Spatial distribution, density and life history in four Albinaria species (Gastropoda, Pulmonata, Clausiliidae)

In this study, we analysed field sequential data on density, mortality, and spatial distribution of four Albinaria species. We also recorded and compared a series of life-history traits, including the onset and end of aestivation, copulation, oviposition, and hatching. Our aim was to obtain more information on the ecology of Albinaria, to reveal possible life-history patterns, and to understand the association of life-history characteristics with both extrinsic (density independent) and intrinsic (density dependent) factors and microevolutionary processes. The onset of aestivation period occurs always in April and is independent of the end of rainfall, whereas awakening and copulation is actually synchronous and occurs after the first autumn rains. The duration of the oviposition and hatching period is short, but oviposition can be prolonged under favourable climatic conditions. Density is high, but its fluctuations were not related to climatic or time factors. Any density dependent pattern resulting from competition was not detected. Higher mortality did not coincide with aestivation, and usually relatively high mortality results after hatching. Juveniles usually exhibit higher mortality than adults. Spatial distribution of these rock-dwelling snails is always highly contagious. Clustering behaviour was probably influenced by the substratum, mosaic or uniform, and the occurrence of crevices. Predictions about the population dynamics of these iteroparous, long-lived species were not possible because of sampling inadequacies and/or because fluctuations of population structure, density, mortality and spatial distribution were random.