The inflorescences of Paspalum ( Poaceae, Paniceae ): The Quadrifaria group and the evolutionary pathway towards the fully homogenized, truncated common type (original) (raw)
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Systematic Botany, 2009
Paspalum, an American genus of the x = 10 Paniceae clade, includes about 330 species, four subgenera, and 27 informal groups. Within the genus, the Quadrifaria and Virgata groups are well-represented in South and Central America. Interspecific variability make the delimitation of these groups difficult; hence several species have been included or excluded from Quadrifaria or Virgata depending on the taxonomic treatment. In previous analyses, the Quadrifaria and Virgata groups of Paspalum were polyphyletic. Here we present a new appraisal of the classification of both groups based on the phylogenetic analyses of DNA data from the chloroplast: the rpl16 intron, and the region comprising the trnL and trnF genes. A monophyletic Virgata clade is recovered, consisting of nearly all the species listed in an unpublished manuscript. The Quadrifaria group is restricted to P. quadrifarium and P. quarinii. Other clades grouped species traditionally treated within Virgata or Quadrifaria, althoug...
A Preliminary Approach to the Phylogeny of the Genus Paspalum (Poaceae)
Genetica, 2006
The present work intends to clarify the phylogenetic relationships among the species of Paspalum L. belonging to the informal groups Notata/Linearia and Dilatata, and to raise some preliminary hypotheses on the phylogeny of the genus as a whole. A combined dataset including morphological and molecular characters was used to analyze 28 species of Paspalum plus some representatives of related genera of the tribe Paniceae. Analyses were performed using both parsimony and maximum likelihood. The monophyly of Paspalum is not supported nor contradicted. The circumscription of informal groups of Paspalum is discussed, as well as the cladistic treatment of allopolyploid taxa, especially those comprising the Dilatata group. The relationships of members of the Dilatata with their putative progenitors is confirmed, but the monophyly of the group as a whole is not. A close relationship between P. dilatatum Poir. and P. lividum Trin. ex Schltdl. is shown. Our analysis is consistent with the monophyly of a group comprising Notata+Linearia, with a monophyletic Notata group nested within it. The delimitation of the core Notata is proposed by including P. conduplicatum Canto-Dorow, Valls and Longhi-Wagner, P. notatum Flüggé, P. minus E. Fourn., P. pumilum Nees and P. subciliatum Chase.
Genetic Resources and Crop Evolution, 2007
Genus Paspalum L. comprises approximately 400 species worldwide and about 220 in Brazil. Paspalum is ecologically and economically important, and has been very useful as pasture. Traditionally, taxonomists use informal groups, most of which described by Agnes Chase in 1929. Some groups present a problematic circumscription, this is the case of the Linearia and Notata groups. This work uses a phylogenetic approach to study these groups and related species. DNA sequences from ITS of nuclear rRNA, from chloroplast intergenic spacer psbA-trnH and chloroplast trnL intron were used to perform the analyses. The informal groups studied were considered highly artificial, being the representatives from several informal groups splitted throughout the trees. Only a small core of species from Notata group could be accepted as a good formal clade.
Molecular Phylogenetics and Evolution, 2010
The subtribe Melinidinae (Poaceae: Panicoideae: Paniceae) includes 14 genera that present the PCK photosynthetic subtype in addition to several other unique and also common characters. The purpose of this research was (1) to test the monophyly of the subtribe Melinidinae, including 331 ndhF sequences of Panicoids and related genera, (2) to analyze the phylogenetic relationships among genera of Melinidinae using four cpDNA regions, and to study evolutionary trends in the homogenization of inflorescences. As a result, the monophyly of Melinidinae is supported if Urochloa venosa is excluded from the subtribe. Alloteropsis semialata subsp. semialata, an unusual PCK species, is here confirmed within the Forest shade clade. Within Melinidinae, Urochloa and Eriochloa appeared as paraphyletic and polyphyletic genera, respectively. Finally, the general trend in the evolution of the inflorescences in Melinidinae seems to be the reduction from non-homogenized to complete homogenized inflorescences.
Inflorescence diversity and evolution in the PCK Clade (Poaceae: Panicoideae: Paniceae)
Plant Systematics and Evolution, 2008
The PCK Clade, represented by six to nine genera, is a monophyletic group situated within the Paniceae tribe. The highly diverse inflorescences within the PCK Clade provide an interesting system for the study of morphological evolution and also may aid in better understanding its unclear systematics. The inflorescence structure of 110 members of the PCK Clade has been investigated. Inflorescences are polytelic showing different levels of truncation. At least 21 different inflorescence subtypes were identified. Fourteen variable inflorescence characters were found, among which some have suprageneric or infrageneric value and others are polymorphic.
