Forest type and pH affecting the occurrence and life status of land snails in South American temperate forest

Abstract

The genus Plectostylus (Stylommatophora: Bothriembryontidae) is found in temperate and Mediterranean ecosystems in central Chile, which are highly fragmented landscapes and vulnerable to human perturbations. However, it is unknown what habitat or environmental variables influence their occurrence and life status. This study analyzed how different habitat and environmental predictors influence the occurrence and life status (alive vs. dead) of Plectostylus chilensis species in central Chile. The snails (or shells) were sampled in different fragments (n = 50). In each fragment, land snails were searched in different microhabitats (e.g., leaf litter or trunks) with different environmental conditions (shady, sunny, humid, dry). At the landscape level, temperature, precipitation, and pH at two levels were incorporated into the analysis. Predictors and responses were analyzed with logistic regression models. Land snail abundance was also analyzed with path analysis. The native forest type (open sclerophyllous scrub) was the only variable that influenced the occurrence of land snails. The life status of P. chilensis was also influenced by forest pH at depths of 0–5 cm, with open sclerophyllous forests, and average top layer pH of 6.1 exhibited higher probabilities of finding alive individuals. The Non-Metrical Multidimensional Scaling associated the land snail abundance with the microsite conditions and the dominant tree species. However, path analysis has not shown significant effects. The smaller privately-owned native forest fragments are key for the occurrence and life status of P. chilensis, although the absence of high-quality microhabitats at any forest patch size could limit their abundance/presence of land snails in time. Facing the ecological and climatic crisis that Chile will experience in the coming decades, the resilience of Chile's terrestrial mollusks will depend on the potential measures of management to protect the remaining native forest patches.