Marcin Sielezniew

Host specificity revisited: New data on Myrmica host ants of the lycaenid butterfly Maculinea rebeli

Larvae of Maculinea rebeli, one of the most endangered European butterflies, are obligatory social parasites of Myrmica ants. At present, this relationship is thought to be highly specific, with Myrmica schencki being regarded as the primary host. Here we present data on six populations from Poland and Austria, including the first record of Myrmica specioides as a host, together with published data from other central European countries, which severely questions the inference that M. schencki is the exclusive host of M. rebeli. Our results indicate that Myrmica sabuleti is the most frequently used host ant in central Europe, whereas M. scabrinodis, M. sulcinodis, M. specioides and M. schencki are used as secondary hosts. Possible explanations for this highly variable host use include (1) regional differences in semiochemicals, behaviour or social structure of the potential Myrmica host species and (2) the existence of different ecological subspecies or cryptic species of M. rebeli. Finally, we emphasize the importance of identifying local host ant species prior to further conservation strategies in order to avoid failure of management programs or even damage to populations on the edge of extinction.

Wolbachia Infections Mimic Cryptic Speciation in Two Parasitic Butterfly Species, Phengaris teleius and P. nausithous (Lepidoptera: Lycaenidae)

Deep mitochondrial divergence within species may result from cryptic speciation, from phylogeographic isolation or from endosymbiotic bacteria like Wolbachia that manipulate host reproduction. Phengaris butterflies are social parasites that spend most of their life in close relationship with ants. Previously, cryptic speciation has been hypothesised for two Phengaris species based on divergent mtDNA sequences. Since Phengaris species are highly endangered, the existence of cryptic species would have drastic consequences for conservation and management. We tested for cryptic speciation and alternative scenarios in P. teleius and P. nausithous based on a comprehensive sample across their Palaearctic ranges using COI gene sequences, nuclear microsatellites and tests for Wolbachia. In both species a deep mitochondrial split occurring 0.65–1.97 myrs ago was observed that did not correspond with microsatellite data but was concordant with Wolbachia infection. Haplotypes previously attributed to cryptic species were part of the Wolbachia-infected clades. In both species remaining phylogeographic structure was largely consistent between mitochondrial and nuclear genomes. In P. teleius several mitochondrial and nuclear groups were observed in East Asia while a single haplogroup and nuclear cluster prevailed across continental Eurasia. Neutrality tests suggested rapid demographic expansion into that area. In contrast, P. nausithous had several mitochondrial and nuclear groups in Europe, suggesting a complex phylogeographic history in the western part of the species range. We conclude that deep intraspecific divergences found in DNA barcode studies do not necessarily need to represent cryptic speciation but instead can be due to both infection by Wolbachia and phylogeographic structure.

Differences in genetic variability between two ecotypes of the endangered myrmecophilous butterfly Phengaris (=Maculinea) alcon– the setting of conservation priorities

Abstract.  1. The endangered butterfly Phengaris alcon exists in two ecotypes (P. ‘alcon’ and P. ‘rebeli’), which inhabit contrasting biotopes (wet and warm/dry grasslands respectively) and use different larval food plants. The initially flower‐bud‐feeding caterpillars complete their development as social parasites of Myrmica ants, and the specificity of these relationships shows geographical variation.

Multiple host-ant use by the predatory social parasite Phengaris (=Maculinea) arion (Lepidoptera, Lycaenidae).

Phengaris (=Maculinea) arion is an endangered social parasite of Myrmica ants, and for a very long time was considered as specific to Myrmica sabuleti. Previous studies carried out in Poland suggested some discrepancies within this assumption, and therefore a much more intensive survey was undertaken. The host ant use of P. arion was studied at five sites in different types of biotopes in Poland, i.e. xerothermal grasslands where Thymus pulegioides was used as a larval food plant by the butterfly, and more or less sandy biotopes with Thymus serpyllum. Altogether nine Myrmica species were recorded, and considerable variation in species composition and density of nests was recorded. At four localities M. sabuleti proved to be the most common ant. A total of 529 Myrmica nests were examined, and only 20 of them contained larvae and pupae of P. arion. Host ants belonged to five different species, i.e. M. sabuleti, Myrmica scabrinodis, Myrmica schencki, Myrmica lobicornis and Myrmica hellenica. Only at one site (NE Poland) was a significant heterogeneity in parasitation rates among Myrmica species detected. M. lobicornis was the most often infested ant there, which may suggest local specialisation of the butterfly. Overall low parasitism rates may explain the vulnerability of P. arion in Central Europe but further studies are also necessary.

Mimetic host shifts in an endangered social parasite of ants

An emerging problem in conservation is whether listed morpho-species with broad distributions, yet specialized lifestyles, consist of more than one cryptic species or functionally distinct forms that have different ecological requirements. We describe extreme regional divergence within an iconic endangered butterfly, whose socially parasitic young stages use non-visual, non-tactile cues to infiltrate and supplant the brood in ant societies. Although indistinguishable morphologically or when using current mitochondrial and nuclear sequence-, or microsatellite data, Maculinea rebeli from Spain and southeast Poland exploit different Myrmica ant species and experience 100 per cent mortality with each others hosts. This reflects major differences in the hydrocarbons synthesized from each region by the larvae, which so closely mimic the recognition profiles of their respective hosts that nurse ants afford each parasite a social status above that of their own kin larvae. The two host ants occupy separate niches within grassland; thus, conservation management must differ in each region. Similar cryptic differentiation may be common, yet equally hard to detect, among the approximately 10 000 unstudied morpho-species of social parasite that are estimated to exist, many of which are Red Data Book listed.

