沙丘稀有种准噶尔无叶豆花部综合特征与传粉适应性

Abstract

The only way to get the objective and comprehensive cognition of floral syndrome is to do research on pollination ecology together. The evolution of floral characteristics and pollination adaptation is always one of the core problems in the field of evolutionary ecology. The significance and protection work of rare species under special ecosystem have raised an increasingly concern. Eremosparton songoricum( Litv.) Vass. is a rare species and only distributes on mobile and semimobile sand dunes,which also contributes to desert stabilization. The previous investigation data showed that the fruit set and seed set were both less than 16%,and the rate of germination and seedling establishment was less than 3% and0. 1%,respectively,which indicated that some weakness probably existed in the reproductive cycle. The goals of our study are to analyze the obstacle of sexual reproduction and to understand the adaptive reproductive strategies and,eventually to propose protective plans through a series of field investigation and laboratory analysis on floral traits and pollination characteristics. We did our research in wild population in the north edge of Gurbantunggut Desert,Xinjiang,China. Results showed that the flowering span of the population,infloresence and single flowering were approximately 21 d,7—12 d and 3d,respectively. The life span of single flower would prolong 2 d when overcast and rain occurred. The keel kept closed during whole flowering period. This floral trait is an adaptive exhibition to desert environment. The flowers finished anther dehiscence before standard pedal opened. E. songoricum relied on nectar secretion,fresh color of pedals and the yellow radiate veins at the basal of standard pedal to attract pollinators. There are four effective pollinators and all are bees without exception. The average visiting frequency of effective pollinators was 7. 75 ± 0. 57 times · flower-1· d-1. The visiting frequency showed triple-climax: 13: 00—14: 00,16: 00—17: 00 and 19: 00—20: 00. Colletes popovi Nosk. was the most frequent pollinators of E. songoricum,which accounted for 79. 2% of the whole visiting behavior. Most of the visiting behavior( 65. 8 ± 1. 1) % of C. popovi occurred among inflorescence within the same individual,which indicated that geitonogamy was the main mating pattern in the wild. E. songoricum exhibited a mixed mating system. It was self-compatible with autonomous selfing rarely happening,and reproductive success relied on pollinators. Inbreeding depression played a role during the period from fertilization to fruit maturation. Stigmatic cuticle and pollen brush showed that E. songoricum inclined to outcrossing,because both structures decreased self-pollination at a certain extent. Holding the existing habitat area,artificial apiculture or artificial pollination may be an effective way to improve the sexual reproductive ability of E.songoricum.