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Mollusc communities were sampled quantitatively at eleven sites representing different environmental conditions in the Bieszczady National Park (East Carpathians Mts, Poland). Overall 61 species were recorded. Alder forest in the valleys (AF; Alnetum incanae carpathicum, Caltho-Alnetum, secondary alder forest) hosted the richest fauna, with up to 41 species occurring sympatrically on 100 m 2 of forest floor and average density ca. 750 specimens m −2 . Three important ecological controllers of species composition and community structure were found. The main predictor of mollusc assemblage composition was calcium content; the first DCA axis of molluscs most significantly and highly correlated with calcium content in the leaf litter and organic matter in the upper layer. The second axis significantly correlated with altitude and negatively with annual temperature, and thus can be explained as an elevational gradient. We observed slope aspect to constitute the third significant gradient. On the basis of forward selection in CCA analysis organic matter in the upper layer of soil was the best predictor of species composition, which explained 26% of total variance. It comes to prove that in mountain forest on non-calcareous bedrock molluscs obtain calcium mainly from leaf litter.

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The reproductive biology of three Carpathian clausiliids of the genus Vestia [V. gulo (E.A. Bielz, 1859), V. elata (Rossma¨ssler, 1836) and V. turgida (Rossma¨ssler, 1836)] was studied using two methods: (1) the presence of eggs was examined in uteri of snails collected in the wild; and (2) the reproduction of snails was observed for 2-4 years under laboratory conditions. All three species retained eggs (ovoviviparity sensu lato), but there was a variation in the stage of the development of embryos among the species: V. gulo retained embryos to a size of c. 1.3 embryonic whorls, then laid eggs that hatched after 7-10 days; V. elata retained embryos to a size of 1.8 whorls, then laid eggs that hatched after 2-4 days; and V. turgida retained the largest embryos with up to 2.9 embryonic whorls. Oviposition was observed rarely in the latter species so that most embryos probably hatched inside the parent (ovoviviparity sensu stricto). The number of retained eggs in a uterus differed significantly between V. gulo and V. turgida. The reproductive period of V. turgida was longer than that of V. gulo, with two distinct reproductive peaks in June and August. Eggs were spherical or slightly oval, partly calcified and resilient, but eggs of V. turgida were elongated and less resilient. Mean numbers of eggs in a single batch were: V. gulo, 9.44 + 3.73; V. elata, 4.50 + 2.07; and V. turgida, 3.83 + 2.12. Egg cannibalism was most intense in V. gulo, but was not observed in V. turgida. Under laboratory conditions V. gulo produced 1-4 batches, V. elata 1-7 batches and V. turgida 1-6 batches of eggs. The three species each produce up to 30-34 juveniles per reproductive season, but the interspecific variation and between-season variation were very high. A possible relation of the reproduction mode with habitat preferences of the species is proposed.