The Relationship Between Flowering Phenology And Bisexual Fitness In Hosta Ventricosa

Currently, flowering phenology is still a hot point in plant reproductive ecology. The plant phenotypic selection mechanism also has become a hot spot in evolutionary ecology. It can provide important theoretical basis for plant reproductive success through their study. In this study, we study on Hosta ventricosa, that located in Bi Feng Xia nature scenic spot(N28°51′10″-30°56'40", E101°56′26″～103°23′28″), Ya'an, Sichuan, China. We preliminary studied the flowering phenology, reproductive characteristics, and phenotypic natural selection, over three consecutive years. We discussed the relationship between flowering phenology and bisexual fitness, and tried to explain the bisexual reproductive success with flowering phenology variations, and further understand the selection mechanism of flowering phenology and its adaptive significance. The results showed that:1, The flower of Hosta ventricosa is bisexual. The flowering span of the single flower, individual, population was approximately Id,15 to 18d and 20 to 24 d, respectively. The flowering duration was significant difference in different years. The population flowering median date was significant difference in the three years. The onset date and end date put off year after year, as well as varied significant. Individual flowering amplitude was 1.36 to 1.47, there was no significant difference in different years. The pattern of flowering process was very similar in the three years, with "single peak", was belonged to mass-flowering pattern. The flowering synchrony was lower with only 0.17 to 0.34, there was significant difference in different years.2, The relative flowering intensity frequency distributions of about 70%, indicating that Hosta ventricosa has a higher relative intensity. The skewness is very small,2008: 0.041; 2009:0.372; 2010:-0.124, respectively; indicating that the majority of individuals has emerged strongly flowering phenomenon, so that attracting more pollinators, and thus is of advantage to ensure its reproductive success.3, The flowering phenology index of Hosta ventricosa are closely related. Correlation analysis showed that:There are extremely significant correlations between onset date and median date, total flower numbers, duration; median date and end date; total flower numbers and duration, end date, synchrony index; duration and end date, synchrony index; end date and synchrony index. And showed a high degree of consistency in different years. Indicating that early flowering, more flowers than late flowering, fewer flowers with a longer flowering period. The longer flowering period, the later end date and the lower flowering synchrony. Individuals with early flowering will reach their median date more quickly. The earlier median date, the earlier end date. The later end date, the lower flowering synchrony.4, The fruit set, seed numbers, stigma pollens, export pollens all trend toward increasing year after year, but no significant change from year to year. The seed set in 2009 was significant higher than 2008.5, Analysing phenotypic natural selection on the flowering phenology by using the number of seeds, fruit set, seed set, stigma pollens as the female fitness; and export pollens as the male fitness. The results showed that:partial phenology index was suffered strong phenotypic selection, but it appeared that there were striking variations in target index, selection pattern and intensity between years. The overall performance of the dominant directional selection, there is some disruptive selection pattern, showing that individuals in favour of earlier or later flowering. Early flowering can increase the number of seeds and stigma pollens, late flowering can increase the seed set.