Plant architecture: a dynamic, multilevel and comprehensive approach to plant form, structure and ontogeny

A large collaborative effort has yiel(led a comprehensive study of the phylogeny and a new suhfanilial classification of the grass family (Poaceae/Graminieae). The stu(ly was (con(luc(ted on an integratedl andl representative set of 62 grasses (0.6% of the species and ca. 8% of the genera) plus four outgroup taxa using six molecular sequence (lata sets ({ndhFl, rbcL, rpoC2, phyB, ITS2, and (;BSSI or waxy), chloroplast restriction site (lata, and( morphological idata. A parsimony analysis using 2143 informative characters (the comblined analysis) resulted in a single most parsimonious tree of 8752 steps with an RI of 0.556 and bootstrap support of > 90% for more than half of the internal no(les. Significant relationships that appear consistently in all analyses of all (lata sets and are strongly supported by the combined analysis include the following: Joinvilleaceae are sister to a monophyletic Poaceae; the earliest (liverging lineages of the Poaceae are Anomochlooideae, Pharoideae, and Puelioideae, respectively; and( all remaining grasses form a clade. Multiple monophyletic clades were recovere(, including Bambusoideae s. str., Ehrhartoideae, Pooideae s.l., Aristidoideae, l)anthonioideae, Chloridoideae s. str., Chloridoideae s.l., Panicoideae, Parianeae, Olyreae s. str., Oryzeae, Stipeae, Meliceae, Lygeum + Nardus, and Molinia + Phragmites. 'The PACCAI) Clade is monophyletic, containing Aristidoideae, Danthonioideae, Arundinoideae s. str., Chloridoideae s.l., Centothecoideae, Panicoideae, Eriachne, Micraira, and Gynerium. Based on the phylogeny, a classification of 11 previously published subfamilies (Anomochlooideae, Pharoideae, Puelioideae, Bambusoideae, Ehrhartoideae, Pooideae, Aristidoideae, Arundinoideae, Chloridoideae, Centothecoideae, and Panicoideae) and 1 new subfamily (Danthonioideae) is proposed. Several changes in the circumscription of traditionally recognized subfamilies are included. Previous phylogenetic work and classifications are reviewed in relation to this classification and circumscription, and major characteristics of each subfamily are discussed and described. The matrix, trees, and updated data matrix are available at (http://www.virtualherbarium.org/grass/gpwg/ default.htm).

Phylogeny and subfamilial classification of the grasses (Poaceae)

This paper introduces an integrated system of morphological concepts for gymnosperm fructifications, which does not lean upon any system existing for other higher plants. Comparative analytical treatment of all available characters of the most thoroughly studied fossil genera provided the foundation for an ordered ranking of congregations, each unit being assigned to the status of families, orders and classes. The transformation of the generative and vegetative organs has been traced along various phylogenetic branches. A new large phylogenetic branch (class Ginkgoopsida), beginning with the Lower Carboniferous Calamopityales, has been established. The lineage evolved from this order to Callistophytales and further to Peltaspermales. The family Peltaspermaceae encompasses, among others, plant types formerly regarded as ginkgoaleans. The orders Ginkgoales, Leptostrobales (Czekanowskiales) and Caytoniales evolved from the Peltaspermales. The order Arberiales (glossopterids) evidently evolved from the Calamopityales. In the lineage from Calamopityales to Ginkgoales a common seed type is conserved (platyspermic, non-cupular with two vascular bundles in the integument). Radiospermic seeds are conserved in the class Cycadopsida. In the lineage from Lagenostomales to Trigonocarpales the radially symmetrical cupule underwent modification into an integument of the same type of symmetry. The earliest Lagenostomales with the bilaterally symmetrical cupule evolved into the Cordaitanthales, where the cupule, also undergoing modification, was transformed into a bilaterally-symmetrical integument. In Cordaitanthales and their descendents the Pinales the seeds became secondarily platyspermic (in contrast to the primary non-cupular and primary platyspermic seeds in Ginkgoopsida); their vascularization was progressively reduced. These two orders are grouped into the class Pinopsida. It is believed that angiosperm seeds are in effect radiospermic with a radial cupule, their vascularization also being progressively reduced. If this holds true, the angiosperm ancestry should be sought in the class Cycadopsida. The Caytoniales, Arberiales, Peltaspermales, Leptostrobales and other orders of the class Ginkgoopsida should be excluded from the stock of probable angiosperm ancestors. A new gymnosperm phylogeny has been proposed and the evolution of the phylogenetic branches outlined in terms of the phytochoria system of the geological past. The basic evolutionary innovations took place within the Equatorial Belt and adjacent ecotone areas. Three types of processes, often underrated, have a paramount role in gymnosperm phylogeny. They are defined as follows: (1) homoeotic transformations of organs; corresponding to them are heterotopies, in the morphological aspect, and saltations, in the evolutionary sense; (2) dedifferentiation of the organs (the shift of one ontogenetic program onto various organs); (3) transitive polymorphism (conservation in diversity of a certain organ during phylogeny). These processes probably serve to indicate that rearrangement in the functions of the regulatory genes played an important role in the evolution of gymnosperms.

Basic features of gymnosperm systematics and phylogeny as evidenced by the fossil record

Contents

Summary  25

I. Introduction 28
II. Background 27
III. Asparagales 28
IV. Commelinids: ZHC clade 29
V. Commelinids: Poales 32
VI. Conceptual transitions among floral forms revisited 34
VII. Examples from monocot flowers 37
VIII. Specific cases of ontogenetic transitions between contrasting floral morphs 39
IX. Conclusions 40

Acknowledgements 42


References 42



Summary
Here we explore morphological transitions among monocot flowers and discuss them in terms of modification of existing structures. Monocot flowers are typically arranged in five whorls (carpels, inner and outer stamens, inner and outer tepals), and are radially symmetrical, constructed around a 3-fold axis of rotational symmetry that delineates three planes of bilateral symmetry. Differential development of one or two of the three organs within a whorl inevitably emphasizes one plane of symmetry, by eliminating the other planes, rendering the whorl zygomorphic. Zygomorphy (monosymmetry) has evolved more than once in monocotyledons. Stamen suppression is a widespread aspect of zygomorphy and conforms to two broad categories of pattern. In the more frequent Pattern 1, 1–3(−5) adaxial stamens (both inner and outer) are either reduced in size or entirely suppressed. Pattern 2 involves loss, reduction or modification of at least the outer abaxial stamen. Pattern 2 often characterizes groups that are phylogenetically embedded within Pattern 1 clades, perhaps indicating that this pattern results from loss of function or overexpression of the same genes involved in establishment of Pattern 1. Heterotopy has been an important evolutionary phenomenon among Zingiberales (some stamens becoming petaloid) and perhaps grasses (petals possibly becoming sepaloid). Heterochrony is the most frequent cause of more subtle changes in the degree of bilateral symmetry shown by monocot flowers by enhancing (peramorphosis) or retarding (paedomorphosis) individual organs within specific whorls.

Evolution of zygomorphy in monocot flowers: iterative patterns and developmental constraints

Michel Guédès

Papers

Comparative morphology of lodicules in grasses

Carpel morphology and axis-sharing in syncarpy in some Rutaceae, with further comments on “New Morphology”

Stamen-carpel Homologies

The Peltate (Ascidiate) Carpel Theory and Carpel Peltation in Actinidia chinensis (Actinidiaceae)

Placentation and Possible Partial Stachyospory in Hypericum sect. Eremanthe