Was Myriophyllum spicatum L. (Haloragaceae) recently introduced to South Africa from Eurasia?

- Controversial status of Myriophyllum spicatum in southern Africa, native or exotic.
- Populations sampled across South Africa as well as Eurasia for two genetic markers.
- Genetic analysis suggests long term isolation rather than recent introduction.
- Myriophyllum spicatum is likely a native component of the southern African flora.

There is debate over the native or exotic status of Myriophyllum spicatum L. (Haloragaceae) in South Africa, which has important implications for developing and implementing management strategies. The aim of this study was to determine if M. spicatum was recently introduced from Eurasia by reconstructing the genetic relationships between South African and Eurasian M. spicatum using both a nuclear ribosomal (ITS1-5.8S-ITS2-26S) and a chloroplast intron (trnQ-rps16) sequence from 40 populations. For both these DNA markers, the South African populations were distinct from Eurasian populations, but always stemmed from a European origin. The data suggest that South African and European M. spicatum share a common ancestor, however the divergence of both markers are characteristic of a long period of isolation rather than a recent introduction from Europe. The genetic data from this study suggest that M. spicatum has not been introduced recently, but is most likely a native component of the South African flora.