Variation in Australian and some overseas populations of Emex australis and E. spinosa.

Australian populations of the widespread Emex australis and the more restricted E. spinosa were tested for subspecific variation. The plants were grown for two generations in a glasshouse from seed collected from field populations. The results from growing the first generation showed that two groupings of E. australis could be made on the basis of hierarchical grouping analysis, but the populations were much more similar in the second generation and such groupings could not be made. There were no marked differences between E. australis populations from Australia and South Africa, although one from Hawaii was less vigorous than the others. Amongst Australian populations of E. spinosa, one from Western Australia was less vigorous than the others. It was also found that Australian populations of E. spinosa were generally similar to those from Portugal and slightly more vigorous than those from Morocco.