MOLECULAR GENETIC ANALYSIS OF REMATING FREQUENCIES AND SPERM COMPETITION IN THE SCORPIONFLY PANORPA VULGARIS (IMHOFF- AND LABRAM)

Sperm competition can be a powerful selective force in the evolution of mating systems. The level of sperm competition depends on the remating frequency of females. Several scorpionfly species have been studied with respect to their mating systems. However, remating frequeneies and lifetime patterns of sperm usage are completely unknown. Members of the genus Panorpa (Panorpidae: Mecoptera) display a particularly interesting range of mating systems, and Panorpa vulgaris was selected for study. Remating frequencies of wildcaught females were estimated (a) by comparing sperm quantities in females caught early and late in the season with mean number of sperm transferred by males in one copulation, and (b) by polymorphic microsatellite loci. The paternity of offspring produced during the entire lifetime of females in the lab was determined using three polymorphic microsatellite loci. More than 1200 individuals, collected both from wild and from captivity-bred P. vulgaris, were typed for paternity analyses. Microsatellite typing as well as comparison of sperm quantities showed ( 1 ) that females mated with several males and (2) that the number of mates increased with progressive lifetime. Some females were observed in captivity during their entire lifetime and the complete mating activities were recorded. Analysis of their offspring showed that females allocate paternity in proportion to male eopulalion duration. Renialing and sperm mixing may allow females to gain "high quality" genes for their offspring when females adjust copulation duration to male quality.