Cryptic dioecy and insect pollination in Rosa setigera Michx. (Rosaceae), a rare plant of Carolinian Canada

Abstract

Rosa setigera is unique among known roses because it is truly dioecious, yet the plants and flowers are almost impossible to sex. Subtle differences in the inflorescences have been detected, for example, there are more flowers per inflorescence on male plants than on female plants and petal expansion from the day of opening to the next day is greater in females than in males; in addition, pollen from female plants appears somewhat collapsed and does not germinate. Pollinators (Apis mellifra, other bees (Apidae), Eristalis tenax and other Syrphidae: Diptera) visit the blossoms mostly in the morning to collect pollen (there is no nectar) and in choice experiments do not discriminate between male flowers and female flowers on landing, but do spend significantly more time on the former. They d o discriminate between freshly opened flowers and day-old flowers, and show marked preference for bouquets of five flowers us. single flowers. The female plants, with smaller inflorescences and lesser interest to pollen foraging insects, seem to encourage them to forage at more flowers than do their male counterparts. This may be biologically significant for effective pollen flow in a dioecious pollenonly plant with pollenivorous pollinators.KEY WORDS:-Pollinators -pollinator behaviour -insect foraging -floral size -floral ageing inflorescences -Apis mellijka -Eristalis lenax -Apidae -Syrphidae. 229 0024-4066/90/070229 + 15 S03.00jO

Phylogeny of Rosa sections Chinenses and Synstylae (Rosaceae) based on chloroplast and nuclear markers

“…Synstylae. This species is also the only rose that is dioecious (Focke, 1897;Kevan et al, 1990). R. setigera was recovered as monophyletic with a good support in our phylogenetic trees (Figs.…”

“…4 and 5). Hybridization is easy for Rosa species because of overlapping distribution areas and flowering times, common generalist pollinators, and fertile crossbreeds (Jesse et al, 2006;Kevan et al, 1990;Matthews, 1920). Many studies have reported that hybridization has occurred in this genus not only between closely related species but also between species from different sections (Matthews, 1920;Mercure and Bruneau, 2008;Ritz et al, 2005;Schanzer and Kutlunina, 2010;Uggla and Carlson-Nilsson, 2005;Wissemann and Hellwig, 1997).…”

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

“…Wild roses have open 'dish' to 'bowl' shaped, usually single, hermaphroditic flowers, which yield an edible hip (a fleshy or pulpy receptacle) that contains numerous achenes (one-seeded fruits) (Faegri and van der Pijl, 1979;Kevan et al, 1990). Rose hips are used in making tea, jam, jelly, marmalade, puree, wine, and fruit juice (Uggla and Nybom, 1999).…”

“…Knowledge of rose reproduction is needed to manage the plants for crop production. However, pollination in Rosa has not been well studied experimentally (Kevan et al, 1990). It was once believed that automatic autogamy (self-pollination) occurred in all roses (e.g.…”

“…Many self-compatible species have increased hip set with cross-pollination (Ueda and Akimoto, 2001). Rosa setigera is the only known dioecious rose (Kevan et al, 1990).…”