Who are my guests? Investigating the arthropod activity on high-altitude flowers by video observations, the example of Androsace brevis (Primulaceae)

Little is known about high-mountain arthropod communities and their interaction with flowering plants. We investigated flower-visiting arthropods behavior with the innovative approach of video observations, focusing on Androsace brevis, a vulnerable endemic plant of the Central Alps, living above 2000 m asl, and characterized by a very short and early flowering. The work was conducted in the Lepontine Alps (Como, Italy) and in the Orobic Alps (Bergamo, Italy), where we recorded about 300 videos (for a total of about 87 hours) of arthropod activity on the flowering plants in two years of sampling. Environmental parameters (i.e., wind, light and temperature) were also recorded to unravel any correlation with the abundance and diversity of flower-visiting arthropods. The videos were analyzed using BORIS, a software that allows building an ethogram of displays of interest and tracking the behaviour of multiple subjects on the basis of the codified displays. We observed a high variability in behaviour among taxa in terms of mean number of flowers visited, corolla tubes entered, time spent on flower and inside the corolla tube. Our results lead us to hypothesize the possible ecological role of flower-visiting arthropods, highlighting the role of Diptera Brachycera and Hymenoptera Apoidea in pollination. Moreover, we observed that some arthropods use A. brevis as a refuge (i.e., Thysanoptera) or hunting ground. This innovative approach, less invasive than direct observation and manual sampling, represents a powerful tool to describe the behavior of arthropods and their relationship with plants in this vulnerable environment.