Host plant use drives genetic differentiation in syntopic populations of Maculinea alcon

The rare socially parasitic butterfly Maculinea alcon occurs in two forms, which are characteristic of hygric or xeric habitats, and which exploit different host plants and host ants. The status of these two forms has been the subject of considerable controversy. Populations of the two forms are usually spatially distinct, but at Răscruci in Romania both forms occurs syntopically. We examined the genetic differentiation between the two forms using eight microsatellite markers, using samples from a nearby hygric site as out group. Our results showed that while the two forms are strongly differentiated at Răscruci, it is the xeric form there that is most similar to the hygric form at Şardu, and Bayesian clustering algorithms suggest that these two populations have exchanged genes relatively recently. We found strong evidence for population substructuring, caused by high within-nest relatedness, not association with host ants use, indicating very limited dispersal of most ovipositing females. Our results are consistent with the results of larger scale phylogeographic studies that suggest that the two forms represent local ecotypes specialising on different host plants, each with a distinct flowering phenology, and is an example of a genetic barrier operating on a temporal scale rather than spatial

Host plant use drives genetic differentiation in syntopic populations of Maculinea alcon

The rare socially parasitic butterfly Maculinea alcon occurs in two forms, which are characteristic of hygric or xeric habitats, and which exploit different host plants and host ants. The status of these two forms has been the subject of considerable controversy. Populations of the two forms are usually spatially distinct, but at Răscruci in Romania both forms occurs syntopically. We examined the genetic differentiation between the two forms using eight microsatellite markers, using samples from a nearby hygric site as out group. Our results showed that while the two forms are strongly differentiated at Răscruci, it is the xeric form there that is most similar to the hygric form at Şardu, and Bayesian clustering algorithms suggest that these two populations have exchanged genes relatively recently. We found strong evidence for population substructuring, caused by high within-nest relatedness, not association with host ants use, indicating very limited dispersal of most ovipositing females. Our results are consistent with the results of larger scale phylogeographic studies that suggest that the two forms represent local ecotypes specialising on different host plants, each with a distinct flowering phenology, and is an example of a genetic barrier operating on a temporal scale rather than spatial

An unexpected record of Myrmica schencki EMERY, 1895 as a secondary host ant of the hygrophilous form of a small and isolated population of the Alcon Blue butterfly Phengaris (=Maculinea) alcon (DENIS et SCHIFFERMÜLLER, 1775) (Lepidoptera, Lycaenidae) in NE Poland

Phengaris alcon is a socially parasitic butterfly species showing ecological variation across its distribution range. Host ant specificity was studied on a site (a mineral island surrounded by wetlands) in the Narew National Park in NE Poland, inhabited by a highly isolated and small population (estimated at several dozen individuals). We examined nests of their potential hosts, i.e. Myrmica ants, in patches of habitat where the initial larval food plant i.e. Gentiana pneumonanthe was recorded. The Myrmica species composition was shown to be unusual for such habitats because of the presence of M. schencki together with the dominant M. scabrinodis. In 2013 we found just one prepupa of P. alcon in a nest of M. schencki, which had never yet been recorded as a host of the hygrophilous form of this butterfly, and none of the M. scabrinodis nests were infested. However, in 2014 a very typical pattern for eastern Europe was observed, i.e. larvae were recorded exclusively in M. scabrinodis colonies and the parasitisation rate was 33%. In both seasons we recorded similar numbers of egg shells on gentians, which indicated a similar population size of adult butterflies. The results are discussed in the context of the ecology and conservation of P. alcon as well as the sampling design.