Silvana M. Sede

Phylogeny of the Paniceae (Poaceae: Panicoideae): integrating plastid DNA sequences and morphology into a new classification

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. clade (x = 10), while the combined x = 10 clade is sister to the x = 9 clade that contains the remaining genera of Paniceae. 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, shows a plesiomorphic C4 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 C3. 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.

Biodiversity characterization of cellulolytic bacteria present on native Chaco soil by comparison of ribosomal RNA genes

Sequence analysis of the 16S ribosomal RNA gene was used to study bacterial diversity of a pristine forest soil and of two cultures of the same soil enriched with cellulolytic bacteria. Our analysis revealed high bacterial diversity in the native soil sample, evidencing at least 10 phyla, in which Actinobacteria, Proteobacteria and Acidobacteria accounted for more than 76% of all sequences. In both enriched samples, members of Proteobacteria were the most frequently represented. The majority of bacterial genera in both enriched samples were identified as Brevundimonas and Caulobacter, but members of Devosia, Sphingomonas, Variovorax, Acidovorax, Pseudomonas, Xanthomonas, Stenotrophomonas, Achromobacter and Delftia were also found. In addition, it was possible to identify cellulolytic taxa such as Acidothermus, Micromonospora, Streptomyces, Paenibacillus and Pseudomonas, which indicates that this ecosystem could be an attractive source for study of novel enzymes for cellulose degradation.

Phylogenetic Studies in the Paniceae (Poaceae) : a Realignment of Section Lorea of Panicum

Abstract The taxonomic status of Panicum section Lorea has remained as “incertae sedis” within Panicum. To resolve its position within the Paniceae and to test the monophyly of this section, phylogenetic analyses based on chloroplast sequence data (ndhF) and morphology were conducted for the Paniceae with particular emphasis on Panicum section Lorea. The results did not support the monophyly of this section. The species of this group were resolved in two clades which are not sister groups and neither of them is closely related to Panicum s.s. As a result, two new genera are proposed and described: Apochloa and Renvoizea, which are restricted to the Guiana highlands and eastern Brazil. New combinations are: Apochloa animara, A. bahiense, A. chnoodes, A. cipoense, A. eligulata, A. euprepes, A. jauana, A. lorea, A. lutzii, A. molinioides, A. poliophylla, A. sipapoense, A. steyermarkii, A. subtiramulosa, A. tijucae, Renvoizea acicularifolia, R. durifolia, R. glaziovii, R. lagostachya, R. marauense, R. restingae, R. sacciolepoides, R. teretifolia, R. trinii, and R. vaginiviscosa.

Phylogenetic Studies in the Paniceae (Poaceae-Panicoideae): Ocellochloa, a New Genus from the New World

Abstract The present contribution continues a critical revision of Panicum, particularly with the delimitation of “incertae sedis” taxa. A phylogenetic analysis of Paniceae based on cpDNA sequence data (ndhF) was performed with special emphasis on section Stolonifera of Panicum. Fourteen sequences of species of sect. Stolonifera and Echinolaena were added to a panicoid grass matrix previously published giving a total of 140 sequences. As a result, Ocellochloa is here described as a new genus including 12 new combinations: O. andreana, O. biglandularis, O. brachystachya, O. chapadensis, O. craterifera, O. irregularis, O. latissima, O. piauiensis, O. pulchella, O. rudis, O. soderstromii , and O. stolonifera. The position of Panicum venezuelae, previously placed in section Stolonifera with the above mentioned species, clearly indicates that this species is not closely related to the Ocellochloa clade. This conclusion is supported by several morphological characters, such as the presence of axillary inflorescences, cleistogamous spikelets, and glands of the lower lemma depressed, not crateriform. Ocellochloa differs from Panicum s. s. by the unilateral spikelet disposition, the smooth surface of the upper anthecium, and a C3 photosynthetic pathway. This new genus is described and compared with other allied genera of the Paniceae.

The Phylogenetic Affinities of Two Mysterious Monotypic Mimosoids from Southern South America

Abstract Two monotypic genera of Mimosoideae from southern South America, Mimozyganthus and Piptadeniopsis, have been particularly difficult to classify and there has been disagreement about their relationships to other legume genera. We undertook a phylogenetic study based on molecular data from the chloroplast and nucleus, and synthesized it with new data from morphology, cytology, and palynology, in order to determine where these genera belong in the mimosoid phylogenetic tree. Mimozyganthus, an enigmatic genus whose unique morphology led workers to consider it transitional between the subfamilies Mimosoideae and Caesalpinioideae, is instead nested among the higher mimosoids on the molecular tree. Careful evaluation of the characters that were considered to be caesalpinioid-like reveals that they are not identical and are independently derived. Piptadeniopsis is most closely related to Prosopidastrum, a primarily Argentinian genus with lomentiform fruits. This is in close agreement with most morphological characters, although the pollen is different in the two genera. Piptadeniopsis, Mimozyganthus, and Prosopidastrum form a monophyletic group on all molecular trees, a result consistent with vegetative and fruiting morphology, but not floral characters. Although the relationship of this group to other taxa is unresolved in the individual molecular analyses, a combined analysis of all molecular data for a subset of the taxa reveals that the three taxa are more closely related to the Leucaena group than to Prosopis. We hypothesize that the unique floral characters of Mimozyganthus may have evolved in response to pollinator selection, and a pollination study is needed to test this hypothesis.

