Pinellia discolor: A new cryptic species distinguished from P. cordata in Mainland China

Pinellia cordata (Araceae) is a perennial herb species distributed in China and Japan. Several studies have shown that there are two types of this species, and chromosome counts have shown irregular variation among populations. In this study, we investigated the morphological characteristics, established the chromosome number in root tips, reconstructed phylogenetic relationship based on whole chloroplast genomes, and elucidated biogeographic patterns based on data collected from the Chinese Virtual Herbarium (CVH) and the Plant Photo Bank of China (PPBC) for the two types of P. cordata, including type I (greenish leaf blade) and type II (colored leaf blade). We found stable significant differences in morphometric characteristics (color of the leaf blade abaxially, petiole, spathe, and appendix) and the number of chromosomes. The results of the phylogenetic analysis showed that types I and II were located in different places in the evolutionary tree compared to the group. The distribution regions of these types of P. cordata were also slightly different in Mainland China. These findings suggested that P. cordata should be divided into P. cordata (Type I) and P. discolor (Type II, a cryptic species), and the latter is here described as a new species.

Methods
Morphometric analyses: Mature individuals during sexual reproductive stage (43 for Pinellia cordata and 52 for P. discolor, from the end of March to the middle of May, 2021) were used to determine 44 morphological characteristics. Statistical analysis should be carried out with Excel 2010® based on 18 quantitative traits among these 44 determined characteristics. Chromosome numbering: Root tips were used to chromosome preparation: stained and crushed in carbol fuchsin, and then were observed and photographed (Olympus® BX53) (Liu et al., 1987). Chloroplast genome analysis and phylogenetic analyses: The complete chloroplast genome annotation (Tillich et al., 2017) and SSRs analysis (Thiel et al., 2003) for P. discolor were carried out. Furthermore, whole chloroplast genome comparision between P. discolor and P. cordata (MT863558, Luo et al., 2021) were executed on the basis of re-annotation. Biogeographic pattern analysis: Chinese Virtual Herbarium (CVH, https://www.cvh.ac.cn/) and Plant Photo Bank of China (PPBC, http://ppbc.iplant.cn/) were used to collected geographic distribution information of P. cordata and P. discolor in field.