THE OCCURRENCE AND DISTRIBUTION OF XIPHINEMA SPECIES (NEMATODA, DORYLAIMIDA) IN SPANISH FIR WOODLANDS

A comparative study was made to investigate the influence of some edap hic factors on the occurrence and relative abundance of four Xiphinema species found in the soils of five selected fir forests (Abies pinsap o Boiss.) in southern Spain. The samples were taken seasonally for one year. Univariate (one-way analysis of the variance) and multivariate (cluster and correspondence analyses) methods were applied in order to relate species to habitat characteristics and to reveal their distrib ution patterns throughout the studied areas. Three of the species seem to be distributed in accordance with the textural gradient of the soi ls. X. sphaerocephalum Lamberti, Castillo, Gomez-Barcina & Agostinelli , 1992 showed the largest frequency of occurrence and relative abundan ce in soils on calcareous rocks, but was not found on peridotites, i.e . more sandy soils. It prefered the most silty textures. X. pachtaicum (Tulaganov, 1938) Kirjanova, 1951 was found in clayey textured soil m ore clearly subjected to Mediterranean climatic conditions; X. diversi caudatum (Micoletzky, 1927) Theme, 1939 gave evidence of a strong rela tionship with more sandy textured, acid soils with high silt content. Finally, X. turcicum Luc & Dalmasso, 1964 was rarely found and at such very low numbers that its distribution becomes obscure in these soils .