Chromosome studies in the Complex Galactia-Collaea-Camptosema (Diocleinae, Phaseoleae, Papilionoideae, Fabaceae)

Abstract The genera Galactia, Camptosema and Collaea are grouped in a complex due to exomorphological similarities and different criteria have been adopted to delimit them. The objective of this contribution is to analyse the chromosomal characteristics in some species from the austral regions of South America. Chromosome numbers and karyotypes of four species of Galactia (G. texana, G. latisiliqua, G. fiebrigiana var. sericophylla and G. striata), one species of Collaea (C. stenophylla) and one species of Camptosema (C. rubicundum) were studied. Chromosome numbers of G. texana (2n=20), G. striata (2n=20) and Collaea stenophylla (2n=20) confirm previous reports, while those of G. latisiliqua (2n=20), G. fiebrigiana var. sericophylla (2n=20) and Camptosema rubicundum (2n=22) are presented for the first time. The karyotypes of Galactia (16m + 4m-sm) and Collaea species (14m + 2m-sm + 4sm) showed no distinctive characteristics, since both genera are characterised by small median chromosomes. Camptosema rubicundum presented a different chromosome number, as well as a distinctive karyotype morphology: 12m + 2m-sm + 4sm + 4st-t; these features permit to characterise this species from the others included into this study.

Chromosome studies in American Paniceae (Poaceae, Panicoideae).

Abstract Chromosome numbers and meiotic behavior of 60 individuals of American Paniceae, Poaceae, are provided, including six previously uncounted species: Axonopus andinus G. A. Black (2n  =  20), A. iridifolius (Poepp.) G. A. Black (2n  =  20), Dichanthelium hebotes (Trin.) Zuloaga (2n  =  18), Paspalum geminiflorum Steud. (2n  =  ca. 20), P. heterotrichon Trin. (2n  =  20), and Setaria tenacissima Schrad. ex Schult. (2n  =  36). Of the remaining 54 counts, 17 correspond to new ploidy levels in species of Echinochloa P. Beauv., Eriochloa Kunth, Hymenachne P. Beauv., Panicum L., Parodiophyllochloa Zuloaga & Morrone, Paspalum L., and Setaria P. Beauv., and 37 are confirmations of previous reports.

Phylogeny of Nassella (Stipeae, Pooideae, Poaceae) Based on Analyses of Chloroplast and Nuclear Ribosomal DNA and Morphology

Abstract The genus Nassella, as currently circumscribed, includes 116–117 American species. It is characterized by florets with a strongly convolute lemma, a conspicuous or inconspicuous crown, and a short palea. Using 53 species of Nassella and 22 outgroup species we conducted phylogenetic analyses to test the monophyly of Nassella and relationships among species. Two plastid (trnT-trnL and rpl32-trnL) and two nuclear ribosomal (ITS and ETS) regions and morphology were used. Our DNA data alone and combined with morphology showed Nassella to be paraphyletic with respect to a monophyletic Amelichloa. Two main clades were recovered: one with species of Nassella distributed in regions of high elevation from Mexico to northwestern Argentina and one composed of the remaining species of Nassella and those of Amelichloa. The latter is mainly concentrated in southern South America in a variety of habitats with generally lower elevation than the other clade. The monophyly of the close relative of Nassella, the South American genus Jarava s. s., was rejected. None of the groups previously circumscribed as subgenera of Stipa, that are now considered to be composed of species in Nassella, were recovered as monophyletic. The close phylogenetic relationship of Nassella and Amelichloa is supported by only one morphological synapomorphy: the lemma margins flat and strongly overlapping.

Phylogenetic relationships among southern South American species of Camptosema, Galactia and Collaea (Diocleinae: Papilionoideae: Leguminosae) on the basis of molecular and morphological data

The neotropical genus Camptosema in its southern distribution is represented by the following four species: Ca. paraguariense, Ca. praeandinum, Ca. rubicundum and Ca. scarlatinum. Ca. rubicundum is the only species with all the diagnostic characters of the genus, i.e. tubular calyx. The other three taxa are related morphologically and cytologically to Galactia and Collaea, two closely allied genera in the subtribe Diocleinae. Individual and combined phylogenetic analyses of morphology, ITS and trnL-F were conducted to examine the position of these species as well as to explore their relationship with Galactia and Collaea species in southern South America. In none of the analyses does Camptosema species form a monophyletic group. Instead, they are scattered in different groups. These results together with cytological, morphological and AFLP data provide good support for re-evaluating the taxonomic position of these species within Camptosema.

Phylogenetic analysis of Jarava (Poaceae, Pooideae, Stipeae) and related genera: testing the value of the awn indumentum in the circumscription of Jarava

Jarava, a genus of the tribe Stipeae with 31 American species, is considered polyphyletic. In previous phylogenetic analyses, despite a few species of Jarava were used, they were included in the Major American Clade (MAC) together with species of Achnatherum, Amelichloa and Nassella. The main goal of this study is to test the monophyly of Jarava and to estimate relationships of Jarava species and allied genera. Eighty-nine species of Stipeae (17 species of Jarava) were included in the analyses of trnH-psbA and ITS regions from plastid and nuclear genomes, respectively. Morphological characters were optimized on one of the shortest trees derived from the combined analysis. Jarava splits into different lineages. Jarava ichu, the type species of the genus, and other eight species of Jarava were grouped into subclade B; another four species were associated with Achnatherum in subclade A. Both subclades A and B were included into the MAC. Three species: Jarava neaei, J. psylantha, and J. subplumosa, were grouped with Pappostipa in subclade C. The close relationship between Jarava and Pappostipa appears as a novelty and they should be considered within this genus or recognized as a new genus sister to Pappostipa. The awn indumentum (hair length and position of long hairs, either in part or the entire awn) and the subacute or acute callus are useful to recognize the group (subclade C). Geographical distribution of Jarava from subclade C overlaps completely with that of Pappostipa. The shared geographical distribution is in accordance with major groupings in our phylogenetic topology.