English

Sex-ratios and the extent of parthenogenetic reproduction in some collembolan populations

The study of the Collembolan community in a Danish beech wood has demorrstrated for a number of the larger Collembolan species that males constitute from about a third to about a half of the adult population. Seven of the most abundant smaller species, however, can safely be attributed a parthenogenetic ( thelytokous) mode of reproduction which in these particular populations appears to be obligatory. At least 8 additional species which are less common in the beech wood site are probably also parthenogenetic. Parthenogenetic populations seem to be especially characteristic of the species conforming to the eu-edaphic life form, and they are more important in the soil than in the litter Iayer. The pure female populations of the abundant species constitute together 72% of the annual mean density and 22% of the annual mean biomass of the total Collembolan population and are therefore considered a significant element of the Collembolan community. Tullbergia macrochaeta (Rusek 1976) is found as pure female populations in the beech wood, in a Calluna heathland, and in the inner vegetational zone of a sandy beach, but as a bisexual population in the outer zone of the same beach. The two be

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