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Polyploidy is a significant mechanism in eukaryotic evolution and is particularly prevalent in the plant kingdom. However, our knowledge about this phenomenon and its effects on evolution remains limited. A major obstacle to the study of polyploidy is the great difficulty in untangling the origins of allopolyploids. Due to the drastic genome changes and the erosion of allopolyploidy signals caused by the combined effects of hybridization and complex post-polyploid diploidization processes, resolving the origins of allopolyploids has long been a challenging task. Here we revisit this issue with the interesting case of subtribe Tussilagininae (Asteraceae: Senecioneae) and by developing HomeoSorter, a new pipeline for network inferences by phasing homeologs to parental subgenomes. The pipeline is based on the basic idea of a previous study but with major changes to address the scaling problem and implement some new functions. With simulated data, we demonstrate that HomeoSorter works efficiently on genome-scale data and has high accuracy in identifying polyploid patterns and assigning homeologs. Using HomeoSorter, the maximum pseudo-likelihood model of Phylonet, and genome-scale data, we further address the complex origin of Tussilagininae, a speciose group (ca. 45 genera and 710 species) characterized by having high base chromosome numbers (mainly x = 30, 40). In particular, the inferred patterns are strongly supported by the chromosomal evidence. Tussilagininae is revealed to comprise two large groups with successive allopolyploid origins: Tussilagininae s.s. (mainly x = 30) and the Gynoxyoid group (x = 40). Two allopolyploidy events first give rise to Tussilagininae s.s., with the first event occurring between the ancestor of subtribe Senecioninae (x = 10) and a lineage (highly probably with x = 10) related to the Brachyglottis alliance, and the resulting hybrid lineage crossing with the ancestor of Chersodoma (x = 10) and leading to Tussilagininae s.s. Then, after early diversification, the Central American group (mainly x = 30) of Tussilagininae s.s., is involved in a third allopolyploidy event with, again, the Chersodoma lineage and produces the Gynoxyoid group. Our study highlights the value of HomeoSorter and the homeolog-sorting approach in polyploid phylogenetics. With rich species diversity and clear evolutionary patterns, Tussilagininae s.s. and the Gynoxyoid group are also excellent models for future investigations of polyploidy.
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Synotisjinpingensis (Asteraceae, Senecioneae), a new species from Jinping county in southeastern Yunnan province, China, is described and illustrated. This species is distinguished by having white ray florets in the genus Synotis, in which only species with yellow ray florets have been hitherto known. In habit and leaf shape S.jinpingensis is most closely similar to S.duclouxii, a species occurring in southwestern Guizhou, southern Sichuan and northeastern Yunnan, China, but differs, in addition to the color of ray florets, by having fewer lateral veins of leaves, obviously longer bracts of calyculus, and larger phyllaries. The membership of the new species within Synotis is strongly corroborated by evidence from floral micromorphology and phylogenetic analyses based on ITS sequence data. Color photographs of living plants, a distribution map, and provisional IUCN status of S.jinpingensis are provided.
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Ranunculusluanchuanensis (Ranunculaceae), a new species from Laojun Shan in Luanchuan county, Henan province, central China, is here illustrated and described. It is morphologically similar to R.limprichtii in having 3-lobed and subreniform basal leaves, 3-lobed cauline leaves, and small flowers with reflexed and caducous sepals, but differs by having slender and basally slightly thickened roots (vs. fusiform), prostrate stems (vs. erect), obliquely ovoid and glabrous carpels and achenes (vs. widely ovoid and puberulous), longer styles in the carpels (ca. 1.2 mm vs. 0.6-0.8 mm) and achenes (ca. 1.8 mm vs. 0.6-0.8 mm), and glabrous receptacles (vs. sparsely puberulous). Ranunculusluanchuanensis, currently known only from its type locality, is geographically isolated from R.limprichtii, a species widely distributed in Gansu, Qinghai, Sichuan, Xizang (Tibet) and Yunnan, China. The distribution map of this new species and its putative closest ally, R.limprichtii, is also provided.
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Ranunculusjiguanshanicus (Ranunculaceae), a new species from Chongzhou in Sichuan province, China, is here described and illustrated. The new species is easily distinguishable from other Chinese members of the genus by an array of characters, including small stature, glabrous and prostrate stems, 3-foliolate leaves with obvious petiolules (3-5 mm long), unequally 3-sected leaflets, lanceolate to linear ultimate leaflet segments, small flowers (5.2-6 mm in diameter), and long styles in the carpels and achenes (ca. 0.8 mm long). A distribution map of this new species is also provided.
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Ranunculusmaoxianensis (Ranunculaceae), a new species from Jiuding Shan in Maoxian county, northwestern Sichuan province, China, is here illustrated and described. The species is morphologically similar to R.chongzhouensis, a species also occurring in Sichuan, in having reniform leaves and puberulous receptacles, carpels and achenes, but differs by having leaves adaxially puberulous with shorter appressed hairs 0.16â0.28 mm long (vs. longer appressed hairs 0.55â0.85 mm long), larger flowers (1.8â2 cm vs. 1.4â1.6 cm in diameter), larger (8â10 × 5.5â6.5 mm vs. 6â7 × 4.5â5 mm) and widely obovate petals (vs. obovate), more numerous stamens (35â55 vs. 12â18), and subglobose gynoecium and aggregate fruit (vs. ellipsoid). The two species are also different in chromosome number and chromosome morphology. Ranunculuschongzhouensis has a karyotype of 2n = 2x = 16 = 10m + 6sm while R.maoxianensis has a karyotype of 2n = 4x = 32 = 16m + 16sm. An emended description of R.chongzhouensis is provided, and its geographical distribution is largely extended.
