Observing different mating tactics in the Japanese scorpionfly
Due to high competition and the prevalence of natural selection, many male insects have to develop alternative tactics to mate with a female. Weaker males who lose in a match (or loser males) may resort to hovering or prowling to find a mate. Recent studies have also shown that alternative mating behavior is influenced by environmental factors such as food availability, predation and population density. For example, scorpion flies, which are often used to study the mating behavior of insects, use three alternative mating tactics: feeding nutritive saliva, feeding and forced mating to get a mate. Male Japanese scorpion flies also practice feeding mating (i.e., mate while females feed without donating anything to them or releasing pheromones).
Previous studies on alternative mating tactics in scorpion flies have shown that the weaker males of closely related species use different methods of reproduction, but no research has been done on the alternative mating tactics of males within the same species from different geographic locations. To this end, Dr. Ryo Ishihara (affiliated with the School of Agriculture and a recipient of the Special Educational and Research Fellowship) and Professor Takahisa Miyatake (of the Faculty of Environmental and Life Science) of Okayama University, Japan, a study in the Journal of Ethology on June 15, 2022. This study describes the differences in alternative mating tactics of Japanese scorpion flies originating from two different places: Aichi and Okayama prefectures in Japan.
“A recent study of scorpion flies from Okayama reported their mating behavior and I noticed that the results were very different from those reported in previous studies on scorpion flies from Aichi. This piqued my curiosity and I wanted to find out if there were any real behavioral differences between the two regions, said Dr. Ishihara, who has a great interest in entomology.
The researchers observed mating behavior in a total of 25 males in Aichi and 30 males nearly 300 km away in Okayama, over a six-hour period in designated feeding areas. They noticed that one of the first behaviors in both populations was waiting for loser males.
Okayama’s loser males resorted to “sneaking” back to the feeding area, where they positioned themselves near the food offered by the winning male as a wedding gift and waited for another female to arrive. They would then offer the food as a wedding gift and attempt to mate with this female. Of the 28 loser males who use this tactic, 24 have mated successfully. On the other hand, 17 males ran away from among the scorpion flies in Aichi, seven were found “creeping” (although even these scorpion flies left after one or two failed mating attempts), and one attempted to mate vigorously with visiting females.
A significant number of reported male scorpion flies from the Aichi population, the researchers concluded, chose to leave the feeding area, while a majority of Okayama males preferred to “sneak” and try to mate again. It was also noticeable that the defeated males from Okayama waited longer than those from Aichi.
Why was this so?
“Well, there are certain factors that are thought to influence alternative mating in Japanese scorpion flies. One of them is the frequency and number of females visiting the feeding grounds,” explains Dr. Ishihara out. Females in Okayama appeared more often and in greater numbers in feeding areas. As a result, defeated males waited longer and used “creeping” tactics for successful mating with visiting females. The females in Aichi visited the feeding grounds less frequently, leading to defeated males seeking other feeding grounds, or resorting to vigorous mating attempts.
The findings in the wild were confirmed with laboratory experiments. From these results, the researchers concluded that there is also a genetic component that influences alternative mating and courtship habits.
dr. Emphasizing the importance of the study, Ishihara said: “This is the first example of two regionally distinct populations of the same scorpion fly species showing variations in alternative mating tactics. Our study can be used to evaluate long-term environmental indicators of habitat, strength and predict direction of sexual selection and identify early factors in the evolution of mating tactics.”
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Ryo Ishihara et al, Differences in mating tactics performed by males from two local populations of the Japanese scorpion fly Panorpa japonica, Journal of Ethology (2022). DOI: 10.1007/s10164-022-00753-2
Quote: Observation of different mating tactics in the Japanese scorpion fly (2022, June 27) retrieved June 27, 2022 from https://phys.org/news/2022-06-tactics-japanese-scorpionfly.html
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