Data from: Anatomy of a cline: dissecting anti-predatory adaptations in a marine gastropod along the U.S. Atlantic coast

The scope of anti-predatory adaptation is expected to be greater in warm
than in cold environments. High temperatures lower the costs associated
with the production and maintenance of energetically expensive traits and
enable ecological interactions to intensify. We tested this hypothesis by
characterizing the expression of anti-predatory morphology within a marine
gastropod species (the knobbed whelk, Busycon carica) over a large
(>1,400 km) geographic area that spans more than 10°C annual
temperature variation. We also conducted experimental predation studies
with a powerful durophagous predator, the stone crab (Menippe), to verify
the anti-predatory advantages of a heavily ornamented shell morphology
(e.g., increased thickness, pronounced spines), and we used repair scar
data to assess clinal variation in selective pressure from predators. We
predicted that repair scar rates would be greatest in warm southernmost
latitudes, and that expression of energetically costly anti-predatory
morphology would peak in concert with elevated predation pressures.
Experiments confirmed that whelks with energetically costly, heavily
ornamented shells had higher survivorship rates than those with weakly
ornamented shells. As predicted, we also found that the expression of
anti-predatory traits was greatest in the southern part of B. carica’s
range. After standardizing shells for size, shape, and exposure time to
enemies, repair scar rates also peaked to the south. Taken together, these
results suggest that the expression of anti-predatory traits along the
geographic cline is governed by the interaction of two selective factors:
temperature and predation, with the former acting as the ultimate control
on the scope of adaptation both by escalating predation pressure in the
southern part of B. carica’s range and by physically limiting (to the
north) and facilitating (to the south) the production of anti-predatory
traits. Feedbacks between temperature and predation thus causally interact
to enable and drive, respectively, the observed geographic cline in
energy-intensive anti-predatory shell traits.