Traveset Anna
Institut d'Estudis Avançats de les Illes Balears, Crtra. de Valldemossa, Km 7'5, E-07071, Palma de Mallorca, Spain.
Oecologia. 1995 Jul;103(1):118-126. doi: 10.1007/BF00328432.
The factors that reduce the pre-dispersal reproductive potential of Euphorbia dendroides are identified and the magnitude and variability of their effects are examined, both on a spatial and on a temporal scale. The aims of the study were: (1) to assess whether such variation was related to plant attributes describing size and/or fecundity, and (2) to determine the consistency of those effects in plant reproductive success. Pre-dispersal losses were measured over 3 years in a total of 45 plants from two populations in Cabrera island (Balearic Islands, western Mediterranean). Two types of insect-plant interactions (a moth that preys on the inflorescences and a wasp that feeds on the seeds) significantly reduced the potential number of seeds of E. dendroides, whereas lack of ovary in the cyathium, ovary abortion or seed abortion were the causes of reproductive loss that can be considered "intrinsic" to the plant. Significant variation was found both spatially and temporally in their effects, though such variation could not be attributed to the plant traits measured. Moths and wasps were not found to exert any opposing selective pressure on the plant, and their effect was additive. Key factor analyses performed with the data obtained over three seasons showed that the influence of a factor on among-plant variation in total reproductive losses cannot be predicted by the magnitude of the loss caused by such a factor; thus, seed abortion, while representing a low reproductive loss (< 20% of the potential seed production) accounted for the greatest among-plant variation in total losses. The analyses also showed that the contribution of the plant-insect interactions to the variation in total losses varied significantly both spatially and temporally. This lack of consistency, together with the lack of association with the plant traits measured, suggests that the demographic changes produced by these interactions are unlikely to translate into adaptive changes.
确定了降低绿玉树（Euphorbia dendroides）传播前繁殖潜力的因素，并在空间和时间尺度上研究了其影响的程度和变异性。该研究的目的是：（1）评估这种变异是否与描述大小和/或繁殖力的植物属性相关，以及（2）确定这些影响在植物繁殖成功中的一致性。在卡布雷拉岛（巴利阿里群岛，地中海西部）两个种群的总共45株植物中，对传播前的损失进行了3年的测量。两种类型的昆虫与植物的相互作用（一种捕食花序的蛾和一种以种子为食的黄蜂）显著降低了绿玉树的潜在种子数量，而杯状聚伞花序中缺乏子房、子房败育或种子败育是可被视为植物“内在”的繁殖损失原因。在其影响方面，在空间和时间上均发现了显著变异，尽管这种变异不能归因于所测量的植物性状。未发现蛾和黄蜂对植物施加任何相反的选择压力，并且它们的影响是累加的。对三个季节获得的数据进行的关键因素分析表明，一个因素对植物间总繁殖损失变异的影响不能通过该因素造成的损失大小来预测；因此，种子败育虽然代表较低的繁殖损失（<潜在种子产量的20%），但在植物间总损失变异中占比最大。分析还表明，植物与昆虫相互作用对总损失变异的贡献在空间和时间上均有显著差异。这种缺乏一致性，以及与所测量的植物性状缺乏关联，表明这些相互作用产生的种群统计学变化不太可能转化为适应性变化。
