Seasonal changes in the distribution and abundance

Acta (Ecologica,

1995, 16 (4), 431-445

Seasonal changes in the distribution and abundance of isopod species in different habitats within the Mediterranean region of northern Israel Elisabeth Hornung (*) and Michael R. Warburg (**) (*) Department

of Ecology, lATE University, 6701 Szeged, Pf 659, Hungary. (**) Department of Biology, Technion, Haifa 32000, Israel.

Abstract Mediterranean isopod distribution and abundance were studied in four habitats: in pine forest, oak woodland. and two grasslands. Eleven species were identified. Six of them were particularly abundant: Porcellio ficulneus, and Armadillo sp. ("brown") were typical of grasslands, Schizidium tiberianurn was also most abundant there, although it was found in other habitats as well. Armadillo officinalis proved to be a characteristic species of woodlands. Chaetophiloscia spp. (the complex contains three species, which co-occur in the same habitat and they can be distinguished by their males only) and Porcellionides pruinosus were abundant in all types of habitats studied here. Isopod species diversity [R(S)] ranged between 1.14 and 2.07 being highest in the climax plant association of the oak woodland. ' . Decreasing numbers of specimens reflected mainly seasonal changes during spring time due to dry conditions. The most abundant species were, at the same time, the largest in size or body mass and constituted the bulk of isopod biomass (P. ficulneus and A. officinalis). The total biomass ranged between 18.3 and 186.4 mg/m2 in the different habitats during the two seasons. Keywords: Mediterranean region, Isopoda, habitats, spatial and temporal distribution, species diversity, density, biomass.

Resume La distribution et l' abondance d'isopodes mediterraneens ont ete etudiees dans quatre habitats: une foret de pins, un bois de chene et deux prairies. Onze especes ont ete identifiees. Six d' entre elles sont particulierement abondantes : Porcellio ficulneus et Armadillo sp. (