Relationship within the Centrospermae

As discussed above, a convincing phylogenetic analysis of the Centrospermae is still hardly possible. The monophyly of several families is at least doubtful (see Carolin 1983; Brown and Varadarajan 1985; Rogers 1985; Carolin 1987; Bittrich and Hartmann 1988; Hershkovitz 1989; and contributions in this Volume). This applies to the

  • Amaranthaceae and Chenopodiaceae (unclear delimitation of both families, especially with regard to tribe Polycnemeae);
  • Molluginaceae (characterized by ancestral characters only);
  • Nyctaginaceae (lack of synapomorphies and uncertain relationship with monocarpellate Phytolaccaceae);
  • Phytolaccaceae (lack of synapomorphies and inclusion of some poorly known genera of uncertain affinity); and
  • Portulacaceae (possibly paraphyletic due to exclusion of Basellaceae, Didiereaceae, Hectorellaceae, and perhaps even Cactaceae).

Of the larger families the Cactaceae seem to be best supported as a monophyletic taxon. The uncertainties concerning the naturalness of most families should be kept in mind when reading any scheme of intraordinal relationships of Centrospermae. The scheme presented here (Fig. 1) is not intended to be a cladogram but rather to express relationships of the families in their present circumscription, as far as evidence is available (see contributions in this Volume).

For a long time the Phytolaccaceae were assumed to be the basal taxon within the order. However, apart from their specialized gynoecium morphology and presence of betalains, this is not even supported by their advancement index (Sporne 1980) (50 in contrast to 37 in Molluginaceae, and 45 in Aizoaceae). The Caryophyllaceae and Molluginaceae are probably basal branches of the Centrospermae (Reznik 1955; Ehrendorfer 1976). Recently, Behnke et al.

Didiereaceae Basellaceae Hectorellaceae

Didiereaceae Basellaceae Hectorellaceae

Cladogram For Molluginaceae
Fig.1. Presumed phylogenetic relationships among families of Centrospermae

(1983) claimed a "central position" not only for the Molluginaceae but even for a particular genus, Ma-carthuria. They argued that "the multiple intertwine-ment of different genera of the Molluginaceae with many other centrospermous families" supports the hypothesis of the basal position of this family. However, one must not forget that the monophyly of the Molluginaceae is still dubious (Gilbert 1987). It should also be borne in mind that many of these "in-tertwinements" that can be similarly demonstrated for the Aizoaceae are in fact simple parallelisms, which are certainly not rare in the Centrospermae.

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  • peter
    How many families in centrospermae?
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    How many orders in centrospermae?
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