Biodiversity reduction in the entomofauna of pinewoods in Attica peninsula, Greece caused by the pine scale (Marchalina hellenica, Hemiptera: Margarodidae)

The pine scale (Marchalina hellenica Gennadius, Hemiptera, Sternorrhyncha, Margarodidae) is a late Roman introduction into Greece on timber for ship building. Recently, cooperatives of beekeepers were financed for a large scale and unplanned augmentation of the insect population. This was believed to increase the honeydew resources for bees. The causes behind the reduction of biodiversity are primarily associated with the severe reduction of the crown density of pine trees. The comparison of biodiversities was done by estimating the biodiversity in a set of eight sites each containing two line-transects –pine scale free (PSF) and pine scale infested (PSI)– with several tenth hectare plots in proportion to transect length. Transect were unequal so rarefaction curves were used for the estimation of species richness in site. The insect species in the studied transects (158 species) can survive the winter cold and summer drought of Mediterranean biotopes but are unable to survive the results of anthropogenic introductions. Insect species that are associated with pine scale infestations were studied by means of the indicator values (Dufrêne – Legendre method) of insect species on the topology of sites inferred from plant coverage. According to this method a measure is assigned to each insect species in proportion to its fidelity to indicate the sites (biotopes). The main findings of this study are [1] the reduction of insect biodiversity and populations resulting from the introduction of the pine scale; [2] the causes of the reduction are associated with the increase of transparency of pine tree crowns in PSI sites but the floristic and vegetation differences among sites do not appear in the coverage alteration in PSI-PSF paired transects at each site; [3] many insect species can characterize the different site groups but none of them are characteristic of PSI sites. An important feature of this study is the estimation of anthropogenic influences. [more on www.fria.gr]