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

Abstract

Peripheral 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.

New insights on habitat use by larval Northern Emerald dragonflies (Somatochlora arctica)

“…Though this may exclude generalist species, the specialised conditions in peatlands can provide habitats for specific taxonomic groups e.g. species of odonates such as the pigmy damselfly (Nehalennia speciosa Charpentier, 1840) (Batzer et al 2016;Minayeva et al 2017;Orioli et al 2021). However, relying on specialised habitat requirements can put species at risk, for example, a study on the decline in odonate diversity in low-elevation mountain wetlands (including peatlands) in Italy, found that approximately 32.6% of the odonate species historically occupying the area had either been extirpated or strongly declined compared to previous years, in part due to land-use change, environmental pollution and anthropogenic-driven climate warming (Assandri 2021).…”