Egg diapause and demographic strategy in Lepidocyrtus lignorum Fabricius (Collembola; Entomobryidae)

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Abstract
In this study we found that the surface-dwelling Collembolan Lepidocyrtus lignorum reproduces mainly in autumn. Eggs have a diapause terminated by cold. Hatching occurs synchronously in spring, producing a distinct cohort I. The species overwinters in different stages of postembryonic development, primarily as adults. Some of the overwintering animals lay non-diapause eggs in late spring and summer. This reproduction results in a second, less synchronized cohort II. The egg diapause cannot be explained as an adaptation for winter survival, but it ensures that hatching will occur at an optimal time for low juvenile mortality. Cohort I differs phenologically from all other surface-dwelling Collembola in the area, and we suggest that the timing effect of the diapause reduces interspecific interactions. Cohort II, hatching together with other surface-dwelling species, showed higher mortality than cohort I. The differential mortality of the two cohorts, however, is influenced by environmental conditions. After part of the study area had been clear cut, cohort II gradually increased in dominance. This effect of environmental changes may explain the dimorphic reproductive strategy of L. lignorum.