The evolution of mating systems in black scavenger flies (Diptera: Sepsidae) [dissertation]

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Black scavenger flies are characterized by sexual behaviors that are very unusual in insects. The author studied two of the most remarkable elements of their mating systems: the timing of copulations immediately after an oviposition bout (post-oviposition matings) and the males’ escorting of ovipositing females. In a study of the patterns of sperm precedence in one sepsid species, the author found that the sepsids’ peculiar timing of matings is not associated with unusual patterns of sperm precedence: sepsid males displace rival sperm and achieve a large last male advantage, which is the most common outcome of sperm competition in insects. The potential significance of sperm transfer mechanisms for the sepsids’ timing of matings is discussed, and factors that may favor the maintenance of postoviposition matings in sepsid populations are considered. In a survey of sepsid mating patterns, the author found that post-oviposition matings are typical of many black scavenger flies and that mating systems characterized by the absence of copulations with gravid females may have arisen early in the family's evolutionary history. In several black scavenger flies, ovipositing females are commonly accompanied by an escorting male, and in all but one of the species studied, escorting is pre-copulatory. In several species, pronounced geographic variation in the expression of this trait was found. The author argues that sepsids share certain characteristics which may have facilitated multiple independent origins of escorting behavior. In order to investigate the adaptive significance of escorting, a comparative study was conducted of patterns of sexual size dimorphism and sex ratios at oviposition sites in conspecific populations that show great divergence in the expression of this trait. The results of this research support the pre-copulatory mate guarding hypothesis for the adaptive significance of escorting behavior, and they suggest that conspecific populations vary significantly in the degree or nature of sexual selection acting both on morphology and behavior of males. Furthermore, in a study of the genetic architecture of escorting behavior, the observed behavioral variation was found to have a genetic basis: the expression of escorting behavior is a quantitative trait with a significant sex-related component of inheritance.

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ELECTRONIC FILE - Zoology: Invertebrates

Citation (CSE style): Schulz KS. 1999. The evolution of mating systems in black scavenger flies (Diptera: Sepsidae) [dissertation]. [Tuscon (AZ)]: University of Arizona. 200 p.