Ragusa-Netto J
Departamento de Ciências Naturais, Universidade Federal do Mato Grosso do Sul - UFMS, Campus Três Lagoas, Três Lagoas, MS, Brazil.
Braz J Biol. 2014 Nov;74(4):837-43. doi: 10.1590/1519-6984.04713. Epub 2014 Nov 1.
Seed predation has major effects on the reproductive success of individuals, spatial patterns of populations, genetic variability, interspecific interactions and ultimately in the diversity of tree communities. At a Brazilian savanna, I evaluated the proportional crop loss of Eriotheca gracilipes due the Blue-Fronted Amazon (Amazona aestiva) during a fruiting period. Also, I analyzed the relationship between proportional crop loss to Amazons and both fruit crop size and the distance from the nearest damaged conspecific. Trees produced from 1 to 109 fruits, so that Amazons foraged more often on trees bearing larger fruit crop size, while seldom visited less productive trees. Moreover, the relationship between fruit crop sizes and the number of depredated fruits was significant. However, when only damaged trees were assessed, I found a negative and significant relation between fruit crop size and proportional crop loss to Blue-Fronted Amazons. Taking into account this as a measure more directly related to the probability of seed survival, a negative density dependent effect emerged. Also, Amazons similarly damaged the fruit crops of either close or distant neighboring damaged trees. Hence, in spite of Blue-Fronted Amazons searched for E. gracilipes bearing large fruit crops, they were swamped due to the presence of more fruits than they could eat. Moderate seed predation by Blue-Fronted Amazons either at trees with large fruit crops or in areas where fruiting trees were aggregated implies in an enhanced probability of E. gracilipes seed survival and consequent regeneration success.
种子捕食对个体的繁殖成功率、种群的空间格局、遗传变异性、种间相互作用以及最终对树木群落的多样性都有重大影响。在巴西的一片稀树草原上，我评估了在结果期蓝额亚马逊鹦鹉（Amazona aestiva）对细叶 Eriotheca gracilipes 的果实损失比例。此外，我分析了对亚马逊鹦鹉的果实损失比例与果实产量大小以及与最近受损同种树木的距离之间的关系。树木结出的果实数量从1个到109个不等，因此亚马逊鹦鹉更频繁地在果实产量较大的树上觅食，而很少光顾产量较低的树。此外，果实产量大小与被掠食果实的数量之间存在显著关系。然而，当仅对受损树木进行评估时，我发现果实产量大小与蓝额亚马逊鹦鹉的果实损失比例之间存在负向且显著的关系。将此作为与种子存活概率更直接相关的一种衡量标准，出现了负密度依赖效应。此外，亚马逊鹦鹉对相邻的近距或远距受损树木的果实产量造成的破坏程度相似。因此，尽管蓝额亚马逊鹦鹉会搜寻果实产量大的细叶 Eriotheca gracilipes，但由于果实数量多得吃不完，它们也只能望“果”兴叹。蓝额亚马逊鹦鹉对果实产量大的树木或结果树木聚集区域进行适度的种子捕食，意味着细叶 Eriotheca gracilipes 种子存活及后续更新成功的概率增加。
