Looking out for the little guy: species distribution modeling and conservation implications of the elfin skimmer Nannothemis bella (Odonata: Libellulidae)

Abstract

Nannothemis bella Uhler, 1857 (Odonata: Libellulidae), the smallest dragonfly in North America, inhabit bogs and sedge fens across their distribution, spanning from Quebec (Canada) south to Florida and west to Minnesota and Louisiana (USA). While common in the northern part of their range, N. bella is of conservation concern in the southern populations where they are disjunct and rare. Little work has been done on the ecology and geographic conservation of this species. To fill this knowledge gap, we constructed species distribution models (SDMs) to analyze the spatial distribution and climatic niche of N. bella, define factors in habitat suitability and estimate potential niche shifts under climate change and inform conservation efforts. Our present-day SDMs indicate the dominant environmental elements determining habitat suitability include the proportion of silt in soil, temperature seasonality, percentage of clay and coarse components in soil, and soil class. Our paleodistribution models show a southern distribution within the last glacial maximum, with a shift northward 8,326 to 4,200 years ago. Our projected SDMs for 2050 under RCP 2.6 and RCP 8.5 predict a significant decrease in habitat suitability throughout the entire range of N. bella. As such, N. bella is a species of conservation concern and conservation measures are imperative for its continued existence as a much-needed bioindicator for these freshwater ecosystems. Additionally, this ecological knowledge provides the foundation for identifying population sites from which to collect N. bella for future population genetic studies.