Latta R G, Linhart Yan B
Department of E.P.O. Biology, University of Colorado, Boulder, CO 80309, USA fax: (303)-492-8699, e-mail:
Oecologia. 1997 Jan;109(2):251-258. doi: 10.1007/s004420050080.
We analyzed the pattern of correlations among fitness components, herbivory, and resin characteristics in a natural all-aged stand of ponderosa pine, to infer the strength and mechanism of natural selection on plant chemistry. Male and female cone production were monitored yearly for 15 years, and levels of herbivory for 9 years in 165 trees. Resin flow rate and monoterpene composition were determined for these same trees. Multiple regression of fitness components on resin characteristics showed significant associations consistent with directional selection for increased resin flow rates and increased proportions of α- and β-pinene, myrcene and terpinolene. However, negative correlations among monoterpene fractions of the resin constrained the overall selection. Selective herbivory by aphids approached statistical significance and monoterpenes showed some (non-significant) effect as deterrents against deer browse. Resin characteristics were not correlated with attack by cone insects or porcupines. However, the association between resin characteristics and fitness is significantly different from that predicted by the path coefficients involving herbivores. Therefore the hypothesis that these herbivores mediate selection on the resin is not supported by the observed pattern of correlations among resin characteristics, herbivory, growth and fecundity. In this population, most of the association between resin characteristics and fitness appears to be mediated by some other factor independent of attack by herbivore species present.
我们分析了黄松天然老龄林中健康组分、食草作用和树脂特性之间的相关性模式，以推断植物化学特征上自然选择的强度和机制。连续15年每年监测雄球果和雌球果的产量，并对165棵树进行了9年的食草作用水平监测。测定了这些树的树脂流速和单萜成分。健康组分对树脂特性的多元回归显示出显著的相关性，这与树脂流速增加以及α-蒎烯、β-蒎烯、月桂烯和萜品油烯比例增加的定向选择一致。然而，树脂单萜组分之间的负相关限制了整体选择。蚜虫的选择性食草作用接近统计学显著水平，单萜类物质对鹿的啃食表现出一定（不显著）的威慑作用。树脂特性与球果昆虫或豪猪的侵害没有相关性。然而，树脂特性与健康之间的关联与涉及食草动物的通径系数所预测的情况显著不同。因此，这些食草动物介导对树脂的选择这一假设，并未得到树脂特性、食草作用、生长和繁殖力之间观察到的相关性模式的支持。在这个种群中，树脂特性与健康之间的大部分关联似乎是由一些独立于现有食草动物物种侵害的其他因素介导的。
