Does Reproductive Success in Natural and Anthropogenic Populations of Generalist Epipactis helleborine Depend on Flower Morphology and Nectar Composition?

Abstract

The purpose of our study was to determine the role of flower structure and nectar composition in shaping the reproductive success (RS) of the generalist orchid Epipactis helleborine in natural and anthropogenic populations. We supposed that the distinct character of two groups of habitats creates different conditions for plant–pollinator relationships, thus influencing reproductive success in E. helleborine populations. Both pollinaria removal (PR) and fruiting (FRS) were differentiated between the populations. On average, FRS was almost two times higher in the anthropogenic than in the natural populations. The difference between the two population groups in PR was smaller but still statistically significant. RS parameters were correlated with some floral display and flower traits. Floral display influenced RS only in three anthropogenic populations. Flower traits had a weak influence on RS (10 of the 192 cases analyzed). The more important trait in shaping RS was nectar chemistry. The nectar of E. helleborine is relatively diluted with a lower sugar concentration in the anthropogenic than in the natural populations. In the natural populations, domination of sucrose over hexoses was found, while in the anthropogenic populations, hexoses were more abundant and the participation of sugars was balanced. In some populations, sugars influenced RS. In E. helleborine nectar, 20 proteogenic and 7 non-proteogenic amino acids (AAs) were found with a clear domination of glutamic acid. We noted relationships between some AAs and RS, but distinct AAs shaped RS in different populations, and their impact was independent of their participation. Our results indicate that the flower structure and nectar composition of E. helleborine reflect its generalistic character and meet the requirements of a wide range of pollinators. Simultaneously, the differentiation of flower traits suggests a variation in pollinator assemblages in particular populations. Knowledge about the factors influencing RS in distinct habitats helps to understand the evolutionary potential of species and to understand mechanisms and processes crucial for shaping interactions between plants and pollinators.

The Effect of Stimulants on Nectar Composition, Flowering, and Seed Yield of Common Buckwheat (Fagopyrum esculentum Moench)

“…In turn, Aloisi et al [ 44 ] suggest that polyamines in pear and pummelo nectar are involved in temperature-dependent pollen–pistil interactions and self-incompatibility response. These data may explain the high content of polyamines in the nectar of common buckwheat, which is characterized by strong self-incompatibility and sensitivity to high temperature increasing the degeneration of embryo sacs and embryos [ 12 , 18 ].…”

“…Fertilization requires cross-pollination between these different types of flowers, and consequently, common buckwheat demonstrates strong self-incompatibility [ 14 , 15 , 16 ]. An additional problem is that a flower is available for fertilization for only one day [ 14 , 17 , 18 ]. Common buckwheat shows also high female sterility, even though its pollen demonstrates high viability amounting to over 90% [ 19 ].…”

“…The reproductive success of other plant species also depends on the composition of the nectar. Buckwheat nectar contains sugars, mainly hexoses (glucose and fructose), sucrose, vitamins, and amino acids [ 17 , 18 ]. Although the primary pollinators of common buckwheat are honeybees, other insects, such as Apis cerana , Bombus spp., Andrena spp., Osmia spp., and Diptera species, also visit buckwheat flowers [ 9 ].…”

“…It is therefore obvious that the composition of the nectar is important for the frequency of visiting pollinators [ 8 , 14 , 19 ]. Plants evolutionarily adapted to pollinating insects offer them various compounds such as oils, nectar, resin, wax, pollen and fragrances; however, nectar is the most effective [ 18 ]. According to Brzosko et al [ 18 ], the nectar of plants adapted to pollination by butterflies is characterized by high amino acid concentration, while that of plants pollinated by birds or flies is characterized by lower concentration.…”

“…Plants evolutionarily adapted to pollinating insects offer them various compounds such as oils, nectar, resin, wax, pollen and fragrances; however, nectar is the most effective [ 18 ]. According to Brzosko et al [ 18 ], the nectar of plants adapted to pollination by butterflies is characterized by high amino acid concentration, while that of plants pollinated by birds or flies is characterized by lower concentration. Nectar produced by different plant species has a different content of individual amino acids, from very high to their absence.…”