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ABSTRACT: Sequence data from nuclear (ITS) and chloroplast (trnL-F) regions for 89 accessions representing 56 out of 64 species from all five genera of the tribe Chorisporeae (plus Dontostemon tibeticus) have been studied to test the monophyly of the tribe and its component genera, clarify its boundaries, and elucidate its
phylogenetic position in the family. Both data sets showed strong support for the monophyly of the Chorisporeae as currently
delimited, though the position of its tentative member D. tibeticus was not resolved by ITS. Parrya and Pseudoclausia are poly- and paraphyletic with regard to each other, and Chorispora is either polyphyletic or at least paraphyletic (comprising Diptychocarpus) within a weakly supported monophyletic clade. The incongruence in branching pattern among the markers was most likely caused
by hybridization and possibly influenced by incomplete lineage sorting. The present results suggest uniting Pseudoclausia, Clausia podlechii, and Achoriphragma with Parrya and transferring P. beketovii and P. saposhnikovii to Leiospora (Euclidieae). We also obtained support for splitting Chorispora into two geographically defined groups, one of which is closer to Diptychocarpus. Both data sets revealed a close relationship of the Chorisporeae to Dontostemoneae, while ITS also indicated affinity to
Hesperideae. Therefore, the position of Chorisporeae needs further verification.
KeywordsBrassicaceae–Chorisporeae–Generic delimitation–Phylogeny–Parrya
Plant Systematics and Evolution 04/2012; 294(1):65-86. · 1.34 Impact Factor
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ABSTRACT: Sequence data from the nuclear encoded ribosomal internal transcribed spacer (ITS) region were used to determine monophyly
of tribes, tribal limits, and tribal relationships of 96 so far unassigned or tentatively assigned genera (represented by
101 taxa/accessions) within the Brassicaceae. Maximum-parsimony and maximum-likelihood analyses of 185 ITS Brassicaceae sequences,
which also included representatives of each of the 34 currently recognized tribes, supported the separate phylogenetic distinctness
of these tribes and permitted the tribal assignment of all but 12 of the unassigned genera into tribal clades. The data support
the recognition of eight new, well-resolved, uni- or oligogeneric tribes recognized herein as the Alyssopsideae [96% bootstrap
support (BS); including the central and southwestern Asian Alyssopsis and Calymmatium], Asteae (100% BS; including the Mexican Asta), Eudemeae (97% BS; South American Brayopsis, Eudema, and Xerodraba), Kernereae (96% BS; European Kernera and Rhizobotrya), Notothlaspideae (100% BS; New Zealandic Notothlaspi), Oreophytoneae (100% BS; eastern African Oreophyton and southern European Murbeckiella), and Yinshanieae (100% BS; Chinese Yinshania), as well as the moderately supported Microlepidieae (75% BS; Australian Microlepidium and Carinavalva). Furthermore, the results fully support the recent findings that the tribes Schizopetaleae and Thelypodieae ought to be
recognized as two distinct tribes instead of a single tribe, as well as provide some support for the re-establishment of the
tribe Cremolobeae, bringing the total number to 44 tribes in the family. Nearly 92% (308) of the 336 genera in the family
have been assigned to a tribe. The earlier-published Anastaticeae is taken here to replace the Malcolmieae.
KeywordsBrassicaceae-ITS region-Phylogeny-Systematics-Tribal assignments
Plant Systematics and Evolution 04/2012; 285(3):209-232. · 1.34 Impact Factor
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ABSTRACT: Sequence data from the nuclear ribosomal internal transcribed spacer (ITS) region for 189 accessions representing 184 species
in 121 genera of Brassicaceae were used to determine monophyly of tribes and genera, tribal boundaries, and component genera.
Parsimony analysis and Bayesian inference suggest that the tribes Camelineae and Arabideae are polyphyletic and should be
subdivided into smaller tribes. The study also supports the recent recognition of the new tribes Aphragmeae, Biscutelleae,
Buniadeae, Calepineae, Conringieae, Dontostemoneae, Erysimeae, Malcolmieae, Megacarpaeeae, and Turritideae. The data argue
for the placement of Borodinia in the tribe Boechereae, Litwinowia and Pseudoclausia in the Chorisporeae, Atelanthera and Streptoloma in the Euclidieae, and Megacarpaea and Pugionium in the Megacarpaeeae, and exclusion of Asperuginoides, Didymophysa, and Ptilotrichum from the Alysseae, Macropodium, Pseudoturritis, and Stevenia from the Arabideae, and Crucihimalaya, Irenepharsus, Pachycladon, and Turritis from the Camelineae. Finally, the findings support the expansion of Stevenia to include both Berteroella and Ptilotrichum, Sterigmostemum to include Oreoloma and one species of Anchonium, Crucihimalaya to include Transberingia and several species of Arabis, and Parrya to include Pseudoclausia. The data also suggest that Calymmatium and Olimarabidopsis may be congeneric.
