Taxonomic status of 𝘐𝘮𝘱𝘢𝘵𝘪𝘦𝘯𝘴 𝘴𝘶𝘣𝘤𝘰𝘳𝘥𝘢𝘵𝘢 𝘈𝘳𝘯. (Balsaminaceae)

Abstract

𝘐𝘮𝘱𝘢𝘵𝘪𝘦𝘯𝘴 𝘴𝘶𝘣𝘤𝘰𝘳𝘥𝘢𝘵𝘢 𝘈𝘳𝘯. (Family Balsaminaceae) is a herbaceous species endemic to Sri Lanka. The species is morphologically similar to 𝘐. 𝘤𝘰𝘳𝘥𝘢𝘵𝘢 Wight, a species endemic to India. These morphological parallels raise a critical taxonomic question of whether these two geographically separated populations are distinct species, or conspecific. Resolving this taxonomic ambiguity is important for biodiversity conservation, as 𝘐. 𝘴𝘶𝘣𝘤𝘰𝘳𝘥𝘢𝘵𝘢, endemic to Sri Lanka, was thought to be extinct but recently rediscovered in the wild. The objective of the present study was to re-evaluate the taxonomic positions of 𝘐. 𝘤𝘰𝘳𝘥𝘢𝘵𝘢 and 𝘐. 𝘴𝘶𝘣𝘤𝘰𝘳𝘥𝘢𝘵𝘢 to discern whether the two were distinct species or not. This was done by performing both a morphometric analysis and a molecular phylogenetic analysis. Four different populations of 𝘐. 𝘴𝘶𝘣𝘤𝘰𝘳𝘥𝘢𝘵𝘢 were sampled to obtain morphological and molecular data. Morphological data were subjected to a cluster analysis using PAST software. The ITS, 𝘢𝘵𝘱β-𝘳𝘣𝘤L and 𝘵𝘳𝘯L – 𝘵𝘳𝘯F regions (chosen based on the availability of data for 𝘐. 𝘤𝘰𝘳𝘥𝘢𝘵𝘢) were sequenced. Maximum likelihood and Bayesian inference analyses were performed to reconstruct the phylogeny using𝘏𝘺𝘥𝘳𝘰𝘤𝘦𝘳𝘢 𝘵𝘳𝘪𝘧𝘭𝘰𝘳𝘢 (L.) Wight & Arn. as the outgroup. Morphometric analysis of 16 characters revealed significant variation patterns, where I. subcordata populations clustered distinctly from 𝘐. 𝘤𝘰𝘳𝘥𝘢𝘵𝘢. Zero genetic distance was found between the I. subcordata populations. The reconstructed phylogenies strongly supported (bootstrap value of 100% from Bayesian inference analysis and posterior probability value of 1 from maximum likelihood analysis) 𝘐. 𝘴𝘶𝘣𝘤𝘰𝘳𝘥𝘢𝘵𝘢 as a monophyletic group, sister to 𝘐. 𝘤𝘰𝘳𝘥𝘢𝘵𝘢. Furthermore, morphological analysis indicates that the two species are also morphologically distinct. Overall results strongly indicate that while closely related, the Sri Lankan and Indian species are distinct, resolving a longstanding uncertainty about the validity of the species and thereby confirming the endemic status of 𝘐𝘮𝘱𝘢𝘵𝘪𝘦𝘯𝘴 𝘴𝘶𝘣𝘤𝘰𝘳𝘥𝘢𝘵𝘢 to Sri Lanka. This will contribute to the accurate documentation of endemic plant diversity and development of appropriate conservation strategies.