As indicated above, Viscum has speciated to its greatest extent in Africa, which has 45 species, with a further 30 in Madagascar. The African species have been revised recently by Polhill and Wiens (1998). They can be divided provisionally into eleven groups. The more obvious characters on which the species have been recognised for floristic purposes are shown in Table 4 and a data matrix for the species and these characters are given in Table 5. A more rigorous evolutionary investigation would no doubt reveal new characters, but even a preliminary assessment may be helpful in giving some idea of the radiation of the genus over the continent. Much insight is provided by chromosomal features. A considerable coverage of basic information has been achieved, but there are still substantial gaps in the total number of species examined and more significantly in detailed comparison of the karyotypes needed to score characters for evolutionary analysis. The biological characters of sex distribution within populations and host specificity have also been omitted.
The other data has been analysed using the computer program Hennig86 (Farris 1989). Owing to the time that would have been required to run the analysis using empirical methods, faster, hueristic algorithms were employed instead. These algorithms estimate a minimal length tree by a single pass through the data, the branches of that
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