Species distribution and habitat features in lentic Odonata

Abstract

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 holbrooki and the positive effect of the riparian vegetation on the number of Odonata species appear particularly interesting for restoring or creating Odonata habitats.

Relationships between the presence of odonate species and environmental characteristics in lowland ponds of central Italy

“…The CCA analysis also indicated a negative effect of increasing nitrogen concentration on the odonate species richness in agreement with a study of lowland ponds (Carchini et al 2003) and of mountain ponds (Carchini et al 2005), in which high levels of ammonium and phosphorus concentrations led to the absence of Odonata.…”

“…This finding is also quite intriguing, because the positive relation between habitat size and species number is well known (Houston 1994). We have contrasting results from other cited studies in central Italy, in which size had an effect in lowland ponds (Carchini et al 2003, Bazzanti et al 2003, but not in mountain ponds (Carchini et al 2005). (6) However, in the present study, several multiple regression models were possible, which did not completely exclude the potential influence of either area or other variables linked to the temporary-permanent status of the ponds on the number of odonate species.…”

“…These two characteristics were shown to have an influence in other studies (Moore 1991, Rith-Narajan 1998, Sahlén 1999, Bazzanti et al 2003. However, two studies in central Italy agree with the present study (Carchini et al 2003, Carchini et al 2005, because neither shade nor the amount of forest surrounding the ponds appeared related to the odonate fauna. It is probable that the uniformity of conditions among the ponds studied here caused the absence of correlation of these two variables with odonate fauna.…”

“…The species reported in the present study have all been recorded as adults in the Carchini et al (2003) study on lowland ponds of central Italy. In contrast, they are different from the 14 species reported in the study of Carchini et al (2005) on mountain ponds, except C. scitulum, C. lindeni, I. elegans, A. imperator, C. erythraea and S. fonscolombii that were common to both.…”

Gambusiain New Zealand: Really bad or just misunderstood?

“…However, a potentially greater concern arising from predation on these key food-web components is ecosystem alteration by mosquitofish to encourage phytoplankton growth and a decline in water clarity (Hurlbert et al 1972;Hurlbert & Mulla 1981;Angeler et al 2002;Nagdali & Gupta 2002;Ortega-Mayagoita et al 2002). All of these studies have principally considered effects on water quality rather than invertebrate biodiversity, however, mosquitofish have been implicated in declines in dragonfly abundance in New Zealand and Italy (Rowe 1987;Carchini et al 2003).…”