巴西东北部半干旱卡廷加地区蚂蚁的种子传播
Seed dispersal by ants in the semi-arid Caatinga of North-East Brazil.
作者信息
Leal Inara R, Wirth Rainer, Tabarelli Marcelo
机构信息
Departamento de Botânica, Universidade Federal de Pernambuco, 50670-901, Recife, PE, Brazil.
出版信息
Ann Bot. 2007 May;99(5):885-94. doi: 10.1093/aob/mcm017. Epub 2007 Apr 12.
BACKGROUND AND AIMS
Myrmecochory is a conspicuous feature of several sclerophyll ecosystems around the world but it has received little attention in the semi-arid areas of South America. This study addresses the importance of seed dispersal by ants in a 2500-km(2) area of the Caatinga ecosystem (north-east Brazil) and investigates ant-derived benefits to the plant through myrmecochory.
METHODS
Seed manipulation and dispersal by ants was investigated during a 3-year period in the Xingó region. Both plant and ant assemblages involved in seed dispersal were described and ant behaviour was characterized. True myrmecochorous seeds of seven Euphorbiaceae species (i.e. elaiosome-bearing seeds) were used in experiments designed to: (1) quantify the rates of seed cleaning/removal and the influence of both seed size and elaiosome presence on seed removal; (2) identify the fate of seeds dispersed by ants; and (3) document the benefits of seed dispersal by ants in terms of seed germination and seedling growth.
KEY RESULTS
Seed dispersal by ants involved one-quarter of the woody flora inhabiting the Xingó region, but true myrmecochory was restricted to 12.8 % of the woody plant species. Myrmecochorous seeds manipulated by ants faced high levels of seed removal (38-84 %) and 83 % of removed seeds were discarded on ant nests. Moreover, seed removal positively correlated with the presence of elaiosome, and elaiosome removal increased germination success by at least 30 %. Finally, some Euphorbiaceae species presented both increased germination and seedling growth on ant-nest soils.
CONCLUSIONS
Myrmecochory is a relevant seed dispersal mode in the Caatinga ecosystem, and is particularly frequent among Euphorbiaceae trees and shrubs. The fact that seeds reach micro-sites suitable for establishment (ant nests) supports the directed dispersal hypothesis as a possible force favouring myrmecochory in this ecosystem. Ecosystems with a high frequency of myrmecochorous plants appear not to be restricted to regions of nutrient-impoverished soil or to fire-prone regions.
背景与目的
蚁播是世界上几种硬叶生态系统的显著特征，但在南美洲半干旱地区却很少受到关注。本研究探讨了巴西东北部卡廷加生态系统2500平方公里区域内蚂蚁传播种子的重要性，并研究了蚁播给植物带来的益处。
方法
在辛戈地区进行了为期3年的蚂蚁对种子的搬运和传播研究。描述了参与种子传播的植物和蚂蚁群落，并对蚂蚁行为进行了特征描述。在实验中使用了7种大戟科植物的真正蚁播种子（即带有油质体的种子），目的是：（1）量化种子清理/搬运的速率以及种子大小和油质体的存在对种子搬运的影响；（2）确定蚂蚁传播种子的去向；（3）记录蚂蚁传播种子在种子萌发和幼苗生长方面的益处。
主要结果
蚂蚁传播种子涉及辛戈地区四分之一的木本植物区系，但真正的蚁播仅限于12.8%的木本植物物种。被蚂蚁搬运的蚁播种子有很高的搬运率（38 - 84%），83%被搬运的种子被丢弃在蚁巢上。此外，种子搬运与油质体的存在呈正相关，油质体被去除使发芽成功率至少提高了30%。最后，一些大戟科植物在蚁巢土壤上的发芽和幼苗生长都有所增加。
结论
蚁播是卡廷加生态系统中一种重要的种子传播方式，在大戟科树木和灌木中尤为常见。种子到达适合定居（蚁巢）的微生境这一事实支持了定向传播假说，即这可能是该生态系统中有利于蚁播的一种力量。蚁播植物频繁出现的生态系统似乎并不局限于土壤养分贫瘠的地区或易发生火灾的地区。
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