Unraveling the Molecular Phylogeny of Welwitschia mirabilis Hook f.: A Millennia-Old Plant with Affinities to Pinaceae

AbstractGymnosperms originated in the Middle Devonian (~385 million years ago) and have undergone a long and complex evolutionary history characterized by episodic bursts of speciation and extinction. This evolutionary trajectory has led to the emergence of four morphologically distinct extant groups: cycads, Ginkgo, conifers, and gnetophytes. Gnetophytes consist of three monotypic families: Ephedraceae, Gnetaceae, and Welwitschiaceae. Cycads are divided into two families: Cycadaceae and Zamiaceae. Phylogenetically, Ginkgo is sister to cycads but not to conifers. The morphological similarities between Ginkgo and conifers are attributed to parallel evolution rather than shared ancestry. Conifers are paraphyletic, with gnetophytes nested within them–indicating that gnetophytes are derived conifers. The newly defined clade Coniferophytes, equivalent to Pinopsida, comprises three subclasses: Pinidae, Gnetidae, and Cupressidae. The family Welwitschiaceae contains only one living genus, Welwitschia, which consists of the single species Welwitschia mirabilis. Among gymnosperms, Welwitschia mirabilis stands out as one of the most remarkable plant species on Earth due to its unique phylogeny, morphology, and ecology. This review explores its distribution, structural features, eco-physiology, and molecular phylogeny, highlighting a species capable of surviving for thousands of years.