In this paper, molecular phylogenetic analyses were used to investigate a putative hybrid origin for Dendrochilum acuiferum, a species endemic to Mount Kinabalu, Sabah, Malaysia. Phylogenetic analyses of the plastid (pt) accD-psaI intergenic spacer region and a unique shared 117 bp indel indicate that D. grandiflorum and D. acuiferum are closely related. Direct sequencing of PCR products from the ITS 1 and 2 of the nuclear ribosomal repeat region revealed single site nucleotide polymorphisms in D. acuiferum that were additive between two hypothesized parents in addition to other sampled species. Dendrochilum acuiferum within-individual cloned ITS allelic sequence variants were analyzed in a phylogenetic context to determine the relative support for a hybrid (biphyletic) origin versus a nonhybrid (monophyletic) origin of the alleles. Because there was a significantly higher level of support for a hybrid origin of the alleles (P < 0.05), we subsequently compared likelihood scores for multiple parent pairs that could have hybridized. Although ptDNA evidence suggests Dendrochilum grandiflorum was the most likely maternal parent of D. acuiferum, ITS results are ambiguous about paternity because the phylogenetic results support D. grandiflorum D. stachyodes and D. grandiflorum D. kamborangense as equally likely parents of D. acuiferum. In addition, two other parent pairs could not be rejected (P > 0.05).

Communicating Editor: Jeff H. Rettig