Kickass Mutualisms: Lycaenids+Ants

17 08 2011

The Lycaenidae (gossamer-winged butterflies) is the second largest family of butterflies, with ~5000 species, including some of the more famous butterflies, such as the Theclinae (hairstreaks), the Polyommatinae (blues) and the Lycaeninae (coppers). They are mostly found in the Old World (de Jong, 2003), where 28 of the 33 lycaenid tribes are endemic.

They are a monophyletic group, as seen in the tree above, based on a combined molecular and morphological analysis (orange branches; Wahlberg et al., 2005).

However, they are in need of systematic revision – the only complete classification available is in Eliot (1973), but is not based on phylogenetic methodology. Afaik, no cladistic analysis of them has been published. The cladogram above (Pierce et al., 2002) is a handmade compromise solution and should not be viewed as definite, not even for the higher taxa.

ResearchBlogging.org
Pierce, N., Braby, M., Heath, A., Lohman, D., Mathew, J., Rand, D., & Travassos, M. (2002). The ecology and evolution of ant association in the Lycaenidae (Lepidoptera) Annual Review of Entomology, 47 (1), 733-771 DOI: 10.1146/annurev.ento.47.091201.145257

Anyway, on to the topic of this post: the best example of a mutualism I know of. It’s the mutualism between the lycaenid caterpillar and ants: the ants, being top predators, protect the defenceless herbivorous caterpillar in exchange for a nutritive reward.

This reward consists of carbohydrates (Maschwitz, 1975) secreted from an exocrine gland, the dorsal nectary organ. When a caterpillar feels threatened, it will release a signal, most likely pheromonal, which attracts ants; once they arrive, it pumps out the secretion (Agrawal & Fordyce, 2000), making it attractive for the ants to stay and protect this easy source of valuable nutrients (Cushman et al., 1994). It’s my personal favourite example of a mutualism, and one I use in every lecture I give on the subject.

Those who have been to one of those lectures will know how much I stress the fluid nature of such associations, and how they can easily lapse into cases of parasitism (and vice versa; it’s all on a spectrum, both on ecological and evolutionary timescales). This can also be seen here: several of these lycaenid caterpillars have secondarily become entomophagous – they use the same attractants to gather ants, and eat them before they realise there’s no reward (Akino et al., 1999).

The Pierce paper has all the details. [Contact me if you want it.]

References:

Agarwal AA & Fordyce JA. 2000. Induced indirect defense in a lycaenid-ant association: the regulation of a resource in a mutualism. Proc. R. Soc. B 267, 1857–1861.

Akino T, Knapp JJ, Thomas JA & Elmes GW. 1999. Chemical mimicry and host specificity in the butterfly Maculinea rebeli, a social parasite of Myrmica ant colonies. Proc. R. Soc. B 266, 1419–1426.

Cushman JH, Rashbrook VK & Beattie AJ. 1994. Assessing benefits to both participants in a lycaenid-ant association. Ecology 75, 1031–1041.

de Jong R. 2003. Are there butterflies with Gondwanan ancestry in the Australian region? Invertebrate Systematics 17, 143–156.

Eliot JN. 1973. The higher classification of the Lycaenidae (Lepidoptera): a tentative arrangement. Bulletin of the British Museum of Natural History (Entomology) 28, 371-505.

Maschwitz U, Wüst M & Schurian K. 1975. Bläulingsraupen als Zuckerlieferanten für Ameisen. Oecologia 18, 17–21.

Pierce NE, Braby MF, Heath A, Lohman DJ, Mathew J, Rand DB & Travassos MA. 2002. The ecology and evolution of ant association in the Lycaenidae (Lepidoptera). Annual Review of Entomology 47, 733-771.

Wahlberg N, Braby MF, Brower AVZ, de Jong R, Lee M-M, Nylin S, Pierce NE, Sperling FAH, Vila R, Warren AD & Zakharov E. 2005. Synergistic effects of combining morphological and molecular data in resolving the phylogeny of butterflies and skippers. Proc. R. Soc. B 272, 1577-1586.

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