Zungu Manqoba M, Downs Colleen T
School of Life Sciences, University of KwaZulu-Natal, Private Bag X 01, Scottsville, 3209, Pietermaritzburg, South Africa.
School of Life Sciences, University of KwaZulu-Natal, Private Bag X 01, Scottsville, 3209, Pietermaritzburg, South Africa.
Behav Processes. 2015 Feb;111:84-9. doi: 10.1016/j.beproc.2014.12.003. Epub 2014 Dec 16.
Tannins are common secondary compounds in plant material and are known for their ability to bind to protein which reduces nitrogen availability in the diet. In fruits, these compounds are responsible for their astringency which is thought to result in reduced food intake. In this study, the repellent effects of tannins were examined in three species of frugivorous birds: red-winged starlings Onychognathus morio, speckled mousebirds Colius striatus and Cape white-eyes Zosterops virens. Birds were fed artificial fruit diets containing varying levels of tannins in paired choice tests with the amount of food eaten by birds used to determine preference. Red-winged starlings were attracted to the control diet, indifferent to the medium tannin diet and deterred by the high tannin diet whereas speckled mousebirds and Cape white-eyes were not deterred at all concentrations. The discrepancy in the results was attributed to differences in taste sensitivity, tolerance levels and detoxification mechanisms of secondary compounds between species. Because fruit selection and ultimately fruit removal rates affect plant community composition, the disparity in the results suggests that frugivorous birds do not contribute equally to plant community dynamics. However, plant secondary compounds in fruits are diverse and their effects are similarly diverse and there is potential that different groups of secondary compounds generate disparate effects. Similar studies on other types of secondary compounds may thus contribute towards a broader understanding of the role of secondary compounds in mediating fruit-frugivore interactions.
单宁是植物材料中常见的次生化合物，因其能够与蛋白质结合而闻名，这种结合会降低饮食中的氮利用率。在水果中，这些化合物会导致水果产生涩味，人们认为这会减少食物摄入量。在本研究中，研究了单宁对三种食果鸟类的驱避作用：红翅椋鸟（Onychognathus morio）、斑鼠鸟（Colius striatus）和海角白眼鸟（Zosterops virens）。在配对选择试验中，给鸟类喂食含有不同单宁水平的人工水果饲料，通过鸟类的食物摄入量来确定其偏好。红翅椋鸟被对照饲料吸引，对中等单宁含量的饲料无偏好，而被高单宁含量的饲料驱赶；而斑鼠鸟和海角白眼鸟在所有浓度下都未被驱赶。结果的差异归因于不同物种之间味觉敏感性、耐受水平和次生化合物解毒机制的差异。由于果实选择以及最终的果实去除率会影响植物群落组成，结果的差异表明食果鸟类对植物群落动态的贡献并不相同。然而，水果中的植物次生化合物种类繁多，其影响也同样多样，不同组别的次生化合物有可能产生不同的效果。因此，对其他类型次生化合物进行类似研究可能有助于更广泛地理解次生化合物在介导果实与食果动物相互作用中的作用。
