Molecular phylogeny of the subtribe Melinidinae (Poaceae: Panicoideae: Paniceae) and evolutionary trends in the homogenization of inflorescences (original) (raw)
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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.
Phylogenetics of Panicoideae (Poaceae) based on chloroplast and nuclear DNA sequences
Phylogenetic relationships among major subfamilies in Poaceae and among major tribes within Panicoideae were evaluated using parsimony and Bayesian analyses of chloroplast trnL-F and atpβ-rbcL DNA sequences and a nuclear ribosomal DNA sequence, ITS1-ITS2. The Panicoideae-Aristidoideae-Chloridoideae-Micrairoideae-Arundinoideae-Danthonioideae (PACMAD) clade was well resolved. A close relationship between Aristidoideae and Chloridoideae was found. The monophyly of Micrairoideae was resolved but the relationships of three tribes (Eriachneae, Isachneae, Micraireae) within Micrairoideae were unclear, only Eriachne and Isachne were monophyletic. Panicoideae sensu stricto were supported as monophyletic and sister to a clade of Danthoniopsis and Tristachya. Within Panicoideae, only a clade of Andropogoneae + Arundinella + Garnotia was supported. None of the analyses supported the monophyletic status of Paniceae. Within Paniceae, the bristle clade (excluding Cenchrus) + Alexfloydia, and the forest shade clade sensu , were found, but their circumscription remains ambiguous. A sister relationship between the endemic and rare Australian grasses Homopholis and Walwhalleya was also resolved. Arundinelleae were found to be polyphyletic. This study supported the separation of Arundinella and Garnotia from the remaining Arundinelleae and the inclusion of both genera in their own subtribes (Arundinellinae Honda sensu stricto and Garnotiinae Pilger) within the Andropogoneae. Arundinelleae should be abandoned as a taxonomic tribe within the Centothecoid + Panicoid clade. Within Andropogoneae, five out of a total of 11 subtribes (Chionachninae, Coicinae, Dimeriinae, Germainiinae, and Tripsacinae) were monophyletic.
American Journal of Botany, 2003
Panicum L. is a cosmopolitan genus with approximately 450 species. Although the genus has been considerably reduced in species number with the segregation of many taxa to independent genera in the last two centuries, Panicum remains a heterogeneous assemblage, as has been demonstrated in recent years. The genus is remarkably uniform in its floral characters but exhibits considerable variation in anatomical, physiological, and cytological features. As a result, several classifications, and criteria of what the genus should really include, have been postulated in modern literature. The purpose of this research, based on molecular data of the chloroplast ndhF gene, is to test the monophyly of Panicum, to evaluate infrageneric classifications, and to propose a robust phylogenetic hypothesis. Based on the present results, previous morphological and molecular phylogenetic studies, and inferred diagnostic morphological characters, we restrict Panicum sensu stricto (s.s.) to the former subgenus Panicum and support recognition of Dichanthelium, Phanopyrum, and Steinchisma as distinct genera. We have transfered other species of Panicum to other genera of the Paniceae. Most of the necessary combinations have been made previously, so few nomenclatural changes have been required. The remaining species of Panicum sensu lato (s.l.) are included within Panicum incertae sedis representing isolated species or species grouped within monophyletic clades. Additionally, we explore the performance of the three codon position characters in producing the supported phylogeny.
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.
2001
DNA sequence data from the chloroplast gene ndhF were analyzed to estimate the phylogeny of the subfamily Panicoideae, with emphasis on the tribe Paniceae. Our data suggest that the subfamily is divided into three strongly supported clades, corresponding to groups with largely identical base chromosome numbers. Relationships among the three clades are unclear. In unweighted parsimony analyses, the two major clades with x ϭ 10 (Andropogoneae and x ϭ 10 Paniceae) are weakly supported as sister taxa. The third large clade corresponds to x ϭ 9 Paniceae. In analyses under implied weight, the two clades of Paniceae are sisters, making the tribe monophyletic. Neither resolution is strongly supported.
American Journal of Botany, 2001
DNA sequence data from the chloroplast gene ndhF were analyzed to estimate the phylogeny of the subfamily Panicoideae, with emphasis on the tribe Paniceae. Our data suggest that the subfamily is divided into three strongly supported clades, corresponding to groups with largely identical base chromosome numbers. Relationships among the three clades are unclear. In unweighted parsimony analyses, the two major clades with x ϭ 10 (Andropogoneae and x ϭ 10 Paniceae) are weakly supported as sister taxa. The third large clade corresponds to x ϭ 9 Paniceae. In analyses under implied weight, the two clades of Paniceae are sisters, making the tribe monophyletic. Neither resolution is strongly supported.
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.
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.