Phylogeography of the threatened butterfly, the woodland brown Lopinga achine (Nymphalidae: Satyrinae): implications for conservation

Abstract

We have studied the phylogeography of the red-listed Palearctic butterfly Lopinga achine (Nymphalidae: Satyrinae) based on 1,450 base pairs of mitochondrial DNA sequences from 86 individuals representing 12 populations. Our results indicate a strong structuring of genetic variation, with among-population differences accounting for ca. 67% of the variation and almost all populations being significantly differentiated from each other. We surmise that the insular nature of populations as well as the low dispersal ability of the species has given rise to such a pattern. The genetic diversity within populations is low compared to that in other butterflies. Our results point to a scenario where the species originated in the Eastern Palearctic and expanded into Europe. Based on the analyses, we suggest that the Czech population merits the highest conservation priority. The two Swedish populations represent a distinct evolutionary lineage, and hence merit high conservation attention. The Estonian and Asian populations had the highest genetic diversity, and although we do not consider them to be under immediate threat, their genetic diversity should be conserved in the long term.

Appendices

Appendix 1

Description of habitats of some Lopinga achine populations, based both on our personal observations and that obtained from literature

The presence of a ground layer of its larval host plants, fine-leaved sedges (Carex spp.), was found to be a prerequisite for patch occupancy in Sweden, Czech republic and Finland (Bergman 2000; Konvicka et al. 2008). Nevertheless, the species has been recorded on other larval host plants including various species in the genera Lolium, Triticum, Aryropyron, Dactylis and Melica (all Poaceae grasses; Tolman and Lewington 1997; Tuzov 2000).

Sweden

The Swedish mainland population (Linköping) is found in grazed oak (Quercus robur) forests interspersed with hazel shrubs (Corylus avellana). The population on Gotland occurs in a quite different habitat of pine forests (Pinus sylvestris) on calcareous soils that are opened up by clearings, bogs and small dirt roads, with a shrub layer of Juniper (Juniperus communis), Swedish Whitebeam (Sorbus intermedia) and Glossy buckthorn (Frangula alnus). According to a recent inventory of the area, the species is found abundantly in pine forests of 30–40 years of age as well as older and denser forests. However, the species was largely absent from clear cuts and more recently planted pine forests (Kullingsjö 2006). Apparently suitable habitats are found in several other parts of Sweden that are not inhabited by L. achine (Bergman 1999).

Czech Republic

The only surviving population inhabits 40 km² lowland woods surrounded by intensive farmlands, preserved due to bedrock unsuitable for farming (partly Quaternary sands, partly boggy alluvium). Originally dominated by oak (Quercus robur), a half of the wood area now consist of pine (Pinus sylvestris) plantations. L. achine is restricted to ca 6 km² central section, located on sandy hummocks alternating with boggy depressions, and there the distribution is patchy (map: Konvicka et al. 2008). It occurs in mature and sparse (canopy closure ca 80%) oak-domianted growths with trees of uneven age, located on base-rich but nitrogen poor sandy soils, with sparse shrub layer (mainly Tilia spp., Crataegus spp.) and rich ground layer with a high representation of forbs and sedges, including locally used host plants Carex fritschi and C. michelii. These growths were historically grazed and coppiced, which is still evident on trees growth forms, and also utilised for litter raking and animal fodder harvest. After cessation of these uses (ca. 1950 s), the canopy is closing, whereas ground layer succumbs to eutrophication caused by litter accumulation. Apart from further conifer plantation and clear-felling, completely detrimental for L. achine but hopefully prevented in the central part by Natura 2000 status, future risks include spontaneous canopy closure and continuing eutrophication.

Estonia

The typical habitat of L. achine in Eastern Estonia is moist woodland with grassy openings, crossed by minor roads, and with Alnus incana as the dominant tree species. The butterflies are typically found at forest edges, and flying along forest roads. On Saaremaa—which differs in having limestone as the bedrock—the diversity of available habitats is higher, with L. achine also being found in more arid conditions like wooded meadows with Corylus avellana as the dominant woody plant.

Finland

The occurrence of L. achine in Finland has recently been reviewed (Piirainen et al. 2009). The species was first recorded in 1900 in southeatern Finland. It was documented to spread northwestwards to Tavastia until the 1960s, when the populations suddenly crashed. It survived the next 30 years in a few isolated populations in SE Finland and Tavastia, but began expanding again in the 1990s and is still expanding. In Finland, L. achine is found in spruce dominated wet forests on the edges of mires, or in spruce dominated mires. Characteristic of these forests is a patchy structure, with open sunny spots and shady spots. Larvae are known to feed on Carex sp. and Poa sp., both of which are common in all types of forests of Finland, and are thus not restricting the occurrence of the butterfly.

Germany

The species is known to be associated with coppice forests (Weidemann 1995), whereas it occurs in wooded savannahs in the Carpathian mountains (Kralicek and Gottwald 1984) and open evergreen forests in the Alps (Lepidopterologen-Arbeitsgruppe 1987).

Appendix 2

See Table 4.

Table 4 List of samples used in this study along with their collection locality, Genbank accession numbers and their haplotypes as identified in this table

Appendix 3

See Table 5.

Table 5 Comparison of haplotype diversity (H) and nucleotide diversity (πn) values reported in phylogeographic studies on European butterfly species based on mtDNA