| Monitoring dragonflies population through exuvia collection |
| Paper ID : 1139-3IICE |
| Authors: |
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Alice Denis1, Abel Delbreil2, Samuel Danflous1, Laurent Pelozuelo *3 1Laboratoire ECOLAB, Université Paul Sabatier, Toulouse 2Laboratoire d’Ecologie fonctionnelle et Environnement. Université Paul Sabatier 3Université Paul Sabatier - FRANCE |
| Abstract: |
| Due to human pressure on both their aquatic and terrestrial habitats, dragonflies and damselflies are among the most threatened insects. In the Mediterranean basin, 4 species are already considered as regionally extinct and up to 19% are assessed as threatened in the regional red list (Riservato et al. 2009). The situation is similarly alarming in Europe (15% threatened species, Kalkman et al. 2010) and France (11% threatened species, IUCN et al 2016). In France, the riverine species Macromia splendens (splendid cruiser), Oxygastra curtisii (orange-spotted emerald) and Gomphus graslinii (pronged clubtail) suffer an unfavorable conservation status and benefit a national and European legal protection. However they are poorly considered in legal procedures of environmental impact assessment. Monitoring theses species populations is difficult because of adult’s behavior: adult pass through a maturation period away from the river, female of all three species are discrete, territorial males of M. splendens and O. curtisii do not allow other males to stand close the water and all species activity is highly dependent on meteorological conditions. Thus, we propose a standardized protocol based on exuvia collection during two visits to track local population response to anthropogenic pressure. By collecting all available exuvia from a canoe along two 100m long transects, we obtain exuvia linear densities (number of exuvia per m) that can be compared from one site to another, from one year to another. This protocol was tested on three rivers of southern France. Prospecting a 100m river bank portion 100m is proved to be sufficient to detect around 100% of the dragonflies species and is an acceptable distance as it takes 14 min up to 2h30min, depending on the rank of visit, dragonflies’ abundance and vegetation structure. Exuvia collection allow a much better estimation of dragonflies local specific richness than adult observation. This protocol was thus set up in two European Natura 2000 sites in 2017 and 2018. |
| Keywords: |
| Dragonflies, Population monitoring, Exuvia |
| Status : Paper Accepted (Oral Presentation) |