Plant Systematics and Evolution 04/2012; 283(1):33-56. · 1.34 Impact Factor
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ABSTRACT: Gametophytic apomixis is a common form of asexual reproduction in plants. Virtually all gametophytic apomicts are polyploids, and some view polyploidy as a prerequisite for the transition to apomixis. However, any causal link between apomixis and polyploidy is complicated by the fact that most apomictic polyploids are allopolyploids, leading some to speculate that hybridization, rather than polyploidy, enables apomixis. Diploid apomixis presents a rare opportunity to isolate the role of hybridization, and a number of diploid apomicts have been documented in the genus Boechera (Brassicaceae). Here, we present the results of a microsatellite study of 1393 morphologically and geographically diverse diploid individuals, evaluating the hypothesis that diploid Boechera apomicts are hybrids. This genus-wide dataset was made possible by the applicability of a core set of microsatellite loci in 69 of the 70 diploid Boechera species and by our ability to successfully genotype herbarium specimens of widely varying ages. With few exceptions, diploid apomicts exhibited markedly high levels of heterozygosity resulting from the combination of disparate genomes. This strongly suggests that most apomictic diploid Boechera lineages are of hybrid origin, and that the genomic consequences of hybridization allow for the transition to gametophytic apomixis in this genus.
Evolution 04/2012; 66(4):985-95. · 5.15 Impact Factor
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ABSTRACT: Life without the mustard family (Brassicaceae) would be a world without many crop species and the model organism Arabidopsis (Arabidopsis thaliana) that has revolutionized our knowledge in almost every field of modern plant biology. Despite this importance, research breakthroughs in understanding family-wide evolutionary patterns and processes within this flowering plant family were not achieved until the past few years. In this review, we examine recent outcomes from diverse botanical disciplines (taxonomy, systematics, genomics, paleobotany and other fields) to synthesize for the first time a holistic view on the evolutionary history of the mustard family.
Trends in Plant Science 02/2011; 16(2):108-16. · 11.05 Impact Factor
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ABSTRACT: The new tribe Crucihimalayeae and three new genera Schrenkiella, Leiocarpaea and Ladakiella are described, and their diagnostic characters are discussed. Spirorhynchus is reduced to synonymy of Goldbachia, Ptilotrichum and Berteroella are merged with Stevenia, and Phaeonychium and Eurycarpus are merged with Solms-laubachia. Thirteen new combinations are proposed: Goldbachia sabulosa (Kar. & Kir.) D. German & Al-Shehbaz, Ladakiella klimesii (Al-Shehbaz) D. German & Al-Shehbaz, Leiocarpaea cochlearioides (Murr.) D. German & Al-Shehbaz, Schrenkiella parvula (Schrenk) D. German & Al-Shehbaz, Stevenia dahurica (Peschkova) D. German & Al-Shehbaz, Stevenia maximowiczii (Palib.) D. German & Al-Shehbaz, Solms-laubachia albiflora (T. Anderson) D. German & Al-Shehbaz, Solms-laubachia kashgarica (Botsch.) D. German & Al-Shehbaz, Solms-laubachia lanuginosa (Hook. f. & Thomson) D. German & Al-Shehbaz, Solms-laubachia marinellii (Pamp.) D. German & Al-Shehbaz, Solms-laubachia parryoides (Kurz ex Hook. f. & T. Anderson) D. German & Al-Shehbaz, Solms-laubachia surculosa (N. Busch) D. German & Al-Shehbaz, and Solms-laubachia villosa (Maxim.) D. German & Al-Shehbaz.
