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Conservation of native biological diversity is one of the major challenges of this century. Invasive alien species (IAS) are a part of this challenge because a small but a significant fraction of IAS contribute to the demise of native species. The present paper reviews current literature on the phenomenon of hybridization in plants supporting the evolution of invasiveness, which is identified as a major threat to the extinction of native species. Further, the phenomenon of hybridization is been reviewed on a Sri Lankan context by citing evidence from a preliminary study between the native Nymphaea nouchali and an introduced violet flowered water-lily that has got established in water-bodies of Sri Lanka. This violet flowered water-lily has been incorrectly identified as the native Nymphaea nouchali, the National flower of Sri Lanka ('Nil Manel'). Revealing the flawed identity of the violet flowered Nymphaea, its hybrid origin and the hybridization with the native N. nouchali, provides an excellent opportunity for initiating studies on a novel area in hybridization between natives and invasive alien species of plants in Sri Lanka.

A multivariate statistical analysis was carried out to evaluate the morphological variation between Nymphaea pubescens Willd., and a deep purplish red flowered Nymphaea that occur in Sri Lanka. The plant resembles N. rubra Roxb. ex Andrews, a species that had been sometimes circumscribed as a variety under N. pubescens Willd. DNA sequences data of matK and psbA-trnH regions were used to obtain further support. Morphological data were scored from collected samples and analyzed using PAST software. Extracted DNA were amplified for matK and psbA-trnH gene regions. Obtained sequences were matched with the related accessions deposited in the GenBank. Multivariate analysis supported the recognition of deep purplish red flowered Nymphaea as a different species from N. pubescens, and was identified as N. rubra based on literature. GenBank accessions for the matK region of N. rubra showed 99% similarity while it gave only a 96% similarity for N. pubescens with query coverage of 97% and 96% respectively, corroborating with the morphological analysis. Comparison of the sequence divergence between N. pubescens and N. rubra sequences indicated a 95% similarity for matK gene region while 92% similarity for psbA-trnH gene region. The sequences generated during the present study would provide additional reference sequences for the two taxa.Bangladesh J. Plant Taxon. 23(2): 107-117, 2016 (December)

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