Seasonal differentiation of soil mesofauna in a littoral dune of the Egyptian Mediterranean coast

Abstract

Soil mesofauna (sensu Ghilarov, i.e., larger than 1 mm) was sampled from under four shrub species (Lygos raetam, Thymelaea hirsuta, Lycium shawii, and Josonia candicans) growing on the littoral oolitic sand dunes at Gharbaniat, 53 km W of Alexandria, Egypt, for a period of more than 30 months, spanning 3 years. Population density (PD) was calculated in relation to area of shrub canopy. Seasons were considered, according to the prevailing climatic conditions as well as to earlier physiological studies on the animals concerned, as: four “winter” months, four “summer” months and two months for each of the transitional seasons “spring” and “autumn”. The PD values obtained for each season thus defined were combined for the 41 taxa that were sampled. The table of these data was treated by correspondence analysis (CA) and ascending hierarchic classification (AHC), by the Roux DATA-VISION programme (suitable for Apple). Results from such treatment show that fauna as related to shrub species are differentiated along the first factorial axis, while as related to seasons they are differentiated along the second axis. Taxa common to all shrubs and to all seasons are centrally placed and cause some confusion in the resolution. Summer taxa are more distantly placed than those related to the other three seasons. Fauna under Lygos is richer, more diverse, and more complementary as regards trophic levels (with predators), and could probably be the source for replenishing the fauna of the other shrubs at all seasons. The AHC method did not show a similarly clear differentiation.