Data from: Intersexual 'arms race' and the evolution of the sphragis in Pteronymia butterflies

Sexual reproduction is often associated with intra- and intersexual
conflict, especially in species where females mate multiple times. A
strategy that has evolved in males to ensure offspring paternity is the
ability to produce a complex, external mating plug called a sphragis. The
sphragis has been found in 273 butterfly species; however, little is known
about the sphragides of the butterflies in the nymphalid genus Pteronymia.
In this study, we describe the sphragides of all sphragis-bearing species
in Pteronymia, including the newly discovered sphragides of P. alissa
(Hewitson), P. andreas (Weeks), P. ozia (Hewitson), and P. zerlina
(Hewitson). Three additional species, P. fulvimargo Butler &
Druce, P. oneida (Hewitson), and P. ticida (Hewitson), are found to bear
an irregular sphragis-like structure. We use molecular and morphological
data from a recent study to construct a phylogeny of species in the genus
and examine the number of independent origins of the sphragis. Our
ancestral state reconstruction using Bayesian inference suggests that the
sphragis evolved three times in Pteronymia, whereas parsimony character
optimization performed on a maximum likelihood tree suggests only one
origin of this structure. Our data on ancestral state patterns, frequency
of incomplete sphragides, and morphology of female external genitalia
suggest that sphragis-bearing Pteronymia may be in active intersexual
conflict, where females develop strategies to prevent male plugging.