Cladistics, 2012
Included in the PACMAD clade of the family Poaceae (Panicoideae, Arundinoideae, Chloridoideae, Micrairoideae, Aristidoideae, Danthonioideae), the tribe Paniceae s.l. is one of the largest tribes of the subfamily Panicoideae, with more than 2000 species. This tribe comprises a huge morphological, cytological, and physiological diversity represented by different inflorescence types, several basic chromosome numbers, and at least four major photosynthetic pathways. The tribe Paniceae has been the subject of molecular studies that have confirmed its paraphyly: two major clades were recognized based on their basic chromosome numbers (x =9 ,x = 10). The x = 10 Paniceae clade is sister to the Andropogoneae-Arundinelleae s.s. x =1 0c l a d ea n dt h ex = 9 clade with a subsample of Paniceae genera. As a result of a recent realignment within the tribe in terms of the phylogenetic position of minor and major Paniceae genera, a reanalysis of the whole sampling is performed and new underrepresented taxa are discussed. A total of 155 genera, currently considered within subfamily Panicoideae, are represented here by almost all genera of Paniceae s.l., representatives of Andropogoneae and Arundinelleae s.s., and the endemic and small tribe Steyermarkochloeae; we also included specimens of subfamily Micrairoideae, tribes Isachneae and Eriachneae. The sampling includes as outgroups 18 genera of the PACMAD clade (excluding Panicoideae) and four genera from the BEP clade (Bambusoideae, Ehrhartoideae, Pooideae), rooting with Bromus inermis. A matrix with 265 taxa based on the combined evidence from ndhF plastid sequences (2074 bp) and 57 morphological characters was subjected to parsimony analyses. Jackknife resampling was used to calculate group support. Most clades are characterized by morphological, cytological, anatomical, and ⁄ or physiological characters. Major tribal changes are based on the basic chromosome number; the pantropical x =9 clade is here recognized as Paniceae s.s., while the American x = 10 Paniceae s.l. is restricted to the reinstated tribe Paspaleae. The optimization of the photosynthetic pathway for the Paspaleae-Andropogoneae-Arundinelleae s.s. clade, including the monotypic Reynaudia, show a plesiomorphic C 4 state while the ancestral state for Paniceae s.s. is ambiguous. If Reynaudia were not included or placed elsewhere, the ancestral photosynthetic pathway for both the Paspaleae-Andropogoneae-Arundinelleae s.s. clade and the Paniceae s.s. would be unambiguously C 3 . In order to explore character evolution further, the morphological characters were mapped onto one of the most parsimonious trees. A relationship between photosynthetic pathways and inflorescence morphology is suggested here for the first time. Based on the optimization of morphological characters and additional data, we propose names for almost all inner clades at the rank of subtribe with a few groups as incertae sedis. With this extensive sampling, we resolved the phylogenetic relationships and the assignation of synapomorphies, and improved the support in subtribe sorting; consequently a robust circumscription of the tribe Paniceae s.l. is proposed.
Systematic Botany, 2007
Molecular phylogenetic analyses using the chloroplast marker ndhF and a single copy nuclear marker, knotted1, show that the panicoid grasses bearing sterile branches (bristles) in their inflorescences form a monophyletic group. The genus Cenchrus is monophyletic, and monophyly of Pennisetum cannot be ruled out. Setaria is not monophyletic, either as a whole, excluding the palm-leaved species from section Ptychophyllum, or excluding various uncertainly placed species such as S. grisebachii. There is also no evidence that Setaria and Paspalidium form a monophyletic group. The Australian genera Zygochloa, Spinifex, and Pseudoraphis are placed in the 'bristle clade', confirming that inflorescences of these grasses are homologous with the inflorescences composed of spikelets and sterile branchlets (bristles). Comparison of the nuclear and chloroplast gene trees identifies several taxa as tetra-or higher polyploids; these are confirmed by southern hybridization. In particular, the Australian species of Paspalidium are allopolyploid, a novel and unexpected result. Zuloagaea bulbosa, a species that lacks the synapomorphic bristles in its inflorescence, is confirmed as a morphologically anomalous member of the clade, and is clearly allopolyploid. This study demonstrates the utility of knotted1 as a phylogenetic marker; we show that it is single copy in diploid taxa and that it exhibits adequate variation to distinguish closely related species. Interestingly, inflorescence morphology correlates only partially with relationships suggested by either nuclear or chloroplast trees, suggesting that inflorescence form is easily changed over evolutionary time.
Taxonomy, Phylogeny, and Inflorescence Development of the Genus Ixophorus (Panicoideae: Poaceae)
International Journal of Plant Sciences, 2004
Patterns of morphological variation within the grass genus Ixophorus have led to uncertainty in its phylogenetic position and also to disagreement about the number of species in the genus. We use molecular phylogenetic, developmental, and morphometric approaches to address taxonomic and evolutionary problems in the genus. DNA sequence data for the gene ndhF place Ixophorus within the ''bristle grass'' clade, which includes Setaria and Pennisetum, and data for the trnL intron plus the trnL-F intergenic spacer show low levels of variation within the genus. Inflorescence development of Ixophorus was compared with that of several Setaria species to identify the stages of development that make Ixophorus so distinctive. Ixophorus is distinguished by (1) abaxially oriented tertiary axes that develop as spikelets, (2) a fixed, low number of orders of branching, (3) synchronous development of spikelets within an inflorescence, and (4) uniform elongation of primary and secondary axes late in development. However, these developmental character states are also shared with various other bristle grass clade members, making them unsuitable for circumscribing the genus. Specimens representing the geographical and morphological ranges of Ixophorus were used to detect groupings based on morphological variation. Principal components analyses, as well as many separate variables, weakly correlated morphological variation with latitude but supported recognition of a single species, Ixophorus unisetus (J. Presl) Schltdl. Common garden experiments show that much morphological variation results from plasticity. A formal taxonomic revision of the genus is presented.