Dataset Information

Centaurea Subsect. Phalolepis (Compositae, Cardueae): A Case Study of Mountain-Driven Allopatric Speciation in the Mediterranean Peninsulas.

ABSTRACT: Centaurea subsection Phalolepis has been thoroughly analyzed in previous studies using microsatellites in four centers of speciation: Anatolia, Greece, the Italian Peninsula and the Iberian Peninsula. Evidence suggests a correlation between taxon diversity and mountains. This group constituted a good case study for examining the mountain-geobiodiversity hypothesis (MGH), which explains the possible reasons for the many radiations occurring in mountains across the world. We combined all the datasets and carried out analyses of their genetic structure to confirm the species of subsect. Phalolepis are grouped according to a geographic pattern. We then checked whether climatic fluctuations favored the "species pump" hypothesis in the mountains by using the Climatic Stability Index (CSI). Finally, the relief of the terrain was tested against the rate of allopatric speciation by region by means of Terrain Ruggedness Index and environmental gradients through our new Climate Niche Breadth Index. Our results supported the MGH hypothesis and confirmed that the main triggers, namely altitudinal zonation, climatic oscillations and rugged terrain, must be present for the development of a radiation.

SUBMITTER: Garcia-Jacas N

PROVIDER: S-EPMC9823864 | biostudies-literature | 2022 Dec

REPOSITORIES: biostudies-literature

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Centaurea Subsect. Phalolepis (Compositae, Cardueae): A Case Study of Mountain-Driven Allopatric Speciation in the Mediterranean Peninsulas.

Garcia-Jacas Núria N López-Pujol Jordi J Nualart Neus N Herrando-Moraira Sonia S Romaschenko Konstantin K Ren Ming-Xun MX Susanna Alfonso A

Plants (Basel, Switzerland) 20221220 1

Centaurea subsection Phalolepis has been thoroughly analyzed in previous studies using microsatellites in four centers of speciation: Anatolia, Greece, the Italian Peninsula and the Iberian Peninsula. Evidence suggests a correlation between taxon diversity and mountains. This group constituted a good case study for examining the mountain-geobiodiversity hypothesis (MGH), which explains the possible reasons for the many radiations occurring in mountains across the world. We combined ...[more]

PMID: 36616140

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Project description:Background and aimsThe geographic distribution of the genus Plectocephalus comprises a single species in Ethiopia, two in North America and possibly four more in South America, in a striking disjunction that is exceptional for genera of the tribe Cardueae. The enormity of this disjunction cast doubts on the precise taxonomic delineation of the genus, which is not unanimously recognized as a natural entity. The aims of this study were to define the generic boundaries of Plectocephalus and to formulate a hypothesis that would explain its natural range.MethodsA combined molecular approach, using nuclear internal transcribed spacers (ITS) and external transcribed spacers (ETS), and plastid trnL-trnL-F, rpl32-trnL(UAG) and ndhF markers, was chosen for phylogenetic reconstruction by maximum parsimony and Bayesian inference.Key resultsPhylogenetic analysis shows that Plectocephalus is a natural genus that includes the African species P. varians, together with all the native South American species, currently classified as Centaurea, C. cachinalensis, C. floccosa and C. tweediei. The recognition of Centaurodendron as an independent genus, which we consider appropriate, would make Plectocephalus paraphyletic. Affinities of Plectocephalus should lie with eastern representatives of Centaureinae. Geographic disjunction is explained as a consequence of dispersal via the Bering Land Bridge during the Miocene--Pliocene. The phylogeny of the basal grade of Centaureinae differs from previous phylogenies, and artefacts resulting from differences in mutation rates of annual and perennial taxa are confirmed. Sensitivity of ITS to these differences was the highest observed for all DNA regions used in this study.ConclusionsThe natural status of the genus Plectocephalus is confirmed and several nomenclatural combinations are proposed. New evidence contributes to the debate concerning problems posed by the use of ITS in the phylogenetic reconstruction of groups that differ in terms of their life cycles. Dispersal from Caucasus and Anatolia along the Siberian route and then across the Bering Land Bridge follows a route previously proposed for other taxonomic groups.

Project description:BackgroundThis study explored chromosome number variation, phylogenetic divergence, and mechanisms underlying speciation in East Asian thistle Cirsium Mill. sect. Onotrophe (Cass.) DC. subsect. Nipponocirsium Kitam. (Compositae). The study focused on the newly identified species from Taiwan: Cirsium pengii Y.H. Tseng, P.C. Liao & Chih Y. Chang. Utilizing phylotranscriptomic data to reconstruct evolutionary relationships between the Taiwanese and Japanese taxa of Cirsium subsect. Nipponocirsium as well as their divergence times and chromosomal characteristics. Additionally, the chromosome number, morphology, and pollen morphology of the unknown Cirsium taxon are compared with other known subsect. Nipponocirsium taxa from Taiwan.ResultsPhylotranscriptomic analysis reveals a division within subsect. Nipponocirsium into Japanese and Taiwanese clades. In the Taiwanese clade, C. pengii is basal, while C. tatakaense remains monophyletic with other Taiwanese species despite higher genetic diversity. The prevalent chromosome number in this subsection is tetraploid (2n = 4x = 68), common in Japanese taxa, while Taiwanese members have 2n = 4x = 64. Notably, C. pengii has a diploid number (2n = 32), indicating descending dysploidy followed by polyploidization in Taiwan. This polyploidization, driven by glaciations, likely shaped the evolution of Nipponocirsium. Divergence time estimates suggest the separation of Japanese and Taiwanese clades around 0.74 million years ago (Myr) during glacial periods. Cirsium pengii diverged around 0.47 Myr, while tetraploid species C. kawakamii and C. tatakaense diverged around 0.35 Myr. These species likely evolved in separate refugia, with distinct species boundaries confirmed through species delimitation analysis, karyotype, morphology, and pollen morphology comparisons.ConclusionsThese findings enhance our understanding of chromosomal evolution and speciation within subsect. Nipponocirsium and underscore the importance of integrating transcriptomic data in phylogenetic studies. This study provides a comprehensive framework for further investigations into the genetic diversity and adaptive mechanisms of this ecologically vital group.

Dataset Information

Centaurea Subsect. Phalolepis (Compositae, Cardueae): A Case Study of Mountain-Driven Allopatric Speciation in the Mediterranean Peninsulas.

Publications

<i>Centaurea</i> Subsect. <i>Phalolepis</i> (Compositae, Cardueae): A Case Study of Mountain-Driven Allopatric Speciation in the Mediterranean Peninsulas.

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