2021 年 72 巻 3 号 p. 293-300
The reproductive interference between an invasive alien species, Veronica anagallis-aquatica L., and a native congener, V. undulata Wallich (Plantaginaceae) at the initial stage of invasion by V. anagallisaquatica, is reported. Insect pollinators, interspecific pollen transfer, and seed set rate of the two species were investigated at a site where V. undulata was still dominant. Four and two Dipteran species were observed to visit the flowers of V. undulata and V. anagallis-aquatica, respectively. Two species of Syrphidae (hover flies) were shared by them as pollinators. Pollen transfer from V. undulata to V. anagallisaquatica was observed, but transfer in the reverse direction was not detected. The lower rate of seed set in V. anagallis-aquatica is suggested to have been due to reproductive interference from V. undulata and represents a case of frequency-dependent reproductive interference of two congeneric species at the initial stage of invasion of an alien species into the population of a dominant native species.
