Polyommatus damon: Decline and Conservation

Bartoňová, Alena Sucháčková, Konvička, Martin, Marešová, Jana, Bláhová, Dana, Číp, David, Skala, Pavel, Andres, Miloš, Hula, Vladimír, Dolek, Matthias, Geyer, Adi, Böck, Oliver, Kadlec, Tomáš & Fric, Zdeněk Faltýnek, 2021, Extremely Endangered Butterflies of Scattered Central European Dry Grasslands Under Current Habitat Alteration, Insect Systematics and Diversity (AIFB) 5 (5), pp. 1-18 : 8-11

Polyommatus damon: Decline and Conservation

The species has been relatively rare in Central Europe throughout the recorded history, occupying 38 grid cells in CZ ( Benes et al. 2002) and

No., number of sequences; H, number of haplotypes; Hd, haplotype diversity; S, number of segregating sites; π, nucleotide diversity. 176 cells in DE ( Reinhardt et al. 2020). After 2000, the distribution shrank to a handful of mutually isolated sites (CZ 2002–2013: 5 cells; DE 34 cells), and the decline continues, e.g., in DE to less than 20 cells now. In AT outside of the Alps, a maximum of four small populations inhabits small isolated reserves or disappeared recently.

In Bavaria, the butterfly declined from 24 grid cells after 1990 to five after 2015. An inventory of 38 localities in 2012–2013 revealed only twelve as still occupied. Out of three populations in the Rhön Mts, where 50– 130 adults were observable per visit ( Geyer 2013), only one site remains with> 10 adults seen per visits. A further two colonies and four sites with single observations exist in the Rhön Mts and one in the Frankenalb. In BadenWürttemberg, 10 grid cells were occupied after 2000, only six after 2015, two cells containing a metapopulation in Ostalb, and four cells in the middle Schwäbische Alb (Swabian Jura). In Thuringia, 13 grid cells were occupied after 1990, 10 after 2000, and four after 2015. A former P. damon stronghold in the Thuringian part of the Rhön Mts is close to extinction, with only single records in 2016 and 2018. The last larger population survives at an active MTA (Ohrdruf) and its surroundings.

In CZ, two disjoint occupied areas existed after 2010: south-eastern Moravia (4 sites; three of them close to each other) and České středohoří (2 nearby sites). The most abundant locality in Moravia, Kamenný vrch near Kurdějov, declined from hundreds recorded per visit and total estimates of several hundred in 2000– 2007, to only five individuals seen in 2018 ( Andres and Skala 2019) and a single egg found in 2019. In the nearby Na Adamcích reserve, the last three individuals were observed in 2018. In České středohoří, only three adults were recorded in 2019. In 2020, no adults were recorded in the country ( Skala et al. 2020).

In lowland AT, the largest population persists in Leithagebirge (Grosshöflein), where only a small reserve (<5 ha) is actively managed, whereas its environs are succumbing to shrubs succession ( Höttinger 2008).

Outside the Alps, typical Central European localities were calcareous xeric grasslands on deeper soils, often on loess or clay substrates, with taller but sparse forb-rich sward. This species is affected by grassland abandonment relatively lately, as pre-hibernation larvae utilize blooming and senescing Onobrychis host plants ( Slancarova et al. 2012). On the other hand, the plants mainly grow at spots that were heavily disturbed in the past (old cart tracks, quarries, roadsides), implying that such spots are needed for their germination. Some local colonies (e.g., Kamenný vrch, CZ) were destroyed by conservation management based on grazing by sheep, who preferentially consume legumes (cf. Kudrna 1998). Gradually, such methods as patchy mowing or grazing with temporary exclosures were proposed ( Andres and Skala 2019). In DE, the managers strive to graze when most individuals are pupated and thus not exposed to direct damage, but precise timing varies with inter-annual phenology variation. Local extinctions of the host plant pose another problem. Onobrychis seedlings do not survive extreme droughts and the mature plants do not bloom in extremely dry years, thus failing to produce suitable oviposition sites. In CZ, the exceptionally dry years 2015–2018 caused premature desiccation of the host plants at sites with targeted management.

Ex situ breeding was attempted during the extremely dry seasons, with stock from České středohoří ( CZ) (2018: 6 eggs collected, 2 adults obtained; 2019: 20 of 30 field-located eggs collected, 1 adult obtained). The larvae did not display cannibalism and despite facultative myrmecophily ( Fiedler 1989), developed without the presence of ants. Currently, no stock for breeding exists in the entire country .