No abstract

A phylogenetic study of Roscoea (Zingiberaceae), a high-altitude genus of an otherwise tropical plant family, was undertaken using sequence data from the internal transcribed spacers (ITS) of the nuclear ribosomal DNA (nrDNA). Two species of Cautleya and two species of Curcuma were used as outgroups. This resulted in an aligned matrix of 436bp (ITS1, 203bp; ITS2, 233bp). Sequence divergence of ITS1 and ITS2 within the ingroup ranged from 0–13.9% and 0–7.6% respectively. The results suggest that Roscoea is monophyletic (BS=99%; DI=>3) with the genus Cautleya as sister group. Roscoea itself is divided into two sister clades which correlate with geography: a ‘Chinese’ clade (BS=67%; DI=+2) and a ‘Himalayan’ clade (BS=59%; DI=+1). These two groups are disjunct across the ‘Brahmaputra gap’, a region in which no Roscoea spp. have been recorded. The only species which occurs on both sides of the Brahmaputra gap is Roscoea tibetica. However, the western populations of Roscoea tibetica (from Bhutan) show numerous morphological differences. It is therefore possible that Bhutanese R. tibetica represents a distinct taxon, possibly more closely allied to Himalayan species.

A phylogenetic analysis of the tribe Zingibereae (Zingiberaceae) was performed using nuclear ribosomal DNA (ITS1, 5.8S and ITS2) and chloroplast DNA (trnL (UAA) 5p exon to trnF (GAA)). The tribe is monophyletic with two major clades, the Curcuma clade and the Hedychium clade. Paracautleya, sampled for the first time, comes out as predicted while Caulokaempferia comes out in a different position from that found in another recent study. The genera Boesenbergia and Curcuma are apparently not monophyletic.

Genetic variation and molecular phylogeny of 22 taxa representing 14 extant species and 3 unidentified taxa of Boesenbergia in Thailand and four outgroup species (Cornukaempferia aurantiflora, Hedychium biflorum, Kaempferia parviflora, and Scaphochlamys rubescens) were examined by sequencing of 3 chloroplast (cp) DNA regions (matK, psbA-trnH and petA-psbJ). Low interspecific genetic divergence (0.25-1.74%) were observed in these investigated taxa. The 50% majority-rule consensus tree constructed from combined chloroplast DNA sequences allocated Boesenbergia in this study into 3 different groups. Using psbA-1F/psbA-3R primers, an insertion of 491 bp was observed in B. petiolata. Restriction analysis of the amplicon (380-410 bp) from the remaining species with Rsa I further differentiated Boesenbergia to 2 groupings; I (B. basispicata, B. longiflora, B. longipes, B. plicata, B.pulcherrima, B. tenuispicata, B. thorelii, B. xiphostachya, Boesenbergia sp.1 and Boesenbergia sp.3; phylogenetic clade A) that possesses a Rsa I restriction site and II (B.curtisii, B. regalis, B. rotunda and Boesenbergia sp.2; phylogenetic clade B and B. siamensis; phylogenetic clade C) that lacks a restriction site of Rsa I. Single nucleotide polymorphism (SNP) and indels found can be unambiguously applied to authenticate specie-origin of all investigated samples and revealed that Boesenbergia sp.1, Boesenbergia sp.2 and B. pulcherrima (Mahidol University, Kanchanaburi), B. cf. pulcherrima1 (Prachuap Khiri Khan) and B. cf. pulcherrima2 (Thong Pha Phum, Kanchanaburi) are B. plicata, B. rotunda and B. pulcherrima, respectively. In addition, molecular data also suggested that Boesenbergia sp.3 should be further differentiated from B. longiflora and regarded as a newly unidentified Boesenbergia species.

A new species of Caulokaempferia from southern Thailand, C. sirirugsae Ngamriab. is described and illustrated. The new species is morphologically similar to C. saksuwaniae, from which it differs by having large flying rhombic staminodes, ovate anther crest, obovate labellum and untoothed acuminate calyx tip.