Associational plant refuges: convergent patterns in marine and terrestrial communities result from differing mechanisms
Associational plant refuges: convergent patterns in marine and terrestrial communities result from differing mechanisms
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DOI：
10.1007/bf00380934
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发表时间：
1988-10
期刊：
影响因子：
2.7
通讯作者：
C. Pfister;M. Hay
中科院分区：
文献类型：
--
作者：
C. Pfister;M. Hay
An associational plant refuge occurs when a plant that is susceptible to herbivory gains protection from herbivory when it is associated with another plant. In coastal North Carolina, the abundance of the palatable red algaGracilaria tikvahiaeis positively correlated with the abundance of the unpalatable brown algaSargassum filipenduladuring times of increased herbivore activity. To see if grazing by the sea urchinArbacia punctulatacould generate this pattern, controlled experiments were conducted in out-door microcosms and in the laboratory.Gracilariabeneath a canopy ofSargassumwas eaten significantly less thanGracilariaalone. WhenArbaciawere excluded,Gracilariaalone grew significantly more thanGracilariabeneathSargassum, demonstrating thatSargassumis a competitor ofGracilaria. Experiments investigatingSargassum's deterrent role indicated thatSargassumdecreased the foraging range ofArbaciaand the rate at which it fed onGracilaria. Additional experiments with plasticSargassummimics indicated that the decreased grazing onGracilariawas not a result ofSargassummorphology, but was probably attributable to some chemical characteristic ofSargassum. The pattern of increased grazing in monocultures (onlyGracilariapresent) versus polycultures (bothGracilariaandSargassumpresent) demonstrated in this study also has been demonstrated for plant-insect interactions in terrestrial communities. In these communities, insect density is higher in monocultures than in polycultures because insects find and immigrate to monocultures more rapidly, and once in a monoculture, they emigrate from them less often than from polycultures. In this study, urchins did not find and immigrate to monocultures more rapidly, nor did they tend to stay in them once they were found; in fact, they emigrated from monocultures ofGracilariamore rapidly than fromGracilariaandSargassumpolycultures. Increased grazing inGracilariamonocultures resulted from increased rates of movement and feeding of individual herbivores, not from increased herbivore density as has been reported for terrestrial systems.
