Taxonomic uncertainty of Stachytarpheta (Verbenaceae) in the Asia-Pacific and implications for invasive weed recognition and management

Stachytarpheta indica has been regarded as an agricultural weed occurring throughout south-east Asia. In Australia, it is classified as a prospective invasive weed by the Northern Australia Quarantine Strategy (Brown et al. 2008). After examining several papers from the 1990’s, we conclude that there is no evidence to support S. indica being in this region at all and that the name has been historically misapplied to several other species of Stachytarpheta. A table of characters is provided for four species of Stachytarpheta showing major character differences and highlights the confusion still surrounding some of the species. Additionally, Stachytarpheta cayennensis should be added to the flora of Christmas Island, while the taxonomic status of S. urticifolia needs to be examined in further detail.