Nordic Journal of Botany 11/2010; 28(6):646 - 651. · 0.55 Impact Factor
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ABSTRACT: The relationships and taxonomy of the genus Thysanocarpus (Brassicaceae) are reassessed based on molecular phylogenetic analyses of nuclear ribosomal (ITS) and chloroplast (trnL-F) sequences and a critical re-examination of morphology and nomenclatural types. Based on these results, Thysanocarpus is well-supported as a member of tribe Thelypodieae, but no illuminating phylogenetic structure is found within the tribe. The independent origin of similar fruit morphology in Thysanocarpus and Athysanus is confirmed. Within Thysanocarpus, seven species are recognized: T. conchuliferus, T. curvipes, T. desertorum, T. erectus, T. laciniatus, T. radians, and T. rigidus comb. nov. Thysanocarpus laciniatus is found to have originated through hybridization. However, T. desertorum and T. rigidus, which have previously been included within T. laciniatus (as T. laciniatus var. hitchcockii and T. laciniatus var. rigidus, respectively), do not share that species' hybrid origin and are distinct both phylogenetically and morphologically. Within T. curvipes, five subspecies are recognized: T. curvipes subsp. amplectens comb. nov., T. curvipes subsp. curvipes, T. curvipes subsp. elegans comb. nov., T. curvipes subsp. longistylus comb. nov., and T. curvipes subsp. eradiatus comb. nov. Thysanocarpus curvipes subsp. elegans and T. curvipes subsp. longistylus form clades in ITS and/or trnL-F cladograms as well as showing morphological distinction. The remaining three subspecies are recognized based on a combination of morphology and geography.
Systematic Botany 06/2010; 35(3):559-577. · 1.52 Impact Factor
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ABSTRACT: The circumscription of the genus Arabis underwent many and drastic changes within the past. Using DNA sequence information from the nuclear ribosomal RNA and parts of the plastid genome (trnL-trnLF), as well as a critical evaluation of herbarium material from East Asia and North America, we circumscribe the various Arabis taxa of North America. The American and East Asian Arabis species are closely related and, contrary to what was previously believed, they are not closely related to the Eurasian A. hirsuta. Using cpDNA, we found five North American lineages of Arabis with distinct distribution patterns, of which only the purple/red-flowered lineage consists of proven diploids that evolved directly from East Asian progenitors. All other four lineages evolved via ancient hybridization either on the Asian continent prior to migration to North America or showed significant evidence for hybridization and reticulation while diversifying on the American continent. We also provide the first evidence for the systematic circumscription of East Asian Arabis taxa, which together with the North American taxa, form one clade distantly related to European A. ciliata and Eurasian A. hirsuta. The findings also represent the first record of A. pycnocarpa for the floras of China, Japan, and Russian Far East.
American Journal of Botany 06/2010; 97(6):1040-57. · 2.66 Impact Factor
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ABSTRACT: a b s t r a c t Systematics of the genus Isatis (Brassicaceae) is difficult and controversial, and previous studies were based solely on morphological characters. Sequence variation of the internal transcribed spacer (ITS) regions and the 5.8S gene of nuclear ribosomal DNA (nrDNA) were analyzed using parsimony and Bayesian methods. Twenty-eight taxa of Isatis and related genera of the tribe Isatideae were sampled, including 20 Isatis species representing almost all major morphological lineages, all three species of Pachypterygium, two of nine species of Sameraria, and monospecific Boreava, Myagrum, and Tauscheria. Two well-supported clades were resolved in the ITS tree, and they demonstrate the artificiality of the present delimitation of the tribe. One clade includes I. emarginata, I. minima, I. trachycarpa, P. brevipes, P. multicaule, P. stocksii, and T. lasiocarpa. The second clade includes I. buschiana, the polymorphic I. cappadocica with five subspecies, I. gaubae, I. kotschyana, I. leuconeura, I. pachycarpa, I. takhtajanii, I. tinctoria, and S. armena. Pachypterygium is polyphyletic and, together with Boreava, Sameraria, and Tauscheria, all are nested within Isatis. This study is a continuation of our recent systematic survey based on seed-coat microsculpturing (Moazzeni et al., 2007. Flora 202, 447–454) and reveals that fruit characters mapped onto the molecular tree show considerable convergence. The reliance on fruit characters alone in the delimitation of genera may well lead to erroneous phylogenetic results and thus to incorrect taxonomic conclusions.
