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

Ana Carolina Mezzonato-Pires,Michaele Alvim Milward-De-Azevedo,Cláudia Barbieri Ferreira Mendonça,Vania Gonçalves-Esteves

doi:10.1590/0102-33062016abb0414

Abstract

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.

Highlights

Passiflora subgenus Astrophea is one of five subgenera belonging to the genus Passiflora
Seed morphology was described in detail for 25 species of Passiflora subgenus Astrophea, a subgenus that until now did not exist
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

Summary

Introduction

Passiflora subgenus Astrophea is one of five subgenera belonging to the genus Passiflora. It is comprised of about 60 species distributed in South and Central America, with only two species in the latter, Passiflora pittieri and Passiflora tica (Escobar 1994). The major center of diversity for Passiflora subg. Astrophea is in areas of low altitude in northern South America (Ulmer & MacDougal 2004). According to Ulmer & MacDougal (2004), species of Passiflora subg. Astrophea are similar to typical Passiflora but with unique morphological characteristics, and so are considered the most unusual of the genus. The majority of species of this group are rare and difficult to find in nature. Species identification of specimens in the absence of flowers is usually impossible since most of the diagnostic characters are in the flowers, and so when specimens are only fruits, seeds can serve as a valuable identification tool

Methods

Results

Conclusion