Data from: Body size evolution in an old insect order: no evidence for Cope’s Rule in spite of fitness benefits of large size

We integrate field data and phylogenetic comparative analyses to
investigate causes of body size evolution and stasis in an old insect
order: odonates (“dragonflies and damselflies”). Fossil evidence for
“Cope's Rule” in odonates is weak or non-existent since the last
major extinction event 65 million years ago, yet selection studies show
consistent positive selection for increased body size among adults. In
particular, we find that large males in natural populations of the banded
demoiselle (Calopteryx splendens) over several generations have consistent
fitness benefits both in terms of survival and mating success.
Additionally, there was no evidence for stabilizing or conflicting
selection between fitness components within the adult life-stage. This
lack of stabilizing selection during the adult life-stage was
independently supported by a literature survey on different male and
female fitness components from several odonate species. We did detect
several significant body size shifts among extant taxa using comparative
methods and a large new molecular phylogeny for odonates . We suggest that
the lack of Cope's rule in odonates results from conflicting
selection between fitness advantages of large adult size and costs of long
larval development. We also discuss competing explanations for body size
stasis in this insect group.