Flora - Morphology Distribution Functional Ecology of Plants 01/2010; · 1.64 Impact Factor
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ABSTRACT: Brassicaceae is an important family at both the agronomic and scientific level. The family not only includes several model species, but it is also becoming an evolutionary model at the family level. However, resolving the phylogenetic relationships within the family has been problematic, and a large-scale molecular phylogeny in terms of generic sampling and number of genes is still lacking. In particular, the deeper relationships within the family, for example between the three major recognized lineages, prove particularly hard to resolve. Using a slow-evolving mitochondrial marker (nad4 intron 1), we reconstructed a comprehensive phylogeny in generic representation for the family. In addition, and because resolution was very low in previous single marker phylogenies, we adopted a supermatrix approach by concatenating all checked and reliable sequences available on GenBank as well as new sequences for a total 207 currently recognized genera and eight molecular markers representing a comprehensive coverage of all three genomes. The supermatrix was dated under an uncorrelated relaxed molecular clock using a direct fossil calibration approach. Finally, a lineage-through-time-plot and rates of diversification for the family were generated. The resulting tree, the largest in number of genera and markers sampled to date and covering the whole family in a representative way, provides important insights into the evolution of the family on a broad scale. The backbone of the tree remained largely unresolved and is interpreted as the consequence of early rapid radiation within the family. The age of the family was inferred to be 37.6 (24.2-49.4) Ma, which largely agrees with previous studies. The ages of all major lineages and tribes are also reported. Analysis of diversification suggests that Brassicaceae underwent a rapid period of diversification, after the split with the early diverging tribe Aethionemeae. Given the dates found here, the family appears to have originated under a warm and humid climate approximately 37 Ma. We suggest that the rapid radiation detected was caused by a global cooling during the Oligocene coupled with a genome duplication event. This duplication could have allowed the family to rapidly adapt to the changing climate.
Molecular Biology and Evolution 10/2009; 27(1):55-71. · 5.55 Impact Factor
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ABSTRACT: Sequence data from the nuclear ribosomal internal transcribed spacer (ITS) region and plastid gene ndhF of 95 species, represented by 147 accessions, were used to determine the tribal limits, monophyly status, and phylogenetic intra-tribal relationships of genera within the New World tribe Schizopetaleae (formerly Thelypodieae; Brassicaceae). Maximum parsimony, Bayesian, and maximum-likelihood analyses all support the separate recognition of three distinct and generally well-supported clades. The largest corresponds to the North-South American Thelypodieae (27 genera: Catadysia, Caulanthus, Chaunanthus, Chilocardamum, Chlorocrambe, Coelophragmus, Dictyophragmus, Dryopetalon, Englerocharis, Hesperidanthus, Mostacillastrum, Neuontobotrys, Polypsecadium, Pringlea, Pterygiosperma, Romanschulzia, Sibara, Sibaropsis, Stanleya, Streptanthella, Streptanthus, Thelypodiopsis, Thelypodium, Thysanocarpus, Warea, Weberbauera, and Werdermannia). The remaining six South American Schizopetaleae genera were divided into two clades: SCHIZ I of four genera (Aschersoniodoxa, Brayopsis, Eudema, and Onuris) and SCHIZ II Schizopetaleae s.str.: Mathewsia, and Schizopetalon). Resolution within the Thelypodieae clade was limited in both the ITS- and ndhF-based phylogenies. Based on ITS sequence data, elements of the Old World tribe Brassiceae were sister to the Thelypodieae, whereas the ndhF data strongly supported the Sisymbrieae as sister to the Thelypodieae, and the Brassiceae as sister to both tribes. Sister groups to the Schizopetaleae clades I and II were not clearly resolved. Morphological and cytological data support the separation of these three clades. In SCHIZ II, the sepals are always erect to form a closed tube, and the trichomes are mostly dendritic, although other types also occur. In both the Thelypodieae and SCHIZ I clades, the sepals are variously oriented but never form a closed tube, whereas the trichomes are either absent, or simple, forked, or rarely dendritic. The latter clade differs from both SCHIZ II and Thelypodieae by lacking trichomes or rarely having forked ones and by having exclusively basal, entire