Boulay Raphaël, Carro Francisco, Soriguer Ramón C, Cerdá Xim
Estación Biológica de Doñana, CSIC, Avenida María Luisa s/n, 41013 Sevilla, Spain.
Proc Biol Sci. 2007 Oct 22;274(1625):2515-22. doi: 10.1098/rspb.2007.0594.
The evolution of pollination and seed dispersal mutualisms is conditioned by the spatial and temporal co-occurrence of animals and plants. In the present study we explore the timing of seed release of a myrmecochorous plant (Helleborus foetidus) and ant activity in two populations in southern Spain during 2 consecutive years. The results indicate that fruit dehiscence and seed shedding occur mostly in the morning and correspond to the period of maximum foraging activity of the most effective ant dispersers. By contrast, ant species that do not transport seeds and/or that do not abound near the plants are active either before or after H. foetidus diaspores are released. Experimental analysis of diet preference for three kinds of food shows that effective ant dispersers are mostly scavengers that readily feed on insect corpses and sugars. Artificial seed depots suggest that seeds deposited on the ground out of the natural daily time window of diaspore releasing are not removed by ants and suffer strong predation by nocturnal rodents Apodemus sylvaticus. Nevertheless, important inter-annual variations in rodent populations cast doubts on their real importance as selection agents. We argue that traits allowing synchrony between seed presentation and effective partners may constitute a crucial pre-adaptation for the evolution of plant-animal mutualisms involving numerous animal partners.
传粉和种子传播互利共生关系的演化取决于动植物在空间和时间上的同时出现。在本研究中，我们连续两年探究了西班牙南部两个种群中一种蚁播植物（臭嚏根草）的种子释放时间以及蚂蚁的活动情况。结果表明，果实开裂和种子脱落大多发生在上午，且与最有效的蚂蚁传播者的最大觅食活动期相对应。相比之下，不传播种子和/或在植物附近数量不多的蚂蚁种类，在臭嚏根草传播体释放之前或之后活动。对三种食物的饮食偏好进行的实验分析表明，有效的蚂蚁传播者大多是食腐动物，它们很容易以昆虫尸体和糖类为食。人工种子库表明，在传播体自然每日释放时间窗口之外放置在地面上的种子不会被蚂蚁搬走，并且会遭受夜间啮齿动物（林姬鼠）的强烈捕食。然而，啮齿动物种群的重要年际变化让人怀疑它们作为选择因子的实际重要性。我们认为，使种子呈现与有效伙伴之间实现同步的性状可能是涉及众多动物伙伴的植物 - 动物互利共生关系演化的关键预适应特征。
