Pollen characters and their evolutionary and taxonomic significance: using light and confocal laser scanning microscope to study diverse plant pollen taxa from central India

Increasing the taxonomic resolution of fossil pollen identification and establishing the kinship and similarity among phylogenetically related plant groups are inevitable for advancing the Quaternary palaeoecological, palaeoclimatological and palaeoenvironmental research. We, in the present study, examined and determined the pollen morphological characteristics of nine plant taxa belonging to seven families from central India by a combined light microscopic (LM) and confocal laser scanning microscopic (CLSM) study. The prime object was to observe, document and describe, as well as illustrate the prevalent variation in pollen shape, size, aperture number and diameter, diameter of the polar axis and equatorial distance, as well as exine thickness and pattern (i.e. pollen wall architecture) of the studied plant taxa. Pollen identification key was developed to demonstrate variations in pollen features and delimit taxa for correct identification. Principal component analysis (PCA) suggests exine and aperture number as dominant characters, as well as hierarchical clustering analysis (HCA), applied to the pollen morphological characters of nine plant taxa to understand the variability among the taxa, and to cluster them, respectively, suggest three clusters. The cophenetic correlation coefficient also substantiates the three group of clustering. The present study has significance in taxonomy and systematics, as well as in phylogeny and evolution. In addition, the preservation potential of different pollen grains has been ascertained, based on the pollen wall architecture. The study, moreover, will improve the precise fossil pollen identification, which is critical for advancing Quaternary palaeoecology in India and also in similar tropical and subtropical areas of the globe.