Molecular Phylogeny of the Cuscuta californica Complex (Convolvulaceae) and a New Species from New Mexico and Trans-Pecos

Multiple DNA sequences from plastid (trnL-F region and rbcL) as well as nuclear (ITS and 26S rDNA) genomes, were used to infer the phylogeny of the Cuscuta californica complex. This group is currently circumscribed to include nine species distributed mostly in western North America. Four well-supported lineages have been revealed within this complex. The first lineage includes the controversial C. californica s. l., an assemblage of taxa characterized by their lack of infrastaminal scales; the second lineage consists of a single species, C. subinclusa, with short fimbriate scales. The third lineage groups C. howelliana, C. salina, and C. suksdorfii, with scales that exhibit a reduction trend, while the forth includes C. decipiens and a new species from New Mexico and trans-Pecos Texas, C. draconella, both with well-developed infrastaminal scales. Stereo, compound, and scanning electron microscopy were used to investigate the new species and compare it with C. decipiens, its closest relative, as well as to update the taxonomic treatment of C. californica s l. Cuscuta decipiens, in its original delimitation, is polyphyletic and was thus recircumscribed. In contrast to previous taxonomic treatments of C. californica s. I., phylogenetic relationships in conjunction with morphological data support the delimitation of three species: C. brachycalyx, C. californica, and C. occidepitalis.