Circadian rhythm and time of mating in Bactrocera cucurbitae (Diptera: Tephritidae) selected for age at reproduction.

Chrono-biological traits were changed by selecting for life-history traits via a genetic linkage controlling both time-related behavioural and life-history traits. Behavioural traits were compared between lines selected for young (Y-lines) and old (O-lines) age at reproduction in the melon fly, Bactrocera cucurbitae (Coquillett). Adults from O-lines, which survive longer than flies from Y-lines, mated later in the day and had a longer period of circadian rhythm in the locomotor activity than those from Y-lines. Flies from F(1) reciprocal crosses had an intermediate time of mating and periods of circadian rhythm between that of the parents, indicating a genetic basis to these traits. The presence of these behavioural differences across the selection lines indicates that chrono-biological traits exhibit correlated responses to selection on age at reproduction. The correlated responses in the behavioural traits to selection for life-history traits are discussed from two points of view: pleiotropy and inadvertent selection.