植物次生代谢物含量的季节性变化及其对高原鼠兔食物选择的影响

The seasonal changes of plant secondary metabolites and their influence on the food selection of plateau pika

2008年6～9月在中国科学院海北高寒草甸生态系统定位站通过自助餐式食物选择实验测定了高原鼠兔对20种植物的取食量,采用紫外可见分光光度计法测定了不同季节20种植物中黄酮、缩合单宁、简单酚和总酚4种植物次生代谢物的含量,分析了植物次生代谢物含量与高原鼠兔食物选择之间的相互关系。结果表明,在选定的20种植物中高原鼠兔喜食的植物有7种,可食的植物有7种,厌食的植物有6种。植物次生代谢物的含量在不同的植物间表现出一定的差异,且有生长季节早期含量低,随后逐渐增高的季节性变化趋势。高原鼠兔对植物的选择性与植物中黄酮含量有显著的负相关性,喜食植物的黄酮含量显著低于厌食植物,喜食植物的单宁含量显著小于可食植物,可食植物的单宁含量显著大于厌食植物。在喜食植物中,高原鼠兔取食量与简单酚和总酚含量呈显著负相关性。以上结果部分验证了植物次生代谢物作为植物的防御对策明显影响高原鼠兔对食物选择的假说。黄酮类次生代谢物明显抑制高原鼠兔的取食,缩合单宁对高原鼠兔食物选择也有一定的抑制作用,高原鼠兔有少量取食但避免大量取食简单酚和总酚含量高的植物的选择策略。

The research was carried out from June to September 2008 in the Haibei Alpine Meadow Ecosystem Research Station, Chinese Academy of Science, Qinghai Province. Plateau pikas （ Ochotona curzoniae ） were fed 20 different plants and the amounts of consumed food were measured using a cafeteria preference test. Seasonal changes of 4 plant secondary metabolites （ PSMs ）, flavonoids, condensed tannins, simple phenols and total phenols in the 20 plants were determined by ultraviolet spectrophotometer. The results for the 20 plants showed that the groups of favored plants and edible plants for plateau pikas comprised 7 species each, the remaining 6 species were anorectic plants. There were some differences between plant species for the 4 PSMs some of which showed seasonal changes - they tended to be the lowest in the beginning of growing season and gradually increased in the following months. The contents of condensed tannins in the favored group was significantly lower than in the edible group, and the content of flavonoids in the favored group was significantly lower than in the anorectic group. There was a significant negative correlation between the amount of food intake and the contents of flavonoids in all 20 plants. Within the favored plant group, the plant intake amount was negatively correlated with simple phenols and total phenols content. The results partly verified the hypothesis that plant secondary metabolites serve a defense strategy that could significantly influence the plants＇ selection as food by Ochotona curzoniae. Flavonoids were the factor which significantly restrained the plant food selection of plateau pikas and condensed tannins could deter the plant food selection of plateau pikas in some extent, and results demonstrated that plateau pikas might have a food selection strategy to forage on the plants with high contents of simple phenols or total phenols in relative small quantities, but avoid foraging them in large doses.