Dispersal patterns of Lonicera periclymenum determined by genetic analysis

Colonization of Lonicera periclymenum L. (honeysuckle) was studied by RAPD analysis of young ramets in two woodlots planted 20 years ago, and in all ramets in older woodlots within a range of 1 km. Mature ramets that climbed in a particular tree always belonged to one individual. Twenty-five percent of the mature individuals had reproduced vegetatively to other trees or patches nearby, which indicates that the larger part of reproduction is sexual. Some young plants that were growing at close distances from each other were genetically highly similar and shared high similarities to the same mature plants. They may be the product of one dispersal event. Detection of parents of young individuals by exclusion was not successful, because of the dominant nature of the bands. Average distances from young plants to genetically most similar mature plants were variable, due to the small number of colonization events. However, four ways of analysis of genetic similarity among all individuals indicated that exchange of genetic material by seed and pollen occurs to a large extent over small distances and within woodlots: (i) using the Mantel test, pairs of individuals with highest similarity were found significantly more often in the same woodlot than in different woodlots; (ii) genetic similarities between individuals decreased significantly with geographical distance, but only for distances up to 300 m; (iii) individuals of woodlots in the Western part of the study area were hardly related to individuals in the Eastern part of the study area, a distance of 2-3 km; (iv) phi(ST) in the study area was 0.186, indicating a limited gene flow between woodlots. These results are consistent with the dispersal distance as estimated from the average distance between colonized woodlots and the nearest occupied old woodlot in earlier research.