Gregarious larval settlement within a restricted intertidal zone and sex differences in subsequent mortality in the polygynous saltmarsh isopod Paragnathia formica (Crustacea: Isopoda)

Abstract

The highly restricted ranges of many intertidal invertebrates, and the relative importance of physical and biological factors on settlement and subsequent mortality, have attracted much attention from ecologists. Most workers have concentrated on rocky shore communities, where patterns of zonation are often very clear (for reviews, see Stephenson & Stephenson, 1949, 1972; Southward, 1958; Lewis, 1955, 1961, 1964), whilst few have looked for such effects within saltmarshes (for reviews, see Long & Mason, 1983; Foster, In Press). Since most saltmarsh invertebrates are infaunal, patterns of zonation are not immediately obvious, but may be of particular interest; the influence of tidal regimes on invertebrate ranges may be more precise in sheltered saltmarsh habitats than on rocky shores, where exposure to wave action is a major confounding variable.