Importance of palynology in the taxonomy of Piptolepis Sch.Bip. (Asteraceae: Lychnophorinae), a genus endemic to Brazil.

Claudia B.F Mendonça,Raquel M.B Souza-Souza,Roberto L Esteves,Grace K.R De Sousa,Vania Gonçalves-Esteves

doi:10.1590/0001-3765202220201244

Claudia B.F Mendonça, Raquel M.B Souza-Souza + Show 3 more

Open Access

https://doi.org/10.1590/0001-3765202220201244

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Abstract

Lychnophorinae comprises 19 genera and 117 species. Its representatives are found mostly in the rocky grasslands ("campos rupestres") of Minas Gerais, Bahia, and Goiás States, Brazil. This study presents a palynological investigation of 10 species belonging to the genus Piptolepis, endemic to the rocky grasslands of the Espinhaço Mountains, in Minas Gerais State. The plant material used in this investigation was obtained from specimens deposited in Brazilian herbaria. Pollen grains were processed by the acetolysis method, measured, described, and photomicrographed in light microscopy and scanning electron microscopy. Morphological observations revealed Piptolepis pollen to be large, prolate spheroidal in most species, 3-colporate, ectoapertures long, sexine subechinolophate or sublophate. Endoapertures vary from almost circular, lalongate or lalongate, with a median constriction observed only in three species. Three types of spines were identified: prostrate and disorganized, elongated and narrow, and conical, erect, apex acute in the other species. This first palynological study of Piptolepis species allowed the separation of representatives of the genus using pollen keys. The most significant characters were pollen shape, ornamentation, endoaperture, and presence of median constriction in the endoaperture. The findings presented here do not support the infrageneric classification of Piptolepis, as pollen characters were not unique to any section.

Highlights

Its 129 recognized genera were grouped into 21 subtribes mainly based on inflorescence pattern, pollen morphology, chemical composition, and chromosome number (Keeley & Robinson 2009), but newly Loeuille et al (2015b) in their study on the systematics and evolution of Syncephaly in American Vernonieae synonimized Centratherinae and Sipolisiinae under Lychnophorinae, reducing the number of subtribes to 19
The importance of palynology in the taxonomy of Vernonieae is evidenced by the study of Robinson (1999), in which pollen characters were fundamental for the separation of several genera from Vernonia Schreb
Pollen grains were prepared for light microscopic (LM) examination by the acetolysis method of Erdtman (1960), with the modifications proposed by Melhem et al (2003)

Summary

Introduction

The Vernonieae is one of the largest tribes of the family Asteraceae, consisting of about 129 genera and 1,100 species distributed in all tropical regions of the world. Its 129 recognized genera were grouped into 21 subtribes mainly based on inflorescence pattern, pollen morphology, chemical composition, and chromosome number (Keeley & Robinson 2009), but newly Loeuille et al (2015b) in their study on the systematics and evolution of Syncephaly in American Vernonieae synonimized Centratherinae and Sipolisiinae under Lychnophorinae, reducing the number of subtribes to 19. Many other studies provided valuable contributions to the classification of groups and species of Vernonieae, such as, for instance, Mendonça et al (2007a, b, 2009, 2010), Peçanha et al (2001), Souza-Souza et al (2016) and Siniscalchi.

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