The megadrile fauna (Annelida: Oligochaeta) of Maghreb: a biogeographical and ecological characterizationThe 7th international symposium on earthworm ecology · Cardiff · Wales · 2002

Abstract

Summary In the last two decades, the earthworm fauna of western North Africa, poorly known previously, has received many original contributions. These and additional new data (including five new regional records) from the authors' collecting make it possible to outline a satisfying picture of its ecological and biogeographical traits. In Maghreb, extensive land areas have not yet experienced the methods and effects of modern agriculture, and cultivated fields can host dense and diverse earthworm assemblages. Some species maintain narrow habitat preferences: Allolobophoridella eiseni is frequently corticicolous; Eisenia xylophila lives in decaying logs of Quercus suber , protected by the cork sleeve; Octodrilus complanatus does not occur in forests but dwells in pastures and grassland with sparse trees, whereas O. maghrebinus is only to be found in oak forests. The litter-dwelling species are few: A. eiseni, Dendrobaena lusitana, D. byblica and Dendrodrilus rubidus the last two being rare and scanty and probably of recent introduction. None of the autochthonus species recorded is adapted to arid soils, except for Hormogaster redii which, owing to its long aestivation period, can tolerate inhabiting areas where the rainy season is restricted to a few weeks per year. In contrast, the diversity of the aquatic forms is remarkable: Criodrilus lacuum, Eiseniella neapolitana, E. tetraedra, Allolobophora molleri complex, Helodrilus cfr. oculatus, H. rifensis , and Nicodrilus sp. The list of taxa so far recorded (38) is shorter than that of other Palaearctic territories of similar size and environmental variety. However, it comprises some narrow-range and broad-range endemics which strongly characterise it. The most evident affinities are with the Iberian (and Macharonesian) fauna: they concern A. molleri complex, D. lusitana, Allolobophora borellii and Lumbricus friendi . A comparable relationship is indicated by the Franco-Iberian genus Prosellodrilus , represented in Maghreb by P. doumandjii and P. festai . Instead, the two endemic species of Octodrilus (O. maghrebinus and O. kabylianus) and E. xylophila suggest unexpected relationships with the Balkan fauna.