Variation in strong interactions in the intertidal zone along a geographical gradient: a Washington-Alaska comparison

Abstract

Identical and simultaneous experiments involving the removal of an abundant herbivore, the chiton Katharina tunicata, were performed in the low intertidal zone in Washington and southeast Alaska. While in Washington this manipulation resulted in dramatic changes in community structure, in Alaska there was little coupling between K. tunicata and other community components over the same 3 yr interval. A persistent intertidal kelp bed developed in Washington in the absence of K. tunicata, whereas in Alaska kelp abundance was highly variable, and unrelated to chiton abundance. This difference was probably attributable to the predominance of a perennial kelp in Washington and an annual kelp at the Alaskan site. Limpets declined in abundance following chiton removal in both regions, but the increase in abundance and diversity of other algae that occurred in Washington did not take place in Alaska. Our experiments show that the presence of a strong interaction in one region does not guarantee its existence in another, even if community composition is very similar in the 2 locales.

Recovery of the brown alga Fucus gardneri following a range of removal intensities

“…However, Fucus germlings were no more or less abundant in open areas over the course of our experiment. Canopy-forming algae have also been shown to enhance (McCook and Chapman, 1991;Albrecht and Reise, 1994) or suppress (Dethier and Duggins, 1988) herbivore abundance, and thus may indirectly influence recovery rates, but herbivore abundances in our experiment did not differ between treatments. Similarly, the removal of Fucus canopies often leads to blooms of other algal species (Southward and Southward, 1978;van Tamelen et al, 1997), which may suppress recovery.…”

Light availability indirectly limits herbivore growth and abundance in a high rocky intertidal community during the winter

“…Although the diet of juvenile Littorina is unknown, it likely does not contain many of the larger food items consumed by limpets and older conspecifics. Limpets may enhance juvenile littorine's food resources by removing larger algae that are unavailable to juvenile snails; similar positive associations have been noted for other molluscan herbivores (Paine 1980;Dethier and Duggins 1988). Although the exact nature of the association between limpets and juvenile snails remains unclear, the differing responses of the two size classes of Littorina illustrates the dangers of treating different ontogenetic stages as ecological equivalents.…”

Divergent Induced Responses to an Invasive Predator in Marine Mussel Populations

“…Species interactions can differ on various geographic scales because of local selection and other processes (31,32). Similarly, there is considerable potential for the evolutionary history of invasive and native species interactions to vary spatially and temporally.…”