Phenological patterns of ground spiders (Araneae, Gnaphosidae) on Crete, Greece

The phenology of one of the dominant families of ground spiders of Greece and along the whole Mediterranean, the Gnaphosidae, is presented. Phenological patterns of the 11 most common and abundant species of this family are compared in relation to each other and between 17 sites situated on the island of Crete, Greece. A major difference between lowland and high elevation sites is recorded for some species. This difference is attributed to a restriction of activity and/or a shifting of one to two months towards the summer and early autumn. Based on the similarities which exist among species a model that describes phenological patterns of ground spiders in Mediterranean ecosystems is proposed. Most species present single peaks of activity during the dry period, from mid spring to mid autumn, which lead to a spectrum of high activity within this period. Most Gnaphosidae species on Crete are considered to be high competitors, which can very efficiently take advantage of the favourable period for this area. Based on their phenology, it is conjectured that they either have annual biological cycles or that they may produce two generations per year, although, in other latitudes, the same species may have biennial cycles. The flexibility of species, as far as their presence in both time and space is concerned, reveals the combined effect of their own physiological tolerance and the environmental heterogeneity in their niche definition.