What Do Nectarivorous Bats Like? Nectar Composition in Bromeliaceae With Special Emphasis on Bat-Pollinated Species

Abstract

Floral nectar is the most important reward for pollinators and an integral component of the pollination syndrome. Nectar research has mainly focused on sugars or amino acids, whereas more comprehensive studies on the nectar composition of closely related plant species with different pollination types are rather limited. Nectar composition as well as concentrations of sugars, amino acids, inorganic ions, and organic acids were analyzed for 147 species of Bromeliaceae. This plant family shows a high diversity in terms of floral morphology, flowering time, and predominant pollination types (trochilophilous, trochilophilous/entomophilous, psychophilous, sphingophilous, chiropterophilous). Based on the analyses, we examined the relationship between nectar traits and pollination type in this family. Nectar of all analyzed species contained high amounts of sugars with different proportions of glucose, fructose, and sucrose. The total concentrations of amino acids, inorganic cations, and anions, or organic acids were much lower. The analyses revealed that the sugar composition, the concentrations of inorganic cations and anions as well as the concentration of malate in nectar of bat-pollinated species differed significantly from nectar of species with other pollination types. Flowers of bat-pollinated species contained a higher volume of nectar, which results in a total of about 25-fold higher amounts of sugar in bat-pollinated species than in insect-pollinated species. This difference was even higher for amino acids, inorganic anions and cations, and organic acids (between 50 and 100-fold). In general, bat-pollinated plant species invest large amounts of organic and inorganic compounds for their pollinators. Furthermore, statistical analyses reveal that the characteristics of nectar in Bromeliaceae are more strongly determined by the pollinator type rather than by taxonomic groups or phylogenetic relations. However, a considerable part of the variance cannot be explained by either of the variables, which means that additional factors must be responsible for the differences in the nectar composition.

Sugar, amino acid and inorganic ion profiling of the honeydew from different hemipteran species feeding on Abies alba and Picea abies

“…It could be assumed that this difference is caused by different ratios of sugars-to-inorganic ions in honeydew and floral nectar, assuming that they are lower in nectar. However, the sugar-to-cation and the sugar-to-anion ratios ( Table 4) were similar or even higher in honeydew than in floral nectar of other plant species [38,55]. Therefore, differences in the content of inorganic ions in both types of honey must have further and other reasons.…”

“…Amino acid analyses. The analysis of free amino acids was performed according to Göttlinger et al [38]. Amino acids with a primary amino group were processed by precolumn derivatization with o-phtaldialdehyde, amino acids with a secondary amino group (e.g.…”

“…Analyses of inorganic ions. Anions and cations were analyzed separately according to Göttlinger et al [38]. The ions were detected by their electronic conductivity.…”

Influence of light, dark, temperature and drought on metabolite and ion composition in nectar and nectaries of an epiphytic bromeliad species (Aechmea fasciata)

“…Besides sugars, a wide range of amino acids, inorganic ions, organic acids and other secondary compounds can be found in the nectar, albeit at much lower concentrations (Baker & Baker, 1973; Calder & Hiebert, 1983; Adler et al, 2006; Seo et al, 2013). As the proportions of the three sugars in nectar are relatively consistent for a given species, they have often been related to the plant’s pollinator type (Nicolson & Thornburg, 2007; Krömer et al, 2008; Tiedge & Lohaus, 2018; Göttlinger et al, 2019).…”

Pollinators drive floral evolution in an Atlantic Forest genus

“…Although a recent study showed hummingbirds as efficient as bees and ants in facilitating pollination per visit in V. neoglutinosa , fruit set was reduced when only insects are allowed to visit the flowers, insects potentially bring more self-pollen and seed quality was not examined in order to assess viability ( Magalhães et al 2018 ). Additionally, Vriesea flowers produce large volume of nectar which results in higher amount of sugar, reinforcing the strong association with vertebrate pollinators whose energetic needs are higher than insects ( Sazima et al 1995 ; Göttlinger et al 2019 ). Some cases of bat-pollinated flowers have been reported to be visited by hummingbirds at dawn, but when hummingbirds feed on the small amount of nectar left by bats in withered flowers, it does not compete with the performance of primary pollinators ( Sazima et al 1995 ; Aguilar-Rodríguez et al 2019 ).…”