Nectar traits in Nicotiana section Alatae (Solanaceae) in relation to floral traits, pollinators, and mating system

Abstract

Nicotiana section Alatae exhibits great diversity among species in floral morphology, mating system, and predominant pollinators. As a first step towards estimating nectar's role in floral evolution, we studied nectar traits to determine whether they vary in association with predominant pollinators and mating system. Daily phenology determines when nectar becomes available to pollinators and differed between hummingbird- and moth-pollinated species. Nectar volume and concentration varied significantly among most species and pollinator groups, but were inversely correlated, so that total energy was similar among most species. In general, nectar volume was positively correlated with corolla length. The autogamous species, N. plumbaginifolia, had a nectar volume that matched expectations based on corolla length, but with lower concentration and total energy than predicted by corolla length, while nectar volume was lower than predicted by corolla length in the autogamous population of N. longiflora. Sugar and amino acid components (determined through HPLC) were similar among species, although differences did exist. The nectar of most species was sucrose-dominant, but the autogamous N. plumbaginifolia had nectar that contained similar proportions of sucrose, glucose, and fructose. Many nectar traits varied in association with the predominant pollinators and, in some cases, with the mating system.

Insights into the pollination requirements of the only African wild tobacco, Nicotiana africana (Solanaceae) from the Namib Desert

“…Pollinator preferences for different Nicotiana species may be linked to traits such as nectar volume and concentration (Kaczorowski et al, 2005) and corolla length (Nattero and Cocucci, 2007). The self-compatibility and self-fertility indices suggest that N. africana is at least partially dependent on pollinators.…”

“…Furthermore, N. africana lacks a distinct floral scent, although the flowers of hummingbirdand hawkmoth-pollinated Nicotiana species have been shown to share floral volatiles, regardless of pollinator affinity (Raguso et al, 2003(Raguso et al, , 2006. Three main pollination systems have been reported for Nicotiana species; hawkmoths, hummingbirds and sunbirds, and other pollinators such as bumblebees and small moths (Kaczorowski et al, 2005). Species of Nicotiana show interspecific variability in nectar volume and concentration (Kaczorowski et al, 2005) and in floral odour complexity and emission rates (Raguso et al, 2003(Raguso et al, , 2006, and this may influence pollinator preferences.…”

“…Three main pollination systems have been reported for Nicotiana species; hawkmoths, hummingbirds and sunbirds, and other pollinators such as bumblebees and small moths (Kaczorowski et al, 2005). Species of Nicotiana show interspecific variability in nectar volume and concentration (Kaczorowski et al, 2005) and in floral odour complexity and emission rates (Raguso et al, 2003(Raguso et al, , 2006, and this may influence pollinator preferences. Although certain species of Nicotiana are capable of self-pollination and others are not (Kaczorowski et al, 2005;Raguso et al, 2003;Adler et al, 2012), in many species seed production is significantly higher when the plants are exposed to pollinators (Geerts and Pauw, 2009;Schueller, 2004).…”

“…Species of Nicotiana show interspecific variability in nectar volume and concentration (Kaczorowski et al, 2005) and in floral odour complexity and emission rates (Raguso et al, 2003(Raguso et al, , 2006, and this may influence pollinator preferences. Although certain species of Nicotiana are capable of self-pollination and others are not (Kaczorowski et al, 2005;Raguso et al, 2003;Adler et al, 2012), in many species seed production is significantly higher when the plants are exposed to pollinators (Geerts and Pauw, 2009;Schueller, 2004). Adler et al (2012) examined the pollinator reliance and alkaloid levels of 32 species of Nicotiana, excluding N. africana, and found that the nectar, floral and leaf nicotine concentrations were significantly lower in outcrossing than in selfing species.…”

Effects of nicotine on the digestive performance of nectar-feeding birds reflect their relative tolerance to this alkaloid

“…Despite the presence of nicotine in nectar, many Nicotiana species are pollinated by hummingbirds and moths (Kaczorowski et al 2005;Raguso et al 2003) and sunbirds consume nicotine in the nectar of invasive Nicotiana glauca in South Africa and Israel (Geerts and Pauw 2009;Tadmor-Melamed et al 2004). Assessment of the nicotine tolerance of nectar-feeding birds showed that generalist bulbuls tolerated much higher nicotine concentrations than sunbirds and white-eyes (Lerch-Henning and Nicolson 2013).…”