Bowers Michael A
Laboratory of Biomedical and Environmental Sciences, University of California, 90024, Los Angeles, CA, USA.
Oecologia. 1985 Sep;67(2):224-230. doi: 10.1007/BF00384289.
Dynamical aspects of flower usage and forager body size in sympatric and experimentally-induced allopatric populations of Bombus flaviforns and Bombus rufocinctus were studied in 10 discrete subalpine meadows and over the last half of one summer. Results indicate that there is a high degree of asymmetry in the competitive effects and that B. flavifrons is the clear competitive and numerical dominant. When occurring alone, B. rufocinctus used the same spectrum of flowers in similar frequencies to that of B. flavifrons whose flower use was invariant over all meadows and treatments. When sympatric with B. flavifrons, B. rufocinctus was relegated to secondary, less preferred flowers. Shifts in flower use by B. rufocinctus were accompanied by changes in forager body-size: body weights were greater in allopatric populations of B. rufocinctus and smaller in those sympatric with B. flavifrons. Competitive dominance may be related to differences in species phenologies. Bombus flavifrons initiated colonies in the spring three weeks before B. rufocinctus and maintained higher densities over the summer; by virtue of greater numbers of foragers, it may control exploitation of the most profitable flowers.
在10个离散的亚高山草甸中，以及在一个夏季的后半段，研究了黄足熊蜂（Bombus flaviforns）和红腹熊蜂（Bombus rufocinctus）同域和实验诱导的异域种群中花朵利用和觅食者体型的动态方面。结果表明，竞争效应存在高度不对称，黄足熊蜂是明显的竞争优势种和数量优势种。单独出现时，红腹熊蜂使用的花朵种类与黄足熊蜂相似，频率也相近，而黄足熊蜂在所有草甸和处理中的花朵利用情况是不变的。与黄足熊蜂同域时，红腹熊蜂只能选择次等的、不太受欢迎的花朵。红腹熊蜂花朵利用的转变伴随着觅食者体型的变化：红腹熊蜂异域种群的体重更大，而与黄足熊蜂同域的种群体重更小。竞争优势可能与物种物候差异有关。黄足熊蜂在春季比红腹熊蜂提前三周建立蜂群，并在夏季保持更高的密度；凭借更多的觅食者，它可能控制着最有利可图花朵的利用。