leaves. Thelypodieae circumscription should be restricted in future to the Thelypodieae clade, Schizopetaleae circumscription to the SCHIZ II clade, while a new tribe is needed for the SCHIZ I clade.Les auteurs ont utilisé les données des séquences provenant de l'espaceur interne transcrit (ITS) de l'ADN nucléique ribosomal et du gène plastidique ndhF de 95 espèces représentant 147 accessions, afin de déterminer les limites tribales, le statut monophylétique et les relations phylogénétiques intra-tribales des genres, chez les Schizopetalae (anciennement Thelypodieae) (Brassicaceae). Les analyses de parcimonie, Bayésiennes et de ressemblance la plus probable supportent toutes la reconnaissance de trois clades distincts et généralement bien supportés. Le plus grand de ces clades correspond au Thelypodieae des Amériques du Nord et du Sud (27 genres: Catadysia, Caulanthus, Chaunanthus, Chilocardamum, Chlorocrambe, Coelophragmus, Dictyophragmus, Dryopetalon, Englerocharis, Hesperidanthus, Mostacillastrum, Neuontobotrys, Polypsecadium, Pringlea, Pterygiosperma, Romanschulzia, Sibara, Sibaropsis, Stanleya, Streptanthella, Streptanthus, Thelypodiopsis, Thelypodium, Thysanocarpus, Warea, Weberbauera, and Werdermannia). On divise les six genres restants des Schizopetaleae de l'Amérique du Sud en deux clades: SCHIZ I avec 4 genres (Aschersoniodoxa, Brayopsis, Eudema, and Onuris) et SCHIZ II Schizopetalae s.str. (Mathewsia, and Schizopetalon). La résolution au sein du clade Thelypodieae reste limitée à la fois chez les phylogénies basées sur les ITS et le gène ndhF. En se basant sur les données des séquences ITS, les éléments de la tribu des Brassiceae du Nouveau Monde sont apparentés aux Thelypodieae, alors que les données provenant du gène ndhF supportent les Sisymbrieae comme apparentés aux Thelypodieae et les Brassiceae comme apparentés aux deux tribus. On n'arrive pas à résoudre clairement les groupes apparentés aux clades I et II des Schizopetalae.
Botany 09/2009; 87(10):961-985. · 1.25 Impact Factor
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ABSTRACT: The Brassicaceae family is of great scientific interest because it contains the plant model organism Arabidopsis thaliana. Currently, contemporary plant research activities expand to other Brassicaceae taxa. Despite that, the phylogeny of this family is only partly understood. The present study deepens our understanding of a family-wide phylogeny by using two new approaches in phylogenetic family-wide research. We used a molecular marker from the mitochondrial genome and utilised a relaxed molecular dating method. Our data generally confirms a recent tribal alignment of Brassicaceae. We present for the first time a biogeographical scenario for the broad-scale Brassicaceae evolution. We suggest that Brassicaceae most likely evolved some 19 mya in or near the eastern Mediterranean region from a common ancestor of its sister family Cleomaceae. The early Brassicaceae formed a lineage adapted to more open/drier habitats than its capparoid progenitors. The early Brassicaceae evolution was very rapid and the radiation was most likely driven by climatic changes that created open habitats and the well-documented expansion of open grass-dominated ecosystems. Moreover, our dating suggests that the radiation events correlate with an ancient genome duplication in the early history of the family, which is evidenced by recent genomic studies.
Taxon 04/2009; 58(2):425-437. · 2.70 Impact Factor
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ABSTRACT: The genus Leavenworthia (Brassicaceae) has long been a focus of research on mating system evolution, due to the presence of both self-incompatible and self-compatible species within the genus. A phylogenetic hypothesis invoking multiple transitions between mating systems has been proposed for Leavenworthia, but this hypothesis has not been subject to molecular phylogenetic analysis. DNA sequence variation from four non-coding chloroplast regions (the trnL intron; and the trnT-trnL, trnL-trnF, and psbA-trnH intergenic spacers) was used to reconstruct the generic phylogeny, to test the validity of several proposed species, and to assess the number of mating system transitions within the genus. The strict consensus tree largely reflected the long-standing phylogenetic hypothesis for Leavenworthia, although additional data are needed to fully validate the recognition of L. crassa and L. alabamica. Unexpected results included the placement of L. uniflora as sister to the rest of the genus, and the apparent hybridization between L. exigua and L. torulosa. Finally, our data strongly supported a minimum of three mating system transitions within Leavenworthia.
