<i>Serjania piscatoria</i> (Paullinieae, Sapindaceae) as a symbol of vascular variants polymorphism

Abstract Serjania is the only genus of the Paullinieae tribe that exhibits all patterns of vascular variants and includes S. piscatoria which shows a complex vascular structure that has intrigued botanists for centuries. Here, we analysed the stem development of S. piscatoria in an evolutionary context. We studied four individuals using standardized anatomical techniques and employed DNA sequencing to determine the species’ phylogenetic position. Additionally, we explored the evolution of stem developmental diversity using stochastic character mapping of the categories and patterns of vascular variants. We find that disparate ontogenetic processes determine the stem development in S. piscatoria, which results in vascular variants derived from procambial variants, cambial variants, and ectopic cambia. This diversity underscores the developmental lability of vascular meristems, making the species' vascular system structurally diverse and polymorphic. The complex vascular system observed in S. piscatoria evolved within a lineage composed of species with compound stems. These findings provide evidence for the intricate and labile evolutionary history of stem vasculature in Serjania, and the value of studying vascular variants to unravel the patterns and processes shaping plant diversity.