Microhabitat Selection and Population Density of Nehalennia Speciosa Charpentier, 1840 (Odonata: Coenagrionidae) in a Peripheral Microrefugium

Abstract

AbstractPeripheral populations of boreal tyrphophilic animals and plants often occupy relict Alpine peatlands, which act as microrefugia. Ecological conditions within local peatlands can lead to uncommon adaptations, highly valuable for the long-term conservation of species and habitats. The pigmy damselfly (Nehalennia speciosa) is an endangered Odonata distributed in Central and Eastern Europe with peripheral populations in the Alps. We investigated the microscale species-habitat association and the conservation status of one of these populations in a relict raised bog. We applied dynamic N-mixture models to assess population ecology and density, while disentangling predictors’ effect on ecological and observation process. We counted N. speciosa individuals in spring 2018 along with vegetation, water, soil and weather conditions during surveys. Final model resulted reliable according to performance measures. Spatial variation in N. speciosa abundance was driven by vegetation type, with a strong selection for flooded hollows where C. rostrata, R. alba and S. palustris vegetation occupy acidic and oligotrophic shallow pools. Population density showed a peak in the first decade of June and increased with accumulation of superficial water. Detection probability was generally low and decreased further when wind blew. The reduced ecological plasticity of the species imperil the species to habitat and climate changes, which will be particularly threatening for its peripheral Alpine populations in the near future, causing water imbalance and rapid vegetation turnover within the peatlands’ fragile microhabitat. The studied peat bog could thus be retained a key future microrefugium for the long-term conservation of tyrphopilous wildlife and habitats.