Feeding behaviour and food preferences of native and introduced snail species from the Lomas formations, threatened seasonal fog oases

The Lomas formations are ephemeral seasonal oases found along the Pacific arid coast of South America. Whereas fast-growing plants are characteristic in the Lomas, other organisms such as land snails are also conspicuous. In the Lomas, several snails can occur sympatrically and therefore they might have adapted their food requirements to the limited available items while avoiding competing for food (resource partitioning). Since the dietary items and food preferences of Lomas’ snails are almost completely unknown, our study aimed to document these in three snails occurring sympatrically, two native (Succinea peruviana and Bostryx conspersus) and one introduced (Cornu aspersum) species in Lomas de Lucumo, a threatened Lomas from Central Peru. We recorded the snails’ activity, host, and food items. We also carried out dual-choice bioassays to evaluate the feeding preferences of B. conspersus and C. aspersum when offered leaf disks of the two dominant plant Lomas species, Senecio abadianus and Sicyos baderoa. Whereas we were unable to record any food item used by C. aspersum, we recorded the two native Lomas species (B. conspersus and S. peruviana) having contrasting patterns of feeding as they were on different hosts (plants vs soil) and food items (vascular plants vs. lichens/organic material/mosses/algae). Although the feeding preferences were similar between B. conspersus and C. aspersum (i.e., both species preferred the leaves of Si. baderoa over Se. abadianus), C. aspersum, after feeding stimulation, consumed significantly less leaf area of Se. abadianus than B. conspersus. Sicyos individuals are fast-growing plants and might be less herbivore-resistant, while Senecio species are characterized to produce defensive alkaloids which make plants less palatable. Our results indicate that Lomas’ snail species have evolved distinct trophic niches by partitioning the limited food resources and native herbivorous species are better adapted to feed on Lomas’ native plants given their common evolutionary history.