A role for copula duration in fertility of Queensland fruit fly females mated by irradiated and unirradiated males

Females of many tephritid fruit flies can mate more than once, and can store ejaculates from multiple males. As well as being an important element of reproductive biology, multiple mating by females is of particular relevance for sterile insect technique programs used to control major tephritid pests. Here we investigate the consequences of multiple mating on fertility of Queensland fruit fly (Bactrocera tryoni) females sequentially mated to irradiated ('sterile') and unirradiated ('normal') males. Females mated by two normal males showed persistent high fertility whereas females mated by two sterile males showed persistent low fertility. Despite lack of association between copula duration and sperm number, fertility of females mated to a normal and then a sterile male increased with duration of the first copulation and decreased with duration of the second. Fertility of females mated to a sterile male and then a normal male was not influenced by duration of the first copulation but increased with duration of the second. These findings reveal a need for increased attention to how factors other than sperm number influence post-copulatory sexual selection in tephritid flies, and in particular how copula duration is linked to sperm storage and usage.