Dispersal Patterns of some Phyteuma Species (Campanulaceae)

Abstract

In the genus Phyteuma spadix-shaped spikes or capitula are composed of xerochasic poricidal capsules, holding unspecialized seeds. Phyteuma betonicifolium VILL., Phyteuma hemisphaericum L., Phyteuma scheuchzeri ALL., and Phyteuma spicatum L. were examined in wind tunnel experiments to determine the minimum wind speed necessary for seed release, and the relationship between wind speeds and dispersal distances. In a simplified practical simulation the dispersal strategies of these species were described with a leptokurtic curve. The short-distance seed dispersal of Phyteuma hemisphaericum allows a limited enlargement of the occupied area, while the seeds of P. scheuchzeri are dispersed more remotely from the mother plant. P. spicatum and P. betonicifolium mainly disperse closely around the mother plant but provide a certain percentage of seeds for colonization of more distant areas. It is demonstrated that the dispersal modes are determined by the characteristics of fruits, infructescences, and seeds. It is also shown that plants with similar morphological organization show different dispersal patterns, which must be interpreted as a fine-tuned adaptation to the habitat with all its biotic and abiotic factors.

Key words

Dispersal patterns - Phyteuma