Lindström K
Department of Ecology and Systematics, Zoological Laboratory, P.O. Box 17, University of Helsinki, FIN-00014 Helsinki, Finland.
Am Nat. 2001 Jul;158(1):64-74. doi: 10.1086/320867.
I describe the results of an experimental manipulation of resource availability (nest substrate) and distribution (nest size), leading to effects on the opportunity for sexual selection and the survival of male sandgobies Pomatoschistus minutus competing for these resources. This study represents one of few such experimental manipulations. It shows a clear-cut effect of male-male competition on the survival of males, and it shows temporal variation in the opportunity for sexual selection, suggesting that short-term assessment of sexual selection could be misleading. Males breeding under male-male competition for nest sites lived on average 18 d less than males in the high-nest-availability treatment. This considerable cost of reproduction probably stems from increased stress levels as a result of higher levels of aggression. The opportunity for sexual selection was high throughout the 2-mo experiment in the low-nest-availability treatment, while in the high nest availability, it changed in a complex manner over the season. In the latter case, sexual selection was initially low but increased during midseason to values nearly as high as in the nest-site-limited environment and then decreased again toward the end of the season. Previous studies have shown that temporal variation in sexual selection follows variation in population density and sex ratio. This study demonstrates that there can be considerable temporal variation in the opportunity for sexual selection without changes in population parameters.
我描述了一项关于资源可用性（巢穴基质）和分布（巢穴大小）的实验性操纵结果，该结果对性选择机会以及争夺这些资源的雄性细鳞沙塘鳢（Pomatoschistus minutus）的生存产生了影响。这项研究是为数不多的此类实验性操纵之一。它显示了雄性间竞争对雄性生存的显著影响，并且显示了性选择机会的时间变化，这表明对性选择的短期评估可能会产生误导。在雄性为巢穴而进行竞争的情况下繁殖的雄性，其平均寿命比在高巢穴可用性处理组中的雄性短18天。这种相当大的繁殖成本可能源于更高水平的攻击行为导致的压力增加。在低巢穴可用性处理组的整个两个月实验中，性选择机会一直很高，而在高巢穴可用性处理组中，它在整个季节中以复杂的方式变化。在后一种情况下，性选择最初较低，但在季节中期增加到几乎与巢穴受限环境中的值一样高，然后在季节结束时再次下降。先前的研究表明，性选择的时间变化遵循种群密度和性别比例的变化。这项研究表明，在种群参数没有变化的情况下，性选择机会可能会有相当大的时间变化。
