A Taxonomic Review of Corybas rivularis (Orchidaceae) - Inferred from Molecular and Morphological Analyses
Coffin, A. J. (2016). A Taxonomic Review of Corybas rivularis (Orchidaceae) - Inferred from Molecular and Morphological Analyses (Thesis, Master of Science (MSc)). University of Waikato, Hamilton, New Zealand. Retrieved from http://hdl.handle.net/10289/10538
Permanent Research Commons link: http://hdl.handle.net/10289/10538
This research has expanded the level of precision utilised in critically examining the morphology of Corybas rivularis Rchb.f (Orchidaceae), related species and undescribed populations. Corybas rivularis and related species have undergone taxonomic revisions, incorporating errors that took decades to discover. Utilising morphological and molecular analyses has provided insights into this problematic group. A new protocol for examining the morphological characteristics of C. rivularis has been developed, based on concepts of floral morphometrics, to determine the level of morphological variation within the species, closely related species and a range of undescribed populations, some of which have tag-names. The use of morphological techniques with multivariate statistics has not been previously used in this group. A suite of precisely defined continuous characters relevant to the four species and five undescribed tag-named populations studied is established, and a distance matrix collating all of the respective characters for each sample is generated. A Linear Discriminant Analysis (LDA) found the characters most capable of discriminating natural groups to be three aspects of the flower labellum; the length and width of the labellum bib, and the length of a furrow in the labellum formed from a developmental pinching of the labellum tube, which leads to the column. The LDA, along with a cluster analysis (UPGMA) allowed all species and tag-named populations studied to be determined as distinctive, except for two; C. aff. rivularis (AK251833; Kaitarakihi) and C. ‘veil’, which together form a distinct group. There are two morphological syndromes present in the studied species and tag-named populations; One group, allied to Corybas iridescens Irwin & Molloy, tends to have a long and wide bib, with a small furrow and petiolate leaf, the other group, allied to C. rivularis sensu stricto tending to have a narrow and short bib, with a long furrow and sessile leaf. Sequence variation of the nuclear ribosomal Internal Transcribed Spacer (ITS) region was used reconstruct relationships. Consistent with other studies (Clements et al. 2007), many samples shared identical sequences. C. iridescens, and tag-named populations C. aff. rivularis (AK251833; Kaitarakihi) and C. “veil” formed a highly supported clade. Corybas rivularis from the far North has variation from all other species and tag-named populations. The tag-named populations regarded as C. aff. rivularis (CHR 518313 “whiskers”), C. aff. rivularis (CHR 518025; Kaimai) and C. “pollok” shared identical sequences. Consistent with the morphological findings, there are two highly supported monophyletic groups present in the plants studied; one composed of C. rivularis and allied species, and another group composed of C. iridescens and allied species. The evidence suggests a taxonomic revision is warranted however further research into this group is still required to further delimit species boundaries. Any taxonomic revision undertaken will have ramifications for conservation, both the threat classification status of some species, and the conservation management strategies
University of Waikato
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- Masters Degree Theses