First records of Myrmica vandeli Bondroit and M. tulinae Elmes, Radchenko et Aktaç (Hymenoptera: Formicidae) for Poland, with a key for the scabrinodis- and sabuleti-complexes

The first records from Poland of Myrmica vandeliand the recently described M. tulinae, both belonging to the scabrinodis-group,are reported. These species are poorly recorded and may be less rare than hitherto supposed. The current knowledge of their distributions and ecologies are summarised. The characteristic morphological features of the two species are illustrated and a key for separating them from their closest relatives in Poland is given.

Contrasting genetic structure of rear edge and continuous range populations of a parasitic butterfly infected by Wolbachia

BackgroundClimatic oscillations are among the long-term factors shaping the molecular features of animals and plants and it is generally supposed that the rear edges (i.e., the low-latitude limits of distribution of any given specialised species) situated closer to glacial refugia are vital long-term stores of genetic diversity. In the present study, we compared the genetic structure of several populations of an endangered and obligate myrmecophilous butterfly (Maculinea arion) from two distinct and geographically distant parts of its European distribution (i.e., Italy and Poland), which fully represent the ecological and morphological variation occurring across the continent.ResultsWe sequenced the COI mitochondrial DNA gene (the ‘barcoding gene’) and the EF-1α nuclear gene and found substantial genetic differentiation among M. arion Italian populations in both markers. Eleven mtDNA haplotypes were present in Italy. In contrast, almost no mtDNA polymorphisms was found in the Polish M. arion populations, where genetic differentiation at the nuclear gene was low to moderate. Interestingly, the within-population diversity levels in the EF-1α gene observed in Italy and in Poland were comparable. The genetic data did not support any subspecies divisions or any ecological specialisations. All of the populations studied were infected with a single strain of Wolbachia and our screening suggested 100% prevalence of the bacterium.ConclusionsDifferences in the genetic structure of M. arion observed in Italy and in Poland may be explained by the rear edge theory. Although we were not able to pinpoint any specific evolutionarily significant units, we suggest that the Italian peninsula should be considered as a region of special conservation concern and one that is important for maintaining the genetic diversity of M. arion in Europe. The observed pattern of mtDNA differentiation among the populations could not be explained by an endosymbiotic infection.

Distribution, host specificity and the potential for cryptic speciation in hoverfly Microdon myrmicae (Diptera: Syrphidae), a social parasite of Myrmica ants

1. In 2002 Microdon myrmicae, a social parasite of Myrmica ants, was taxonomically separated from Microdon mutabilis. The original study in the U.K. found Microdon myrmicae to be specific to one ant species, Myrmica scabrinodis, yet it became apparent that the range of Microdon myrmicae includes at least the western Palaearctic.

Population demography of the endangered large blue butterfly Maculinea arion in Europe

Demographic parameters such as survival, sex ratio and abundance can profoundly affect the viability of populations and thus are of primary importance in species of conservation concern. Although numerous studies have been published on certain aspects of the ecology and evolution of the endangered Large Blue butterfly Maculinea arion, there is still a lack of detailed knowledge on its populations’ demography. Moreover, M. arion populates a variety of xerothermic habitats throughout its European range using various food plants and host ants, which leads to complications in its conservation. Our aim was to estimate demographic parameters of M. arion populations in different parts of its European range. Detailed mark-recapture sampling was conducted on populations in four different countries. We often found that daily apparent survival probability declined with increasing age of individuals, but there was no difference between male and female survival. In smaller populations, the sex ratio was rather female-biased. Our most interesting result was the lack of protandry in some populations that might be a consequence of selection against reproductive asynchrony in small populations or a polyandrous mating system. The perfect coincidence of male and female phenology can positively affect the effective population size, because the lack of reproductive asynchrony increases the chance of male–female encounters. Abundance of the studied populations ranged between 100 and 1,600 individuals, smaller populations were on the verge of extinction. Habitat of the threatened small populations was either overgrazed or abandoned, while habitat of larger, stable populations was lightly grazed.

Geographical Variation in Wing Pattern in Phengaris (=Maculinea) Arion (L.) (Lepidoptera: Lycaenidae): Subspecific Differentiation or Clinal Adaptation?

Abstract. Socially parasitic and globally threatened Phengaris (=Maculinea) arion (L.) is one of the most intensively investigated insect species in Europe. Although current studies focus on ecology and genetics, the butterfly has also attracted attention because of its morphology. An extremely variable black pattern on the blue background of the wing upperside has resulted in the description of many different forms or even subspecies. We studied the variation of 148 individuals from five regional populations at a latitudinal gradient in Poland: two north-eastern populations, one middle-eastern populations and two southern populations. A proportion of the area covered with marginal strips and spots was measured, and the presence/absence of particular elements was also analyzed. For all except one, the most northern region, we found significant sexual dimorphism, with females being darker than males. Within sexes, the melanization level was higher in the north-east than in the south, and the mid — eastern region showed intermediate characteristics. Differences in colouration overlapped with variation in host ant use, but neither feature corresponded with the available genetic data and therefore clinal variation is a more likely explanation for the observed pattern. Melanization level may be an adaptation to climatic conditions, but it remains unclear which strategy of dorsal basking is applied by P. arion.