Changes in latitudes, changes in aptitudes:: Nucella canaliculata (Mollusca: Gastropoda) is more stressed at its range edge

A paradigm in biogeography is that organisms have 'abundant center' distributions, with abundances peaking at the range center and declining towards the range boundaries. One explanation for this pattern is that abundances are associated with organisms' physiological stress levels and performances, with organisms experiencing more stress at the range edges. Here we explored whether the intertidal dogwhelk Nucella canaliculata was distributed in an 'abundant center' pattern. We addressed the role of stress in setting the species' range limits. We determined dogwhelk abundances at range-center and range-edge sites and measured physiological stress levels by quantifying the 70 kDa heat-shock protein as a biochemical stress index. N. canaliculata was less abundant and more stressed at its southern range edge than at the range center, suggesting that populations at the range edge may be most impacted by global climate change.