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

Robert Rutkowski,Marcin Sielezniew,Agnieszka Szostak

doi:10.14411/eje.2009.058

Abstract

We analysed the polymorphism of cross-amplified microsatellite loci in two endangered butterflies of the genus Phengaris, which inhabit warm grasslands. Specimens of P. arion and P. 'rebeli' collected in Poland showed contrasting levels of variability in the investigated loci. All six tested microsatellites were highly variable in P. arion, whereas in P. 'rebeli' one locus was monomorphic and the other four loci showed a rather low level of polymorphism. Genetic differentiation was small or moderate among P. arion populations and high among P. 'rebeli' populations. We hypothesise that these differences reflect: (1) the relatively high genetic variability of P. arion compared with other members of the genus, indicated by previous studies on allozymes; (2) the small, in the majority of cases, genetic differentiation among populations of P. arion, which suggests recent gene flow; (3) a decrease in the genetic variability and increased isolation of peripheral populations of P. 'rebeli'. In both species, the occurrence of null alleles was suggested for some loci, which should be taken into consideration in future studies of the population structure. Additional analysis performed on the corrected frequency of alleles indicated that null alleles constitute only a minor problem when estimating genetic differentiation, using FST and AMOVA, however they strongly influence estimates of heterozygosity and FIS, and inferences about the number of genetic groups and assignment of individuals, especially in the case of ' P. rebeli'.

Highlights

Butterflies of the Palearctic genus Phengaris Doherty, which according to Fric et al (2007) is a senior synonym of Maculinea Van Eecke, are among the most intensively studied insect species in Europe (Settele et al, 2005)
No successful amplification was reported in cross-amplification of microsatellites from Erynnis propertius in E. pacuvius (Hesperiidae) and it was very low in three other members of the genus (6–33%), in E. tristis it was quite high (85%), with a substantial ratio of polymorphic loci among those amplified (58%)
18–27% of these microsatellites were amplified in two other species from the same genus and only 13% of those were polymorphic (Franck et al, 2005). This is to be expected as the microsatellites flanking regions differ between Lepidoptera species (Meglecz et al, 2004)

Summary

Introduction

Butterflies of the Palearctic genus Phengaris Doherty, which according to Fric et al (2007) is a senior synonym of Maculinea Van Eecke, are among the most intensively studied insect species in Europe (Settele et al, 2005) This is mainly because of their conservation status, i.e. they are vulnerable or endangered in many countries (van Swaay & Warren, 1999), and complicated and fascinating life history. There, Phengaris caterpillars transform into social parasites, spending 11 months underground, or 23 if they take two years to complete their development. They exploit ant colonies, either preying directly on the ants’ brood or being fed by the workers (Thomas, 1995; Thomas & Settele, 2004)

Objectives

Methods

Results

Conclusion