Impact of genet size and flowering stage on fruit set in Iris pumila L. clones in wild

Abstract

The interplay between vegetative propagation and sexual reproduction in clonal plants affects the fitness of individuals as well as the structure of genetic diversity. The relevance of studies of that interaction depends on how well chosen genotypes and environmental conditions reflect the real situation in natural populations. In order to analyze the relationship between genet size (and consequently its vegetative success) and fruit set (its female reproductive success) under undisturbed natural conditions I utilized 2916 ramets that bear hermaphrodite flowers on 137 naturally growing Iris pumila clones in a protected area of Deliblato Sand, Serbia. The number of flowers (i.e. flowering ramets) served as a fair estimator of genet size and the larger clones produced more fruits than the smaller ones. However, the smaller clones had significantly higher fruit to flower ratio compared to the larger ones and that difference was detectable in later flowering stages of a clone but not in the earlier ones. In the large clones, flowers that opened later had significantly lower fruit to flower ratio. Since the deleterious effect of geitonogamy on fruit set in I. pumila was documented by hand pollinations, the reduction of fruit to flower ratio in more abundant genets and in later flowering stages is most likely the result of increased geitonogamy. That reduction could lead to a different genetic structure in the seed bank compared to the structure in aboveground population, which can imply important ecological and micro-evolutionary consequences.