Life histories of limpets and the limpet-laminarian relationship

Abstract

In California, two species of acmaeid limpets display contrasting life history patterns. Acmaea insessa (Hinds) has an obligate association with the brown alga, Egregia laevigata (Setchell), which has an annual life cycle in the intertidal zone. Acmaea insessa must be able to grow to maturity and produce gametes before the inevitable but unpredictable loss of its attachment and feeding substratum. On the other hand, A. digitalis (Rathke), like most limpets, lives on permanent hard surfaces not subject to catastrophic loss. Predictably, A. insessa has a shorter expectation of further life, higher growth rate, greater reproductive effort, and shorter time to sexual maturity compared with A. digitalis. Habitat selection of A. insessa ensures that it will not interact with any of the other co-occurring species of acmaeid limpets during its adult life history; it avoids interspecific competition and in relation to other conventional limpets has a specialized mode of life. It may be argued that previous episodes of interspecific competition influenced this pattern of habitat selection and that these Californian limpets provide an example of a positive relationship between specialized modes of life and the number of co-occurring ecologically similar species. Data on limpet species abundance and habitat selection from other parts of the world are confusing. Both southern Africa and northern Europe support well established limpet-algal associations but the former has many and the latter few related limpet species. Northern New Zealand has a more diverse fauna of limpets and herbivorous gastropods than northern Europe but has no algal associated limpets despite the presence of suitable hosts. The relative abundance of limpet species does not provide a good basis for predicting the occurrence of obligate limpet-algal associations.