Patterns of host ant use by sympatric populations of Maculinea alcon and M. ‘rebeli’ in the Carpathian Basin

Abstract

Maculinea butterflies show social parasitism via obligatory myrmecophily as their larvae are adopted and raised to pupation by Myrmica ants. Suitable hosts differ for different Maculinea species, and host ant specificity can further differ at the population-level. Although early studies suggested single ant species as main hosts for each Maculinea species, it has recently become clear that their host ant specificity is more complex. Maculinea alcon and Maculinea rebeli have variously been separated according to adult and larval morphology, phenology, and their use of different ecosystems, including host plant and host ant species. However, recent genetic evidence has questioned their separation as good species. Here we compare the use of host ants by M. alcon and M. rebeli at the regional scale in NE-Hungary and Transylvania (Romania), where molecular studies have found no species-level separation between the two forms. We opened 778 nests of Myrmica ants and searched for Maculinea specimens (larvae, pupae and exuviae) shortly before imago emergence from the nest in seven M. alcon sites, six M. rebelisites and one site where both M. alcon and M. rebeli are syntopic. In all, Maculinea caterpillars were found in the nests of seven different ant species (M. alcon was recorded mainly with Myrmica scabrinodis and occasionally with M. salina and M. vandeli; M. rebeli used mainly M. scabrinodis, M. sabuleti and M. schencki and occasionally M. lonae and M. specioides). Myrmica scabrinodis was found to be a general host of both M. alcon and M. rebeli, which is the first record for a common host ant of these two closely related butterflies within the same region. However there were also differences in host ant use patterns between the sites occupied by the two Maculinea taxa, which reflect differences in Myrmica communities between the two types of habitat. Possible explanations for the similar but not identical host use patterns of M. alcon and M. rebeli, and their relevance for the question of whether they are separate species are discussed.

Contrasting levels of polymorphism in cross-amplified microsatellites in two endangered xerothermophilous, obligatorily myrmecophilous, butterflies of the genus Phengaris (Maculinea) (Lepidoptera: Lycaenidae)

“…However, there are inconsistencies in recent papers concerning both the generic and specific names (compare e.g. Tartally et al, 2008;Árnyas et al, 2009;Barbero et al, 2009). In the present paper we call the controversial taxon P. 'rebeli' to avoid any possible confusion.…”

“…For example P. arion, which is supposed to be specific to M. sabuleti Mein., can also survive in the nests of other ants (Sielezniew & Stankiewicz, 2008). On the other hand, in addition to the different host-races of P. 'rebeli' there are also populations that are not host specific (Steiner et al, 2003;Tartally et al, 2008;Sielezniew & Dzieka ska, 2009).…”

What keeps ‘living dead’ alive: demography of a small and isolated population of Maculinea (= Phengaris) alcon

“…There is a controversy surrounding the taxonomic status of M. alcon, with its two distinct forms associated with wet meadows and xerothermic grasslands, regarded as separate species or, more frequently, merely as different ecotypes (Als et al 2004;Pecsenye et al 2007;Sielezniew et al 2012;Bereczki et al 2018). Consequently, the conservation status of the species is uncertain, and it is classified as least concern (LC) in Europe (van Swaay et al 2010), even though many authors regard both forms to be clearly under threat (WallisDeVries 2004;Tartally et al 2008;Czekes et al 2014).…”

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).…”