Abstract
Dragonflies are commonly used as indicators of environmental quality and different methods have been employed to monitor odonate assemblages, such as surveys of all adults, evaluations based on breeding adults, sampling of larvae and collection of exuviae. Results obtained with different sampling methods may not be interchangeable, as the different life stages (e.g. larvae, adults) differ in mobility (aquatic, aerial) and as they are subjected to different ecological constraints. Therefore generalization about habitat quality based on only one survey method might be questionable. Additionally, detectability of species might vary when different methods are used. In this study, nine retrodunal ponds in the Migliarino, San Rossore, Massaciuccoli Regional Park (Tuscany, Italy) were repeatedly and contemporaneously sampled during May–September 2008 with the following methods: all adults, breeding adults, larvae and exuviae. In total, 22 species were detected and the results showed that the four methods were no...
Highlights
Fresh water quality has considerably declined over the last few decades throughout the world and aquatic ecosystems are subjected to increasing threats (Strayer, 2006)
All the adults were successfully identified to species, 93% of the exuviae could be attributed to a species, while only 58% of the larvae could be determined to the species level
The only exception was the surveys of exuviae, for which the upper confidence limit was considerably higher than the expected number of species computed using the Chao2 index (Figure 3a)
Summary
Fresh water quality has considerably declined over the last few decades throughout the world and aquatic ecosystems are subjected to increasing threats (Strayer, 2006). Populations of many aquatic organisms are endangered, often far more than their terrestrial counterparts (Strayer & Dudgeon, 2010). Dragonflies (Insecta, Odonata), which depend on the availability of suitable water bodies to complete their life cycle, are no exception to this trend. This leads to rising concerns about the status of their populations throughout Europe, America, Asia and Africa (Bried & Mazzacano, 2010; Clausnitzer et al, 2009; Kalkman et al, 2010)
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