Alien balsams, strawberries and their pollinators in a warmer world

Kamil Najberek,Andrzej Kosior,Wojciech Solarz

doi:10.1186/s12870-021-03282-1

Kamil Najberek, Andrzej Kosior + Show 1 more

Open Access

https://doi.org/10.1186/s12870-021-03282-1

Copy DOI

Abstract

BackgroundStrawberries are a common crop whose yield success depends on the availability of pollinators. Invasive alien plants, such as Impatiens glandulifera and I. parviflora, are also attractive for bees and hoverflies, respectively, and occur in close proximity to strawberry cultivation areas. The aim of the study was to test whether alien plants may decrease pollination of strawberry cultivation. However, even if the pollinators are abundant, efficiency of their pollination may decrease as a result of revisits of flowers that were already probed. It is addressed by pollinators by scent marking. Moreover, such revisits can be determined by nectar replenishment, which may occur rapidly in nectar-rich flowers. We studied revisits to I. glandulifera by bumblebees and defined the factors that influence the probability of revisits (air temperature; pollinator species; family caste and size; flower area; sun radiation; and time of day).ResultsWe found that the two alien species decreased the number of pollinators visiting strawberries. Apoidea, Bombini and Syrphidae significantly decreased on Fragaria × ananassa when alien Impatiens were present. We also revealed the influence of increasing air temperature on bumblebee foraging, which was particularly significant for female workers. At very high temperatures (> 37°C), bumblebee males revisited probed flowers less often than female workers.ConclusionsOur results demonstrate that in experimental conditions attractive alien species decrease pollination of strawberries, which may negatively affect production of this crop. Although the results have not been verified in real-life strawberry fields yet, we recommend that alien plant species that share the same pollinators and occur in close proximity of strawberries are controlled. Moreover, we found that revisits of probed flowers may weaken feeding efficiency of bumblebees. If revisits are not induced by nectar replenishment, then global warming may pose a serious threat to the survival of colonies, which may have consequences also for the plants that attract them, e.g., for strawberries.

Highlights

Strawberries are a common crop whose yield success depends on the availability of pollinators
We found that the total numbers of Bombini and Syrphidae recorded on Fragaria × ananassa were significantly higher when it was the only species available (Fr; Table 1) than when it was accompanied by I. glandulifera (FrIm; Table 1)
Alien plant species are often distributed in close proximity to cultivation fields; their influence on crop yields has not been experimentally tested to date

Summary

Introduction

Strawberries are a common crop whose yield success depends on the availability of pollinators Invasive alien plants, such as Impatiens glandulifera and I. parviflora, are attractive for bees and hoverflies, respectively, and occur in close proximity to strawberry cultivation areas. An opposite scenario is possible, because invasive alien plants growing in high-density populations could act as “magnet” species that increase pollination of neighboring native plants [16] These mechanisms have not been experimentally studied to date in cultivated plants. To bridge this gap, we selected two invasive alien plant species, Himalayan balsam (Impatiens glandulifera) and small balsam (I. parviflora) and tested whether they may decrease pollinators availability in cultivations of strawberry (Fragaria × ananassa) or enhance the pollination effect of this crop. The success of I. parviflora is driven mainly by its autonomous selfing ability [20]; in addition, its nectar is very attractive for many species of syrphidae [21,22,23]

Objectives

Methods

Results

Discussion

Conclusion