The systematic significance of seed morphology in Stenocereus (Cactaceae)

Seed morphology of 24 species of Stenocereus was examined by scanning electron microscopy. Quantitative and qualitative features were evaluated to identify groups of species using a phenetic analysis. Two groups were distinguished based on morphological variations of seed size, luster, multicellular sculpture, keeling, cell‐size, periclinal wall sculpture, microrelief and HM complex shape and position relative to rim. All species studied were keeled, with isodiametric cells in the lateral region. Stenocereus alamosensis , S . kerberi and S . beneckei are unique among Stenocereus species in that their seeds are flat but lack micro‐relief. Stenocereus aragonii and S . eichlamii have large, glossy seeds lacking micro‐relief unlike other Stenocereus species, but like most Pachycereus , are unique in that cells in the lateral region display partly convex, low domes. Quantitative and qualitative congruence and discordance among characters that determine species groups in stenocereus are discussed.