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Factors affecting the intertidal zonation of Tegula funebralis and T. brunnea

The two intertidal species of Tegula, T. funebralis and T. brunnea show distinct vertical zonation patterns. T. funebralis is found throughout the mid intertidal zone and into the low zone, while T. brunnea is found in the low intertidal and shallow subtidal zones. Experiments were conducted to test whether desiccation, predation, or microhabitat preferences were affecting the distributions of the two species. Results indicate that the inability to tolerate prolonged exposure to heat and desiccation keeps T. brunnea low in the intertidal zone. The predators Pisaster ochraceous and Cancer antenarius, which live low intertidally, were not shown to preferentially eat T. funebralis in the lab or the field. Predation pressures on both species were shown to be low at Hopkins Marine Station, suggesting that predation was not a major force maintaining the lower limit of T. funebralis. Microhabitat preferences of the two species differ, indicating that microhabitat choice may play a role in maintaining zonation patterns. The role of other factors such as competition, behavior, and larval settlement are discussed.

Intertidal Zonation, Environmental, Tissue, and Upper Lethal Temperatures in High Intertidal Gastropods

Intertidal transect studies of northern Monterey Bay.

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