Vergleichende Untersuchungen zur Bestäubungs- und Reproduktionsbiologie mitteleuropäischer Alsinoideae-Arten (Caryophyllaceae)

Abstract

In a comparative study 14 morphological and six reproductive flower characters from 16 European species of Alsinoideae were studied. A cluster-analysis on base of the ascertained data made it possible to distinguish between two different flower types: evolutionary older species with bigger flowers and a facultative autogamous to facultative xenogamous reproductive system and evolutionary derived species with small flowers and an obligatory autogamous reproductive system. Flower visitors, however, had a significant positive effect on the seed production of these species. All investigated species showed human-white flowers with UV-reflecting petals. The yellow-green UV-absorbent center seems to be especially attractive for flower visiting insects. Flower perception for insects was facilitated by the radial symmetry and the highly irregular outline of the flowers. Scent production was only weak and very variable in all investigated species. The nectar composition of all species showed a clear hexose dominance. The pollinator spectrum of Alsinoideae was very variable. The main flower visitors were Thysanoptera, Empididae, Formicidae, Muscidae, Syrphidae, and small unspecialized bees. By a statistical analysis it could be proved that habitat conditions and flowering time are the main reasons for the high variability. It was not possible to show a correlation between different flower types of Alsinoideae and certain pollinators. That is why all species can be equally foraged by all types of different pollinators which are all able to transfer pollen grains and cause pollination. These complex network of interactions allow the plant species an optimal use of all types of insect pollen vectors in space and time and therefore a highly flexible reaction to changing environmental conditions.