RESUMEN
The genus Argentina Hill belongs to the tribe Potentilleae Sweet and contains approximately 75 species predominantly distributed in the Sino-Himalayan region and the Malesian archipelago. So far we have less knowledge on the phylogenetic relationships within Argentina owing to limited sampling of Argentina taxa or gene fragments in previous studies. Moreover, to date there is no phylogenetic study on Argentina from the perspective of comparative chloroplast (cp) genomics. Here we performed comparative genomic analyses on the cp genomes of 39 accessions representing 18 taxa of Argentina. The Argentina cp genomes presented the typical quadripartite structure, with the sizes ranging from 155 096 bp to 157 166 bp. The 39 Argentina cp genomes contained a set of 112 unique genes, comprising four ribosomal RNA (rRNA) genes, 30 transfer RNA (tRNA) genes, as well as 78 protein-coding genes (PCGs). The cp genome organization, gene content and order in Argentina were highly conserved, but some visible divergences were present in IR/SC boundary regions. Ten regions (trnH-GUG-psbA, trnG-GCC-trnfM-CAU, trnD-GUC-trnY-GUA, rpl32-trnL-UAG, atpH-atpI, rps16-trnQ-UUG, trnS-GCU-trnG-UCC, ndhF-rpl32, trnR-UCU-atpA, and accD-psaI) were identified as excellent candidate DNA markers for future studies on species identification, population genetics and phylogeny of Argentina. Our results indicated that Argentina is monophyletic. In the current sampling, the A. smithiana - A. anserina clade was sister to the remainder of Argentina. Our results corroborated the previous taxonomic treatments to transfer A. phanerophlebia and A. micropetala from the genus Sibbaldia L. to Argentina. Our results showed close relationships among A. stenophylla, A. microphylla, A. taliensis, and A. tatsienluensis, congruent with previous studies based on the morphology of these species. Twenty-six genes (rps3, rps15, rps16, rps19, rpl16, rpl20, rpl22, rpoA, rpoB, rpoC1, rpoC2, atpA, atpF, psbB, psbF, ndhA, ndhB, ndhC, ndhD, ndhF, rbcL, accD, ccsA, matK, ycf1, ycf2) were with sites under positive selection, and adaptive evolution of these genes might have played crucial roles in Argentina species adaptation to the harsh mountain environment. This study will facilitate future work on taxonomy, phylogenetics, and adaptive evolution of Argentina.
RESUMEN
The tribe Potentilleae comprises approximately 1700 species in 13 genera, making it one of the largest of the 16 tribes in Rosaceae. Our understanding of the composition and relationships among members of Potentilleae has advanced dramatically with the application of molecular markers in the last two decades. Yet there is still much work remaining toward a robust phylogenetic framework for the entire Potentilleae and a comprehensive genus-level dating framework for the tribe. The goals of the present study were to establish a phylogenetic framework for Potentilleae, infer the origin and diversification of the tribe using a temporal framework, and explore the taxonomic implications in light of the updated phylogenetic framework. We used the plastome sequences from 158 accessions representing 139 taxa covering all 13 recognized genera of the tribe to reconstruct the Potentilleae phylogeny. High phylogenetic resolution was recovered along the Potentilleae backbone. Two major clades were recovered within Potentilleae, corresponding to the two subtribes Fragariinae and Potentillinae. Within Fragariinae, two subclades were recovered. In one subclade, Sibbaldia sensu stricto is sister to a clade containing Sibbaldianthe, Comarum, Farinopsis, and Alchemilla sensu lato. In the other subclade, Fragaria is sister to a clade comprising Chamaerhodos, Chamaecallis, Drymocallis, Dasiphora, and Potaninia. Within Potentillinae, Argentina is sister to Potentilla sensu stricto. Within Potentilla sensu stricto, clade Himalaya is sister to Alba, and the Himalaya-Alba clade together is sister to a clade comprising Reptans, Potentilla ancistrifolia Bunge, Fragarioides, Ivesioid, and Argentea. Divergence time estimates indicated that tribe Potentilleae originated during the middle Eocene, and subtribes Fragariinae and Potentillinae diverged around the Eocene-Oligocene transition, and divergence times dated for Potentilleae genera ranged from the early Miocene to the late Pleistocene.