The taxonomic significance of seed morphology in the Passiflora subgenus Astrophea (Passifloraceae)

The center of diversity for Passiflora subg. Astrophea is in low altitude areas of northern South America. The majority of species of this group are difficult to find in nature. Seed morphology was described in detail for 25 species of Passiflora subgenus Astrophea, a subgenus that until now did not exist. For morphological analysis, 20 seeds per species were measured for length, width and thickness, and the arithmetic means calculated. The seeds varied in length, width and thickness. Eight types of ornamentation were found. The margins varied among crestate, dentate, parted, entire and parted-crestate. The seed apex can be distinguished by the shape and position of the apical appendage. Seed shape varied among obovate, lanceolate, cordiform, and oblong to elliptical. An identification key was developed and a PCA was performed both using the principal morphological characters. Morphological characters of seeds are a new source of data for delimiting taxa with quite conflicting morphological boundaries, such as seen here with the Passiflora subgenus Astrophea. Furthermore, seed morphology is especially useful for the identification of specimens with only fruits and, consequently, seeds available.