Pollinator communities in saltmarshes and dykes : comparing habitat value in agroecosystems

Abstract

Pollinators that visit croplands rely on adjacent ecosystems to provide essential resources such as pollen, nectar and nesting habitat. However, the relative amount of pollination services associated with different types of habitat bordering farms in coastal environments is poorly understood. This study compared insect pollinator assemblages on saltmarshes and dykes, two habitats in coastal dykelands proximal to cropland. It was hypothesized that dykes would have a greater abundance and diversity of pollinators compared to saltmarshes due to greater showy floral abundance and diversity, and availability of nesting habitat. Pollinators from dyke and saltmarsh sites in the Bay of Fundy dykelands in Nova Scotia Canada were sampled using pan traps. Floral resources were measured using an abundance index, and flowering species were recorded. Average pollinator abundance was similar between the two habitats with dykes having slightly higher counts than saltmarsh. Average pollinator taxon richness, and standard deviation in richness was greater on dykes, compared to lower richness, and a smaller range on saltmarshes.. Floral abundance and taxon richness were significantly higher in dyke habitats. These results seem to contradict other studies that indicate a tight relationship between floral and pollinator abundance. One explanation is an underestimation of floral resources in saltmarshes. This is validated by a field observation of Bombus and Megachilidae bees visiting flowers of Spartina pectinata, a wind-pollinated saltmarsh grass that was not included in my measures of floral abundance. Further research is needed to understand how pollinators use saltmarshes and dykes (i.e. potentially visiting wind-pollinated species, and availability of nesting habitat) to conserve these wild pollinators and maximize their ecological and economic benefits.