Pollination in Campalto’s saltmarshes: how distance from inland defines pollinator community and entomophile plants’ reproduction fitness.

Abstract

Habitat filtering determines the pool of species that can persist within a community according to their tolerance to the local environment. The influence of habitat filtering on local communities is generally assessed by tracing changes in communities’ composition across environmental gradients. Many studies highlighted the influence of altitude, climate, and urban gradients, in shaping pollinator communities, and the subsequent consequences for plant reproduction and occurrence. Salt marshes are regularly flooded communities which occupy the upper intertidal zone, between inland and open water. Although few animal-pollinated species occur in salt marsh communities, these can reach high local abundance, forming dense populations from the inland to the open water. The aim of this study was to determine if, in saltmarsh communities, the distance from inland filters pollinator richness and abundance, and the reproductive success, of two dominant animal-pollinated species; the self-incompatible Limonium narbonense and the facultative autogamous Tripolium pannonicum. We monitored each plant species pollination interactions in 60 plots, following a distance gradient from inland. We monitored pollination interaction during the peak of flowering and we counted the number of flowers in three marked inflorescences. At the end of the flowering period, we collected inflorescences to calculate fruit-flower ratio as a measure of plants’ reproductive success. Our results revealed that pollinator richness and abundance of both plant species decrease with increasing distance from the inland. Specifically, this trend was particularly evident when considering the richness and abundance of hymenopterans. On the other hand, the richness and abundance of dipterans visiting L. narbonense was highest at intermediate distance from the inland, while no significant relationships could be observed for T. pannonicum. The fruit-flower ratio of L. narbonense decreases with increasing distance from the inland, while no significant results could be observed for Tripolium pannonicum, probably because facultative autogamous. In conclusion, habitat filtering can be considered an important process in shaping pollinator richness and abundance of animal-pollinated species of salt marshes communities, with consequences to plans’ reproductive success.