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Paleotropical lineage of Indian Water Primrose (Ludwigia L., Onagraceae) using pollen morphometric analysis

Farooqui, Anjum, Tripathi, Swati, Garg, Arti, Shukla, Achuta Nand, Murthy, Srikanta, Prasad, Vandana, Sinha, Gopal Prasad
Review of palaeobotany and palynology 2019 v.269 pp. 64-77
Late Cretaceous epoch, Ludwigia adscendens, Ludwigia hyssopifolia, Pleistocene epoch, ecosystems, fossils, light microscopes, morphometry, morphs, pollen, principal component analysis, scanning electron microscopes, scanning electron microscopy, sediments, India
The late Cretaceous Corsinipollenites from central India and its nearest living fossil pollen Ludwigia from Pleistocene Karewa sediments in Kashmir shows morphometrical affinities with pollen of seven extant Ludwigia species (L. octovalvis (Jacq) P.H. Raven, L. octovalvis subsp. sessiliflora (M.Micheli) Raven, L. adscendens (L.) H. Hara, L. perennis (L.), L. hyssopifolia (G.Don) Exell, L. peruviana (L.) H. Hara and L. decurrens Walt.) commonly growing in swampy ecosystems of India. The Field Emission Scanning Electron Microscope (FESEM) and Light Microscope (LM) study draws plausible lineage of extant Ludwigia species with that of fossil specimens recovered at two different time frames based on similarities in pollen morphometry. The pollen aperture and its character along with the sexine pattern were main identifiable features to distinguish different species of extant/fossil Ludwigia pollen. The aspidote aperture varies from brevi-colporate to slit-like colpi (colporate). The sexine is stenopalynous type characterized by rugulate to reti-rugulate pattern. The multivariate principal component analysis (PCA) was applied on the numerical data obtained from pollen morphometry of living and fossil Ludwigia spp. The Pleistocene Ludwigia morphotype with slit-like colpi shows close proximity to L. octovalvis, L. octovalvis subsp. sessiliflora and L. adscendens. However, Late Cretaceous, Corsinipollenitis characterized by brevicolpi is closer to L. perennis and L. hyssopifolia with respect to primary pollen characters and inferred as primitive species having lineage to the “Old World” (paleotropical) species. A short pollen key of Ludwigia spp., is presented here to enable the identification of living/fossil pollen.