Collembolan assemblages in Lesvos, Greece. Effects of differences in vegetation and precipitation

Epigeic Collembola were studied in a number of sires in Lesvos island in the north-eastern Aegean, Greece. The aim of the study was to detect differences, either at the species level or in the structure of the assemblage that can be attributed to environmental factors. Sites with two vegetation types, deciduous oak woodland and phrygana, under three different precipitation regimes were studied. Cluster analysis was applied and characteristic species were identified for the clusters produced. Geographic proximity was found to be the major grouping factor. Characteristic species were also identified for the different vegetation types revealing that species have individualistic responses and do not necessarily follow the classification obtained for the whole assemblages by cluster analysis. The relative abundance patterns observed showed two distinct features: a great number of extreme subordinate species in the oak sites and a change in dominance patterns also in the same sites with more abundant species becoming more strongly dominant at more humid sites. Assemblages from phrygana sites have a much more even species-abundance distribution. Differences were observed at the species level that can be attributed to environmental factors, but the geographic distance between sites should be taken into account in order to arrive at safe conclusions. At the assemblage level, the relative abundance patterns observed in the more humid oak sites were distinct from the patterns observed in sites less favourable in terms of vegetation cover and precipitation. (C) 2000 Editions scientifiques et medicales Elsevier SAS.