How citizen science helps to expand the distribution and describe predictors related to a native land snail, while also introducing spatial biases

Abstract

Although mollusks represent Earth's second most diverse invertebrate group, their natural history and ecology are still scarcely known. The compilation of non-traditional data, such as those from citizen science, represents an alternative to fill these gaps, particularly on striking land snail species such as Macrocyclis peruvianus. Based on long-term citizen science, we aimed to update and describe some basic ecological aspects, such as the distribution and protected area types used by M. peruvianus. We performed pairwise comparisons to test potential changes in occurrence and occupancy among administrative regions, forest types, and protected area types using chi-squared tests. The citizen scientists were also asked to provide the number of M. peruvianus individuals observed and the tree species that dominated their habitat. Thus, we tested if the number of land snails found by citizen scientists could be related to forest and protected area types using a generalized linear mixed model. We expanded the northern distributional limit, with Nothofagus, evergreen, and mixed forests far the most frequented by M. peruvianus. Parallelly, the occurrence of M. peruvianus in official protected areas (65.73%) was significantly higher than in privately owned areas. Moreover, we did not find associations between forest and protected area types with the number of M. peruvianus recorded. Although citizen science is a helpful method for obtaining novel information regarding the ecology of neglected species such as M. peruvianus, it also introduces spatial and occurrence biases explained by the access and attractiveness of the officially protected areas compared to privately owned patches of native forest.