露蕊乌头(毛茛科)不同海拔居群的传粉生态学

对青藏高原东北部两个不同海拔地点（互助，2460m和海北，3200m）的露蕊乌头Aconitum gymnandrum的传粉生态学进行了比较研究。研究结果表明高海拔居群的单花花期、雄性期持续时间、雌性期持续时间比低海拔长。露蕊乌头不存在无融合生殖现象，尽管高度自交亲和，但产生种子必须依赖传粉媒介。熊蜂是露蕊乌头的主要传粉昆虫，两个居群均存在传粉限制。熊蜂取食花蜜为主，在同一个花序上的访问顺序以由下向上为主，但在互助居群和海北居群有3．9％和2．7％的访花是由上向下进行的。统计发现有37．7％和29．3％的访问行为发生在同一植株内；因此，同株异花传粉造成的自交在露蕊乌头中仍然不能避免。低海拔居群的熊蜂种类和访花频率均高于高海拔居群，但自然状态下两个居群的结实率并没有显著差异。高海拔露蕊乌头居群可能具有较长的柱头持续时间，从而补偿了由于访花频率低带来的结实率降低。

Pollination ecology of Aconitum gymnandrum (Ranunculaceae) at two sites with different altitudes

In this paper, we compared pollination characteristics ofAconitum gymnandrum at two sites respectively with elevations of 2460 and 3200 m in the northeast Qinghai-Tibetan Plateau. This species is an alpine biennial with unique systematic position and floral morphology in the tribe Delphinieae, Ranunculaceae. We found that the floral longevity and male and female phase durations in the high altitude population were significantly longer than those in the low altitude population. Seeds cannot be set through apomixis in this species. Aconitum gymnandrum is highly self-compatible, but autonomous self-pollination within the individual flower is ruled out through a combination of protandry and herkogamy during floral development, suggesting that pollen vectors were indispensable for successful seed sets of A. gymnandrum. Bumblebees are main pollinators of A. gymnandrum in both populations. Within each raceme, pollinators visited flowers at the bottom first, and then spirally moved upwards; however, 3.9% and 2.7% of the visits were downward respectively in the low altitude population and the high altitude population. In addition, 37.7% and 29.3% of the movements occurred between different racemes within the same plant; therefore geitonogamous self-pollination could not be completely avoided. The higher seed sets of artificially pollinated flowers than the intact flowers suggested the existence of pollination limitation in both populations. Visiting frequency of bumblebees at the low altitude was higher than that at the high altitude, but seed sets of the intact flowers in both populations did not differ remarkably, probably due to that the longer duration of the stigmatic receptivity in the high altitude population compensates the decrease of seed sets because of the low visiting frequency of pollinators at this site.