A statistical analysis of the vegetative characters of Sri Lankan asparagas (𝘍. 𝘢𝘴𝘱𝘢𝘳𝘢𝘨𝘢𝘤𝘦𝘢𝘦)

Abstract

𝘈𝘴𝘱𝘢𝘳𝘢𝘨𝘶𝘴 is an important genus of medicinal plants used in ayurvedic medicine in Sri Lanka. The circumscriptions in different taxonomic treatments of the taxa differ with splitting and lumping of species. Four species are recognised, 𝘈. 𝘳𝘢𝘤𝘦𝘮𝘰𝘴𝘶𝘴, 𝘈. 𝘧𝘢𝘭𝘤𝘢𝘵𝘶𝘴, 𝘈. 𝘨𝘰𝘯𝘰𝘤𝘭𝘢𝘥𝘰𝘴 and 𝘈. 𝘻𝘦𝘺𝘭𝘢𝘯𝘪𝘤𝘶𝘴 by upgrading the endemic 𝘈. 𝘳𝘢𝘤𝘦𝘮𝘰𝘴𝘶𝘴 var. 𝘻𝘦𝘺𝘭𝘢𝘯𝘪𝘤𝘶𝘴 to species status. The latest revision in the Flora recognises only three species where the endemic 𝘈. 𝘻𝘦𝘺𝘭𝘢𝘯𝘪𝘤𝘶𝘴 is reduced under 𝘈. 𝘳𝘢𝘤𝘦𝘮𝘰𝘴𝘶𝘴. Field experience suggests the occurrence of several morphological variants with very distinct character combinations that are not listed under the presently recognised species descriptions. Because of these discrepancies, the present study was undertaken to elucidate the number of different Asparagus species that occur in Sri Lanka.

Live specimens were collected from all recorded locations and several other locations covering all climatic zones. Plants were studied in detail and characters showing variations were identified. These characters were coded into a data matrix and were subjected to cluster analysis.

A total of 50 characters was recorded; but as floral data were not complete for a few specimens, only 23 vegetative characters were included in the analysis. The resulted dendrogram identified five major clusters. Each of these identified clusters was evaluated on the basis of the character combinations of the individuals included within the cluster.

Two of these clusters unequivocally agreed with the character combinations of 𝘈. 𝘨𝘰𝘯𝘰𝘤𝘭𝘢𝘥𝘰𝘴 and 𝘈. 𝘧𝘢𝘭𝘤𝘢𝘵𝘶𝘴. The other three clusters together corresponded to the character combination described during the latest revision under 𝘈. 𝘳𝘢𝘤𝘦𝘮𝘰𝘴𝘶𝘴. However, the clear separation of this large cluster into three sub clusters at an acceptable distance indicates the heterogenic nature of the species. Each of these clusters could be supported by character combinations which are unique to each of them; 𝘈𝘴𝘱𝘢𝘳𝘢𝘨𝘶𝘴 with shorter, trigonous, and sickle shaped cladodes of higher elevation; 𝘈𝘴𝘱𝘢𝘳𝘢𝘨𝘶𝘴 with shorter, trigonous, and sickle- shaped cladodes of lower elevation and 𝘈𝘴𝘱𝘢𝘳𝘢𝘨𝘶𝘴 with longer, trigonous, straight cladodes of lower elevation.

The results of the cluster analysis using vegetative characters unambiguously identify the species 𝘈. 𝘨𝘰𝘯𝘰𝘤𝘭𝘢𝘥𝘰𝘴 and 𝘈. 𝘧𝘢𝘭𝘤𝘢𝘵𝘶𝘴. Species of 𝘈𝘴𝘱𝘢𝘳𝘢𝘨𝘶𝘴 described under 𝘈. 𝘳𝘢𝘤𝘦𝘮𝘰𝘴𝘶𝘴 is an assemblage of different species of 𝘈𝘴𝘱𝘢𝘳𝘢𝘨𝘶𝘴. The group of 𝘈𝘴𝘱𝘢𝘳𝘢𝘨𝘶𝘴 that occur in the higher elevations with shorter, trigonous, sickle-shaped cladodes is possibly the group that was recognized as 𝘈. 𝘻𝘦𝘺𝘭𝘢𝘯𝘪𝘤𝘶𝘴 (Baker) Hook. f. in 1892