Taxus baccata L.

Molecular Analysis of Phylogenetic Relationships among Myrmecophytic Macaranga Species (Euphorbiaceae)

Plastid matK and a fragment of the low-copy nuclear gene PHYC were sequenced for 30 genera of Phyllanthaceae to evaluate tribal and generic delimitation. Resolution and bootstrap percentages obtained with matK are higher than that of PHYC, but both regions show nearly identical phylogenetic patterns. Phylogenetic relationships inferred from the independent and combined data are congruent and differ from previous, morphology-based classifications but are highly concordant with those of the plastid gene rbcL previously published. Phyllanthaceae is monophyletic and gives rise to two well-resolved clades (T and F) that could be recognized as subfamilies. DNA sequence data for Keayodendron and Zimmermanniopsis are presented for the first time. Keayodendron is misplaced in tribe Phyllantheae and belongs to the Bridelia alliance. Zimmermanniopsis is sister to Zimmermannia. Phyllanthus and Cleistanthus are paraphyletic. Savia and Phyllanthus subgenus Kirganelia are not monophyletic.

/pdf/molecular-phylogenetics-of-phyllanthaceae-evidence-from-ft1vrk4mcp.pdf

Molecular phylogenetics of Phyllanthaceae: evidence from plastid MATK and nuclear PHYC sequences

Phylogenetic relationships within tribe Phyllantheae, the largest tribe of the family Phyllanthaceae, were examined with special emphasis on the large genus Phyllanthus. Nuclear ribosomal ITS and plastid matK DNA sequence data for 95 species of tribe Phyllantheae, including representatives of all subgenera of Phyllanthus (except Cyclanthera) and several hitherto unplaced infrageneric groups, were analyzed. Results for ITS and matK are generally concordant, although some species are placed differently in the plastid and ITS trees, indicating that hybridization/paralogy is involved. Results confirm paraphyly of Phyllanthus in its traditional circumscription with embedded Breynia, Glochidion, Reverchonia, and Sauropus. We favor the inclusion of the embedded taxa in Phyllanthus over further generic segregation. Monophyletic Phyllanthus comprises an estimated 1269 species, making it one of the "giant" genera. Phyllanthus maderaspatensis is sister to all other species of Phyllanthus, and the genus appears to be of paleotropical origin. Subgenera Isocladus, Kirganelia, and Phyllanthus are polyphyletic, whereas other subgenera appear to be monophyletic. Monotypic Reverchonia is sister to P. abnormis, arborescent section Emblica to herbaceous Urinaria, free-floating aquatic P. fluitans to the weed P. caroliniensis, and the phyllocladous section Choretropsis to the delicate leafy P. claussenii. The unique branching architecture known as "phyllanthoid branching" found in most Phyllanthus taxa has been lost (and/or has been derived) repeatedly. Taxonomic divisions within Phyllantheae based on similar pollen morphology are confirmed, and related taxa share similar distributions. We recommend recognition of six clades at generic level: Flueggea s.l. (including Richeriella), Lingelsheimia, Margaritaria, Phyllanthus s.l. (including Breynia, Glochidion, Reverchonia, and Sauropus), P. diandrus, and Savia section Heterosavia.

Phylogenetics of tribe Phyllantheae (Phyllanthaceae; Euphorbiaceae sensu lato) based on nrITS and plastid matK DNA sequence data

SUMMARY

1
The morphology of the female conifer cones has long been a matter of dispute. In 1900 an account of the theories put forward so far was given by Worsdell. After a brief characterization of the situation at that time, the present article deals with the later history of the subject.

2
At the turn of the century there were rivalling concepts of the nature of the so-called ovuliferous scale in the conifers: (a) the Excrescence or Ligular theory of Sachs-Eichler, (b) the general Brachyblast theory of Braun, Caspary, celakovský and others, (c) van Tieghem's modification of the Brachyblast theory, and (d) the Foliolar theory of Delpino-Penzig.

3
In the subsequent three decades the discussion proceeded on the same or similar lines. The Excrescence theory retained a strong position until the end of the nineteen-twenties, but, as before, some morphologists professed the general Brachyblast theory. Herzfeld and Wettstein considered that the axillary conifer strobilus had one or more reduced carpels (megasporophylls) which were used up in the formation of terminal ovules, as well as an ‘ovuliferous scale’ consisting of secondary outgrowths from the strobilar axis. In Goebeľs opinion these outgrowths were instead produced by the megasporophylls. Doubts were expressed of the unity of the true conifer group, but Eames showed that the apparently widely different female cones of the Pinaceae and Araucariaceae are homologous, and that the Araucariaceae, Taxodiaceae and Podocarpaceae exhibit complete transitions by fusion and reduction from types with distinctly compound strobilar units–each with an ‘ovuliferous scale’ in the axil of a bract–to others of the most simple form. In contradistinction to the true conifers, the genus Taxus has no compound strobilus, and its ovule is a direct continuation of the axis of the fertile short shoot (Dupler).

4
In the first half of the period after 1930 opinions differed as much as ever, although the general Brachyblast theory now prevailed over the Excrescence theory and other concepts. Chadefaud believed the ‘ovuliferous scale’ and the bract to represent between them a carpel derived from a prototype analogous to the pinnate megasporophyll of Cycas. Hirmer interpreted the ‘ovuliferous scale’ and the bract as formed by a serial splitting of one single member. Lanfer supported Goebeľs views of the terminal position of the conifer ovules on reduced megasporophylls, and of the nature of the ‘ovuliferous scale’. In Hagerup's opinion the female cones of most true conifers are compound and have a short secondary axis developed axillary to each bract. This axis was supposed to carry two transversal prophylls, fertile (megasporangial) or sterile, and a varying number of sterile leaves; and the megasporophyll, with a megasporangium on its upper side, to constitute the integument of the ovule, and be homologous to a lycopod sporophyll.

5
Florin (1938-45) found that the Palaeozoic cordaites and conifers furnished the principal clue to the interpretation of the true conifer cones of Mesozoic and more recent age. Primarily, the fertile seed-scale complex in the axil of each bract was a radially symmetrical short shoot (strobilus) with several sterile scales and one to a few uniovulate megasporophylls; the ovules were terminal in position. The later types of cones have arisen by the reduction and transformation of this primitive organization, which in the majority of cases has differentiated the strobilus into a proximal fertile part facing the cone axis and a distal sterile part (‘ovuliferous scale’), while its anterior sector facing the bract became totally suppressed. Exceptionally, no ‘ovuliferous scale’ at all was developed, and the strobilus became wholly fertile. The ovular integument is a continuation of the megasporophyll, and appears to arise out of two transversal primordia at its apex. The taxads differ from the true conifers by their simple strobili being placed axillary on reduced vegetative shoots. Their ovules are seated terminally on the strobilar axis itself; megasporophylls are accordingly absent. The living and extinct genera which have previously as a rule been considered coniferous represent therefore two separate subdivisions of the gymnosperms–the true conifers, and the taxads.

6
Earlier concepts of the morphology of the female cones of the conifers, and of the nature of the integument of their ovules, are in part or wholly untenable.

F. Pax

Papers

Euphorbiaceae-Acalypheae-Mercurialinae

Grundzüge der Pflanzenverbreitung in den Karpathen

Euphorbiaceae - Phyllanthoideae - Phyllantheae

Die Tierwelt Schlesiens

Euphorbiaceae-Acalypheae-Chrozophorinae