Pollen morphology of Bignoniaceae from Brazilian forest fragments and its systematic significance

Abstract

Bignoniaceae Juss. are widely distributed in tropical and subtropical regions. Most of their Neotropical species have a climbing habit, which makes the family one of the most ecologically important in the Americas. This study of pollen morphology from 23 Bignoniaceae species in Brazilian forest fragments aimed to investigate new pollen characteristics of the family by light and scanning electron microscopy, which can assist in delimitating Bignoniaceae species and taxonomy. Another aim of the study was to analyze the evolution of the family’s pollen characteristics. The pollen grains were acetolyzed, measured and photographed. We describe the pollen grains based on qualitative data, and quantitative data were analyzed using descriptive and multivariate statistics. Based on the qualitative data, an ancestral reconstruction of pollen morphology characteristics was performed for the taxa analyzed. We used the pollen data to understand the relationships established by previous phylogenies. The pollen grains are monads or tetrads, apolar or isopolar, and medium to large, with circular, subcircular to subtriangular amb; oblate to oblate-spheroidal; inaperturate, 6-colpate, (7)-8-(9)-colpate or 3-colporate with short or long colpi that are narrow, wide or very wide and with or without margo; lalongate endoapertures sometimes not evident; and psilate perforate, microreticulate or reticulate exine, homo- or heterobrochate, with simpli or duplicolumellate muri. This result confirms Bignoniaceae as a eurypalynous family, and it allows the identification of pollen morphological characteristics shared by genera and species studied.