Limited ability of Palestine SunbirdsNectarinia oseato cope with pyridine alkaloids in nectar of Tree TobaccoNicotiana glauca

Abstract

Summary1. Secondary compounds are common in floral nectar but their relative effects on nectar consumption and utilization in nectarivorous birds are unclear. 2. We studied the effect of two pyridine alkaloids, nicotine and anabasine, present in Tree Tobacco ( Nicotiana glauca ) nectar, on food consumption, gut transit time and sugar assimilation efficiency of the Palestine Sunbird ( Nectarinia osea ), a pollinator of N. glauca in east Mediterranean ecosystems. 3. Sunbirds demonstrated dose-dependent deterrence; they were not deterred by the lowest natural concentrations of these alkaloids in nectar (0·1 ppm nicotine and 0·6 ppm anabasine) but they were significantly deterred by the average concentrations detected in nectar (0·5 ppm nicotine and 5 ppm anabasine). 4. The two pyridine alkaloids reduced gut transit time (by 30 -42%) and sugar assimilation efficiency (by 9-17%) compared with the control alkaloid-free diet. 5. Sunbirds are able to cope with low, but not average, concentrations of nicotine and anabasine in N. glauca nectar. If sunbirds are efficient pollinators of N. glauca they may induce selection on it to reduce pyridine alkaloid production in the nectar. Alternatively, high concentrations in some N. glauca plants may lead the birds to visit more plants with lower alkaloid concentrations. Hence, they will be more efficient pollinators, especially if other nectar-producing plants are scarce.

Protein and alkaloid patterns of the floral nectar in some solanaceous species

“…already such low concentrations of the above alkaloids were found to cause deterrence. For pyridine alkaloids a dose-dependent deterrence was reported by [57]. According to the results of Detzel and Wink [28] the alkaloid concentrations measured in all the nectars in our study (Table 2) would have a negative effect on the foraging behaviour of honeybees; and even if the data of Singaravelan et al [54] are taken into consideration, at least one of the three Nicotiana species investigated would deter honeybees from feeding on its nectar.…”

“…Previous studies determined 0.1-0.5 µg/mL and 0.6-5 µg/mL as the concentration range of nicotine and anabasine, respectively, in the nectar of N. glauca [57]; whereas in N. tabacum 0.33 µg/mL was measured as the concentration of nicotine and anabasine [3]. In the nectar of N. attenuata the concentration of nicotine was 3 ± 0.35 µg/mL [13].…”

“…However, by using modern analytical techniques such as gas chromatography (GC) and high performance liquid chromatography (HPLC), a number of researchers have already succeeded in identifying as well as quantitatively determining the characteristic alkaloids in the floral nectar of various Solanaceae species [3, 13, 17, 28-29, 44, 57]. Some of these alkaloids, like hyoscyamine, scopolamine, tropin, nicotine and anabasine were reported to cause feeding deterrence to animal pollinators [28,55,57]. Alkaloids, along with some non-protein amino acids and phenolic components, belong to the most common nectar toxins [52].…”

Secondary metabolites in floral nectar reduce parasite infections in bumblebees

“…Exposure to numerous alkaloid, terpenoid and phenolic compounds is lethal to Trypanosoma species, probably via interruption of protein synthesis, DNA intercalation, interaction with neurotransmitters or induction of programmed cell death [41,42]. Second, secondary metabolites could affect bee immune function, including by upregulating bee immune response [43], stimulating bees' endosymbiotic gut bacteria [44], causing physical or chemical changes to gut lining [45], or simply by inducing diuresis [17].…”

Honeybees and nectar nicotine: Deterrence and reduced survival versus potential health benefits

“…Most nectar SM studied so far repel pollinators (Adler and Irwin, 2005;Detzel and Wink, 1993;Tadmor-Melamed et al, 2004). The feeding response to nectar SM is dose-dependent: low concentrations of some phenolics and alkaloids are preferred by honeybees to sugar-only controls, while high concentrations inhibit ingestion (Hagler and Buchmann, 1993;Singaravelan et al, 2005).…”