<i>Hedysarum</i> L. (Fabaceae: Hedysareae) Is Not Monophyletic – Evidence from Phylogenetic Analyses Based on Five Nuclear and Five Plastid Sequences

<div><p>The legume family (Fabaceae) exhibits a high level of species diversity and evolutionary success worldwide. Previous phylogenetic studies of the genus <i>Hedysarum</i> L. (Fabaceae: Hedysareae) showed that the nuclear and the plastid topologies might be incongruent, and the systematic position of the <i>Hedysarum</i> sect. <i>Stracheya</i> clade was uncertain. In this study, phylogenetic relationships of <i>Hedysarum</i> were investigated based on the nuclear ITS, ETS, <i>PGDH</i>, <i>SQD1</i>, <i>TRPT</i> and the plastid <i>psbA-trnH</i>, <i>trnC-petN</i>, <i>trnL-trnF</i>, <i>trnS-trnG</i>, <i>petN-psbM</i> sequences. Both nuclear and plastid data support two major lineages in <i>Hedysarum</i>: the <i>Hedysarum s</i>.<i>s</i>. clade and the <i>Sartoria</i> clade. In the nuclear tree, <i>Hedysarum</i> is biphyletic with the <i>Hedysarum s</i>.<i>s</i>. clade sister to the <i>Corethrodendron + Eversmannia + Greuteria + Onobrychis</i> clade (the CEGO clade), whereas the <i>Sartoria</i> clade is sister to the genus <i>Taverniera</i> DC. In the plastid tree, <i>Hedysarum</i> is monophyletic and sister to <i>Taverniera</i>. The incongruent position of the <i>Hedysarum s</i>.<i>s</i>. clade between the nuclear and plastid trees may be best explained by a chloroplast capture hypothesis via introgression. The <i>Hedysarum</i> sect. <i>Stracheya</i> clade is resolved as sister to the <i>H</i>. sect. <i>Hedysarum</i> clade in both nuclear and plastid trees, and our analyses support merging <i>Stracheya</i> into <i>Hedysarum</i>. Based on our new evidence from multiple sequences, <i>Hedysarum</i> is not monophyletic, and its generic delimitation needs to be reconsidered.</p></div>