Pollination Biology Of Elaeagnus Stellipila Rehd. Populations At Different Altitudes

The floral phenology, visitors, efficient pollinators and their behaviors, breeding system, nectar secretion of Elaeagnus stellipila Rehd. were investigated at three different altitudes in Sichuan Tangjiahe National Nature Reserve through field survey and laboratory analysis. Exploring to the differences of pollination biology between different altitudes. The main conclusions were as follows:1. The results of floral phenology research showed that the anthesis was in 4-5 month. The early florescence, flourishing florescence and final florescence would be delayed with the increase of altitude both at the individual and population level. We also could find that the higher the altitude, the later the anthesis, the longer the interval, the longer the flowering duration, and single flowering lasted more time, too. As a whole, the floral phenology of E.stellipila Rehd. was affected by the altitude gradient, obviously.2. The research of the floral morphological structure and parameter measurement results explained that the main features of E.stellipila Rehd. were bisexual, off-white, small, so many, fascicular, scented, nectared, style was often higher than stamen and stigma inflation. Comparing them by one-way analysis of variance between different altitudes, it revealed that there existed distinct differences about diffrent floral components at different altitudes, especially, between high-altitude and low-altitude.3. According to detecting efficient pollinators of E.stellipila Rehd. and observing their behaviors, we could draw a conclusion that the pollinator functional groups contained 4 orders, 8 genera and about 14 species. There were some differences of pollinator functional groups at different altitudes. The main pollinators of low-altitude population included Bombus festivus Smith, Bombus pyrosoma Morawitz, Apis mellifera Linnaeus, Aethopyga gouldiae, Eristalis tenax Linnaeus and Syrphus nitens Zetterstedt. The main pollinators of mid-altitude population contained B.festivus Smith, A.mellifera Linnaeus, A.gouldiae, E.tenax Linnaeus, S.nitens Zetterstedt and Rhopalocera. The pollinator functional groups of high-altitude population were consisted of B.festivus Smith, A.mellifera Linnaeus, A.gouldiae, E.tenax Linnaeus and Muscidae. Analysising visitation frequency and pollen deposition on stigmas of difffrent pollinators, A.mellifera Linnaeus and E.tenax Linnaeus were primary efficient pollinators and B.festivus Smith was secondary efficient pollinator, in the low-and mid-altitude populations; A.gouldiae was primary efficient pollinators and B.festivus Smith was secondary efficient pollinator, too, in the high-altitude populations. In most cases, pollinators sucked nectar, but Syrphidae visited for pollen, at the same time.4. Detection of breeding system indicated that certain differences were existed in the stigma receptivity of different altitudes. The stigma receptivity of high-altitude populations was not so strong as low-and mid-altitude populations, however, the most suitable time of stigma receptivity was longer to high-altitude populations. Under different pollinated conditions of three altitudes suggested that all of them had no apomixis; automatic self-pollination not in low-and mid-altitude populations, but weak automatic self-pollination existed in high-altitude populations. Hand-pollination increased the fruit set compared to the natural situation. In high-altitude populations, the fruit set was lowest.5. The least amount of nectar in bagged flowers occurred at around 13:00 and all of them with an oblique "N" trend in diurnal and the higher the altitude, the larger the volume of nectar. Along with anthesis, the largest amount of nectar appeared in third day at every altitude and the variation tendency submitted to nearly "∧" in the low-and mid-altitude populations, however, the variation tendency of high-altitude populations not so acute compared to low-and mid-altitude populations.In conclusion, pollination limitation was obvious in E.stellipila Rehd.. It needed pollinators and belonged to melittophilae and ornithophilous cross-pollinated.