The local species richness of Dragonflies in mountain waterbodies: an indicator of climate warming?

Beat Oertli

doi:10.3897/biorisk.5.853

Abstract

With climate warming, many Odonata species are extending their geographical area. In Switzerland, as in many parts of the world, this phenomenon may lead to a regional increase in species richness. The local richness (the richness of individual waterbodies) is also expected to increase, particularly in the alpine or subalpine areas where the waterbodies are particularly species–poor. Based on the species richness recorded in 109 waterbodies scattered all across Switzerland, a model is presented here relating the local species richness (adult dragonflies) to environmental variables, including the mean annual air temperature. This model predicts a sharp increase in species richness for alpine or subalpine waterbodies, which is expected to double or even treble before the end of this century. This increase would mainly be the consequence of the immigration of eurythermal species extending their geographical range, together with potential local extinctions of the cold stenothermal species.

Highlights

Global changes, and climate warming, are likely to have various impacts on Odonata, such as a shift in species’ geographical distribution, an earlier timing of emergence, or a shorter duration of the aquatic liveCopyright Beat Oertli
Other important variables were identified by calculating their correlation with the residuals of the linear regression between species richness and annual air temperature. This analysis highlighted a significant relation with pond area (r= 0.47), proportion of the environment covered by forest (r= - 0.32), fish presence (r= 0.30), and mean pond depth (r= 0.23). Based on these preliminary analyses, a selection of 15 variables was used to build the model relating the Odonata species richness to the air temperature: mean annual air temperature, pond area, pond age, mean depth, shore development, water conductivity, water transparency, pond eutrophication state, proportion of pond shaded, fish presence, proportion of pond area covered by floating vegetation or by submerged vegetation, proportion of agricultural landcover in the catchment, and proportion of the environment covered by forest and the connectivity in a radius of 1000 m
The predictions of climate warming presented here point out future drastic changes in the species richness of mountain waterbodies

Summary

Introduction

The northerly shift in the geographical distribution of several species will lead in many areas to an enrichment of the regional species pool, mainly resulting from an increase in the number of eurythermal species. Such an increase will largely encompass the associated decrease in the number of cold stenothermal species. The elevation gradient is often claimed to mirror the latitudinal gradient (Rahbek 1995), conditions at higher altitudes resemble conditions at higher latitudes (Ricklefs 1990)

Methods

Results

Conclusion