What limits the distributions of coastally restricted terrestrial invertebrates? The case of coastal landhoppers (Crustacea: Amphipoda: Talitridae) in southern Tasmania
Richardson, AMM and Swain, R and McCoull, CJ (2003) What limits the distributions of coastally restricted terrestrial invertebrates? The case of coastal landhoppers (Crustacea: Amphipoda: Talitridae) in southern Tasmania. Journal of Biogeography, 30 . pp. 687-695.
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Official URL: http://dx.doi.org/10.1046/j.1365-2699.2003.00850.x
Aim A number of terrestrial invertebrates are known to have distributions limited to the
immediate coastal zone, but the factors controlling their distributions are not well understood.
This study was planned to correlate the distribution of a coastal terrestrial
amphipod, Austrotroides maritimus Friend 1987, which is only found within 100 m of
the high tide mark, with soil characteristics and salt deposition.
Location South Cape Rivulet Bay on the south coast of Tasmania (146 degrees 47' E, 43 degrees 36' S).
Methods Abundance of the amphipods was examined at four sites c. 200 m apart that
varied in their exposure to onshore westerly winds. At each site four replicate transect
lines were established 3 m apart, with pitfall traps set at 2-m intervals. The lines were at
right angles to the high water mark and extended beyond the inland limit of A. maritimus.
Amphipods were trapped at three times of the year, in winter, spring and summer
(1993-94), and the sodium content, organic content and moisture content of the soil at
each trap site were measured. The sodium content of rain falling on the transects, was
also measured, and lysimeters were used to assess the concentration of sodium in water
penetrating the soil profile.
Results The inland penetration of A. maritimus varied between 18 and 44 m from the
seaward edge of woody terrestrial vegetation (itself <10 mhorizontally from the high tide
mark). Inland penetration increased from west to east around the bay, following an
apparent gradient of increased exposure to onshore winds. At the most easterly and
apparently most exposed site, however, the species penetrated only 18 m, but this site
differed markedly from the others in its topography, caused by erosion of the dunes, with an
8-m cliff at its seaward end. The soils at this site were also unusually clayey and waterlogged.
Amphipod abundance did not correlate strongly with any of the soil parameters.
The salt content of rainfall generally declined inland, as did the concentration of lysimeter
leachate, but the inland declines were not all smooth, and both rainfall and lysimeter
leachate concentration showed some tendency to increase inland at the most sheltered site.
Main conclusions Austrotroides maritimus is strongly restricted to the immediate
coastal zone. The extent of its inland penetration correlates with exposure to onshore
winds, and circumstantial evidence supports the hypothesis that this may be due to
differences in the amount of salts deposited.
|Additional Information:||The definitive version is available at www.blackwell-synergy.com|
|Keywords:||Amphipods, Talitridae, landhoppers, distribution, salt spray, onshore wind.|
|Deposited By:||A/Prof Alastair Richardson|
|Deposited On:||27 Jul 2007|
|Last Modified:||18 Jul 2008 20:02|
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