Low abundance but high land snail diversity in montane rainforest on the western slope of the Andes in Ecuador

Resumen

ABSTRACT We investigated the land snail fauna along an altitudinal transect in the Los Cedros Biological Reserve on the western slope of the Andes in Ecuador. A total of 510 individuals were collected in 40 plots between c. 1,100 and 2,000 m a.s.l. and assigned to 80 land snail species. The mean iChao1 estimate of species richness was with 109 species (with a 95% confidence interval from 97 to 130 species) much higher because many species were represented only by one or two specimens. On the basis of available data, Los Cedros is the most species-rich locality for land snails in South America. Almost half of the land snail species and 75% of the sampled individuals belong to the carnivorous Scolodontidae, most of which are likely to be new to science. In comparison with an Amazonian rainforest, the proportion of tropical groups such as the Helicinoidea or the Achatinidae is reduced, whereas the proportions of the Labyrinthidae and Charopidae are higher at higher elevations in the Andes than at the margin of the Amazonas basin. Beckianum beckianum, Hirtudiscus sp., Pupisoma mediamericanum, Guppya gundlachii, Eobania vermiculata and Thysanophora plagioptycha are new records for Ecuador. The finding of the Mediterranean Eobania vermiculata in cultivated areas adjacent to the reserve is the first record of this species in South America.