Comparative Genomics and Phylogenetic Analyses of Christia vespertilionis and Urariopsis brevissima in the Tribe Desmodieae (Fabaceae: Papilionoideae) Based on Complete Chloroplast Genomes

Taxonomic and phylogenetic relationships of Christia, Urariopsis, Uraria and related genera within the tribe Desmodieae (Fabaceae: Papilionoideae) have long been controversial. Here, we report the complete chloroplast (cp) genomes of Christia vespertilionis and Urariopsis brevissima and perform comparative and phylogenetic analyses with Uraria lagopodioides and other relatives in the Desmodieae. The cp genomes of C. vespertilionis and U. brevissima are 149,656 and 149,930 bp long, with 128 unique genes (83 protein-coding genes, 37 tRNA genes and 8 rRNA genes), respectively. Comparative analyses revealed 95-129 simple sequence repeats (SSRs) and eleven highly variable regions (trnK-rbcL, rbcL-atpB, ndhJ-trnF, trnL-trnT, psbD-rpoB, accD-cemA, petA-psbL, psbE-petL, rps11-rps19, ndhF-ccsA, and rps15-ycf1) among six Desmodieae species. Phylogenetic analyses clearly resolved two subtribes (Desmodiinae and Lespedezinae) of Desmodieae as monophyletic, and the newly reported C. vespertilionis and U. brevissima clustered in subtribe Desmodiinae. A sister relationship of C. vespertilionis to U. lagopodioides was supported. Evidence was presented to support the treatment of Urariopsis as a distinct genus rather than in synonymy with Uraria. The results provide valuable information for further studies on species delimitation, phylogenetics, population genetics, and the evolutionary process of speciation in the Desmodieae.