Species distribution and habitat features in lentic Odonata

The relationships between species assemblages and pond characteristics were investigated in a well preserved Mediterranean coastal woodland. Data on adult abundance were collected fortnightly. Pond area and depth, shade, riparian vegetation, presence of four classes of aquatic plants, presence of fish and both the distances from pond to pond and from pond to sea were considered as pond features. Results showed the presence of 23 Odonata species on 23 ponds. A Mantel test showed that the matrices of pond to pond topographic distances and that of pond to pond faunistic similarity were independent, which supports the hypothesis that the adult Odonata actively choose their breeding site. A stepwise multiple regression showed that only pond size, minimum water level and riparian vegetation had significant effects (all positive) on the total number of Odonata species in each pond. On the other hand, a canonical correspondence analysis showed that the composition of Odonata species assemblages was sensitive to almost all variables. From the point of view of Odonata conservation, both the moderate effect of Gambusia bolbrooki and the positive effect of the riparian vegetation on the number of Odonata species appear particularly interesting for restoring or creating Odonata habitats.