Abstract
Taxonomy and phylogenesis of Sri Lankan cycad species of the subsection Rumphiae has not been fully resolved and therefore, we conducted an island-wide survey of cycads of the subsection to assess their morphological or genetic variations while exploring the phylogenetic relationship between Sri Lankan Rumphiae and other world cycad species. Further, we assessed the possible distribution of the species in the region through climatic profiling, using maximum entropy modeling approach. We analyzed 21 variable morphological features in collected specimens and used the polymorphism of trnH-psbA locus to understand the phylogeny. The distance tree drawn from the principal component analysis revealed a significant variation in female reproductive structures. The maximum likelihood tree separated Sri Lankan Cycas zeylanica to a well-supported unigeneric clade (bootstrap = 96, posterior probability = 100) with shallow divergence. Ecological niche modeling supported the existence of Cycas zeylanica in South East Asia and in southern Western Ghats in India in addition to the Wet Zone of Sri Lanka. We rename the taxa as Cycas zeylanica complex based on the observed high morphological diversity of female reproductive structures which might have ascended due to multiple introductions of South East Asian cycads by long distance dispersal of seeds through sea currents.
Highlights
The genus Cycas which belongs to the unigeneric family Cycadaceae, is considered as the basal lineage of the order Cycadales[1]
Absence of apical crest-like structure in the seeds[8] is a feature that can be used in differentiating C. zeylanica from C. rumphii, but we were unable to use this feature as mature seeds were not available in all samples examined
In agreement with Lindstrom and Hill[12], the present study identified that the members of the Sri Lankan subsection Rumphiae are closer to C. zeylanica and the study group formed a well-supported unigeneric clade in the Maximum Likelihood (ML) tree despite the high morphological diversity observed in female reproductive structures
Summary
The genus Cycas which belongs to the unigeneric family Cycadaceae, is considered as the basal lineage of the order Cycadales[1]. The combined feature of the presence of spongy tissues in the endotesta or the presence of a fibrous layer in sarcotesta of the seed is a primary attribute of taxonomic significance in differentiating the individuals of the three subsections of the section Cycas[8,11] This feature allows the differentiation of Sri Lankan cycads into two subsections, Cycas and Rumphiae[12,13]. By an island-wide survey of individuals of the genus Cycas www.nature.com/scientificreports in Sri Lanka, Mudannayake et al.[13] have studied 26 reproductive and 23 vegetative features of individuals of the subsection Rumphiae and observed the presence of substantial continuous variation in many of the important morphological features among the individuals, which led to describe the group as C. rumphii complex. The length of trnH-psbA sequences in Gymnosperms ranges from 283–1006 bp[23], and with good priming sites, short read lengths (~ 600 bp) can be efficiently sequenced across many taxa
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
