Pollinator preference and the potential persistence of crop genes in wild radish.

Abstract

Crop-weed hybridization has the potential to influence the evolutionary ecology of wild populations. While it is known that many crops are able to hybridize with their wild weedy relatives, few studies have yet looked at the long-term persistence of crop genes in the wild. This study investigates one step in the hybridization process in radish-differential pollinator visitation to wild (Raphanus raphanistrum) and crop-wild hybrid (R. sativus-R. raphanistrum) radish. In experimental arrays with equal numbers of potted wild (yellow-flowered) and hybrid (white-flowered) plants, total pollinator visitation was significantly biased toward the wild plants. Syrphid flies, the major pollinators, preferred wild plants while bumble bees showed no preference. This was also true when wild plants were rare in the array (12 hybrid:2 wild). However, when hybrid plants were rare (2 hybrid:12 wild), no preference was shown by either pollinator group. These results suggest that crop genes may not be selected against when rare, and therefore, could persist at low frequencies in wild populations. However, the rate at which crop genes move into the wild and the degree to which they persist will depend on the composition of local pollinators.