Abstract
Floral nectar, being a primary reward for insect visitors, is a key factor in shaping plant–pollinator interactions. However, little is known about the variability in nectar traits, which could potentially affect pollinators and the reproduction of the species. We investigated intraspecific variation in nectar traits in 14 populations of a Red-listed plant, Polemonium caeruleum. Populations varied in terms of the proportion of self-compatible and self-incompatible individuals, and insect communities visiting flowers. Using HPLC, we determined the nectar sugar and amino acid (AA) composition and concentration. We also recorded some basic habitat parameters, which could influence nectar chemistry. In seven selected populations, we investigated the taxonomic composition of the insects visiting flowers. Our observations revealed significant intraspecific variability in nectar chemistry in P. caeruleum. Nectar production was male-biased, with male-phase flowers secreting sucrose- and AA-rich nectar. An analysis revealed that variability in P. caeruleum nectar may be slightly shaped by environmental factors. The studied nectar characters, especially sugars, had little effect on insects visiting flowers. We argue that variation in nectar traits in this generalist plant is a matter of random genetic drift or “adaptive wandering” rather than directional specialization and adaptation in the most effective and abundant group of pollinators.
Highlights
Nectar, being primarily a sugar solution, has been perceived as the most crucial floral food reward for pollinators [1]
Our results revealed the effect of the studied macro- and microelements on certain amino acid (AA), which opens a new field for further study
In addition to AAs common in floral nectar, our analysis revealed the presence of sarcosine, tryptophan, and norvaline, which have been rarely reported in earlier analyses [20,50,51]
Summary
Nectar, being primarily a sugar solution, has been perceived as the most crucial floral food reward for pollinators [1]. Its functions extend beyond its relationships with pollinators [2,3,4,5,6] It should be regarded as a complicated multifunctional interface between plants, and their mutualists and antagonists. Earlier studies of nectar diversity have postulated that some nectar features, such as sugar and AA profiles, are species-invariant [7,9,10,11], and some new analyses support a rather conservative proportion of nectar components, that is sugars, between populations of the same species (e.g., [12]) This notion seems to be the result of technical difficulties associated with
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