First records of non-native species Callitriche deflexa (Plantaginaceae), which was previously misidentified as C. terrestris in Japan

Abstract

The cosmopolitan genus Callitriche (Plantaginaceae) is a clade of small herbaceous plants that encompasses terrestrial and aquatic species. In Japan, six Callitriche species have been identified: four native and two naturalised species. Callitriche terrestris, a naturalised terrestrial species, was first reported in 1984 in Kanagawa Prefecture and it is thriving today.We report the presence of a new naturalised terrestrial species, Callitriche deflexa, which has been previously misidentified as C. terrestris because of its similar morphology. Callitriche deflexa can be distinguished from C. terrestris through genetic differences and distinct morphological traits, such as longer pedicels. Re-examination of herbarium specimens in the Kanagawa Prefectural Museum of Natural History confirmed that most of the specimens labelled as C. terrestris, including voucher specimens from the original report, were indeed C. terrestris, but a few were C. deflexa. We also noted that the plants referred to as “C. terrestris” in our previous developmental studies should be corrected to C. deflexa.

Keywords

• <i>Callitriche deflexa</i>
• <i>Callitriche terrest