Distribution of earthworms in the north-west of the Iberian Peninsula

Abstract

A province of Galicia, Lugo, was sampled by collecting the earthworm fauna with the aim of completing the distribution maps of the north-west of the Iberian Peninsula. Qualitative samples of earthworms were made in U.T.M. grids of 10 × 10 km using the “formalin-hand sorting method”. The data obtained allow us to know the distribution of the species in all the west of the Iberian Peninsula, completing the studies carried out in the provinces of A Coruña and Pontevedra (west of our study area), Portugal (in the south) and the provinces of Asturias, León and Zamora (in the east). The interest in this area is due to its particular position at the limit of the so-called Galaico-Lusitanian Province, inside of the Eurosiberian Region. This geographical place is characterised by the presence of Allolobophora caliginosa, A. oliveirae, Dendrobaena madeirensis and D. octaedra, the last two species being exclusives to this area. We have used the data to complete the distribution area of some species, e.g. Criodrilus lacuum and Lumbricus castaneus. Also we relate some geological characteristics that could explain their distribution. We also include some data about the biodiversity of the 25 earthworm species found in this area, and the ratio of dominance among them.