Browsing by Author "Mahi Bansal"

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Early Evolution of Basal Angiosperms: Insights From the Fossil Pollen and Phylogenetics of Myristicaceae
(John Wiley and Sons Inc, 2025) Shalini Parmar; Mahi Bansal; Kadukothanahally Nagaraju Shivaprakash; Robert J. Morley; Shreya Mishra; Omer Babiker Abdelrahim; Shaaeldin Hasan; Srinivasan Prasad; Krishnamurthy Anupama; Harsanti P. Morley; Rajeev Patnaik; Birendra Pratap Singh; Vandana Prasad
Aim: The early evolution of basal angiosperms and the diversification of flowering plants remain unclear due to fragmentary fossil records and unresolved deep phylogenetic relationships. This study focuses on Myristicaceae, an early diverging lineage of flowering plants, to clarify its evolutionary history and broader implications on determining the timing and drivers of basal angiosperm diversification. Location: Tropics. Taxon: Myristicaceae. Methods: We integrated pollen morphology of Myristicaceae fossils from the Maastrichtian of Africa as well as India and early Paleogene of India, and extant species along with molecular sequences of 127 living species to reconstruct a dated phylogeny of Myristicaceae using BEAST2. To assess paleobiogeographic patterns, we applied BIOGEOBEARS in R, and diversification trends were assessed using Lineage-Through-Time (LTT) curve analysis. Further, we conducted mega-analysis optimised with deliberately assessed 44 calibration points including the revised crown age of Myristicaceae to construct a dated megaphylogeny of angiosperms. Results: Our analysis suggests that the crown lineage of Myristicaceae originated ~130 Ma in western Gondwana, and diversified into Myristicoid, Pycnanthoid, and Mauloutchioid clades likely driven by the South America–Africa separation (~120 Ma). The LTT plot shows that Myristicaceae diversification accelerated ~72 Ma, coinciding with the spread of wet tropical climates, and continued post K-Pg extinction (~65 Ma), indicating resilience to mass extinction events. Further, the revised angiosperm megaphylogeny supports a pre-Cretaceous origin for basal angiosperms. Main Conclusions: Myristicaceae likely originated in western Gondwana during the Early Cretaceous and diversified across palaeotropics ensuing deep-time Plate tectonism, climate change, and vicariance. The study also proposes a pre-Cretaceous origin of basal angiosperms in the localised wet-highland habitats of mid- to low paleolatitudes. Overlapping pollen traits between Myristicaceae and earliest angiosperm fossils across Africa and northern mid-latitudes further suggest a boreotropical expansion of basal angiosperms under wet tropical climates of Cretaceous–Paleogene. © 2025 John Wiley & Sons Ltd.
Evolution of family Arecaceae on the Indian Plate modulated by the Early Palaeogene climate and tectonics
(Elsevier B.V., 2023) Shalini Parmar; Robert J. Morley; Mahi Bansal; B.P. Singh; Harsanti Morley; Vandana Prasad
Arecaceae (palms) is a pantropical plant family with an ancient origin. It shows distinct spatial patterns of species richness in tropical regions having greatest diversity within the Neotropical regions and Southeast Asia. The wider palaeobiogeographic records of palms in relation to current distribution requires a re–examination of their palaeobiogeographic history. The present study reports eleven fossil pollen form–species from the early Palaeogene of India, enhancing our understanding of the evolution of four palm subfamilies: Arecoideae, Calamoideae, Coryphoideae and Nypoideae, on the Indian Plate prior to the India–Asia collision. We suggest the dispersal of diverse palms from Africa to India via the Kohistan– Ladakh Island Arc during Maastrichtian–Palaeocene as part of the Africa–India Floristic Interchange. Subsequently, with wet and humid climates across much of the Indian Plate during the Palaeocene–early Eocene, they underwent a phase of diversification and adaptation leading to habitat expansion. Thus, Indian Plate served as an evolutionary hotspot for the diversification of palms during the early Palaeogene. An in–depth investigation of Palaeogene palm fossils revealed that many palms, currently endemic to Southeast Asia, initially evolved and diversified on the Indian Plate and later dispersed to Southeast Asia following India–Asia collision. The present study thus favours the “Out–of–India” dispersal hypothesis for the Asian palms. The expansion of seasonal climates, and aridification during Neogene and Quaternary led extinction in numerous palm lineages on the Indian subcontinent. This study proposes that deep time climate change and plate tectonism have highly influenced the heterogeneity in spatial and temporal distribution of Asian palms. © 2023 Elsevier B.V.