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

Abstract

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-budfeeding caterpillars complete their development as social parasites of Myrmica ants, and the specificity of these relationships shows geographical variation.2. We studied the genetic structure of 16 populations (365 individuals) of both ecotypes in eastern Europe, sampling P. 'rebeli' in two disjunct areas in Lithuania and southern Poland, and P. 'alcon' on Polish localities between them. We analysed the cytochrome c oxidase subunit I (COI) mitochondrial gene, the EF1-a nuclear gene and five polymorphic microsatellite loci.3. All individuals shared an identical COI haplotype, which we hypothesise may be linked to a selective sweep associated with the presence of the Wolbachia B strain in all populations. 4. For nuclear markers, we did not find a clear pattern reflecting division into two putative ecotypes. However, ecotypes differed significantly in their genetic variability, i.e., the P. 'rebeli' ecotype was less polymorphic, and its populations were much more differentiated (F ST : 0.632 for EF1-a and 0.504 for microsatellites) than the P. 'alcon' ecotype (0.177 and 0.082, respectively). 5. Our microsatellite data suggest that all populations of P. 'alcon' form a single clade but that P 'rebeli' can be split into either six or two clades. The former model would indicate many independent origins, especially in the mountainous areas of southern Poland. The latter, not mutually exclusive, grouping clearly reflects the use of different host ants.

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

“…In this context we believe that our findings offer practical hints on demographic features that improve persistence chances of local butterfly populations and thus to identify those that deserve conservation efforts the most. (Sielezniew et al 2012) Parameters presented include sample size within locality (N); number of alleles (A), allelic richness (R), observed and expected heterozygosity heterozygosity (H O and H E respectively), P value for HWE exact test for heterozygote deficiency/excess (ns indicates non-significant values exceeding 0.05), and fixation index (F IS ; Bonferroni corrected P value at α = 0.05, based on 900 randomisations, was 0.0011) Long-term trend in population size is the most evident predictor of extinction risk (Caughley 1994;Keith et al 2015). In the absence of a clear trend, the extent of population size fluctuations, serving as an inverse measure of stability, makes a useful indicator of population viability, as more fluctuating populations are more vulnerable to extinctions (Caughley 1994;Lundberg et al 2000;Nowicki 2017).…”

“…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).…”

“…To complete their life cycle they require two crucial resources, which comprise specific foodplants, on which Maculinea larvae feed in their initial stages, and specific host ants of the genus Myrmica, in the colonies of which the larvae finish their development, acting as social parasites (Thomas 1995;Witek et al 2010). 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).…”

“…For comparative purposes we also used datasets from eight other previously studied populations of M. alcon in Poland (for details see Sielezniew et al 2012), for which the same microsatellite markers were applied and thus the datasets are directly comparable. For each population we calculated the values of basic genetic indices, including the number of alleles (A), allelic richness defined as the number of alleles corrected for sample size using the rarefaction method with a sample of 9 individuals (R; Petit et al 1998), observed (H O ) and expected heterozygosity (H E ; Nei 1978), as well as inbreeding coefficient (F IS ).…”

Adult longevity and its relationship with conservation status in European butterflies

“…The core data set excluded species for which data quality was problematic for various reasons. 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).…”