Short-Term Colonization Success of Lumbricid Founder Populations

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Abstract
Small founder units (2 or 4 individuals) of adult Allolobophora caliginosa (Sav.) and Lumbricus rubellus Hoffm. kept in netbags were introduced into a hayfield in northeastern Iceland. After 14 mo., 82% of the A. caliginosa units and 35% of the L. rubellus units still contained live adults, and the rates of individual survival were of the same magnitude. Differences in survival between units of A. caliginosa were presumably associated with position of the netbags in the field (exposure, etc.) and initial density of founders. Survival seemed to decrease with increasing density. A. caliginosa produced significantly more cocoons and newly hatched individuals than L. rubellus. Colonization success is discussed in relation to the experimental conditions and the difference between the 2 spp. in terms of their ecology. A. caliginosa probably achieves a relatively high post-dispersal colonization success by having a relatively long adult life-span rather than having a high birth rate.