New Extended Thesis of Areole Development

None of the known interpretations of areole development is capable of giving a complete and logical explanation of the specific and pronounced areole development of the genus Coryphantha. A phylogenetic analysis of areole development shows that the oldest taxa (e.g. Ferocactus) produce only very short grooves close to the spiniferous areole, while the somewhat younger Macromeres make shortened grooves which are not transient to the axil. In addition, the Protocoryphanthae (C. poselgeriana, C. robustispina) go through a very long phase with incomplete grooves and in the youngest taxa only the groove develops very fast from the spiniferous areole to the axil, either in two phases (Escobaria type) or in one phase (Protomammillaria and Ortegocactus type). The individual development (ontogenesis) from the juvenile type to the "two-parted" areole, therefore, reflects the phylogenesis, recapitulating the evolutionary history.

The thesis, which Friedrich postulated as a consequence of his analysis of the Protomammillaria areole type (Coryphantha clavata), can be applied to all areole types within the Mammillaria phylad (mainly the two genera Coryphantha and Mammillaria), but it needs to be extended, since it originates from observations of Coryphantha clavata only.

The separation of peripheral spination from protected flowers positioned inside makes sense ecologically and the transfer of the flowers from the areole to the axils can be understood phylogenetically. According to Friedrich's interpretation, there is no major difference between the Coryphantha and the Mammillaria axil; both are homologous organs,however,the Mammillaria type is definitely the more advanced type, because it completes the transposition of the flower to the axil in the most perfect way.

To describe the organs of the areole, or the podarium, of the genus Coryphantha like the groove on the tubercle surface, the nectary glands in the grooves and axils, but also the trichomes, a continuous meristematic tissue from the spiniferous areole to the axil must be postulated with an axillopetal direction of development and formation of buds in serial sequence. Facing the progression of groove prolongation, such a continuous meristem can easily be inferred for the whole genus and can be confirmed either phylogenetically or ontogenetically.

Finally, at the highest stage of development, the Mammillaria areole type, the areole meristem is most differentiated and completely reduced except for the formation of a spine areole and a flower base in the axil. Only here, the possible formation of shoots is transferred from near the spiniferous areole to the axil and the axillary flower base becomes active only after spine growth has been terminated.

Friedrich's extended thesis leads to a new interpretation of Zimmerman's areole theory within the Mammillaria phylad, which, following our own observations, must be complemented by a further areole type already mentioned: the Protocoryphantha type.

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