Variation in the proportion of flower visitors of Arum maculatum along its distributional range in relation with communitybased climatic niche analyses

ran bec pro two by the dist pla ause species–specific interactions between plants and insects require considerable physiological adaptations to blish and be maintained through time and space, highly specialized interactions are rare in nature. Consequently, n if some one-to-one interactions might appear locally specialized, additional partners may be involved at a wider le. Here, we investigate the geographical constancy in the specificity level of the specialized lure-and-trap pollination agonism involving the widespread European Arum maculatum and its associated Psychodid pollinators. Until now, dies concurred in demonstrating that one single insect species, Psychoda phalaenoides, efficiently cross-pollinated plants; arches were, however, performed locally in western Europe. In this study we characterize for the first time the flower tors’ composition at the scale of the distribution range of A. maculatum by intensively collecting plants and insects oughout the European continent. We further correlate local climatic characteristics with the community composition isiting arthropods. Our results show that flowers are generally visited by P. phalaenoides females, but not over the whole distribution ge of the plant. In some regions this fly species is less frequent or even absent and another species, Psycha grisescens, omes the prevailing visitor. This variability is geographically structured and can be explained by climatic factors: the portion of P. grisescens increases with higher annual precipitations and lower precipitations in the warmest trimester, characteristics typical of the Mediterranean zone. Climate thus seems driving the specificity of this interaction, potentially affecting the phenology of one or both interacting species, or even of volatile and heat production in plant. This result therefore challenges the specificity of other presumably one-to-one interactions covering wide ribution ranges, and provides an example of the direct effect that the abiotic environment can have on the fate of nt–insect interactions.