Different phenological behaviour of native and exotic grasses extends the period of pollen exposure with clinical implications in the Madrid Region, Spain

Exotic allergenic species constitute an important element of global change and are an emergent health issue in Europe due to their potential allergenicity. The grass pollen season is of great importance from the allergic point of view because it includes pollen from ubiquitous species which are responsible for high sensitization rates. In this study, we used flowering phenology data for dominant grass species in the city of Madrid (Spain) and airborne pollen data to explore differences between native and exotic species and their potential contribution to the observed peaks of pollen exposure. We found that exotic grasses flowered later than Mediterranean native grasses, and that ornamental grass species (such as Cortaderia selloana and Pennisetum villosum ) cause an unusual second pollen season in autumn with implications for public health. These results support the need to coordinate the efforts of plant ecologists and aerobiologists to protect the population by identifying sources of allergenic pollen and sustain the appropriate urban plans.