Original URL: http://www.mpiz-koeln.mpg.de/~theissen/grouphome/phylogeny.html
Here you can see a simple tree of major taxa of vascular plants. The
time scale (in MYA, i.e. million years ago) given at the nodes of the tree
are rough (and in part controversal) estimations based on different studies.
The topology of the tree is also controversial: that Gnetales are more closely
related to conifers than to angiosperms could be concluded from some of our
studies on MADS-box genes
in these taxa (Winter et al. unpublished data),
but is in contrast to textbook interpretations of morphological data.
Three important stages in the evolution of the megasporangium are depicted
schematically at the left side of the root at the three lower internal
branches. From bottom to top: no integuments are covering the sporangium, a condition
still found in extant ferns; a sporangium surrounded by an integument
(ovule); and a sporangium covered by a carpel.
The gene names besides the branches denote gene subfamilies, not single genes.
These have been established at the latest during the time interval represented by the
respective branches of the phylogenetic tree. This could be
concluded from the presence of respective subfamily members in extant taxa.
For example, AG-, AGL2-, AGL6-, DEF/GLO-, GGM13- and TM3-like genes have
already been isolated from angiosperms and gymnosperms, but not from ferns. At
the root of the phylogenetic tree, the domain structure of a typical MIKC-type
MADS-box gene is shown. Our analyzes have demonstrated that the last common
ancestor of ferns and seed plants had already at least two genes of that
type.
Abbreviations of genes and gene subfamilies:
-AG: AGAMOUS
-AGL2,6,12,15,17: AGAMOUS-like gene No. 2,6,12,15,17
-CRM1,3,6,7: Ceratopteris richardii MADS-box gene No. 1,3,6,7
-DEF: DEFICIENS
-GGM4-7,10,13:
Gnetum gnemon MADS-box gene No. 4-7,10,13
-GLO: GLOBOSA
-SQUA: SQUAMOSA
-TM3,8: Tomato MADS-box gene No. 3,8
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