Complex long-term dynamics of pollinator abundance in undisturbed Mediterranean montane habitats over two decades

Current notions of “pollinator decline” and “pollination crisis” mainly arose from studies on pollinators of economic value in anthropogenic ecosystems of mid-latitude temperate regions. Comprehensive long-term pollinator data from biologically diverse, undisturbed communities are needed to evaluate the actual extent of the so-called “global pollination crisis”. This paper analyzes the long-term dynamics of pollinator abundance in undisturbed Mediterranean montane habitats using pollinator visitation data for 65 plant species collected over two decades. Objectives are (1) to elucidate patterns of long-term changes in pollinator abundance from the perspectives of individual plant species, major pollinator groups, and the whole plant community; and (2) to propose a novel methodological implementation based on combining a planned missing data design with the analytical strength of mixed effects models, which allows one to draw community-wide inferences on long-term pollinator trends in spe...