The phylogeny and geography of Myrceugenia (Myrtaceae)

Myrceugenia is a mainly temperate South American genus with two species on the Juan Fernández Islands, 12 in central and southern Chile and adjacent Argentina, and 25 in the highlands of southeastern Brazil and adjacent regions. The continental populations are separated by about 1000 km. Numerical cladistic procedures based on the criteria of parsimony, compatible characters and a combination of compatible characters and character correlation are used to deduce hypothetical phylogenetic undirected trees. These indicate that 3–8 groups of species bridge the continent of South America. An explanation of how the distribution of the genus could have come about is given based on: 1) the above mentioned numerical analyses, 2) the ecology of the species, 3) the distribution of other plant genera, and 4) theories of the geologic and climatic history of southern South America. Myrceugenia is hypothesized to have grown continuously across South America during the early Tertiary and to have become divided into eastern and western populations probably during the Miocene.