Soil Biol. Biochem. Vol. 24. No. 12. pp. 13O!hl315, 1992 Printed zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA in Great Britain. A ll rights rcxrvcd 0038-07 17.92 55.00 + 0.00 Copyright ‘% 1992 PergamonPress Ltd THE ADAPTATION VALUE OF REPRODUCTIVE STRATEGY AND MODE IN THREE EPIGEOUS EARTHWORM SPECIES DANIEL CLUZEAU,‘* LEONFAYOLLE’ and MONIQLJE HUBERT? ‘Universitt de Rcnnes I, UA CNRS 696, Laboratoire d’Ecologie du Sol et Biologie des Populations. Station Biologique de Paimoont, 35380 Plelan L-e Grand. 21NRA. Station de Recherche sur la Faune du Sol, 17, Boulevard Sully, 2i034.Dijon CCdex and WniversitC de’ Rennes I, Laboratoire de Zoologie et d’Ecophysiologie, LA INRA, Campus de Beaulieu, 263, Ave Gal Leclerc, 35042 Rennes Ctdex, France Summary-Three resource exploitation modes of crushed household refuse on heathland, are associated with three earthworm colonizer typrs. The first colonizer type fits with the unstable environments species selection zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA (Dendrobaenarubida tenuis, Eisen, 1874; Ei.wtiu/etidn, Savigny, 1826; Eiseniu andrei, Bouche. 1972). The mechanisms analysis dealt with the demographic parameters parameters comparison (gener- ation time, fecundity and natality). This analysis is in relation to the reproductive mode (Dendroboeno rubidatenuis parthenogenetic; E.fitida and E. andreiamphigonic). Experimental approach of the anatomy and life history was carried out on D.r. tenth (by isolation or by group of five individuals). The descendant’s demographic profile of the uniparental strain was studied on three generations. E. feetidu and E. andrei populations were studied in the same way to have amphigonic reproduction reference models. Life history parameters of mated and unmated D.r. rent& are similar. E. undrei and E. feridu produce cocoons only after mating. E. andrei showed the capacity to preserve the viability of sperm from the partner for at least 54 weeks after the last insemination. The fecundity is lower for mated worms E. andrei. However, these two groups (D.r. remis and Ei.renirr sp.) have developed two different reproductive strategies, but which give similar capacities of colonization. INTRODUCrION The descriptive approach to the heathland system in central Brittany, France, in terms of soil-vegetation- edaphic fauna inter-relationships after heavy appli- cations of urban compost, has enabled us to distinguish between three types of earthworm colo- nizers. Three types of resource exploitations are associated with these three types of colonizers (Cluzeau and Trehen, 1987). The first type of colo- nizer corresponds to rapid, massive exploitation of readily assimilable resources from urban compost spreads, followed by dispersion beyond the new system. Two epigeal earthworm species of this type, Eisenia andrei (Bouche, 1972) and Dendrobaena ru- bida remis (Eisen, 1874) have developed colonization strategies peculiar to the peregrine species defined by Lee (1987), enabling them to spread from Western Europe to land cleared for cultivation world- wide. Characterization of the colonizing abilities of epigeal species included studies of the response times (ability to rapidly modify population numbers) of populations to temporal and spatial variations in food supply. Mechanistic analysis of response time, consisted of demographic parameter comparisons (generation time, potential and real natalities, population repro- *Author for correspondence. duction rate and relative clutch mass), related to mode of reproduction. Oligochaetes, especially Lumbricidae, are the only common, abundant animal group currently known to exhibit polyploidy as extensive and as varied in plants (Avel, 1959). Casellato (1987) has listed the kary- otypes and modes of reproduction of Lumbricidae species and subspecies. Among the 22 known poly- plaid types of Lumbricidae, 8 have an odd number of chromosomes and are necessarily parthenogenetic. Of the 14 types with an even number of chromo- somes, 5 are parthenogenetic. According to Jaenike and .&lander (1979), parthenogenesis arises prior to polyploidy. Moreover, among the four reproductive categories described by Omodeo (1952) parthenogenesis with premeiotic restitution is very widespread among the Lumbricidae (Casellato, 1987) although generally rare in the animal kingdom. It has been described by Cole (1984) in certain lizards and is common among the pteridophytes (Manton, 1950). The genotypic and phenotypic variability lumbricid populations utilizing this mode of parthenogenetic reproduction with pre- meiotic restitution is theoretically comparable to that of amphimictic diploid lumbricids (Omodeo, 1952). Different types of uniparental reproduction have been described. Cemosvitov (1927) showed that viable cocoons were produced by unmated individ- uals of Tubi& rubifex, by means of internal fertiliza- tion. Kobayashi (I 937) obtained viable cocoons from 1309