Size-dependent Sex Allocation In A Hermaphrodite Herb Flowers, Hosta Rectifolia (Liliaceae)

Sex allocation theory is the most important theoriy in the evolutionary biology, which has been used to explain the diversity of breeding systems and the formation of selfing as well as sex ratio in population. It suggests that there is trade-off between resource allocation and male vs. female function or size at multiple levels, and organisms will adjust sex allocation according to size through male and female functions in the population level. In order to understand the mechanism of evolutionary and adaptation in the perennial hermaphrodite specie, a field study was conduct in the hosta rectifolia (Liliaceae) in 2009-2010, to examine the sex allocation among plants and flowers in individual level, and the fitness relationship between size-dependent and sex allocation. The results are as follows:(1) The flowering of hosta rectifolia (Liliaceae) was in late June and late July. Similar average numbers of flowers per plant were observed in individual level in the two years. As compared to 2010, the flowering duration was longer in 2009, and the onset and end date of flowering was respectively advanced 10d and 2d, but not for the flowering amplitude. Moreover, the numbers of flowering per day increased with the increase of plant size, and showed significant correlation with total flowers.(2) Similar average, maximum and minimum numbers of ovules per flower were observed in individual level in the two years. Meanwhile, the numbers of ovules per flower increased with the increase of plant size, and showed significant correlation with total flowers.(3) There was significant difference in the average numbers of pollens per flower in individual level in the two years. As compared to 2010, the maximum and minimum pollens per flower were higher. Also, the numbers of pollens per flower increased with the increase of plant size, and showed significant correlation with total flowers.(4) Similar average ratios of pollens to ovules per flower were observed in individual level in the two years. As compared to 2010, the minimum ratio of pollens to ovules per plant was higher in 2009, but reverse to the maximum ratio. At the same time, the ratio of pollens to ovules per flower didn't increase with the increase of plant size. Therefore, the sex allocation of hosta rectifolia (Liliaceae) was not size-dependent.(5) Similar average numbers of seed per flower were observed in individual level in the two years, and natural and artificial pollination treatments have litter effects on average numbers of seed per flower in the treatments. The minimum numbers of flowers and seed per plant was obviously different, but not for the maximum numbers of flowers and seed per plant. Meanwhile, the numbers of seed per flower increased with the increase of plant size, and showed significant correlation with total flowers in 2009. The numbers of seed per flower also increased with the increase of total flowers in 2010, and the artificial pollination treatments have litter effects on numbers of seed per flower.