Defensive strategies in Geranium sylvaticum. Part 1: organ-specific distribution of water-soluble tannins, flavonoids and phenolic acids.

A combination of high-resolution mass spectrometry and modern HPLC column technology, assisted by diode array detection, was used for accurate characterization of water-soluble polyphenolic compounds in the pistils, stamens, petals, sepals, stems, leaves, roots and seeds of Geranium sylvaticum. The organs contained a large variety of polyphenols, five types of tannins (ellagitannins, proanthocyanidins, gallotannins, galloyl glucoses and galloyl quinic acids) as well as flavonoids and simple phenolic acids. In all, 59 compounds were identified. Geraniin and other ellagitannins dominated in all the green photosynthetic organs. The other organs seem to produce distinctive polyphenol groups: pistils accumulated gallotannins; petals acetylglucose derivatives of galloylglucoses; stamens kaempferol glycosides, and seeds and roots accumulated proanthocyanidins. The intra-plant distribution of the different polyphenol groups may reflect the different functions and importance of various types of tannins as the defensive chemicals against herbivory.

Differential costs of reproduction in females and hermaphrodites in a gynodioecious plant.

BACKGROUND AND AIMS: Plants exhibit a variety of reproductive systems where unisexual (females or males) morphs coexist with hermaphrodites. The maintenance of dimorphic and polymorphic reproductive systems may be problematic. For example, to coexist with hermaphrodites the females of gynodioecious species have to compensate for the lack of male function. In our study species, Geranium sylvaticum, a perennial gynodioecious herb, the relative seed fitness advantage of females varies significantly between years within populations as well as among populations. Differences in reproductive investment between females and hermaphrodites may lead to differences in future survival, growth and reproductive success, i.e. to differential costs of reproduction. Since females of this species produce more seeds, higher costs of reproduction in females than in hermaphrodites were expected. Due to the higher costs of reproduction, the yearly variation in reproductive output of females might be more pronounced than that of hermaphrodites. METHODS: Using supplemental hand-pollination of females and hermaphrodites of G. sylvaticum we examined if increased reproductive output leads to differential costs of reproduction in terms of survival, probability of flowering, and seed production in the following year. KEY RESULTS: Experimentally increased reproductive output had differential effects on the reproduction of females and hermaphrodites. In hermaphrodites, the probability of flowering decreased significantly in the following year, whereas in females the costs were expressed in terms of decreased future seed production. CONCLUSIONS: When combining the probability of flowering and seed production per plant to estimate the multiplicative change in fitness, female plants showed a 56 % and hermaphrodites showed a 39 % decrease in fitness due to experimentally increased reproduction. Therefore, in total, female plants seem to be more sensitive to the cost of reproduction in terms of seed fitness than hermaphrodites.

Carotenoids in a food chain along a pollution gradient.

Carotenoids are synthesized by plants, therefore insects and birds must obtain them from their diet. They function in pigmentation and as antioxidants. We studied the carotenoid profiles in a model food chain (plant-insect-bird) in an air pollution gradient to find out whether heavy metal pollution affects the transfer of carotenoids across the trophic levels. Birch leaves showed higher beta-carotene and, one of the birch species (Betula pendula), higher total carotenoids levels in the polluted area. There was no difference in the lutein concentration of caterpillars' food source, birch leaves, between the study areas. Autumnal moth larvae accumulated lutein more efficiently than beta-carotene while sawfly larvae accumulated beta-carotene over lutein. Because of different antioxidant profiles in different leaf chewing insects their sensitivity to pollution stress may differ. The lutein concentration of plasma and feathers of Great tit nestlings did not differ along the pollution gradient. The lack of difference in lutein concentration of autumnal moth larvae along pollution gradient may partly explain the lutein concentrations of Great tit nestlings, since the abundance of autumnal moth larvae peak during the nestling phase of Great tit. The lutein concentration of autumnal moth larvae was positively associated to circulating plasma lutein level of Great tit indicating the importance of carotenoid rich diet during the nestling phase. In addition, the higher the plasma lutein concentration the more lutein was deposited to feathers, irrespective of the other possible functions of lutein in nestlings. We found that carotenoid levels differed between the polluted and the unpolluted area especially at lower levels of food chain: in birches and in caterpillars.

Environmental pollution affects the plumage color of Great tit nestlings through carotenoid availability.

Birds need to acquire carotenoids for their feather pigmentation from their diet, which means that their plumage color may change as a consequence of human impact on their environment. For example, the carotenoid-based plumage coloration of Great tit, Parus major, nestlings is associated with the degree of environmental pollution. Breast feathers of birds in territories exposed to heavy metals are less yellow than those in unpolluted environments. Here we tested two hypotheses that could explain the observed pattern: (I) deficiency of carotenoids in diet, and (II) pollution-related changes in transfer of carotenoids to feathers. We manipulated dietary carotenoid levels of nestlings and measured the responses in plumage color and tissue concentrations. Our carotenoid supplementation produced the same response in tissue carotenoid concentrations and plumage color in polluted and unpolluted environments. Variation in heavy metal levels did not explain the variation in tissue (yolk, plasma, and feathers) carotenoid concentrations and was not related to plumage coloration. Instead, the variation in plumage yellowness was associated with the availability of carotenoid-rich caterpillars in territories. Our results support the hypothesis that the primary reason for pollution-related variation in plumage color is carotenoid deficiency in the diet.