Abstract

BARRIENTOS, Zaidett. Population dynamics and spatial distribution of the terrestrial snail  Ovachlamys fulgens  (Stylommatophora: Helicarionidae) in a tropical environment. Rev. biol. trop [online]. 2000, vol.48, n.1, pp.71-87. ISSN 0034-7744.

The introduced snail Ovachlamys fulgens (Stylommatophora: Helicarionidae) occurs on cultivated land habitats in Costa Rica, where its macrodistribution seems to be limited by annual mean temperature (20 - 27.6°C) and annual precipitation (1 530 - 3 034 and 3 420 - 8 000 mm, with no more than six dry months). This species can be found in litter and on vegetation up to 70 cm tall. Random quadrat field sampling was done in leaf litter and understory plants every three months for a total of five dates in Central Costa Rica. At least 150 plots of 25x25 cm were analyzed on each date. Abundance of living specimens and eggs was positively correlated with (1) litter abundance and depth, (2) litter and soil humidity, (3) relative humidity and (4) early morning temperature (6:30 AM), and negatively correlated with temperature later in the morning (10:00 AM). Besides these factors, living snail abundance was correlated with thickness of the herbaceous vegetation and with the occurrence of Yucca elephantiphes (in litter and understory). Egg abundance was also correlated with the sampling date, apparently because of changes in humidity. The correlation pattern of shell abundance was opposite to that of living specimens. Population size and number of empty shells throughout the year parallel the rainfall pattern. Reproduction takes place between May and November (wet season); and up to 92% of the specimens can be found aestivating between December and April (dry season). Clutch size averages three eggs. The maximum density of living specimens was reached in December (43.41 ind/m²) and the minimum in March (8.30 ind/m²). Shells decompose in an average of five months.

Keywords : Land snail; distribution; microdistribution; Helicarionidae; reproduction; demography; shell decomposition; Costa Rica.