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Abstract
Due to overlapping in several of the primary pollen morphological attributes (viz. aperture type and exine sculpturing) throughout the subfamilies and tribes of Rubiaceae, these attributes are less important for delineating the majority of the taxa at subfamilial and tribal levels than at generic and specific levels. This in turn creates difficulties in the identification of rubiaceous pollen grains in various palynological studies. In such cases, where the two major pollen morphological attributes (apertural type and exine ornamentation pattern) are more or less common, we intended to explore whether an additional pollen morphological character could reliably be used in the demarcation of taxa. The present work deals with the pollen morphological details of 17 species of Rubiaceae from the Darjeeling and Arunachal Himalayas. This eurypalynous family exhibits a wide array of pollen morphological attributes, particularly aperture type, exine ornamentation pattern and variable sculpturing on colpus membrane. Principal component analysis (PCA) was performed to determine the major pollen morphological variables responsible for delimiting the studied species; this analysis indicated that variation in colpus membrane ornamentation (psilate, granulate, scabrate, verrucate) is a key attribute in characterizing the studied eastern Himalayan rubiaceous taxa to generic and specific levels.
Acknowledgements
The authors are thankful to the UGC-CAS Phase VII, Department of Botany, University of Calcutta, for providing necessary facilities. The first author is grateful to the Council of Scientific and Industrial Research, New Delhi (Grant No. 09/028(1072)/2018-EMR-I dated 22.02.2019), for financial support. The authors are indebted to the Central National Herbarium (CAL), Botanical Survey of India, for their kind cooperation during consultation, and the Centre for Research in Nanoscience and Nanotechnology, University of Calcutta, for providing SEM facilities. The authors are indebted to Dr. Ruby Ghosh, Scientist D, Birbal Sahni Institute of Palaeosciences, Lucknow, India, for her guidance in the statistical analyses, and to the anonymous reviewers for their valuable comments that improved the quality of the manuscript.
Disclosure statement
All authors declare that they have no conflict of interest.
Additional information
Notes on contributors
Shreyasi Basak
SHREYASI BASAK, CSIR- Senior Research Fellow (NET), is pursuing PhD on the pollen flora of Darjeeling Himalaya in the Centre of Advanced Study, Department of Botany, University of Calcutta. She obtained her master's degree from Hemwati Nandan Bahuguna Garhwal University with specialization in Palynology and Plant Systematics. Her main interest is in pollen morphology and palyno-systematics.
Baishakhi Sarkar
BAISHAKHI SARKAR holds a PhD degree in the arboreal pollen flora of Terai and Dooars, West Bengal from University of North Bengal. She did her masters from University of Calcutta with Palaeobotany and Palynology specialization. Her main interest is in palyno-systematics and Neogene palynology.
Dulal Chandra Patra
DULAL CHANDRA PATRA is working on pollen flora of Arunachal Pradesh, India in the Centre of Advanced Study, Department of Botany, University of Calcutta. He obtained his M.Sc from Vidyasagar University and M.Phil from Vinayak Mission University. His area of interest is palynology and palynotaxonomy.
Sudhansu Sekhar Dash
SUDHANSU SEKHAR DASH, M.Sc, M.Phil, Ph.D is presently working as Scientist E (Joint Director and the Head of Technical Division) in Botanical Survey of India. His professional expertise includes Biodiversity Assessment, Revisionary studies, Phytogeographic analysis, Climate Change Assessments and has been working in international, national, and local level since past 25 years. He has explored extensively all most all parts of Indian Himalayan Region, Eastern Ghats, Indo-gangetic Plains and collected a huge number of Plant specimens. He has discovered one new family, two new genera, 20 species new to science and reported more than 100 plants new to Indian states and flora. He is currently working on a project on reassessment of Himalayan ecosystems in the light change of community structure, floristic composition, alternation of phenology and selection of climatic change indicators. He has authored more than 100 research papers in national and international repute, 10 books, edited 8 books, and three journals. He is the recipient of prestigious “V.V. Sivarajan Gold Medal- 2019” from Indian Association of Angiosperm Taxonomy” (IAAT); S.K. Jain Gold Medal - 2014 from Association of Plant Taxonomist(APT), and Brandis Prize 2012 from Association of Forester.
Debabrata Maity
DEBABRATA MAITY, Assistant Professor, Centre of Advanced Study, Department of Botany, University of Calcutta is an experienced taxonomist working on Eastern Himalayan flora for more than two decades. He has a master's degree specialization in Taxonomy of Angiosperms from University of Kalyani. Debabrata also holds a Ph.D. in Eastern Himalayan flora (Vascular Plant Diversity of Kanchenjunga Biosphere Reserve, Sikkim) jointly from Botanical Survey of India and University of Kalyani. His main interests are in the study of Alpine flora of Eastern Himalaya as well as pollen and pollination behaviour of high altitude plants.
A.P. Das
ABHAYA PRASAD DAS, Professor (retired) of Botany in the University of North Bengal, India, is now working as a visiting research Professor (DBT, Govt. of India) at the Rajiv Gandhi University, Arunachal Pradesh. He is a well-known taxonomist and worked mainly on the flora and vegetation of Eastern Himalaya.
Subir Bera
SUBIR BERA, Professor and programme coordinator, Centre of Advanced Study, Department of Botany, University of Calcutta is a senior Palaeobotanist of India working on vegetation history and climate change of south-east Asia using plant micro and megafossil proxies.