Two species of barnacles, stellate and rock barnacles, occupy the rocky intertidal zone of the Scottish coast and illustrate factors that can determine species distribution in a community.Larvae of both species settle throughout the intertidal zone, but adult barnacles occupy specific zones.The smaller stellate barnacle lives only in higher zones, where the environment dries out between high tides.The larger, faster-reproducing rock barnacle lives only at lower zones.In general, the intertidal zonation seen in the barnacles is due to

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The intertidal zonation seen in the barnacles is due to both competitive interactions and differential susceptibility to abiotic conditions. The smaller stellate barnacle is able to survive in higher zones where there is more competition for space because it is more resistant to desiccation. The larger rock barnacle is better adapted to lower zones with more water because it is faster-reproducing and better able to compete for space with other organisms. Therefore, the distribution of these species is a result of a combination of competition and abiotic factors.

Two Species of Barnacles, Stellate and Rock Barnacles, Occupy the Rocky