Seltenes und zerstreutes Vorkommen: Auswirkungen auf den Paarungserfolg des Speierlings

Abstract

Rare and scattered: consequences for the mating success of the service tree Using a population genetic approach, we studied the effect of the highly scattered occurrence of the rare service tree (Sorbus domestica) in the canton of Schaffhausen (Switzerland) on the realised mating system. Therefore, we mapped all tree individuals in our extended study area and genotyped all 189 trees using microsatellites. Additionally, we genotyped 1183 seeds from 49 different mother trees and assigned the corresponding pollen-donor (father tree). We showed that effective pollinations occur over large spatial distances (>16 km). Because the amount of effectively dispersed pollen decreased with increasing distance from its source, the spatial position of a tree in relation to its conspecific neighbours has a significant impact on the genetic composition of its offspring (seeds) — the more isolated a tree was, the higher was the proportion of self-fertilised offspring. Based on these results, we discuss management strategies aimed at securing the survival and increasing the fecundity, in particular flowering, of adult trees in the study area. If priorities have to be set, trees belonging to denser local groups of service trees should be favoured as they have a higher potential to produce genetically diverse offspring. These progenies can be used to produce high-quality planting material for artificial regeneration, a conservation measure which we consider necessary since we observed no natural regeneration from seeds in the study area. Stands may be managed in a silvicultural practice similar to that of coppice-with-standards. Promoting the regeneration of light-demanding and rare forest tree species, like service tree, wild service tree, wild pear and wild apple, may allow them grow to mature trees of high value, both ecologically and economically.