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Sinoseneciominshanicus (Asteraceae, Senecioneae), a new species from south-eastern Gansu (Wenxian and Zhugqu counties) and northern Sichuan (Pingwu county), China, is described and illustrated. This species is similar to S.rotundifolius, a species locally endemic to Songpan county in northern Sichuan, in having a scapigerous habit, orbicular leaves and solitary capitula, but differs by the presence (vs. absence) of stolons and by having thinner rhizomes (ca. 2 mm vs. more than 5 mm in diameter), stems proximally sparsely fulvous arachnoid or glabrescent (vs. densely sericeous-villous) and obscure (vs. conspicuous) main veins on adaxial surface of leaves. The chromosome number of the new species is reported to be 2n = 60. Colour photographs of living plants in the wild and a distribution map are provided for the new species and S.rotundifolius. The geographical distribution of S.rotundifolius is also corrected, with the previous record of this species from south-eastern Gansu (Wenxian county) actually referring to S.minshanicus.
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Sinoseneciopingwuensis (Asteraceae, Senecioneae), a new species from Pingwu county in northern Sichuan, China, is described and illustrated. This species is distinguished in Sinosenecio by having leathery, glabrous, ovate or ovate-oblong leaves often pinnately-veined and solitary capitula 2.3-4.3 cm in diameter, a unique character combination hitherto never recorded in the genus. Two floral micromorphological characters (configuration of filament collar of stamens and anther endothecial cell wall thickenings) and achene surface features of the new species are reported. Color photographs of living plants and a distribution map are also provided for the new species.
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The tribe Senecioneae is one of the largest tribes in Asteraceae, with a nearly cosmopolitan distribution. Despite great efforts devoted to elucidate the evolution of Senecioneae, many questions still remain concerning the systematics of this group, from the tribal circumscription and position to species relationships in many genera. The hybridization-based target enrichment method of next-generation sequencing has been accepted as a promising approach to resolve phylogenetic problems. We herein develop a set of single-/low-copy genes for Senecioneae, and test their phylogenetic utilities. Our results demonstrate that these genes work highly efficiently for Senecioneae, with a high average gene recovery of 98.8% across the tribe and recovering robust phylogenetic hypotheses at different levels. In particular, the delimitation of the Senecioneae has been confirmed to include Abrotanella and exclude Doronicum, with the former sister to core Senecioneae and the latter shown to be more closely related to Calenduleae. Moreover, Doronicum and Calenduleae are inferred to be the closest relatives of Senecioneae, which is a new hypothesis well supported by statistical topology tests, morphological evidence, and the profile of pyrrolizidine alkaloids, a special kind of chemical characters generally used to define Senecioneae. Furthermore, this study suggests a complex reticulation history in the diversification of Senecioneae, accounting for the prevalence of polyploid groups in the tribe. With subtribe Tussilagininae s.str. as a case study showing a more evident pattern of gene duplication, we further explored reconstructing the phylogeny in the groups with high ploidy levels. Our results also demonstrate that tree topologies based on sorted paralogous copies are stable across different methods of phylogenetic inference, and more congruent with the morphological evidence and the results of previous phylogenetic studies.
Assuntos
Asteraceae/classificação , Asteraceae/genética , Núcleo Celular/genética , Filogenia , Hibridização Genética , PoliploidiaRESUMO
We explored the temporal and spatial diversification of the plant genus Sedum L. (Crassulaceae) in Taiwan based on molecular analysis of nrITS and cpDNA sequences from East Asian Sedum members. Our phylogenetic and ancestral area reconstruction analysis showed that Taiwanese Sedum comprised two lineages that independently migrated from Japan and Eastern China. Furthermore, the genetic distances among species in these two clades were smaller than those of other East Asian Sedum clades, and the Taiwanese members of each clade occupy extremely varied habitats with similar niches in high-mountain regions. These data indicate that species diversification occurred in parallel in the two Taiwanese Sedum lineages, and that these parallel radiations could have occurred within the small continental island of Taiwan. Moreover, the estimated time of divergence for Taiwanese Sedum indicates that the two radiations might have been correlated to the formation of mountains in Taiwan during the early Pleistocene. We suggest that these parallel radiations may be attributable to the geographical dynamics of Taiwan and specific biological features of Sedum that allow them to adapt to new ecological niches.
