Dispersal Patterns of some PhyteumaSpecies (Campanulaceae)

Abstract: In the genus Phyteurnaspadix‐shaped spikes or capitula are composed of xerochasic poricidal capsules, holding unspecialized seeds. Phyteurna betonicifoliurnVILL., Phyteuma hemisphaericumL, Phyteurna scheuchzeriALL., and Phyteurna spica‐turnL. 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 hernisphaericurnallows a limited enlargement of the occupied area, while the seeds of P. scheuchzeriare dispersed more remotely from the mother plant. P. spicaturnand P. betonicifoliurnmainly 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.