Trends of pollen grain size variation in C3 and C4 Poaceae species using pollen morphology for future assessment of grassland ecosystem dynamics

Abstract

This pilot study aims to find whether C3 and C4 Poaceae species can be separated by their pollen grain size. One hundred and sixty Poaceae species were prepared for pollen grain size analyses using standard methods. The whole dataset included 70 species from northern Pakistan, 35 species from Tanzania, 25 from South America and 30 from Germany. We measured four pollen grain parameters, i.e. pollen grain length, pollen grain width, pore diameter and annulus width. Results of the statistical tests and multivariate analyses performed on our specific dataset confirmed that C3 polyploid and C4 polyploid species show trends of larger grain size than the respective diploid species. Results of our fresh Poaceae grains should be applied on fossil pollen embedded in environmental archives for reconstructing past climate, for detecting shifts between their C3/C4 Poaceae compositions and assessing the dynamics of grassland ecosystems.