A butterfly?s chemical key to various ant forts: intersection-odour or aggregate-odour multi-host mimicry?

Abstract

Deception is a crucial yet incompletely understood strategy of social parasites. In central Europe, the Mountain Alcon Blue, Maculinea rebeli, a highly endangered butterfly, parasitises several Myrmica ant species. Caterpillars gain access to host nests probably by faking the ants' odour. We analysed gas chromatography-mass spectrometry data of body surface hydrocarbons of pre-adoption and hibernated larvae of Maculinea rebeli and of their host species Myrmica sabuleti and M. schencki. Data were ordinated by different methods, based on similarities in the relative quantities of compounds between chromatograms. The two Myrmica species exhibit species-specific profiles. The Maculinea rebeli pre-adoption larva has a complex profile that simultaneously contains species-specific substances of the two investigated host species. This evidence leads to the interpretation that, in central Europe, Maculinea rebeli is predisposed for multi-host use by the chemical signature of its pre-adoption larva. The Maculinea rebeli larva clearly does not rely on an "intersection-odour" of compounds common to all host ant species, but synthesises an "aggregate-odour" containing specific compounds of each of the investigated hosts. We term this previously unknown chemical strategy "aggregate-odour multi-host mimicry".

A phylogenetic test of the parasite-host associations between Maculinea butterflies (Lepidoptera: Lycaenidae) and Myrmica ants (Hymenoptera: Formicidae)

“…Such a tactic is close to that described by Schlick-Steiner et al (2004). In Central Europe the cuckoo-feeding Maculinea rebeli has one main and several secondary host species, and rather than emitting a general Myrmica-like odour the pre-retrieval caterpillars synthesise an aggregate odour containing specific compounds of at least two host species.…”

Host ant specificity of large blue butterflies Phengaris (Maculinea) (Lepidoptera: Lycaenidae) inhabiting humid grasslands in East-central Europe

“…Admittedly, the same authors also discovered two neighbouring populations of P. alcon in SE-Poland that simultaneously used M. scabrinodis and M. vandeli Bondroit, 1920 as host ants, but suspected that M. vandeli is a temporary social parasite of M. scabrinodis which is almost identical chemically (Radchenko et al, 2003;Sielezniew & Stankiewicz, 2004;Stankiewicz et al, 2005). Pech et al (2007) pointed out that firm evidence for local specialization of P. alcon exists only for a few Danish populations (Als et al, 2002;Nash et al, 2008) while other observations do not reveal any local specificity (Elmes et al, 2002;Schlick-Steiner et al, 2004). In contrast, our data clearly show that in all the Polish populations of P. alcon investigated high localspecialization occurs.…”

The “Evolutionarily Significant Unit” concept and its applicability in biological conservation

“…All across their European distribution, M. alcon and M. rebeli populations use as hosts more than 10 Myrmica species (see Thomas et al 1989;Elmes et al 1991aElmes et al , 1991bElmes et al , 1994Akino et al 1999;Steiner et al 2003;Schlick-Steiner et al 2004;Sielezniew & Stankiewicz 2004;Tartally et al 2008;Nowicki et al 2009). Such a relatively large number of host switches, together with observations that individual populations are typically highly species-specific with respect to ant association, suggest that cuckoos may be undergoing rapid ecological divergence (Elmes et al 1994;Meyer-Hozak 2000;Als et al 2001Als et al , 2004Steiner et al 2003;Witek et al 2006).…”