Pollen morphology of the Brazilian species of Bernardia Houst. ex Mill. and Tragia L. (Euphorbiaceae, Acalyphoideae)

Mirane De Oliveira Santos,Luciene Cristina Lima E Lima,Juliana Santos Silva,Margareth Ferreira De Sales

doi:10.1590/0102-33062019abb0115

Mirane De Oliveira Santos, Luciene Cristina Lima E Lima + Show 2 more

Open Access

https://doi.org/10.1590/0102-33062019abb0115

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Abstract

ABSTRACT Bernardia and Tragia are the largest genera of the tribes Bernardieae and Plukenetieae (Euphorbiaceae,), with 68 and 125 species, respectively. Very few palynological studies have focused specifically on these genera in spite of the great pollen diversity observed in the family. The present study analyzed the pollen morphology of the Brazilian species of Bernardia and Tragia to identify diagnostic characteristics that could aid in their taxonomic circumscription. The pollen grains of 11 species of Bernardia and five of Tragia were obtained from specimens deposited in the HRB, HUEFS, PEUFR, RB and UFP herbaria, and were analyzed using light and scanning electron microscopy. The analyzed species had small- to medium-sized pollen grains in monads, with shapes from prolate to subprolate. The most significant differences were observed in aperture type and exine ornamentation. The pollen grains of Bernardia are tricolporate, with aperture margins varying from narrow to wide or with just slightly evident margins, and the exine varying between microreticulate and microreticulate-perforate. The pollens of Tragia are tricolpate with the exine varying between intectate pilate and verrucate. Some species of both genera could be diagnosed based on unique pollen characters, and four distinct morphological groups of Bernardia and two of Tragia were observed.

Highlights

Euphorbiaceae s.s. comprises 219 genera and approximately 6,300 species distributed globally, being found predominantly in tropical and subtropical regions (Wurdack & Davis 2009)
In comparing our results of pollen morphology of Bernardia to other published accounts (e.g., Punt 1962; Nowicke et al 1999; Cardinal-McTeague & Gillespie 2016), some morphological differences can be observed in relation to the size and shape of the pollen grains and exine ornamentation
As for B. hirsutissima, the pollen grains were described in both studies as subprolate, but observations diverged in relation to their size and exine ornamentation, as those authors described them as medium-sized grains with the exine profoundly perforate

Summary

Introduction

Euphorbiaceae s.s. comprises 219 genera and approximately 6,300 species distributed globally (with the exception of the coldest regions, such as the Arctic), being found predominantly in tropical and subtropical regions (Wurdack & Davis 2009). 950 species (634 of them endemics), distributed in 64 genera, and they are most common in the Cerrado Biome (395 spp.) (Flora do Brasil 2020 [under construction] 2017). As it displays many pollen types, Euphorbiaceae is considered a euripollinic family (Salgado-Labouriau 1973). Bernardia comprises 68 species distributed in neotropical forests, principally from Brazil to Mexico (Webster 1994; Govaerts et al 2000). Sixteen species occur in Brazil, distributed throughout the country, more common in the Atlantic Forest (Flora do Brasil 2020 [under construction] 2017)

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