Polyommatus dorylas: 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 : 11-12

Polyommatus dorylas: Decline and Conservation

This species, too, has declined rapidly. In DE, 48 grid cells (19% of all cells with records) are occupied after 2000, as contrasted with 255 occupied across all time periods ( Reinhardt et al. 2020). In CZ, the decline was from 113 cells in 1951–2001, to five locations scattered across the country around 2010, and to a single larger colony in the Bílé Karpaty Mts after 2018, plus a few individual records elsewhere (Brno environs, Pálava Hills, Kosíř Mt) ( Laštůvka and Laštůvka 2020), some of them possibly due to unauthorized transfers. The situation is better in eastern AT, SK, and HU ( Fig. 1 ).

In DE, good populations persist in the Alps (11 grid cells, further undetected populations expected). Outside the Alps, ≈20 more cells in four federal states (Saxony-Anhalt, Thuringia, BadenWürttemberg, Bavaria) are occupied at present. The main habitats in the Bavarian Alps are grazed south-facing slopes. In Bavaria outside the Alps (Frankenalb), three populations, two of them with only few individuals, exist after 2015, including two active MTAs and their surroundings. In Thuringia, a stable population survives in the Ohrdruf MTA inhabited also by P. damon , while in the Rhön Mts, a former stronghold with> 30 sites after 1990, the species is close to extinction. In Saxony-Anhalt, a metapopulation exists on calcareous grasslands and limestone quarries in the Oberharz region, and in Baden-Württemberg, an extended metapopulation system is present in the Alb-Wutach region on mown Mesobromion grasslands.

Based on observations from CZ, the butterfly requires a high proportional cover of its host plant, Anthyllis vulneraria . An important factor is a regularly disturbed ground, supporting its germination. Only plants prominently overtopping surrounding sward are used for oviposition (n = 8, 100% of observations). The same applies for nectaring, frequently observed on prominent bunches of another legume, Lotus L. spp., in short sward (n = 28; 96% of observations, CZ), but also on A. vulneraria , purple flowers such as Centaurea L. spp. (DE). Without regular ground disturbance, the dense host plants growths last only briefly, but for their maintenance, nonintensive cattle pasture seems to be sufficient.

Ex situ breeding was attempted in 2018 in CZ (2 males and 5 females, summer generation, from the Bílé Karpaty Mts). The ≈200 produced larvae survived overwintering at dry bases of host plant stems. In 2019, they produced 25 males and 20 females, whose progeny (≈ 600 larvae) were released to a restored site (Týnčany karst).

Figures

Fig. 1. Localities of the study species in Central Europe (AT, CZ, four federal states of DE, HU, SK), distinguishing recently occupied (color), recently (i.e., post- 2010) extinct (white), recently not inventoried (light gray), and (re)introduced (including failed attempts, dark gray) populations of C. briseis (circles), P. damon (triangles), and P.dorylas (stars). See text for comments on their much denser distribution in the region just a few decades ago. Species P.damon and P.dorylas are present also in the Austrian Alps (not displayed on the map), and a few more (sub)recent populations of the two species are expected in lowland eastern AT.