Can global warming be beneficial for Arctic-alpine orchid species? Outcomes from ecological niche modeling for Chamorchis alpina (L.) Rich. (Orchidaceae)

The disjunct Arctic–alpine plants that persist on isolated mountain sites at the limits of their geographical range are particularly sensitive indicators of climate change effects. Here, we investigated a remarkably fragile plant, the smallest orchid in Europe, Chamorchis alpina. The ecological niche modeling (ENM) approach was employed not only to verify the shift in the range of the studied orchid but also to evaluate the future overlap between this plant population and its pollen vectors, Dasytes alpigradus, Formica lemani and Leptothorax acervorum. Our analyses showed that the bioclimatic preferences of the northern (Scandinavian) populations differed from those of the southern populations located in the Alps and Carpathians. Surprisingly, both C. alpina groups will expand their potential ranges under the SSP2–4.5 climate change scenario, and additional suitable niches will become available for the northern group under the SSP3–7.0 scenario. The Scandinavian populations will face significant habitat loss (36 %) in the SSP5–8.5 projection. The southern group will lose suitable niches under both the SSP3–7.0 and SSP5–8.5 scenarios (33 % and 58 %, respectively). For all pollinators of C. alpina, global warming will be favorable, and all three species will expand their potential ranges under all analyzed climate change scenarios. Our research suggests that a "middle of the road" scenario of climate change (SSP2–4.5), which assumes that socioeconomic factors follow historical trends, will not be harmful to the studied orchid or possibly other elements of Arctic–alpine flora, but all other scenarios that predict increases in CO2 emissions will result in a decreases in the coverage of suitable C. alpina niches, especially in the alpine region. At the same time, an overall expansion of alpine dwarf orchid pollen vectors is predicted, so even within a reduced geographical range, the orchid population will be able to reproduce sexually.