Abstract
Aponogeton microphyllus, previously placed under the synonymy of A. undulatus, is recognized here as a distinct species based on morphology, chromosome number, and molecular phylogenetics (nuclear ribosomal internal transcribed (ITS) spacer region). Observations on the type and live specimens revealed morphological differences between the two species. Aponogeton microphyllus flowered regularly and set seeds. Aponogeton undulatus flowered rarely, did not set seeds, but showed formation of young plantlets on the inflorescence axis. Similarly, different chromosome numbers were recorded in Aponogeton microphyllus and the two forms of A. undulatus, viz., AF1 and AF2, which occur in distinct populations. Aponogeton microphyllus exhibited polysomaty with root-tip cells showing 2n=40, 42, and 44 chromosomes. The two forms of A. undulatus, AF1 and AF2, showed 2n=84 and 86 chromosomes, respectively. Based on the ITS data, both species occupied two separate clades. Plastid trnK intron region indicated a close relationship between both species. Our study suggests the need for comprehensive phylogenetic analyses of A. undulatus across its distribution range based on more advanced techniques such as high-throughput sequencing data to understand the A. undulatus species complex and to detect natural hybrids of this species.
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Acknowledgements
The authors are grateful to the Head, Department of Botany, Shivaji University, Kolhapur, for providing necessary research facilities. Thanks are due to Dr. Susanne S. Renner, Honorary Professor of Biology, Washington University in St. Louis, Missouri, for going through previous versions of the manuscript and improving its content. SS thanks Pooja Kumari Shukla for help in sequence data analysis. SRY thanks Mr. Pushpendra Katiyar, NBRI, Lucknow, for his help during the field tour. SRY is grateful to University Grants Commission (UGC), New Delhi, for the award of the BSR faculty fellowship. We thank the Director, Royal Botanic Gardens, Kew, for permitting us to publish the selected images.
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Chougule, R.N., Surveswaran, S., George, A. et al. Roxburgh was right: Aponogeton microphyllus and Aponogeton undulatus are distinct species. J Biosci 48, 53 (2023). https://doi.org/10.1007/s12038-023-00366-y
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DOI: https://doi.org/10.1007/s12038-023-00366-y