Malacocoenoses containing Ruthenica filograna (Rossm.), a forest-dwelling clausiliid, were studied in two localities in Poland: the nature reserve Dêbno nad Wart¹ (Wielkopolska region) and the Valley of Pieniñski Potok (Pieniny Mts). The malacocoenoses were composed of 20 and 42 species, respectively. In Dêbno nad Wart¹ R. filograna was the most frequent and abundant species; in the Valley of Pieniñski Potok the most frequent and abundant species was Vitrea diaphana. The structure of the two communities differed also in other respects. The gastropod density in the two localities was similar (168 and 185 individuals · m -2 , respectively), but their species composition was not, with only six species in common (Nei index 0.22).

Helix lutescens Rossmässler, 1837 is a xerothermophilous species. It reaches its NW distribution border in SE Poland. The studies, carried out in 1990-1997, involved the distribution of H. lutescens in Poland, its biology and ecology. Besides, shell structure and internal organs were studied, with special reference to differences between H. lutescens and the related H. pomatia L. In H. lutescens the shell is roundish-conical, of a yellowish-white colour and much smaller than that of H. pomatia. The body is greyish and covered with numerous wrinkles and grooves; fine, whitish granules are located in the grooves, especially in those that form two delicate light streaks along the darker back of the animal; these streaks are characteristic of the species. The reproductive system of H. lutescens is of a structure similar to that in H. pomatia, but the duct of the gametolythic gland never bears a diverticle while flagellum, epiphallus and penis in adults are pigmented. The diurnal activity of H. lutescens varies seasonally, depending on environmental factors (air temperature and relative humidity in ground layer, and substratum humidity-dew point). The reproductive activity reaches its peak in May and June. Courtship and copulation are in accordance with the typical helicid pattern. The copulation lasts ca. 15 mins, and the entire mating process takes over 3 hrs. Eggs are laid in nests dug in the soil, the mean number of eggs per nest being 35. In two weeks young hatch and remain in the nest for ca. 16 days. The abundance and density of three age classes in a selected population of H. lutescens have been estimated on a permanent sampling plot, using marking-release-recapture method, with JOLLY-SEBER'S model for an open population. The results made it possible to trace seasonal changes in the abundance within the whole population. In Poland H. lutescens, because of its insular occurrence and the threat resulting from confusion with the edible H. pomatia, is a protected species.

Terrestrial malacocoenoses of two neighboring forest complexes in W. Wielkopolska were sampled in [2003][2004]; their structure and abundance were analysed in selected plots of oak-hornbeam forest of different protection status and degree of anthropogenic transformations. Twenty species (10 families) represented by 1,588 specimens were collected. The main components of the malacocoenoses were: Nesovitrea hammonis, Aegopinella nitidula, Ae. pura, Punctum pygmaeum, Cochlicopa lubricella, Perforatella incarnata and Carychium minimum. Both species composition and abundance varied greatly between the plots. The gastropods showed no preference for old oak-hornbeam stands or plots located in nature reserves. This may suggest that even under strong anthropopressure and in much transformed environments the snails are capable of maintaining a high diversity.

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This is the first publication of the series summarising the current state of knowledge on mollusc biodiversity and distribution in Wielkopolska (W. Poland). Here, we give a historical background of the research conducted so far in the region; we describe the geography and environmental conditions which have determined the present shape of the region's malacocoenoses. We also present a short summary of the results of the studies carried out in the region. Data from 89 publications and 73 unpublished papers (4,155 localities) show that 167 mollusc species were recorded from Wielkopolska during the last fifty years.