Article

A Mosaic of Chemical Coevolution in a Large Blue Butterfly

Institute of Biology, University of Copenhagen, Universitetsparken 15, DK-2100 Copenhagen, Denmark.
Science (Impact Factor: 31.48). 02/2008; 319(5859):88-90. DOI: 10.1126/science.1149180
Source: PubMed

ABSTRACT Mechanisms of recognition are essential to the evolution of mutualistic and parasitic interactions between species. One such
example is the larval mimicry that Maculinea butterfly caterpillars use to parasitize Myrmica ant colonies. We found that the greater the match between the surface chemistry of Maculinea alcon and two of its host Myrmica species, the more easily ant colonies were exploited. The geographic patterns of surface chemistry indicate an ongoing coevolutionary
arms race between the butterflies and Myrmica rubra, which has significant genetic differentiation between populations, but not between the butterflies and a second, sympatric
host, Myrmica ruginodis, which has panmictic populations. Alternative hosts may therefore provide an evolutionary refuge for a parasite during periods
of counteradaptation by their preferred hosts.

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    • "A field study ( Elmes et al . 2004 ) and an analysis of pre - adoption chemical profiles ( Nash et al . 2008 ) suggested that similar differentiation may have evolved between the main European form of M . alcon , which exploits Myrmica scabrinodis , and that of Scandinavia and the Netherlands , which is adapted to Myrmica rubra / M . ruginodis . Ant association is therefore a double - edged sword for the conservation of these lycaenid butterfl"
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    ABSTRACT: Abstract Although most conservationists claim to protect “species”, the conservation unit actually and practically managed is the individual population. As resources are not unlimited, we need to focus on a restricted number of populations. But how can we select them? The Evolutionarily Significant Unit (ESU), first conceptualised by Ryder in 1986, may offer some answer. Several definitions have been proposed for the ESU, but all make reference to units “whose divergence can be measured or evaluated by putting differential emphasis on the role of evolutionary forces at varied temporal scales”. Thus, an ESU might be fully identical with a “species”, or a “species” could be composed of multiple ESUs. On the other hand, an ESU might comprise single/multiple populations exchanging a degree of gene flow, such as meta-populations. In an attempt to show strengths and weaknesses of ESU concepts, we present here, among several others, some case studies on the myrmecophilous butterflies of the genus Maculinea. In particular, we analyse the apparently everlasting debate about Maculinea alcon and M. rebeli, whose separation into separate species has been accepted by many authors, on mainly ecological criteria, but has not been fully supported by molecular analyses. We also discuss how the tight association with host ants may have driven selection for increasingly more strictly adapted Maculinea populations, arguably deserving specific taxonomic identity. Finally we discuss how current DNA analyses may fail to detect critical information on differences between taxa recently originated by the action of separate adaptive processes, which non-molecular studies can sometimes reveal. We conclude by discussing some current and often conflicting taxonomic trends, in their relationships with conservation policies.
    Italian Journal of Zoology 06/2014; DOI:10.1080/11250003.2013.870240 · 0.87 Impact Factor
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    • "Indeed, selection by parasites may favour host foundresses with unusual proportions of hydrocarbons, as such foundresses are temporarily " out of reach " of coevolving social parasites. We know that social parasites exhibit host choice by preferentially targeting large colonies (e.g., Nash et al., 2008; Lorenzi and Thompson, 2011) and less aggressive hosts (Foitzik et al., 2001). It seems reasonable that they can also select hosts on the basis of their colony signature, since signature has a key role in parasite adaptation. "
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    ABSTRACT: Nestmate recognition codes show remarkable chemical complexity, involving multiple biochemical pathways. This complexity provides the opportunity to evaluate the ecological and social conditions that favor the evolution of complex signaling. We investigated how the chemical signatures of three populations of the social paper wasp Polistes biglumis differed in terms of concentration of hydrocarbons, proportions of branched hydrocarbons and overall variation. We tested whether the variation in chemical signatures among populations could be explained by the prevalence of social parasites or whether this was just an effect of local abiotic conditions which influenced the composition of the hydrocarbon cuticular layer. We studied the chemical signa-ture in three populations in which obligate social parasites differed in the selection pressures they imposed on host populations. Within each population, we restricted our analyses to non-parasitized hosts, to avoid potential short-term effects of parasite pres-ence on the host chemical signatures. We found that host colonies in parasitized populations had more diverse profiles than the parasite-free population. Moreover, the overall concentration of hydrocarbons and the relative proportion of branched hydrocar-bons were larger in the parasitized populations, relative to the non-parasitized one. This is to our knowledge the first evidence in favour of the hypothesis that different traits in the host chemical signatures as a whole undergo evolutionary changes resulting from directional or balancing selection imposed by social parasites. We conclude that obligate social parasites act as 'engines of diversity' on host chemical signatures and operate in favor of a geographic mosaic of diverging communication codes.
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    • "C 20:0 ) (22% missing values). All peak areas were log-ratio transformed (Nash et al., 2008) and multivariate statistics performed to explore changes in fatty acid composition. Principle component analysis was used to obtain two principle components (PC1, PC2) for each sample using past (Hammer et al., 2001). "
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    ABSTRACT: Acquiring sufficient nutrients is particularly important for insects that are unable to synthesize certain nutrient types de novo, as is the case for numerous parasitoid species that do not synthesize lipids. The lipid reserves of parasitoids are acquired from a single host during larval development. This imposes constraints on the quantity and quality of available lipids. In the present study, the lipid dynamics throughout the trophic cascade are investigated by measuring lipogenic ability, modifications in fatty acid composition and host exploitation efficiency in species at different trophic positions within the community of parasitoids associated with the gall wasp Diplolepis rosae L. (Hymenoptera: Cynipidae). The results obtained show that lipid levels remain stable or decline after feeding in all species, indicating that none of the wasps synthesize lipids. Fatty acid composition is highly similar between the gall wasp, parasitoid and hyperparasitoid species, with the exception of the parasitoid Orthopelma mediator Thunberg (Hymenoptera: Ichneumonidae). The divergence of fatty acid composition in O. mediator suggests that this species is able to modify its fatty acid composition after the consumption of host lipids. The efficiency of exploitation of host resource, in terms of dry body mass acquired, varies among the species (41–70%), although it is high overall compared with the efficiencies reported in other animals. Hence, for parasitoid wasps that lack lipid synthesis capabilities, the efficiency of host exploitation is high and fatty acids are consumed directly from the host without modification, leading to stable fatty acid compositions throughout the trophic cascade.
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