associational, or temporal mechanisms. Seaweeds often avoid herbivores by growing in areas not subject to grazing. For example, on tropical coral reefs, many plants only grow on the sand plains or reef flats where herbivore densities are low (1:369). In addition, seaweeds may also live in small cracks on the sea floor or intertidal areas. In fact, some herbivores purposely create their own spatial refuges. The damselfish, for instance, creates a garden of palatable algae by removing species that it doesn't like. While the damselfish do feed in this garden, they also defend it from other herbivores. Consequently, the plots often experience reduced herbivory compared to other areas (1:369).
Another escape tactic used by seaweeds involves associational refuge. Often, unpalatable species will inadvertently protect nearby palatable ones. In fact, according to Duffy and Hay (1990), in some communities species diversity can be very important for many plants' survival. For example, the red alga, Hypnea musciformis, is quickly eaten by fish when it occurs alone. However, when red algae is in close contact with its unpalatable competitor, the brown alga, Sargassum filipendula, it grows much more rapidly. In addition, it has been found that on coral reefs, nearly twice as many different types of plants occur within 10 centimeters of the chemically noxious brown alga, Stypopodium zonale (1:369).
Thirdly, temporal refuges are yet another escape strategy commonly employed by marine plants. In many environments, herbivore activity varies predictably. For instance, in temperate habitats, most grazing occurs during the summer. Consequently, many plants have evolved to take advantage of these animal behavior patterns. Intertidal alga such as Ulothrix, Urospora, and Bangia have complex life histories. They may actually exhibit different morphologic forms in response to changing selective pressures (1:370).
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