Importance of meteorological variables for aeroplankton dispersal in an urban environment

Passive wind dispersal is one of the major mechanisms through which organisms disperse and colonise new areas. The detailed understanding of which factors affect this process may help to preserve its efficiency for the future. Despite its interest, the analysis of factors affecting the aeroplankton dispersal in urban environments is rare in literature. We sampled the aeroplankton community uninterruptedly every 4 hours from 17 May to 19 September 2011 in the urban garden of Parco d'Orleans, within the campus of the University of Palermo (Sicily). Sampling was performed by means of a Johnson-Taylor suction trap with automatised sample storing. Weather variables were recorded at a local meteorological station. Overall, 11,739 insects were caught during the present study, about 60% of which belonged to the order Hymenoptera, with particular presence of families Agaonidae and Formicidae. The suction trap also captured specimens of very small size, and in some cases, species caught resulted in new records for Italy. Composition and abundance of the aeroplankton community was influenced by alternation of day/night, as well as by daily fluctuations of climatic variables, for example fluctuating temperature. The taxonomic diversity of the samples was also studied, and was higher when the wind blew from the nearby green area. Our findings confirm that passive transport of arthropods strictly depends on weather conditions, and that the presence of natural areas within the urban environment significantly contributes to raising aeroplankton diversity, eventually fuelling overall biodiversity at a local scale.