Systematic Botany 01/2009; · 1.52 Impact Factor
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ABSTRACT: In 2002, a monophyletic group previously unrecognized within Brassicaceae was identified through phylogenetic analysis of morphological characters in combination with data from three DNA sequences (Bailey et al.: Syst. Bot. 27: 318–332). As understood at that time, the halimolobine alliance (herein tribe Halimolobeae) comprised ca. 44 species from Halimolobos, Mancoa, Pennellia, and Sphaerocardamum. Within this group, a number of nomenclatural problems have remained unaddressed, including the polyphyly of both Halimolobos and Mancoa. With a developing understanding of Brassicaceae phylogeny, the Halimolobeae is robust in the context of higher level analyses and therefore in need of formal nomenclatural revision. The present study uses new and existing data in phylogenetic analyses based on trnL-F, ITS, and pistillata intron 1 data along with SEM studies of Synthlipsis elata and S. greggii to provide the bases for recircumscription of taxa assigned to the Halimolobeae. As recognized herein, the tribe includes five genera [Exhalimolobos, Halimolobos (including Synthlipsis elata), Mancoa, Pennellia, and Sphaerocardamum] and 39 species with two centers of distribution, one in north-central Mexico and the other in the Andes. A synopsis and keys to all taxa of the tribe are presented. Fifteen new combinations are proposed (E. arabioides, E. berlandieri, E. burkartii, E. hispidulus, E. palmeri, E. parryi, E. pazense, E. polyspermus, E. weddellii, H. elatus, H. henricksonii, H. pubens, H. stylosus, P. lechleri, and P. parvifolia).
Systematic Botany 01/2009; · 1.52 Impact Factor
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ABSTRACT: Parrya nauruaq Al-Shehbaz, J. R. Grant, R. Lipkin, D. F. Murray & C. L. Parker (Brassicaceae) is described from the Seward Peninsula of Alaska. It differs from the other North American species in Parrya R. Brown by its smaller flowers and fruits, and by its fewer seeds per fruit. A key to the four North American species of Parrya is provided.
Novon A Journal for Botanical Nomenclature 01/2009; · 0.19 Impact Factor
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ABSTRACT: The family Brassicaceae comprises 3710 species in 338 genera, 25 recently delimited tribes, and three major lineages based on phylogenetic results from the chloroplast gene ndhF. To assess the credibility of the lineages and newly delimited tribes, we sequenced an approximately 1.8-kb region of the nuclear phytochrome A (PHYA) gene for taxa previously sampled for the chloroplast gene ndhF. Using parsimony, likelihood, and Bayesian methods, we reconstructed the phylogeny of the gene and used the approximately unbiased (AU) test to compare phylogenetic results from PHYA with findings from ndhF. We also combined ndhF and PHYA data and used a Bayesian mixed model approach to infer phylogeny. PHYA and combined analyses recovered the same three large lineages as those recovered in ndhF trees, increasing confidence in these lineages. The combined tree confirms the monophyly of most of the recently delimited tribes (only Alysseae, Anchonieae, and Descurainieae are not monophyletic), while 13 of the 23 sampled tribes are monophyletic in PHYA trees. In addition to phylogenetic results, we documented the trichome branching morphology of species across the phylogeny and explored the evolution of different trichome morphologies using the AU test. Our results indicate that dendritic, medifixed, and stellate trichomes likely evolved independently several times in the Brassicaceae.
American Journal of Botany 10/2008; 95(10):1307-27. · 2.66 Impact Factor
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ABSTRACT: Arabidopsis thaliana is the preeminent plant model organism. However, significant advances in evolution and ecology are being made by expanding the scope of research beyond this single species into the broader genus Arabidopsis. Surprisingly, few studies have rigorously investigated phylogenetic relationships between the nine Arabidopsis species, and this study evaluates both these and hypotheses related to two instances of intra-generic hybridization. DNA sequences from the 5' flanking region of the nuclear Atmyb2 gene from 12 of the 14 Arabidopsis taxa were used to reconstruct the generic phylogeny. The strict consensus tree was highly concordant with previous studies, identifying lineages corresponding to widespread species but exhibiting a large basal polytomy. Our data indicates that the paternal parent of the allopolyploid A. suecica is A. neglecta rather than A. arenosa s.l., although the need for a detailed phylogeographical study of these three species is noted. Finally, our data provided additional phylogenetic evidence of hybridization between Arabidopsis lyrata s.l. and A. halleri s.l. Taken together, the well-defined lineages within the genus and the potential for hybridization between them highlight Arabidopsis as a promising group for comparative and experimental studies of hybridization.
