Intra- and interspecific temporal mating patterns in Anastrepha fraterculus and Anastrepha obliqua fruit flies

Daily rhythms, such as mating times, play a key role in shaping insect behavior and are pivotal in prezygotic reproductive isolation and speciation. To investigate whether mating behavior follows a daily rhythm under natural light-dark cycles and controlled temperature conditions, we examined the mating times of two related agricultural pest species, Anastrepha fraterculus and Anastrepha obliqua. Our observations revealed distinct patterns in their daily copulatory activities. A. fraterculus shows a unimodal pattern, peaking in the morning, while A. obliqua displays a bimodal pattern, with mating occurring in both the morning and late afternoon, all statistically validated. In A. obliqua, the morning peak is more pronounced before the winter solstice, reversing afterward. These results highlight the adaptability of these fruit flies' biological clocks, allowing them to adjust mating timing according to seasonal environmental changes. Our findings also reveal how each species gauges environmental light-dark durations, even if annual variation is less pronounced in tropical regions, with twilight serving as a daily marker. The observed plasticity, including phase shifts in both species and amplitude changes in A. obliqua, emphasizes their synchronization with environmental cycles, which may explain the absence of specific pre-mating behaviors and the initiation of mating in low-light conditions, as seen in A. fraterculus. This study underscores the importance of biological rhythm plasticity in understanding fruit fly mating behavior, with implications for population management and ecological dynamics, and reinforces the need for 24-h observations to capture these rhythms fully.