<i>Jamesbondia</i>, a new subgenus of <i>Alternanthera</i> (Gomphrenoideae, Amaranthaceae) from Central America and the Caribbean Islands

<i>Jamesbondia</i> is formally proposed here as a new subgenus of <i>Alternanthera</i>, a large Neotropical genus, with four species [<i>A. costaricensis</i> Kuntze, <i>A. geniculata</i> Urb., <i>A. olivacea</i> Urb., and <i>A. serpyllifolia</i> (Poir.) Urb.], mostly found in Central America and the Caribbean Islands. In a recent phylogeny using internal transcribed spacer (ITS), <i>trnL-F</i>, and <i>rpl16</i> data and samples of three of the four species listed above, an unpublished genus <i>Jamesbondia</i> was embedded within <i>Alternanthera</i>. The other three species (not <i>A. costaricensis</i>) clustered in a clade with 97% jackknife (JK) support. Here, to determine the position of <i>A. costaricensis</i> within <i>Alternanthera</i> and taxonomically revise the species in subgenus <i>Jamesbondia</i>, we analyzed ITS, <i>trnL-F</i>, and <i>rpl16</i> data from GenBank accessions for 31 species and our new molecular data for <i>A. costaricensis</i> to reconstruct a phylogenetic tree confirming that <i>A. costaricensis</i> belongs to the <i>Jamesbondia</i> clade (88–97% JK; 0.88–1.0 posterior probability). <i>Alternanthera costaricensis</i>, <i>Telanthera olivacea</i> Urb., and <i>Achyranthes serpyllifolia</i> Poir. were lectotypified, and we document the distribution of <i>A. costaricensis</i> in Mexico for the first time. Insight from nomenclatural notes, taxonomic descriptions, morphological illustrations, distribution, and a key for species of <i>Jamesbondia</i> provided here will be used to propose a new subgeneric classification of <i>Alternanthera</i>.