New morphological and DNA evidence supports the existence of Calligonum jeminaicum Z. M. Mao (Calligoneae, Polygonaceae) in China

Abstract

Calligonum jeminaicum Z. M. Mao, a species regarded as endemic to China, was thought to be nonexistent owing to a lack of scientific records. The similarity of C. jeminaicum to C. mongolicum Turcz. warranted an investigation into the taxonomical relationship between these species. In this study, a naturally occurring population of C. jeminaicum was discovered and the taxonomical relationships of this species with C. mongolicum were resolved. Morphological traits, including fruit and flower characteristics, as well as nuclear (ETS, ITS) and chloroplast (psbA-trnH, ycf6-psbM, rpl32-trnL, rbcL, and trnL-F) DNA sequence data were studied to confirm the taxonomic status of C. jeminaicum. The nrDNA data (ITS1-2 and ETS) from C. jeminaicum reflected variability from the whole C. mongolicum complex, showing distinctive haplotypes in the Calligonum sect. Medusa Sosk. & Alexandr. The cpDNA data supplied similar evidence, showing unique branching in Bayesian and ML tree analyses. The specific status of C. jeminaicum is confirmed based on both morphological and molecular analyses. Here we present a revised description of C. jeminaicum along with its DNA barcode and discuss suggestions for the conservation of this species. Based on current evidence, this species was evaluated as Critically Endangered (CR) according to the IUCN criteria.

A phylogeny of Calligonum L. (Polygonaceae) yields challenges to current taxonomic classifications

“…Information of all the samplings for this study was shown and cited in Table 1. The data generated in our previous study (Shi et al 2019) were also incorporated in the present analyses and the information of samplings can be found therein. We also expanded our sampling by downloading available DNA sequences from GenBank, in which the samples in North Africa have been labeled in the Fig.…”

“…Therefore, we treated the CM complex as well as a complex of C. rubicundum (CR complex, hereafter) each as single species, which we have labeled throughout the study according to the geographic origins of individual samples (see Tab. 1 and Shi et al 2019).…”

“…40 to 85 may represent entities meriting species status (Sanchez et al 2011;Soskov 2011). In several prior studies, plastid and nuclear DNA sequences have been used for phylogenetic reconstructions to aid in species delimitation in this genus (Shi et al 2009;2016;2017;2019) as well as to infer its position within Polygonaceae (Zhou et al 2003;Sanchez et al 2009;2011;Soskov 2011;Sun & Zhang 2012;Schuster et al 2013;) and reconstruct the biogeographic history of its taxonomic sections (Wen et al 2015;2016a;. Nevertheless, there remains a lack of DNA data for elucidating the mechanisms that have contributed to taxonomic complexities in Calligonum, especially to determine the possible roles of reticulate evolution and hybrid speciation in its evolutionary history.…”