The probability of interspecific competitive situations in scale-insects (Homoptera, Coccoidae) : Interspecific...

A large scale survey, covering some 25 million km² of Eastern-Europe, provided distributional data, and a more detailed picture on factors determining species composition and abundance of scale-insects colonizing deciduous orchard trees. No interspecific competition or competitive situations were detected among the 21 scale insect species, when taking into consideration the whole geographic area surveyed. Of all cases, 3.2% showed significant spatial separation in smaller geographic regions. However, no evidence for competition was found between species with overlapping distributions. In the case of introduced species, the role of past competition can also be excluded. Separation was thought to be determined by differences in ecological requirements. There is some probability of competition in the "transitional zone" (significant separation in 0.8% of cases), and somewhat more (2.4%) in the "Southern zone". There was potential competition between species classified as "Mediterranean" and "invader" subguilds (7.1% of frequent species pairs), as well as between the "Southern" and "invader" (2.4% of frequent species pairs) subguilds. Its probability was very low between the species of the "endemic" (0.8% of frequent species pairs) and "invader" (1.6% of frequent species pairs) subguilds.