Nocturnal Bee Pollinators Are Attracted to Guarana Flowers by Their Scents

Abstract

Floral scent is an important component of the trait repertoire of flowering plants, which is used to attract and manipulate pollinators. Despite advances during the last decades about the chemicals released by flowers, there is still a large gap in our understanding of chemical communication between flowering plants and their pollinators. We analyzed floral scents of guarana (Paullinia cupana, Sapindaceae), an economically important plant of the Amazon, using chemical analytical approaches, and determined the attractiveness of the scent to its nocturnal bee pollinators using behavioral assays in the field. Pollen loads of attracted bees were also analyzed. Inflorescences of guarana emit strong scents, both during day and at night, with some semi-quantitative differences between day- and night-time scents. Synthetic scent mixtures containing some of the identified floral scent components, including the most abundant ones, i.e., linalool and (E)-β-ocimene, successfully attracted the nocturnal Megalopta bee pollinators. Pollen analyses revealed that many of the attracted bees had pollen grains from previous visits to guarana flowers on their bodies. Overall, our data show that guarana flowers attract nocturnal bee visitors by their strong scents and suggest that the chemical communication between this plant and its pollinators is a key component in crop production of this economically important plant species.

Nocturnal pollination: an overlooked ecosystem service vulnerable to environmental change

“…Of substantial social and cultural value (but of regional, rather than global commercial value), is Paullinia cupana Kunth (Sapindaceae; guarana), a caffeine-rich seed widely consumed in South America. A substantial proportion of flower visits take place nocturnally shortly after anthesis [66], with variation in floral volatiles between day-and night-time that may be adapted to maximize attractiveness to both diurnal and nocturnal bees [67]. Similarly, species of Jasmine Jasminum spp.…”

“…Floral scent is important in many nocturnal plant-pollinator mutualisms [75]. Floral volatile chemistry has been characterized for taxa pollinated by moths [76][77][78], beetles [38,79,80], nocturnal bees [63,67,81], and to a lesser extent smaller nocturnal and crepuscular pollinators, such as mosquitoes [82] and thrips [47,83]. Parallels can be drawn between floral scent profiles of plants associated with nocturnal pollinator taxa; for example, moth-pollinated flowers often emit a combination of acyclic terpene alcohols (e.g.…”

“…Some compounds are relevant to the attraction of multiple nocturnal taxa, such as linalool, which may attract moths, bees, mosquitoes, thrips and others [47,82,84,85]. However, this may only become apparent when the timing of the release of component volatiles in scent emissions is quantified, since floral scent emissions are often rhythmic [67,86]; for example, in Petunia spp. (Solanaceae) pollinated by hawk-moths (Sphingidae), diurnal volatile emissions are significantly less attractive to pollinators than nocturnal emissions [87].…”

Chemical Characterisation of the Floral Oil of the Murici (Byrsonima sericea): Discovering the Constituents Used in Reproduction by Oil-Collecting Bees

“…Using mass spectrometry, it was also possible to confirm the presence of geranyl linallol in the oil under study. Geranyl linallol is a volatile molecule that is derived from linallol, which in turn is an important terpenoid, commonly found in the composition of floral aromas (Raguso, 2016;Krug et al, 2018). Floral aromas comprise a mixture of volatile compounds which are present in pollen, nectar, petals, sepals and other floral structures (Farré-Armengol et al, 2015), and which play an important role in the plant-animal relationship, being mainly involved in defensive ecological interactions against pathogens and predators and in attracting pollinators (War et al, 2012, Song & Ryu, 2013, Fernandes et al, 2019.…”

Flowers of European pear release common and uncommon volatiles that can be detected by honey bee pollinators

“…a few fruit crops, however, it was just recently demonstrated that the main floral scent constituents are capable of attracting pollinators when offered as single synthetic compounds or synthetic mixtures (e.g., Cordeiro et al 2017;El-Sayed et al 2018;Krug et al 2018). Compounds involved in such interactions are, among others, a mixture of benzyl alcohol, 2-phenylethanol, hexanal, 1-hexanol, (Z)-3-hexen-1-ol, and 1-octanol in cambuci plants (Campomanesia phaea, Myrtaceae; Cordeiro et al 2017), 4-oxoisophorone and 3,5-dimethoxytoluene in Prunus species (apricot, P. armeniaca; European plum, P. domestica; peach, P. persica; all Rosaceae; El-Sayed et al 2018) and linalool and linalool oxides in guarana (Paullinia cupana, Sapindaceae; Krug et al 2018). All these floral scent compounds are also known from non-crop plants (Knudsen et al 2006), and some thereof, such as 2-phenylethanol and linalool, also known to being involved in communication between such plants and their pollinators (Dobson 2006).…”