University of Tasmania

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Subtribe Pterostylidinae : a multidisciplinary approach to investigating and resolving taxonomic confusion

posted on 2023-05-26, 03:52 authored by Janes, JK
The distribution, niche-partitioning, taxonomy and population-level genetic variation of Tasmanian representatives of the subtribe Pterostylidinae were investigated. General ecological data were collected over a two year period to assess changes in the known distribution of Pterostylis species within Tasmania and identify previously unknown populations. Ecological characteristics relating to habitat were used to perform a series of canonical correspondence analyses (CCA) to effectively delimit each species' ecological tolerances and niche hyperspace. A series of Bayesian and maximum parsimony phylogenetic reconstructions were conducted using DNA sequence data from the internal transcribed spacer (ITS) region of nuclear ribosomal DNA to elucidate generic and infrageneric relationships within the Pterostylidinae. Following from these results, the genetic variation within the Tasmanian members of the longifolia‚ÄövÑvp species complex was investigated using amplified fragment length polymorphism (AFLP) and polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP). Ecological survey data indicated that the distribution and abundance of Pterostylis species within Tasmania had changed significantly within the past 10 years, with different species apparently more or less common than previously thought. In addition to the number of populations located, the number of individuals within each population provided insight into the overall level of conservation status applicable to particular species and several recommendations for the management of these species were made. Niche partitioning based on habitat characteristics revealed differences in the ecological tolerances of Pterostylis species and effectively delimited many species along ecological gradients. Significant overlap in the fundamental niches of several morphologically similar species was identified, which suggested that some taxa within Pterostylidinae complexes had been incorrectly assigned to the level of species. This hypothesis was later confirmed through a phylogenetic and population genetic study. Phylogenetic work using ITS sequence data confirmed that Pterostylidinae is embedded within the tribe Cranichideae. Furthermore, the reconstructions strongly supported a monotypic subtribe (Pterostylidinae) comprising the single genus Pterostylis R.Br sensu lato. The analysis found two strongly supported clades that correlated with the morphology of the lateral sepal position within the subtribe and, are herein, delimited as subgenera of Pterostylis. Several closely related species from within species complexes had identical ITS sequences; together with the CCA data the results indicate the presence of over-splitting of the Pterostylidinae. PCR-RFLP analysis of the chloroplast genome in the longifolia‚ÄövÑvp species complex revealed extremely low variation among species and no marker was found that could distinguish between the Tasmanian representatives of this complex. Further work at the population level using AFLP markers indicated high levels of polymorphism within the complex but, again, could not delimit the four longifolia‚ÄövÑvp species. Instead, population structure analysis revealed geographic separation of longifolia‚ÄövÑvp populations irrespective of species. The information from these investigations is essential for taxonomic resolution within the subtribe Pterostylidinae and has clear implications for Pterostylis conservation and management




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