SEXUAL DIMORPHISM AND BETWEEN-YEAR VARIATION IN FLOWERING, FRUIT-SET AND POLLINATOR BEHAVIOR IN A BOREAL WILLOW
SEXUAL DIMORPHISM AND BETWEEN-YEAR VARIATION IN FLOWERING, FRUIT-SET AND POLLINATOR BEHAVIOR IN A BOREAL WILLOW
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DOI：
10.2307/3565663
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发表时间：
1988-07-01
期刊：
影响因子：
3.4
通讯作者：
TUNLID, A
中科院分区：
文献类型：
--
作者：
ELMQVIST, T;AGREN, J;TUNLID, A
研究了北方地区雌雄异株杨柳的花性状、访花行为和结果与种子的两性二态性。雄性和雌性在每个个体上产生的柳絮数量大致相同，但雄性在每个柳絮上产生的花更多。雌蜂的花蜜中糖的浓度高于雄蜂，但常备的花蜜产量为。每朵花的有机碳含量在两性之间没有差异。雌性的花蜜富含己糖，雄性的花蜜以蔗糖为主。大黄蜂会区分雄性和雌性柳树，但它们的偏好在白天发生变化，并且在不同舌头长度的大黄蜂之间存在差异。不同种类大黄蜂的相对丰度在不同年份之间变化很大。在两个种群中，手工授粉显著增加了每枝花序的果实和结实数。雌株花的产量年际变化较大。1981-1985年平均坐果率和单果坐果率均低于50%。坐果比每个果实坐果的差异更大。我们认为，在这种柳树的种群中普遍观察到的较早的开花时间和强烈的雌性偏向性比例（60-80%的雌性）增加了花粉限制的风险。花比果多的生产可能代表了一种下注对冲策略，以匹配果实成熟条件的不确定性，尽管它也可能有价值，因为它可能允许植物选择性地成熟高遗传质量的果实。
Sexual dimorphism in floral characters, flower visitor behavior and fruit and seed set were studied in the boreal dioecious willow Salix myrsinifolia-phylicifolia. Males and females produced approximately the same number of catkins per individual, but males produced more flowers per catkin. Females had a higher concentration of sugars in the nectar than males, but the standing crop of nectar, measured as .mu.g organic carbon per flower, did not differ between the sexes. Females had a hexose-rich nectar and males a sucrose-dominated nectar. Bumblebees discriminated between male and female willows, but their preference changed during the day and differed between bumblebees with different tongue length. The relative abundance of different species of bumblebees varied considerably between years. Hand-pollination in two populations significantly increased both fruit and seed set per catkin. The production of flowers in female plants showed a large between-year variation. Both the average fruit set and seed set bper fruit were below 50% during the period 1981-1985. Fruit set showed greater variation than did seed set per fruit. We suggest that the early time of flowering and the strongly female-biased sex ratios commonly observed in populations of this willow (60-80% females), increase the risk of pollen limitation. The production of many more flowers than fruits may represent a bet-hedging strategy to match the uncertainty in the conditions for fruit maturation, although it may also be of value as it potentially allows the plant to selectively mature fruits of a high genetic quality.