Reproductive Success and Insect Visitation in Wild Roses (Rosa Spp.) - Preliminary Results From 2004

Abstract

The hips of wild roses (Rosa spp.) contain many healthful compounds such as vitamins and antioxidants. There is great interest in commercial cultivation but before this can occur, questions regarding plant reproduction and pollinators need to be addressed. Preliminary trials from 2004 investigated the pollination biology of five native or naturalized roses in Ontario and Prince Edward Island, Canada. The reproductive systems of Rosa blanda, R. canina, R. cinnamomea, R. multiflora and R. virginiana were investigated through pollination trials, and the potential pollinators of these species were surveyed. Hip and seed production by agamospermy, automatic autogamy, geitonogamy, xenogamy, emasculation control and open-pollination were tested for each species. Reproductive success, the number of hips set over the number of flowers, was calculated for each treatment. Rosa blanda and R. multiflora reproduced by open-pollination, geitonogamy and xenogamy; R. canina and R. virginiana were also autogamous. Both R. multiflora and R. virginiana set one hip asexually (through agamospermy). Interestingly, R. cinnamomea did not set fruit in any treatment or site. Pollinator activity was quantified twice in the season for each species. The number, type (most were hover flies (Syrphidae) or bees (Hymenoptera)), and behavior of insect visitors, as well as the time spent foraging, was recorded during 10 minute intervals on an hourly basis. Insect visitation rates were highest between 0900 and 1200, and foraging rates peaked sharply at 0900, indicating the probable period when the most pollen was available. Identified bee genera included Andrena,

Insect visitation and pollination of a culturally significant plant, Hopi tobacco (Nicotiana rustica)

“…Visitation peaked during late morning which is potentially related to when the anthers dehisced and pollen availability is highest, as has been the case in similar studies. 34 Based on observations, the visits of bees were shorter in duration than those by moths. There was one video session that lasted all night due to a full moon, however it showed no moths during the middle portion of the night.…”

“…Since small bees were the most common visitor, pollination of N. rustica could be increased in the field by providing unmanaged land nearby for bee nesting and additional foraging resources, a suggestion made by other studies which have found bees to be the most effective pollinators of a particular plant. 34 The most common species of voucher specimen collected was A. aurata. The conservation status of this species in Ontario is Secure, however globally it has not been evaluated.…”

“…Flower buds were bagged using small mesh bags prior to anthesis to ensure no pollination had occurred prior to treatment. 32 , 34 , 45 , 46 Bags remained in place until blooming was completed. Bags were made of Organza fabric (estimated 1-mm mesh size) and were 5 cm × 7 cm in size.…”

“… 12 , 47 Reproductive success of the plants was determined by fruit set (number of fruits/number of flowers), fruit weight, and seediness. 34 , 46 Seediness was estimated by weighing all seeds from all pods on one plant, dividing this by the total number of pods to get an average mass of seeds per pod (g), and counting the number of seeds within a subset of the sample (0.05g). The number of seeds in the subset of the sample (0.05g) was then factored against the average mass of seeds per pod (g), giving an average seediness per pod.…”

“…32 , 48 , 49 Insects were tallied into the following categories: honey bee, bumble bee, small bee, fly, butterfly/moth, beetle, other, unless they could be identified to species. 32 , 34 Crepuscular recordings included dawn and dusk when there was some limited natural light available. Insects that landed on the outside of the flower were not included in analysis.…”