The diversity of earthworms in 200 Scottish fields and the possible effectof New Zealand land flatworms (Arthurdendyus triangulatus) on earthworm populations

Earthworm populations from 200 fields (132 pasture and 68 arable) in Scotla nd are compared. Earthworms populations from two pasture fields at a Scotti sh farm infested with the New Zealand terrestrial planarian, Arthurdendyus triangulatus (a predator of earthworms), are compared with a subset of thes e 200 fields (none of which had planarians at the time of the survey). A va riety of univariate and multivariate methods are used for comparison. Resul ts from the 200 fields show that the number of individuals, number of speci es, richness and diversity decline eastwards and northwards across Scotland . There is an overall difference between pasture and arable fields at the s ame farm, with fewer anecic earthworms (Aporrectodea longa and Lumbricus te rrestris), but more Aporrectodea rosea, in arable fields. Conversely, speci es richness and cumulative species diversity is greater in arable fields, a nd sample similarity is less. The planarian-infested fields show difference s from the subset of western Scottish pasture fields and from each other. B oth have fewer Aporrectodea caliginosa (and endogeic total) and A. longa (a nd anecic total) than the western pasture fields. One field has fewer L. te rrestris and fewer earthworms in total. Univariate factors show no signific ant differences between the infested fields and similar non-infested fields , but multivariate analysis suggests differences. Waterlogging and recent g rowth of rushes in the infested fields are discussed in relation to the red uced population of earthworms and to rainfall.