Phylogeny of Camphora and Cinnamomum (Lauraceae) Based on Plastome and Nuclear Ribosomal DNA Data

<i>Camphora</i> Fabr. is a genus in the family Lauraceae, comprising over 20 tropical and subtropical tree species. Since the genera <i>Camphora</i> and <i>Cinnamomum</i> Schaeff. were described, there has been a long-lasting controversy regarding the phylogenetic relationships among taxa in both genera. In particular, phylogenetic inferences derived from plastid data remain debated, with varying hypotheses proposed and occasional disputes concerning the monophyly of <i>Camphora</i> taxa. To further investigate the relationships, We analyzed plastomes and nuclear ribosomal cistron sequences (nrDNA) of 22 <i>Camphora</i> taxa, 15 <i>Cinnamomum</i> taxa, and 13 representative taxa of related genera. The <i>Camphora</i> plastomes range from 152,745 to 154,190 bp, with a GC content of 39.1% to 39.2%. A total of 128 genes were identified in the <i>Camphora</i> plastomes, including 84 protein-coding genes, 8 rRNA genes, and 36 tRNA genes. A total of 1130 SSR loci were detected from plastomes of <i>Camphora</i>, and A/T base repeats looked like the most common. Comparative analyses revealed that the plastomes of <i>Camphora</i> exhibit high similarity in overall structure. The loci <i>ycf1</i>, <i>ycf2</i>, <i>trnK (UUU)</i>, <i>psbJ-psbL</i>, and <i>ccsA-ndhD</i> were identified as candidate DNA barcodes for these taxa. Plastome phylogenetic analysis revealed that <i>Camphora</i> is not monophyletic, whereas the nrDNA dataset supported the monophyly of <i>Camphora</i>. We propose that intergeneric hybridization may underlie the observed discordance between plastid and nuclear data in <i>Camphora</i>, and we recommend enhanced taxonomic sampling and precise species identification to improve phylogenetic resolution and accuracy.