Sydney Institute of Marine Science, Evolution and Ecology Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW, Australia.
Oecologia. 2011 Jun;166(2):381-90. doi: 10.1007/s00442-010-1830-y. Epub 2010 Nov 4.
Within-plant variation in susceptibility to herbivory can significantly influence the ecological and evolutionary consequences of plant-herbivore interactions. Seagrasses are marine angiosperms characterised by substantial intra-individual differences in multiple traits, such as nutrients, chemical and structural defences and epibiotic load, all of which can strongly influence herbivore preferences. We quantified the within-plant feeding choices of the two main consumers of the temperate seagrass Posidonia oceanica--the fish Sarpa salpa and the sea urchin Paracentrotus lividus--and determined the plant traits that explained their foraging strategies. We found strong within-plant heterogeneity in both seagrass susceptibility to herbivory and chemical composition, but different consumers exhibited contrasting feeding choices. S. salpa preferred the most nutritious and chemically defended younger leaves, suggesting a full adaptation to consuming this macrophyte and a greater impact of this herbivore on the plant. In contrast, P. lividus consistently preferred the older leaves covered by epibionts, probably attenuating the relative impact of this consumer and helping to explain the weak effects usually recorded for this echinoid in undisturbed meadows. Artificial diet experiments showed that morphology and fine-scale structural defences were the primary determinant of urchin feeding choices, with nutrient content and chemical defences being of secondary importance. Epibiosis did not strongly influence fish feeding, but it did have a strong 'shared-doom' effect on urchin consumption. This effect was driven by a distinct preference towards a mixed diet that included both host tissues and their epibiotic community.
植物体内对食草性的易感性变化会显著影响植物与食草动物相互作用的生态和进化后果。海草是海洋被子植物，其在多个特征上存在显著的个体内差异，例如营养物质、化学和结构防御以及附生负荷，所有这些都强烈影响食草动物的偏好。我们量化了温带海草波西多尼亚海洋草中两种主要消费者——鱼类 Sarpa salpa 和海胆 Paracentrotus lividus——的植物内觅食选择，并确定了解释它们觅食策略的植物特征。我们发现，海草对食草性和化学成分的易感性都存在强烈的植物内异质性，但不同的消费者表现出不同的觅食选择。S. salpa 更喜欢最有营养和化学防御的年轻叶子，这表明它完全适应了这种大型植物的食用，并且这种食草动物对植物的影响更大。相比之下，P. lividus 一直更喜欢覆盖着附生物的旧叶子，这可能减轻了这种消费者的相对影响，并有助于解释在未受干扰的草地中通常记录到的这种海胆的微弱影响。人工饮食实验表明，形态和精细结构防御是海胆觅食选择的主要决定因素，而营养物质含量和化学防御则是次要因素。附生作用对鱼类的摄食没有强烈影响，但对海胆的摄食有强烈的“共同命运”效应。这种效应是由一种明显的偏好混合饮食驱动的，其中包括宿主组织及其附生群落。
