Diporate Pollen Grains of Poaceae Species: High Pollen Resolution for Reconstruction of Grasslands Vegetation

This study documents the relationship between the modern diporate Poaceae pollen grains and fossil diporate Poaceae pollen grains of Quaternary in the southern Brazil. Pollen grains were analyzed to know the number of the apertures of the pollen grains of 95 Poaceae species of Rio Grande do Sul region. These 95 species, five showed diporate aperture and we present the morphological descriptions of pollen grains. In the sedimentary samples of Águas Claras region, seven diporate Poaceae pollen grains were identified in all the profile. Diporate Poaceae pollen grains were absent in the basal ages (10.974-2.000 years BP) and increased in frequency from the Late Holocene (2.000 years BP to the present). The comparison between modern-fossil pollen allowed to identify three palynomorphs in the specie level (Dichantelium sabulorum) also indicating the metabolism type (C3) and two pollen grains indicated the vegetation type (grasslands). C3 diporate Poaceae species that reflect the occurrence of humid climate have increased the concentration since 2.000 years BP in the pollen record. Furthermore, the humid climate increased progressively until the current climate in the region of Águas Claras. The palynomorphs identified can provide important paleoecological information on the dynamics of Poaceae vegetation in the past.