Differences in oviposition strategies between two ecotypes of the endangered myrmecophilous butterfly Maculinea alcon (Lepidoptera: Lycaenidae) under unique syntopic conditions

Abstract

The Alcon Blue Maculinea alcon and the Mountain Alcon Blue Maculinea ‘rebeli’ are obligate ant‐parasitic butterflies with no distinct morphological and genetic differences but clear ecological separation. The two butterflies generally lay their eggs on distinct host plant species: M. alcon on Gentiana pneumonanthe and M. ‘rebeli’ on Gentiana cruciata. The egg‐laying behaviour of these two ecotypes has previously only been investigated in sympatric, but not in syntopic populations. We studied the egg‐laying preferences of M. alcon and M. ‘rebeli’ in a unique area where they co‐occur, and where they use different host plants. The distance to the nearest other host plant does not seem to influence the decision of female butterflies as to whether to lay eggs on a specific host plant. The two butterflies laid their eggs on different parts of their host plants: M. alcon preferred the sepals of G. pneumonanthe flower buds, while M. ‘rebeli’ laid most eggs on the leaves of G. cruciata. The major factor correlated with the number of eggs laid on the host plant seemed to be plant quality (number of flowers, stem length, etc.) for both butterflies. The present study reveals behavioural differences between the two Alcon Blue forms under unique syntopic conditions, a hidden intraspecific diversity that is worth conserving.

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

“…The foodplants are in very short supply in most of the locality, and even within its southern core fragment their density (ca. 300 gentians per ha) is well below the typical levels recorded at M. alcon sites (WallisDeVries 2004;Nowicki et al 2007Nowicki et al , 2009Radchuk et al 2012;Czekes et al 2014; but see; Maes et al 2004). It is worth pointing out that 1000 gentians per ha has been suggested as the threshold value, below which the foodplant density becomes a critical resource for M. alcon populations (WallisDeVries 2004).…”

“…It should be underlined that in the present study we focus on the wet meadow form of M. alcon, which uses almost exclusively the marsh gentian Gentiana pneumonanthe as its foodplant (Nowicki et al 2007;Sielezniew et al 2012;Czekes et al 2014). Unlike the foodplants of other Maculinea species, which tend to grow in high densities within relatively large meadow fragments (Bonelli et al 2013;Nowicki et al 2014), the marsh gentians are typically scarce and occur in highly localised places, and thus their availability constitutes a limiting factor for M. alcon abundances (Nowicki et al 2007).…”

“…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

“…Italian populations of M. rebeli and M. alcon are characterized by marked phenological differences, being respectively on the wing from mid June till mid July, and from the end of July to the end of August. Choices made by adult butterflies during oviposition provide even stronger evidence of sharp ecological separation between M. alcon and M. rebeli, as well as their use of host ant species (Czekes et al 2013) (see the following paragraph).…”

Adult longevity and its relationship with conservation status in European butterflies

“…These included cases of (a) species for which data on adult life span and light period length came from distant populations, representing diferent biogeographic regions; (b) species for which only the data for the second generation was available; and (c) Maculinea alcon, the conservation status of which is questionable, apparently due to its uncertain systematic status, with two distinct forms existing, namely M. alcon 'alcon' and M. alcon 'rebeli' (Als et al 2004;Steiner et al 2005;Pecsenye et al 2007;Sielezniew et al 2012). It is classiied as LC by van Swaay et al (2010), however many authors regard both forms to be under threat in Europe (WallisDeVries 2004; Tartally et al 2008;Czekes et al 2014).…”