Polyommatus damon

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 : 13

Polyommatus damon Biogeography

In this species, a mitochondrial group (BAPSda2) extends from the Alps through Central Europe and the SE Baltic coast to Central Asia and the Tuva region ( Fig. 3 ); it includes samples from eastern Anatolia. Southern Europe hosts separate clusters, one in the Western Alps and Apennines, and one linking the Iberian Peninsula with the western Balkans. As the Balkan samples are separated from the Iberian samples by ≥5 mutations each, a separate Balkan cluster might exist.

The gradual separation of several lineages in the ML analysis of COI haplotypes (Supp Material 2 [online only]) points to a possible origin of the current populations in the slopes of European high mountains, and colonization of lowlands during cooler periods, following the mid Quaternary expansion of steppes. An analogous situation was observed in the steppe butterfly Proterebia phegea (Borkhausen, 1788) ( Lepidoptera : Nymphalidae ), which originated in the Irano-Anatolian mountains ( Bartonova et al. 2018).

The result of the ML analysis for the concatenated dataset ( Fig. 3 ), however, correspond to the BAPS and genetic landscape analyses. These analyses showed that the recent P. damon genetic structure is driven by separation by Pleistocene mountain glaciers, similarly to cold-adapted species, whose distribution had been structured by upper Pleistocene glaciations ( Fig. 5 ) ( Schmitt et al. 2006, 2014, Minter et al. 2020). The mountains separated southern piedmont refugia from wider distributions on unglaciated northern lowland steppes. With Holocene deglaciation, P. damon recolonized higher elevations, so that populations from the Eastern Alps also originated from the BAPSda2 cluster. The distribution models ( Fig. 6 ) resemble cold-adapted species, for which the climatic niche is widest during LGM, and retreat to the mountains is apparent in interglacials (e.g., Marešová et al. 2021).

The BAPSda2 cluster contains several haplotypes with a wide distribution and many unique ones; in contrast to C. briseis , the network reveals a diverse and stable population structure with separation of marginal populations (Baltic and Anatolian), indicating continuous in situ existence, and connection between Central Europe and the Altai region. Two samples from České středohoří (CZ) were disclosed as a haplotype Da18 unique for the region, and one as Da16, which was present also in eastern Kazakhstan. The single successfully sequenced sample from Moravia (CZ), as well as the single sample from Lower Austria, belonged to Da20, present also in Eastern Alps, the Urals, and eastern Kazakhstan. The only sample from lowland Germany, on the other hand, belonged to Da19, together with a sample from north-western Spain.

Notably, one of the two confirmed P. damon larval host plants in Central Europe, Onobrychis viciifolia Scop. , is native to south-eastern Europe and has been cropped as fodder plant only since the early modern era ( Chrtková 1995). Another host plant in Central Europe, Onobrychis arenaria (Kit.) DC. , is a continental steppe element, likely present during glacial times (reported from Poland in the Younger Dryas Stadial, Mirek et al. 2002). Butterflies are capable of colonizing exotic host plants ( Singer and Parmesan 2018) or expanding to novel ranges with planting of their hosts ( Paradiso et al. 2019), and there exist mentions of P. damon developing on cropped O. viciifolia ( Schwarz 1949, Laštůvka and Laštůvka 2020). The genetic structure, however, indicates neither a recent south-north expansion, nor long-distance movements with hay. It favors P. damon ’s long-lasting presence in the region, likely utilizing O. arenaria in the past. Identical host plants are utilized by a related butterfly, Polyommatus ripartii (Freyer, 1830) ( Lepidoptera : Lycaenidae ), with a Ponto-Mediterranean and Central Asian range, and an isolated population present in southern Poland at least from the early Holocene ( Przybyłowicz et al. 2014).

Figures

Fig. 3. Phylogeographic analyses for the butterfly P. damon: (a) distribution range (shaded) with locations of samples colored and symbolized by COI BAPS groups, (b) TCS haplotype network, (c) Maximum Likelihood tree (COI + wingless). Branch labels show bootstrap values higher than 50%. Sequences in the network and the tree were assigned to geographical or political regions (described by the legend). Question marks on the map stand for uncertainty in the species distribution and EX. for extinct populations.

Fig. 5. Genetic landscapes for three steppe butterflies, (a) C. briseis, (b) P. damon, (c) P. dorylas, based on residual COI genetic distances.Warmer colors show higher genetic distances among neighboring populations (barriers).

Fig. 6. Species Distribution Models (MaxEnt) for three steppe butterflies, (a) C. briseis, (b) P. damon, (c) P. dorylas. Diagrams show BIOCLIM variables selected by jackknife procedure and their contribution to the model (explained variation) (x-axes: the value of the variable, y-axes: predicted values).The climatic niche is modelled for the last interglacial period (–130 ky), the glacial maximum (–21 ky),Younger Dryas (–12 ky), mid Holocene (–6 ky), current situation, and the future (2050) with an RCP4.5 climate change scenario.Purple colors show the suitability,including the least suitable training record (minimum training presence threshold), and orange colors the suitability of 90% of the training data (tenth percentile training presence threshold).The glacial sheet was adopted after Ehlers et al. (2011).