Phylogenetic estimation and morphological evolution of Alsineae (Caryophyllaceae) shed new insight into the taxonomic status of the genus Pseudocerastium

Abstract

Pseudocerastium is a monotypic genus in Caryophyllaceae endemic to China. The genus has been widely accepted since it was described in 1998, however its phylogenetic position within Caryophyllaceae has never been studied. In the present study, the whole plastid genome and nuclear ribosomal internal transcribed spacer (ITS) sequences of Pseudocerastium stellarioides was obtained through genome skimming, and the phylogenetic position of the species was studied for the first time. Plastid phylogenomic analysis of Caryophyllaceae revealed that Pseudocerastium is clustered within the tribe Alsineae with strong support. Phylogenetic analyses based on an enlarged taxon sampling of Alsineae using five DNA regions ( matK , rbcL , rps16 intron , trnL-F and ITS) revealed that P. stellarioides was nested deeply within Cerastium with strong support. Analyses of morphological character evolution suggest that the ancestral states in Alsineae include three styles and a six-lobed capsule at the apex, while both Cerastium and Pseudocerastium have five styles and ten lobes at the apex of the capsule, further supporting their close relationship. The species Pseudocerastium stellarioides is similar to Cerastium wilsonii in morphology, but differs in having villous indumentum on the lower part of the filaments and compressed globose seeds. Therefore, based on the present molecular and morphological evidence, the generic name Pseudocerastium is reduced here as a new synonym of Cerastium and the species P. stellarioides is transferred to Cerastium as C. jiuhuashanense .

Intergeneric relationships within the tribe Alsineae (Caryophyllaceae) as inferred from nrDNA ITS and cpDNArps16 sequences: A step toward a phylogenetically based generic system

“…1.6) and those of the isotype (KUN, barcode KUN0603914!). Therefore, we doubt correct identification of the voucher specimen used as P. stellarioides in molecular phylogenetic analyses presented by Yao & al. (2021).…”

“…Furthermore, Sharples & Tripp (2019b) provided a significant contribution on the delimitation of some challenging species of Stellaria , using RAD sequencing technology. A recent phylogenomic study of Alsineae using several plastid markers along with nrDNA ITS reduced the generic name Pseudocerastium to a synonym of Cerastium (Yao & al., 2021).…”

Molecular and morphological evidence for a new species of Pogostemon (Lamiaceae) from Hainan Island, China

“…The models of nucleotide substitution of the six DNA markers used were selected independently under the Akaike Information Criterion ( AIC ) using jModeTest v. 3.7 ( Posada 2008 ): GTR+I+Γ for nrITS , GTR+Γ for matK , TrN+Γ for psbA-trnH , GTR+I for rbcL , TVM+Γ for rps16 and GTR+I for trnL-F . Detailed methods for BI and ML analyses could refer to the phylogenetic study conducted in Yao et al (2021) , except that each of Markov Chain Monte Carlo ( MCMC ) analysis was run for 10,000,000 generations and sampling every 500 generations in BI analysis. Number of generations in BI analysis was sufficient, because the effective sample size ( ESS ) of all parameters were over 200 as evaluated in Tracer v. 1.6 ( Rambaut et al 2014 ), and the average standard deviations ( SD ) of split frequencies for the dataset was below 0.01.…”

Molecular and morphological evidence for a new species of Leptopus (Phyllanthaceae) from Southeast Yunnan, China

“…The models of nucleotide substitution of the two DNA markers used were selected under the Akaike Information Criterion (AIC) using jModeTest v. 3.7 ( Posada, 2008 ): TVM+G for matK and GTR+I+G for nrITS. Detailed information about the parameter setting in BI and ML analyses referred the phylogenetic analyses conducted in Yao et al. (in press) , except that each of Markov Chain Monte Carlo (MCMC) analysis was run for 10,000,000 generations, sampling every 500 generations.…”