Variation in nectar quality across 34 grassland plant species

Abstract

Floral nectar is considered the most important floral reward for attracting pollinators.It contains large amounts of carbohydrates besides variable concentrations of amino acids and thus represents an important food source for many pollinators. Its nutrient content and composition can, however, strongly vary within and between plant species. The factors driving this variation in nectar quality are still largely unclear.• We investigated factors underlying interspecific variation in macronutrient composition of floral nectar in 34 different grassland plant species. Specifically, we tested for correlations between the phylogenetic relatedness and morphology of plants and the carbohydrate (C) and total amino acid (AA) composition and C:AA ratios of nectar.• We found that compositions of carbohydrates and (essential) amino acids as well as C: AA ratios in nectar varied significantly within and between plant species. They showed no clear phylogenetic signal. Moreover, variation in carbohydrate composition was related to family-specific structural characteristics and combinations of morphological traits. Plants with nectar-exposing flowers, bowl-or parabolic-shaped flowers, as often found in the Apiaceae and Asteraceae, had nectar with higher proportions of hexoses, indicating a selective pressure to decelerate evaporation by increasing nectar osmolality.• Our study suggests that variation in nectar nutrient composition is, among others, affected by family-specific combinations of morphological traits. However, even within species, variation in nectar quality is high. As nectar quality can strongly affect visitation patterns of pollinators and thus pollination success, this intra-and interspecific variation requires more studies to fully elucidate the underlying causes and the consequences for pollinator behaviour.

Editorial: Sensory ecology of plant-pollinator interactions

“…Furthermore, the varieties are different in their emission of alkene scent compounds, which may mean that this species is not only food deceptive, but also (quasi-)sexually deceptive. Together, these works on C. angustifolium, G. aurantiaca, N. attenuata and N. ustulata add to the growing body of literature that highlights the vastness of trait variation within species and their implications for the interaction with pollinators and for trait evolution (e.g., Eisen et al, 2022;Venjakob et al, 2022).…”

Intersexual Differences in Behaviour and Resource Use of Specialist Phengaris teleius Butterflies

“…Flowers of S. officinalis are small and frequently visited by P. teleius , which might quickly wear off available nectar resources, and this potentially limits the nectaring time. S. officinalis nectar is rich in amino acids and limited in carbohydrates [ 50 ]. Low carbohydrate content could also explain short feeding times, since sugar is an important chemical stimulus for nectaring in butterflies [ 51 ], provides energy for flight and increases longevity and fecundity [ 52 , 53 , 54 ].…”

“…Low carbohydrate content could also explain short feeding times, since sugar is an important chemical stimulus for nectaring in butterflies [ 51 ], provides energy for flight and increases longevity and fecundity [ 52 , 53 , 54 ]. High content of amino acids is also shown for some Asteraceae plants [ 50 ], and this plant family was a common nectaring source for P. teleius . Only recently amino acids were recognised as important nutrients for butterfly adults, although mainly in long lived species; thus, it could be interesting to explore if amino acids stimulate Phengaris nectaring [ 52 , 55 ].…”

Using eDNA metabarcoding to understand the effect of fire on the diet of small mammals in a woodland ecosystem

“…Carnivorous mammals such as foxes, badgers civets, and insectivorous mammals such as aardvarks, and bats are reported to seasonally augment their diets with plant material such as berries, roots, nectar, and in some instances, foliage (Frick et al, 2014; Koike et al, 2008; Milton & Dean, 2001; Mudappa et al, 2010). Berries, nectar, and seeds contain high carbohydrate levels, amino acids, and other micronutrients (Ball & Golightly, 1992; Venjakob et al, 2022) substantially contributing to an animal's nutritional requirements. Furthermore, acquiring nutrient‐rich sessile plant material while actively foraging for arthropod prey could be an energy‐optimizing strategy.…”