Ecology of tropical hermit crabs (Crustacea Decapoda) at Quirimba Island, Mozambique: a multivariate assemblage perspective

D.K.A. BARNES, S. DE GRAVE

Abstract


The assemblage organisation and macrohabitat segregation patterns of an
intertidal assemblage of hermit crabs was studied at the Quirimba Archipelago
in northern Mozambique. The assemblage exhibits a strong tidal zonation pattern,
with different species dominating the studied tidal zones. Superimposed
onto this, is a macrohabitat segregation pattern. Coastal features such as presence/
absence of sandy beaches or mangroves explained the presence/absence of
certain species, e.g. Coenobita rugosus H. Milne Edwards 1837 and C. cavipes
Stimpson 1858. Smaller islands with less heterogeneous shores (mostly reef)
were dominated by Clibanarius virescens (Krauss 1843). Larger islands with a
range of macrohabitats (mangrove, sand, reef, seagrass, rock) had more complex
patterns. Within each tidal zone, at least two distinct assemblage groups are
recognised, due to differential species presence/absence patterns and differences
in abundance of the constituent species. Superimposed onto these two patterns,
is a further pattern of island size, with in the majority of cases, the within-zone
habitat segregation pattern corresponding to a dichotomous split between larger
and smaller or medium sized islands. These patterns in macrohabitat use illustrate
the importance of habitat segregation patterns in alleviating inter-specific
competition for available resources.
KEY WORDS: hermit crabs, ecology, Mozambique, macrohabitat segregation,
assemblage structure.

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