Ancestral sex-role plasticity facilitates the evolution of same-sex sexual behavior

Wasted Efforts Impair Random Search Efficiency and Reduce Choosiness in Mate-Pairing Termites

AbstractRandom search theories predict that animals employ movement patterns that optimize encounter rates with target resources. However, animals are not always able to achieve the best search strategy. Energy depletion, for example, limits searchers' movement activities, forcing them to adjust their behaviors before and after encounters. Here, we investigate the cost of mate search in a termite, Reticulitermes speratus, and reveal that the costs associated with mate finding reduce the selectivity of mating partners. After a dispersal flight, termites search for a mating partner with limited reserved energy. We found that their movement activity and diffusiveness progressively declined over extended mate search. Our data-based simulations qualitatively confirmed that the reduced movement diffusiveness decreased the searching efficiency. Also, prolonged search periods reduced survival rate and the number of offspring. Thus, mate search has two different negative effects on termites. Finally, we found that termites with an extended mate search reduced the selectivity of mating partners, where males immediately paired with any encountering females. Thus, termites dramatically changed their mate search behavior depending on their internal states. Our finding highlights that accounting for the searchers' internal states is essential to fill the gap between random search theories and empirical behavioral observations.

The significance of social interactions in synchronized swarming flight in a termite

In social insects, individuals of working caste coordinate their actions to manage various collective tasks. Such collective behaviours exist not only in workers but also in winged reproductives (alates). During certain seasons, newly emerged alates fly from the nest to disperse and find mating partners in a synchronized manner. This 'swarming' behaviour is one of the collective behaviours that involve the greatest number of individuals in social insects. However, such synchronization is considered to be caused by the response to specific environmental cues rather than behavioural coordination among colony members. Here, we show that a termite Reticulitermes kanmonensis shows synchronized dispersal flight among alates within the same colony even under the constant temperature environment. Under the semi-field environment with fluctuating temperatures, alates within the same colony synchronized their dispersal flight under higher temperatures, while flight was suppressed under lower temperatures. We observed that termites synchronized their dispersal flights even under constant temperature conditions in the laboratory (20℃), indicating that environmental cues are not always necessary for synchronization. In either case, higher synchronization happened with a larger number of alates. These results suggest that social factors interplay with environmental cues to enable the synchronized swarming flight of social insects.

Extinct and extant termites reveal the fidelity of behavior fossilization in amber

Fossils encompassing multiple individuals provide rare direct evidence of behavioral interactions among extinct organisms. However, the fossilization process can alter the spatial relationship between individuals and hinder behavioral reconstruction. Here, we report a Baltic amber inclusion preserving a female-male pair of the extinct termite species Electrotermes affinis. The head-to-abdomen contact in the fossilized pair resembles the tandem courtship behavior of extant termites, although their parallel body alignment differs from the linear alignment typical of tandem runs. To solve this inconsistency, we simulated the first stage of amber formation, the immobilization of captured organisms, by exposing living termite tandems to sticky surfaces. We found that the posture of the fossilized pair matches trapped tandems and differs from untrapped tandems. Thus, the fossilized pair likely is a tandem running pair, representing the direct evidence of the mating behavior of extinct termites. Furthermore, by comparing the postures of partners on a sticky surface and in the amber inclusion, we estimated that the male likely performed the leader role in the fossilized tandem. Our results demonstrate that past behavioral interactions can be reconstructed despite the spatial distortion of body poses during fossilization. Our taphonomic approach demonstrates how certain behaviors can be inferred from fossil occurrences.