Spatial scale of insect-mediated pollen dispersal in oilseed rape in an open agricultural landscape

To assess the role of feral oilseed rape (OSR) plants as resources for pollinators and avenues for gene flow, we compared occurrence of feral populations in standardized agricultural landscapes, using a landscape ecological approach. The occurrence of feral and volunteer populations was investigated in relation to differences in road length and width, number of OSR fields, and landscape scale. The potential for pollen-mediated gene flow from crop to feral oilseed rape was investigated with fluorescent dye in a field experiment. Moreover, greenhouse estimates of pollen germination rate and pollen tube growth rate were performed to get an indication of siring success in crop and feral plants. Escaped OSR occurred in 14 out of the 16 investigated landscapes, and feral populations were more common alongside large roads than small roads in large-scale landscapes. The number of plants in a habitat ranged from 1-160 individuals, with 1-19 habitats per landscape. In the field experiment with fluorescent dye, no transfer of dye was detected during early flowering in May. At the end of the flowering period in June, transfer of dye was found in 71.4% of the feral plants, showing that significant transfer, most likely by pollinators, occurred from the field to the feral plants. There was no difference in pollen germination rate between crop and feral plants. Pollen tube growth rate was significantly higher in feral oilseed rape than in the crop (P < 0.001). Our results contribute to increased understanding of i) the utilization of feral populations by pollinators in an intensively farmed agricultural landscape, and ii) crop-feral gene flow within OSR.

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Hedgerows Have a Barrier Effect and Channel Pollinator Movement in the Agricultural Landscape

Journal of Landscape Ecology ◽

10.1515/jlecol-2015-0001 ◽

2015 ◽

Vol 8 (1) ◽

pp. 22-31 ◽

Cited By ~ 9

Author(s):

Felix Klaus ◽

Julia Bass ◽

Lisa Marholt ◽

Birte Müller ◽

Björn Klatt ◽

...

Keyword(s):

Agricultural Landscape ◽

Pollen Dispersal ◽

Agricultural Landscapes ◽

Fluorescent Dye ◽

Natural Habitats ◽

Pollination Services ◽

Landscape Elements ◽

Mobile Species ◽

Management Plans ◽

Linear Landscape Elements

Abstract Agricultural intensification and the subsequent fragmentation of semi-natural habitats severely restrict pollinator and pollen movement threatening both pollinator and plant species. Linear landscape elements such as hedgerows are planted for agricultural and conservation purposes to increase the resource availability and habitat connectivity supporting populations of beneficial organisms such as pollinators. However, hedgerows may have unexpected effects on plant and pollinator persistence by not just channeling pollinators and pollen along, but also restricting movement across the strip of habitat. Here, we tested how hedgerows influence pollinator movement and pollen flow. We used fluorescent dye particles as pollen analogues to track pollinator movement between potted cornflowers Centaurea cyanus along and across a hedgerow separating two meadows. The deposition of fluorescent dye was significantly higher along the hedgerow than across the hedgerow and into the meadow, despite comparable pollinator abundances. The differences in pollen transfer suggest that hedgerows can affect pollinator and pollen dispersal by channeling their movement and acting as a permeable barrier. We conclude that hedgerows in agricultural landscapes can increase the connectivity between otherwise isolated plant and pollinator populations (corridor function), but can have additional, and so far unknown barrier effects on pollination services. Functioning as a barrier, linear landscape elements can impede pollinator movement and dispersal, even for highly mobile species such as bees. These results should be considered in future management plans aiming to enhance the persistence of threatened pollinator and plant populations by restoring functional connectivity and to ensure sufficient crop pollination in the agricultural landscape.

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