Poaceae pollen grains from southern Brazilian grasslands: Pollen grain size in species from dry and humid environments

Jefferson Nunes Radaeski,Soraia Girardi Bauermann

doi:10.4013/nbc.2018.132.03

Jefferson Nunes Radaeski, Soraia Girardi Bauermann

Open Access

https://doi.org/10.4013/nbc.2018.132.03

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Abstract

Southern Brazil has a high diversity of grassland Poaceae species in the biomes of the region. However, few data on the morphology and the uniformity of Poaceae pollen grains cause taxonomic low resolution in pollen records. In this study, pollen samples of grassland Poaceae species from different regions of southern Brazil were analyzed. The pollen diversity of 70 grassland Poaceae species (59 genera, 15 tribes, and 6 subfamilies) of the Pampa and Atlantic Forest biomes is presented. Morphometric measurements indicated that pollen grains of humid grasslands species have a larger size than those of dry grasslands species. Though the average of measurements shows a small difference in pollen grain sizes between the Pampa and the Atlantic Forest, such differences cannot be applied to fossil records because non-significant differences occurred between samples. Regarding pollen size, non-significant differences also occurred for the C3 and C4 samples, probably because C3 species had high variance in size. These records provide relevant ecological inferences of Poaceae pollen grains, providing valuable information for reconstruction of vegetation. Furthermore, regarding taxonomic relationships, results suggest the trend of decrease of the size of Poaceae pollen grains towards derived tribes.Keywords: pollen records, Palynology, Pampa biome, grasses, diporate pollen grains.

Highlights

Poaceae pollen grains are major pollen indicators used to analyze the grassland dynamics in South America during the Quaternary
Based on the recent phylogenetic classification of the Poaceae (Soreng et al, 2015) the results suggest a trend of decrease of the size of Poaceae pollen grains towards derived species (Figure 8)
This work constitutes the greatest dataset of grassland Poaceae pollen diversity of South America

Summary

Introduction

Poaceae pollen grains are major pollen indicators used to analyze the grassland dynamics in South America during the Quaternary. They indicate the modification of natural vegetation by the introduction of exotic species (corn and others cultivate) by the human (Behling et al, 2005; Macedo et al, 2009, 2010). The existence of few studies about the morphology of modern Poaceae in South America increases the difficulty to obtain better pollen taxonomic resolution (Heusser, 1971; Salgado-Labouriau, 1973; Markgraf and D’Antoni, 1978; Salgado-Labouriau and Rinaldi, 1990; Corrêa et al, 2005; Dórea, 2011; Bauermann et al, 2013; Radaeski et al, 2014)

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