATESIAN MIMICRY
Batesian mimicry is a phenomenon whereby unprotected prey species (called "mimics") gain protection from predators by mimicking toxic or otherwise protected species (called "models"). Predators learn to avoid models based on prior experience, and subsequently avoid eating mimics due to misidentification. Hundreds of mimetic butterfly species are known in tropical forests. There is tremendous variation in the nature of Batesian mimicry: mimicry can be sexually monomorphic, polymorphic or sex-limited within and across species. Early evolutionists such as Henry Bates (who first proposed the theory of mimicry and in whose honor it is named), Alfred Russel Wallace, Charles Darwin, and Edward Poulton hailed Batesian mimicry as a fine example of natural selection, pointing to the often perfect resemblance between the mimics and their models. They saw this as one of the strongest demonstrations of evolution by natural selection, in this case brought about through the agency of predators such as birds. We now know many other good examples of natural selection but the interest in Batesian mimicry has persisted to this day among evolutionary biologists, and for a good reason. We have a very strong theoretical framework for Batesian mimicry, and extensive field observations as well as numerous laboratory experiments have provided rich detail of the phenomenon under a variety of ecological conditions and in a number of organisms.
Building on this extensive foundation, we study the diversity and evolution of Batesian mimicry in butterflies. Batesian mimicry is common among butterflies. It is also quite diverse with numerous polymorphic and sex-limited mimicry types. Currently there is little understanding of how this diversity is distributed among species, and how different mimicry types have evolved in relation to each other. To answer these questions, we have developed: (a) pathway analysis that connects various mimicry types by hypothetical character state changes within a phylogenetic framework, and (b) a mathematical model of the ecological conditions and selection regimes under which various mimicry types may be favored. The mathematical model shows that different types of mimicry in butterflies may be arranged along a gradient of relative frequency of mimics in a mimic-model community under the influence of frequency-dependent selection.
We are testing the mathematical model with field data on population and community dynamics in the Eastern Himalayan and Western Ghats butterfly "mimicry rings" (a community of mimics and models). Simultaneously, we are applying the pathway analysis to phylogenetic reconstruction of the evolution and diversity of mimicry in butterflies, such as in the Papilio butterflies shown here. This type of analysis provides vital tools to study how various mimicry types are phylogenetically structured within clades. Our initial analysis in Papilio suggests that varied selection for mimicry and its complex genetic architecture may act in a ratcheting manner toward generating greater diversity in Batesian mimicry. The initial evolution of one mimicry type may facilitate evolution of other mimicry types when selection for mimicry changes, sometimes leading to more complex mimicry types such as the ones seen in Papilio. Read more about this work in the papers listed below.
To understand the full spectrum of mimetic diversity in the animal world, we are also interested in diversifying into other Batesian mimetic groups involving moths, beetles, spiders and flies while continuing to study mimicry in butterflies.
Joshi, J., A. Prakash, and K. Kunte. 2017. Evolutionary assembly of communities in butterfly mimicry rings. The American Naturalist, 189(4):E000–E000 (in press). PDF file (12MB, has colour figures).
Su, S., M. Lim, and K. Kunte. 2015. Prey from the eyes of predators: colour discriminability of aposematic and mimetic butterflies from an avian visual perspective. Evolution, 69:2985-2994. PDF file (650KB; or PDF file with supporting information, 1.1MB). This work was featured on the cover of the journal issue, and in several popular science news stories in PhysOrg, EurekAlert, The Hindu, The Statesman, and NCBS News, among others.
Kunte, K., W. Zhang, A. Tenger-Trolander, D. H. Palmer, A. Martin, R. D. Reed, S. P. Mullen, and M. R. Kronforst. 2014. doublesex is a mimicry supergene. Nature, 507:229-232. PDF file (1.2MB). Read more about the story on this webpage. See popular science coverage of this paper in Nature, Nature India, Science, NCBS News, The Scientist, National Geographic's Phenomena blog, Mongabay, New York Times, The Hindu, and ScienceDaily.
Kunte, K., C. Shea, M. L. Aardema, J. M. Scriber, T. E. Juenger, L. E. Gilbert, and M. R. Kronforst. 2011. Sex chromosome mosaicism and hybrid speciation among tiger swallowtail butterflies. PLoS Genetics, 7:e1002274. See the full paper online on the journal website, or its news coverage on the National Science Foundation (NSF, USA) website, the University of Texas at Austin and the College of Natural Sciences websites, in Harvard Gazette, or on MSNBC, and myscience. Read more about this work ...
Kunte, K. 2009. Female-limited mimetic polymorphism: A review of theories and a critique of sexual selection as balancing selection. Animal Behaviour, 78:1029–1036. PDF file (586KB, includes a color figure).
Kunte, K. 2009. The diversity and evolution of Batesian mimicry in Papilio swallowtail butterflies. Evolution, 63:2707–2716. PDF file (987KB, includes a color figure).
Kunte, K. 2008. Mimetic butterflies support Wallace's model of sexual dimorphism. Proceedings of the Royal Society, B, 275:1617-1624. PDF file (404KB).
Image of Small Green Bee-eater (Merops orientalis) eating the male Danaid Eggfly (Hypolimnas misippus): © Shashidhar Hiremath, used with permission.