Systematics and floral evolution in the order Fabales are addressed through ontogeny, developmental genetics and phylogeny. The Fabales hypothesis (Leguminosae, Polygalaceae, Quillajaceae, Surianaceae) has recently emerged from angiosperm molecular phylogenies. Despite good support for the order, interfamilial relationships are contradictory. Employing parsimony and Bayesian approaches, plastid regions (rbcL, matK) were used to infer interfamilial relationships in Fabales. Five alternative hypotheses were recovered. The Shomodaira-Hasegawa test shows higher probability for a resolved interfamilial topology rather than a hard polytomy scenario. Dating of selected clades using penalized likelihood, indicates rapid radiation of the Leguminosae, Polygalaceae and (Quillajaceae + Surianaceae) crown clades. The actinomorphic Quillajaceae and Surianaceae differ in their reproductive- whorl development, Quillaja more closely resembling Leguminosae in this respect. The origin of the highly. characteristic petaloid lateral sepals in Polygalaceae involves integration of the bracteoles to the flower and reduction or loss of the lateral petals. In taxa where the bracteoles are absent, the lateral sepals are not petaloid and resemble other calyx members. Petaloid lateral sepals are petals (by behaviour) and sepals (by position). Evolution of the petaloid sepals involves the bracteole-wing-lateral petal module, which evolved once in the family. This module is here regarded as a morphological noveltylkey innovation. Inclusion of morphology in cladistic analyses of Fabales contributes significantly to the resolution and support of the interfamilial relationships. Combined phylogenetic analyses suggest more confidently (Polygalaceae (Leguminosae (Quillajaceae+Surianaceae ))) as the preferred hypothesis. In species of Polygalaceae with petaloid sepals, expression patterns of the AP3/DEF and PI/GLG (petal and stamen-identity genes) differ; whereas the former is expressed in several floral and vegetative tissues, the latter is restricted to petals, stamens, and in low levels in sepals and early petaloid sepals. Despite the expression of B-genes in early petaloid sepals, it is not possible to associate the identity of the petaloid sepals with these expression patterns; the petaloid sepals show similar expression patterns to sepals. Putative alternative splicing in B-gene transcripts in Polygalaceae was found. Phylogenetic diversification patterns of B-class genes do not fit expectations from different models previously suggested to explain the petaloid identity of the first-whorl organs. Instead, it appears that floral organs, including the petaloid sepals, have recruited different B-gene copies independently. A putative gen0!lle duplication - evidenced by major diversification events of AP 3/DEF and P I/GLO homologs - could be coincident with or have preceded the origin of petaloid sepals and all the morphological changes implied.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:553114 |
| Date | January 2008 |
| Creators | Gutierrez, Maria Angelica Bello |
| Publisher | University of Reading |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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