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

Abstract

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.

Keywords:

• Palyno-morphology
• LM and CLSM
• Herbarium specimen
• statistical analyses
• Quarternary palaeoecology
• central India

Acknowledgements

We are thankful to the Director, Birbal Sahni Institute of Palaeosciences, Lucknow, India for providing the infrastructure facilities needed to complete this research work and also for permission to publish. We are also thankful to Ms. Shivalee Srivastava and Ms. Archana Sonker for their assistance with the CLSM study. Dr. G. P. Sinha, Ex-Director, BSI, Allahabad (BSA) is thanked for the support during the Memorandum of Understanding (MoU), signed between the BSIP (Lucknow) and the BSI (Allahabad, now Prayagraj), India. Four anonymous reviewers are thanked for their authoritative suggestions which helped us to significantly improve the earlier version of the manuscript. M.F.Q. thanks Dr. Encarni Montoya, Handling Editor, Palynology for her suggestions and also for her kind co-operation, Dr. P. Morthekai, Scientist-D, BSIP for his co-operation while conducting statistical analyses. MFQ is grateful to Dr. James B. Riding, Editor-in-Chief, Palynology for encouragement.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Notes on contributors

Md. Firoze Quamar

MOHAMMAD FIROZE QUAMAR is working as a Scientist ‘D’ at the Birbal Sahni Institute of Palaeosciences (BSIP), Lucknow, India. His research interests mainly include the understanding of the hydroclimate variability and vegetation dynamics during the late Quaternary (Late Pleistocene-Holocene) in the central Indian core monsoon zone (CMZ).

Priyanka Singh

PRIYANKA SINGH is working as a Birbal Sahni Research Scholar (BSRS) and pursuing her PhD, focussing on to delineate the contribution of Indian summer monsoon and western disturbances to the palaeoclimate of the Higher Central Himalaya. She has completed her formal education on the Applied Geology from the Banaras Hindu University (Varanasi) and the Lucknow University (Lucknow). Apart from luminescence dating and palaeoclimate studies, she has wide interest that includes applying time series analysis, causality analysis, multivariate statistics in variety of scientific problems, such as this.

Arti Garg

ARTI GARG, presently working as Scientist E and Head of the Office of the Central Regional Centre (Prayagraj; Allahabad; BSA), Botanical Survey of India (BSI), is a renowned palyno-taxonomist with significant revisionary works on Berberis L. and Pedicularis L., palynology, reproductive biology, including adaptation, speciation, plant-pollinator co-evolution and inbreeding-depression of endangered plants, taxonomic documentation of Flora of India - families Asteraceae, Dipsacaceae, Lamiaceae, Lentibulariaceae, Orobanchaceae, Sapotaceae, Scrophulariaceae, Styracaceae and Valerianacea, Floras of Chhattisgarh State, Lakshadweep Islands and Ramsar Sites of U.P. and M.P. She has also discovered the world’s tenth largest Banyan (Ficus benghalensis L.), oldest Adansonia digitata and Manilkara hexandra trees in India. To her credit are 6 books, c.150 Research papers and several popular articles.

Swati Tripathi

SWATI TRIPATHI is currently working as a Scientist-D in the Quaternary Laboratory of the Birbal Sahni Institute of Palaeosciences, Lucknow. Her research interests include Quaternary vegetation and climate change through pollen and non-pollen palynomorphs, examining pollen micro-morphometry of living plants, copropalynology and melissopalynology. She received three Gold Medals including Birbal Sahni Memorial Gold Medal for obtaining the highest percentage of marks in MSc (Botany), Lucknow University in 2007. She received her PhD degree in 2011 from the Department of Botany, Lucknow University. She is also the recipient of Dr BS Venkatachala Memorial Medal (2012) and Dr Chunni Lal Khatiyal Medal (2016) for her outstanding piece of research work as research associate and Scientist-B, respectively. She is an associate of the prestigious Indian Academy of Sciences, Bangalore. She has 51 research papers published in peer-reviewed journals. She has trained several MSc students and currently supervising a DST-INSPIRE Fellow. She is the recipient of Women Excellence Award-2019 from SERB, New Delhi.

Anjum Farooqui

ANJUM FAROOQUI is Scientist ‘F’ at the Birbal Sahni Institute of Palaeosciences, Lucknow. She has developed an expertise in palynology in the last 30 years of her career, working on several issues. The use of palynological study in understanding climate variability, landscape changes, sea level fluctuations and impact on biodiversity was her main forte. Apart from several field excursions in the Indian Peninsula, she has to her credit 110 published papers in reputed National and International Journals.

Achuta Nand Shukla

ACHUTA NAND SHUKLA is working as a Scientist ‘E’ in the Ministry of Environment, Forest and Climate Change, Indira Pryavaran Bhawan, Jorbagh, New Delhi, India. He has published Two Books and 54 research papers. He is the recipient of Swarna Jayanti Puraskar by the National Academy of Sciences, India.

Nagendra Prasad

NAGENDRA PRASAD is a CSIR-JRF and is doing his PhD on the vegetation and hydroclimatic changes in the central Indian CMZ during the late Pleistocene-Holocene under the supervision of Dr Mohammad Firoze Quamar (Scientist-D, BSIP) at the BSIP, Lucknow.