Comparison of genetic population structure of the large blue butterflies Maculinea nausithous and M-teleius

We investigated the genetic population structure of two rare myrmecophilous lycaenid butterflies, Maculinea nausithous and M. teleius, which often liv e sympatrically and have similar biology. In Europe, both species occur in highly fragmented populations and are vulnerable to local extinction. The p roportion of variable allozyme loci, average heterozygosity and genetic dif ferentiation among populations was higher in M. nausithous than in sympatri cally living M. teleius populations. We hypothesise that the differences in heterozygosity are mainly due to the known higher efficiency of typical ho st ant nests in rearing M. nausithous pupae compared to M. teleius pupae. T his implies a larger probability of larval survival in M. nausithous, which buffers populations against environmental and demographic stochasticity. I n contrast, the lower carrying capacity of ant nests in rearing M. teleius pupae requires higher nest-densities and makes M. teleius populations more prone to losing genetic variation through drift if this condition is not fu lfilled. The single investigated Russian population of M. teleius showed mu ch higher levels of heterozygosity than any of the Polish populations, sugg esting a more viable and still intact metapopulation structure.