Assuntos
Evolução Biológica , Ecossistema , Ilhas , Sedum/fisiologia , Teorema de Bayes , Núcleo Celular/genética , DNA de Cloroplastos/genética , DNA Ribossômico/genética , Geografia , Funções Verossimilhança , Filogenia , Folhas de Planta/anatomia & histologia , Sedum/genética , Especificidade da Espécie , TaiwanRESUMO
Phylogenetic analyses were performed using multiple nuclear (ITS and ETS) and chloroplast regions (ndhF-trnL, psbA-trnH, psbD-trnT, and trnT-trnL) to test the monophyly of Aconitum subgen. Lycoctonum (Ranunculaceae) and reconstruct the phylogenetic relationships within the subgenus. The subgenus as currently circumscribed is revealed to be polyphyletic. To achieve its monophyly, sect. Galeata and sect. Fletcherum, both being unispecific and each having a unique array of characters (the latter even having the aberrant base chromosome number of x = 6), must be removed from the subgenus. The subgenus Lycoctonum should thus be redefined to include only two sections, the unispecific sect. Alatospermum and the relatively species-rich sect. Lycoctonum. The section Alatospermum, which is both morphologically and karyologically in the primitive condition, is resolved as the first diverging lineage of the subgenus Lycoctonum clade. The monophyly of sect. Lycoctonum is strongly supported, but all the ten series currently recognized within the section are revealed to be para- or poly-phyletic. Five major clades are recovered within the section. We propose to treat them as five series: ser. Crassiflora, ser. Scaposa, ser. Volubilia, ser. Longicassidata, and ser. Lycoctonia. Thus, a formal reclassification of subgen. Lycoctonum is presented, which involves segregating both sect. Galeata and sect. Fletcherum from the subgenus as two independent subgenera within the genus Aconitum, reinstating one series (ser. Crassiflora) and abolishing six series (ser. Laevia, ser. Longibracteolata, ser. Micrantha, ser. Ranunculoidea, ser. Reclinata, and ser. Umbrosa) within sect. Lycoctonum. The series affiliation of some species within the section is adjusted accordingly.
Assuntos
Aconitum/classificação , Filogenia , Sequência de Bases , Núcleo Celular/genética , DNA de Cloroplastos/genética , DNA de Plantas/genética , DNA Ribossômico/genética , Bases de Dados de Ácidos Nucleicos , Funções Verossimilhança , Análise de Sequência de DNARESUMO
Senecio changii (Asteraceae: Senecioneae), a new species from Muli, Sichuan, southwestern China, is described. It is distinguished in Chinese Senecio s.s. by having lyrate-pinnatisect to pinnatisect leaves and a single terminal large discoid capitulum which is somewhat nodding. Evidence from floral micromorphology, karyology and molecular phylogenetic analyses based on the nuclear ITS/ETS sequence data all support its membership within Senecio s.s.
Assuntos
DNA de Plantas/genética , Folhas de Planta/genética , Senécio/classificação , Senécio/genética , China , Filogenia , Folhas de Planta/crescimento & desenvolvimento , Senécio/crescimento & desenvolvimentoRESUMO
BACKGROUND: Synotis (Asteraceae; Senecioneae) is a genus of about 55 species mostly distributed in the Sino-Himalayan region. During a botanical expedition in southwestern China in 2012, we found an unusual population of Synotis in southwestern Yunnan Province. To determine the taxonomic identity of the population, we carried out gross-morphological, floral micromorphological, and cytological observations. RESULTS: Our gross-morphological observations have shown that the population is most similar to Synotis auriculata C. Jeffrey & Y. L. Chen in leaf shape and in the number of phyllaries and florets, but readily distinguishable by the glabrous stem and petiole (vs. glandular pubescent), the exauriculate petiole (vs. auriculate), the uppermost leaves obviously smaller than the middle ones (vs. almost equally sized), and the larger ray florets (4-4.5 mm vs. ca. 2.5 mm). The floral micromorphological observations on the population agree with previous reports for other species of Synotis. The chromosomes of the population are counted to be 2n = 40. Its karyotype is formulated as 2n = 20m + 14sm + 6st. CONCLUSIONS: The population was determined to represent a new species, i.e. Synotis baoshanensis M. Tang & Q. E. Yang, which is described herein. The species belongs to Synotis ser. Microglossae.
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BACKGROUND: Synotis is one of the several genera within Senecioneae (Asteraceae) with more than 40 species that are mainly distributed in China or in the Sino-Himalayan region. During a botanical expedition in central and southwestern China in 2011, we found an unusual population of Synotis in southwestern Hunan Province. To determine the taxonomic identity of the population, we carried out gross-morphological, floral micromorphological, and cytological observations. RESULTS: Our gross-morphological observations have shown that the population is most similar to Synotis changiana Y. L. Chen, but readily distinguishable in the discoid capitula (vs. radiate), and in the bracts of calyculus 9-10 (vs. 6-8), 6-7 mm long (vs. 3-4 mm). The floral micromorphological observations on the population and S. changiana agree with previous reports for other species of Synotis. The chromosomes of the population are counted to be 2n = 40 + 0-1B. Its karyotype is formulated as 2n = 22m + 14sm + 4st. CONCLUSIONS: The population is determined to represent a new species, i.e. Synotis xinningensis M. Tang & Q. E. Yang, which is described herein. The new species belongs to Synotis ser. Synotis.