Feeding by the plume moth <i>Amblyptilia punctidactyla</i> on seeds of the endangered herb <i>Primula sieboldii</i> in Iwate, northern Japan

<p>Abstract: Ongoing construction activities are impacting the Tokusagawa River, which runs through the cities of Takizawa and Morioka in Iwate Prefecture, Japan. To elucidate and mitigate the impacts, efforts are being made to investigate the distribution of the endangered herb Primula sieboldii, and to preserve strains of the plant originating from the construction area. Observations of P. sieboldii plants have revealed many instances of insects puncturing fruit to reach the seeds within; thus, in this study, we examined the effects of such feeding damage on seed production in the Tokusagawa population of P. sieboldii. Fewer than 20% of fruit were intact, with genet averages of 14% in 2020 and 18% in 2021; 29% of enlarged fruits were damaged by feeding in 2020, and 18% in 2021. In the neighbouring Shizukuishi population, 40% of fruit were intact in 2021 and 6% of enlarged fruits were damaged. This implies that the negative effects of feeding by herbivorous insects—an antagonistic biological interaction—may be more pronounced in the Tokusagawa population. We found several lepidopteran larvae consuming seeds inside fruits, and chrysalises around damaged fruits and peduncles. The insect was identified as the plume moth Amblyptilia punctidactyla. Feeding by A. punctidactyla fluctuated between genets and years; consequently, P. sieboldii from Tokusagawa may remain able to produce seeds and maintain genetic diversity. Although we do not yet see a need to implement urgent conservation measures, such as artificial pollination or bagging to protect fruit, it is important to continue monitoring seed production. Local ecosystems naturally include antagonistic interactions among organisms, and effective ecosystem conservation must reflect this. To this end, it is also important to recognise A. punctidactyla as a component of the local ecosystem along with P. sieboldii, and to continue monitoring the effects of ongoing environmental modification on both the species of the Tokusagawa area and their interactions.</p>