Molecular Phylogenetics and Evolution 02/2007; 42(1):122-30. · 3.61 Impact Factor
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ABSTRACT: In order to examine the systematic application of seed-coat microsculpturing in Isatis, seed surfaces of 23 species (41 populations) in four genera of tribe Isatideae were examined using scanning electron microscopy (SEM). Eight types of basic ornamentation patterns were recognized among the studied specimens. Of these, the reticulate–areolate type was the most common and was found in the genera Isatis, Pachypterygium, Samerari and Tauscheria and 15 species (e.g., I. cappodocica, I. kotschyana and I. tinctoria). The reticulate type, the second most frequent, occurred in 7 species while other types each were represented by only one or 2 species. Although different populations of a given species show similar seed-surface sculpturing in most cases, in some polymorphic species like I. cappadocica and I. kotschyana these patterns were variable among populations. To some extent the variation corresponds to infraspecific taxa for some species, but the differences are not significant enough to be useful in the delimitation of the subspecies recognized by previous workers. Moreover, seed-coat characters do not support the separation of genera Isatis, Pachypterygium, Sameraria and Tauscheria.
Flora - Morphology Distribution Functional Ecology of Plants 01/2007; 202:447-454. · 1.64 Impact Factor
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ABSTRACT: The Brassicaceae is a large plant family (338 genera and 3,700 species) of major scientific and economic importance. The taxonomy of this group has been plagued by convergent evolution in nearly every morphological feature used to define tribes and genera. Phylogenetic analysis of 746 nrDNA internal transcribed spacer (ITS) sequences, representing 24 of the 25 currently recognized tribes, 146 genera, and 461 species of Brassicaceae, produced the most comprehensive, single-locus-based phylogenetic analysis of the family published to date. Novel approaches to nrDNA ITS analysis and extensive taxonomic sampling offered a test of monophyly for a large complement of the currently recognized tribes and genera of Brassicaceae. In the most comprehensive analysis, tribes Alysseae, Anchonieae plus Hesperideae, Boechereae, Cardamineae, Eutremeae, Halimolobeae, Iberideae, Noccaeeae, Physarieae, Schizopetaleae, Smelowskieae, and Thlaspideae were all monophyletic. Several broadly defined genera (e.g., Draba and Smelowskia) were supported as monophyletic, whereas others (e.g., Sisymbrium and Alyssum) were clearly polyphyletic. Analyses of ITS data identified several problematic sequences attributable to errors in sample identification or database submission. Results from parsimony ratchet and Bayesian analyses recovered little support for the backbone of the phylogeny, suggesting that many lineages of Brassicaceae have undergone rapid radiations that may ultimately be difficult to resolve with any single locus. However, the development of a preliminary supermatrix including the combination of 10 loci for 65 species provides an initial estimate of intertribal relations and suggests that broad application of such a method will provide greater understanding of relationships in the family.
Molecular Biology and Evolution 12/2006; 23(11):2142-60. · 5.55 Impact Factor
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ABSTRACT: To estimate the evolutionary history of the mustard family (Brassicaceae or Cruciferae), we sampled 113 species, representing 101 of the roughly 350 genera and 17 of the 19 tribes of the family, for the chloroplast gene ndhF. The included accessions increase the number of genera sampled over previous phylogenetic studies by four-fold. Using parsimony, likelihood, and Bayesian methods, we reconstructed the phylogeny of the gene and used the Shimodaira-Hasegawa test (S-H test) to compare the phylogenetic results with the most recent tribal classification for the family. The resultant phylogeny allowed a critical assessment of variations in fruit morphology and seed anatomy, upon which the current classification is based. We also used the S-H test to examine the utility of trichome branching patterns for describing monophyletic groups in the ndhF phylogeny. Our phylogenetic results indicate that 97 of 114 ingroup accessions fall into one of 21 strongly supported clades. Some of these clades can themselves be grouped into strongly to moderately supported monophyletic groups. One of these lineages is a novel grouping overlooked in previous phylogenetic studies. Results comparing 30 different scenarios of evolution by the S-H test indicate that five of 12 tribes represented by two or more genera in the study are clearly polyphyletic, although a few tribes are not sampled well enough to establish para- or polyphyly. In addition, branched trichomes likely evolved independently several times in the Brassicaceae, although malpighiaceous and stellate trichomes may each have a single origin.
American Journal of Botany 04/2006; 93(4):607-19. · 2.66 Impact Factor
