XVI International Botanical Congess
The last comprehensive revision of Acalypha was published in 1924, when Pax and Hoffmann reviewed this genus of ca. 450 species. Recent work demonstrates that while many species remain to be described, many existing names are synonyms. Furthermore, the subgeneric classification, based mostly on inflorescence position and sexuality, poorly reflects relationships. Two examples are presented. Population studies in western North American show that A. pringlei and A. stokesiae, which had been placed in two sections apart from A. californica, are synonyms of this species. The second example is that of the A. virginica group. Whereas Pax and Hoffmann recognized only a single species, subsequent studies demonstrate that five species exist in eastern North America, but raise questions about the relationships of the group to other Acalypha. Species-level and genus-wide studies are greatly needed.