Pollination biology and breeding system in five nocturnal species of Oenothera (Onagraceae): reproductive assurance and opportunities for outcrossing

Abstract

The capacity to produce seed, both by selfing and outcrossing, or mixed mating strategies, is considered a mechanism for overcoming unpredictable pollinator availability. In the present study, we investigate breeding system, insect visitations and the role of insect visitors in the pollination of five species of Oenothera subsect. Oenothera. Field experiments showed that autonomous selfing occurs at bud stage, prior to the opening of the flower. Control flowers showed similar seed set to hand-pollinated flowers, whereas emasculated flowers and those subject to open pollination set fewer seed. These results are consistent with the hypothesis that the investigated Oenothera exhibit a great capacity for autonomous selfing and that selfing is selected in order to provide reproductive assurance. Although flowers were visited mostly by nocturnal lepidopterans, these insects did not precipitate pollination and are thus considered nectar thieves. Conversely, analysis of pollen loads and behavior during foraging by diurnal insect visitors revealed that honeybees and bumblebees are the probable pollinators. We conclude that production of flowers capable of autonomous selfing at bud stage, followed by anthesis and opportunities for outcrossing, probably improves the invasive potential of these Oenothera in Europe, together with a rapid increase in their populations, even when pollinators are scarce.

Causes and consequences of variation in heterospecific pollen receipt in Oenothera fruticosa

“…We recorded diurnal insect visitation on each flower for approximately 1 h using high-definition video cameras (Sony, San Diego, CA, USA) during pollinator activity (08:00-16:00 hours) on warm, sunny days, capturing a total of 130 h of film. We note that although many Oenothera species are visited by both diurnal and nocturnal floral visitors, the importance of these groups as pollinators varies across species (Rhodes et al, 2017;Antoń and Denisow, 2018;Krakos and Austin, 2021). Prior work has demonstrated that O. fruticosa is visited by diurnal pollinators including, butterflies, bees, and beetles, with no record of nocturnal visitors (Primack and Silander, 1975;Silander and Primack, 1978;Krakos and Austin, 2021).…”

Self-Compatibility and Reproductive Success of Oenothera drummondii subsp. drummondii: Is It Similar between Native and Non-Native Populations?

“…Studies in natural populations indicate wide variability in mating systems, but also show that mixed mating (self-and cross-pollination) are more common than expected [5,38,39]. The genus Oenothera is no exception, since wide variation is recognized in the species mating systems [7] and both cross-and self-pollination can occur in Onagraceae species that present, positive herkogamy [32]. Gallego-Fernández and García-Franco [34] noted positive herkogamy in O. drummondii, but it has not relationship with latitude increase.…”

“…This indicates that, even though nonnative populations are isolated in geographically distant sites, they maintain a high level of self-compatibility and have not modified their potential for a mixed pollination system. This also suggests that these populations can take advantage of local pollinators [29,50], which could allow them to invade new sites [7]. Several Oenothera species have become successfully established in Europe and in other regions of the world, where some taxa are considered to be actively invasive species [7,44,51], similarities in environmental conditions between their native habitats and invaded sites must be important factors in the success of these species.…”

“…Sexual reproduction in hermaphroditic plants generally includes self-pollination and cross-pollination, or a combination of both strategies [5,6]. Selfing resolves competition among individual plants for pollination services when there is a limitation of pollinators or mates [7], while outcrossing reduces inbreeding and increases genetic diversity. However, outcrossing is less efficient because it requires the presence of pollen vectors and neighbouring mates [4].…”

“…The seeds are very small with high germination capacity and some can germinate after floating in seawater for a period of time [30]. The genus Oenothera L. has been widely used for studies related to variation in pollination and breeding systems; some taxa are self-compatible and outcrossing, whereas others just self-compatible and autogamous [7,28,31]. Raven [32] considers that both cross-and self-pollination can occur in Onagraceae species that present positive herkogamy.…”