Abstract
Adaptive evolution relies on both heritable variation and selection. Variation
is the raw material upon which selection acts, so any mechanism that limits
or prevents the generation of heritable variation reduces the power of
selection to lead to adaptation. Such limitations are termed evolutionary
constraints. While it is widely accepted that constraints play an important
role in shaping evolutionary outcomes, their relative importance, as opposed
to adaptation, in determining evolutionary outcomes remains a subject of
debate. Evolutionary constraints are often evoked as the reason behind the
persistence of inaccurate mimicry. Here, we compared the variation and
accuracy of body-shape mimicry in ant-mimicking spiders with that of
ant-mimicking insects, predicting greater constraints, and hence inaccuracy,
in spiders mimicking ants, due to their evolutionary distance from the ant
model. We found high inter-species variation in mimetic accuracy, but dorsally,
no overall difference in mimetic accuracy between spider and insect
mimics, which is inconsistent with a constraint causing inaccurate mimicry.
Our study provides empirical evidence suggesting that imperfect mimicry in
spiders and insects is predominantly shaped by adaptive processes rather
than constraints or chance. Our findings contribute to our understanding
of the mechanisms underlying evolutionary diversity and the processes
that shape phenotypic outcomes.
Funder
Australian Research Council