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Phenetic study of the genus Thelypteris in Thailand

Pankamon Sornsuwan, Thaweesakdi Boonkerd^*, Tosak Seelanan

 
ABSTRACT:     Thelypteris Schmidel s.l. is a genus of the Thelypteridaceae. It comprises about one thousand species, and mostly occurs in tropical and subtropical regions of the world. Up to now, the genera within the Thelypteridaceae have not been clearly classified due to significantly differing taxonomic concepts of pteridologists. Some authors have placed all species in a single genus, whilst others have segregated Thelypteris s.l. into two or more genera. In Thailand, Thelypteris s.l. is commonly found in various habitats throughout. Fifty one species have been reported and were classified into two genera. In contrast, these same species would be classified into 16 genera according to Holttum's classification. In order to clarify this taxonomic inconsistency, 518 operational taxonomic units (OTUs) from 27 species were analysed using cluster and canonical discriminant analyses. A total of 21 quantitative and 11 qualitative characters were employed. In cluster analysis using only quantitative characters, the 518 OTUs could be separated into three groups or genera, i.e., Thelypteris s.s., Macrothelypteris, and Pronephrium, at an average taxonomic distance of 1.50. The same result was obtained when both quantitative and qualitative characters were used. Canonical discriminant analysis also indicated that there were three groups within the genus Thelypteris s.l. The three groups/genera can be distinguished on the basis of scale width, angle of basal pinnae to rachis, number of annulus cells, spore height, and spore diameter. In all, the results from this phenetic study support the segregation of Thelypteris s.l. into three genera, viz. Thelypteris s.s., Macrothelypteris, and Pronephrium.

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* Corresponding author, E-mail: thaweesakdi.b@chula.ac.th

Received 5 Feb 2009, Accepted 6 Nov 2009