| Abstract |
Three congeneric species of fiddler crabs, Uca
pugilator (Bosc, 1802), U. pugnax (Smith, 1870), and
U. minax (LeConte, 1855), co-occur in estuaries along
the east coast of North America, from Cape Cod to
northern Florida. Although U. minax adults are generally
found at lower salinities than the other two species,
the distributions of all three species overlap to some
degree. The distribution of megalopae and juvenile fiddler
crabs (from first crab stage to those with a carapace
width of 3.0 mm) was examined at four sites along
a salinity gradient (from 35.0±2.0& to 3.0±3.0&;
x
SD ) in the North Inlet Estuary, South Carolina,
USA, in August 2002. A PCR-RFLP technique was
developed to identify individuals from the genus Uca to
species from first zoea through the early crab stages. An
examination of the distribution of early life stages
showed that U. minax reinvades low-salinity adult habitats
at settlement, following planktonic larval development
in the coastal ocean. Also, juveniles of U. pugilator
were found to occupy Spartina alterniflora stands, where
adult conspecifics rarely occur. Species frequencies were
different for adults compared to early life stages in lowsalinity
areas of the marsh, where populations overlap.
Settlement and survival dynamics of early life-history
stages in wet and dry years likely determine the distribution
of adult Uca spp. populations along salinity
gradients in estuarine ecosystems. |
