Intersexual ‘Arms Race’ and the Evolution of the Sphragisin Pteronymia Butterflies

摘要

Sexual reproduction is often associated with intra- and intersexual conflict, especially in species where femalesmate multiple times. A strategy that has evolved in males to ensure offspring paternity is the ability to producea 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 thisstudy, we describe the sphragides of all sphragis-bearing species in Pteronymia, including the newly discoveredsphragides of P. alissa (Hewitson), P. andreas (Weeks), P. ozia (Hewitson), and P. zerlina (Hewitson). Threeadditional species, P. fulvimargo Butler & Druce, P. oneida (Hewitson), and P. ticida (Hewitson), are found tobear an irregular sphragis-like structure. We use molecular and morphological data from a recent study toconstruct 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 inPteronymia, whereas parsimony character optimization performed on a maximum likelihood tree suggestsonly 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 intersexualconflict, where females develop strategies to prevent male plugging.