No. 952

Title:

Floral Distribution, Clonal Structure, and Their Effects on Pollination Success in a Self-Incompatible Convallaria keiskei Population in Northern Japan

Author(s):

ARAKI Kiwako(Hokkaido University), SHIMATANI Kenichiro (The Institute of Statistical Mathematics) and OHARA Masashi (Hokkaido University)

Key words:

clonal plant, clonal structure, Convallaria keiskei, fruit set, individual-based model, pollination success, self-incompatibility, spatial distribution

Abstract:

BACKGROUND and AIMS: In plant species, when clonal growth produces a patchy structure and flowering ramets are clustered, the amount of pollen contributing to reproductive success is often regulated by pollinator efficiency and geitonogamy. We examined the clonal structure, the spatial ramet distribution, and their combined effects on fruit set in a natural population of an insect-pollinated, self-incompatible clonal herb, Convallaria keiskei, in northern Japan. METHODS: A 100 × 90-m plot was divided into 5 × 5-m subplots, and the number of shoots, flowers, and fruits in 1-m2 quadrats centred at grid points were counted. From all the quadrats where shoots existed, leaf samples were collected for allozyme analysis. Using these two spatial parameters, we constructed individual-based fruit-set models. KEY RESULTS: A total of 236 quadrats contained shoots, and 135 of them contained flowering ramets. The degree of clustering was highest for flowers, followed by fruits and shoots. Allozyme analysis of 282 samples revealed 94 multilocus genotypes. The largest clone expanded more than 40 m, whereas 56 genotypes were detected from only one sample. Several large clones and many small clones were distributed close to each other in this population. Fine-scale spatial modelling revealed that fruit set was influenced by the number of neighbouring flowers with different genotypes rather than by genet diversity or flower distribution only. These findings indicate the significant effects on reproduction of the potential amount of compatible pollen from a neighbourhood transferred by insect pollinators. The optimized range of the neighbour was 14.5 m. CONCLUSIONS: In this C. keiskei population, the potential amount of compatible pollen transferred by insect pollinators from a neighbourhood has significant effects on reproduction. The spatial structure, which includes both clonal expansion and ramet distribution, has a significant influence on pollination success.