Assessment of pollination ecology of two understudied native mustards and the potential for interference from invasive garlic mustard

From left to right, the inflorescences of Cardamine concatenata, C. diphylla, and Alliaria petiolata. All species are members of the family Brassicaceae and exhibit the same floral anatomy. Images were taken in spring 2024 at the Holden Arboretum, Kirtland, OH, U.S.

by Wilhelm & Miller

The mustard family is agriculturally and economically important. However, knowledge gaps persist for wild species in terms of frequency of pollination and the identity of floral visitors even in parts of the world that have broadly well-studied flora, like eastern North America. Knowledge gaps for two eastern North American species, cutleaf and two-leaved toothworts, are concerning for two reasons. First, these species support rare, specialist insects. Second, invasive confamilial garlic mustard threatens native spring wildflowers, like the toothworts, through competitive exclusion and potentially pollinator sharing within their shared range. Because cutleaf toothwort and two-leaved toothwort have a short growing season, their ability to successfully produce seed is at an increased risk from threats such as these. We found that the flowering period of garlic mustard and two-leaved toothwort overlapped at our study sites. Fourteen identifiable pollinator groups were catalogued in our study, half of which were observed visiting both garlic mustard and two-leaved toothwort. We conclude that garlic mustard attracts the same pollinator groups in similar frequencies as two-leaved toothwort, potentially leading to reproductive consequences for two-leaved toothwort in our study sites. 

Read the scientific publication in JPE. 

Effect of honey bees (Apis mellifera) and wild insect pollination on rapeseed (Brassica napus) yield in the Argentine Pampas: Results of a caging experiment

A honeybee on rapeseed

by Scally et al.

Rapeseed (canola) can produce higher yields when its flowers are visited by insects. In the Argentine Pampas, farming is highly intensive and there are few natural areas that support wild pollinators. This makes it especially important to understand how both managed honeybees and wild insects contribute to crop production.

We studied how insect pollination affects rapeseed by comparing three groups of plants: those open to all insects, those visited only by honeybees (Apis mellifera), and those from which all insects were excluded. Plants visited only by honeybees produced 33% more seeds than plants without insect visits. Plants exposed to all insects produced 20% more seeds than plants without insects.

Higher yields were mainly due to plants producing more fruits and more seeds per fruit. Seed quality was also better in pollinated plants, with higher ripeness, germination, and vigor.

Our results show that insect pollination is important for rapeseed production even in highly intensive farming systems. Supporting wild pollinators through appropriate agricultural practices, and using managed honeybees when needed, could help increase crop yields in the Argentine Pampas and other similarly intensified agricultural regions.

 Read the scientific publication in JPE.