A molecular systematic study of the African endemic cycads
- Authors: Rousseau, Philip
- Date: 2012-08-16
- Subjects: Cycads - Identification , Endemic plants , Cycads - Phylogeny , Cladistic analysis
- Type: Thesis
- Identifier: uj:9566 , http://hdl.handle.net/10210/5990
- Description: M.Sc. , Africa's cycads (66 species and 2 subspecies in two endemic genera: Encephalartos and Stangeria) are extremely endangered with four species extinct in the wild and 80% threatened (CR, EN, or VU) with all included in CITES Appendix 1. Although South Africa has some of the world’s strictest cycad legislation, these plants are still under threat from illegal collection for horticulture and medicine especially where they are seized in an unidentifiable condition. Currently developed legislation demands accurate identification for permit issue. Ex situ conservation of genetic and locality based diversity is paramount. Furthermore, taxonomically many species of unknown origin are difficult to identify especially when diagnostic characters are absent. Species delimitation and numbers are uncertain with field observations often contradicting current understanding. DNA barcoding can assist with all the above-mentioned scenarios. In the current study all proposed DNA barcoding regions (matK, rbcLa, psbA-trnH, and nrITS) along with several additional regions were tested on ~350 samples from which a phylogeny of 63 of the 65 Encephalartos species was also constructed. Results show general good amplification and sequencing success of proposed barcoding regions, although a shift to specialist primers was made in several cases. Genetic variation however was extremely low as is resolution at species level, even when multi-locus barcodes were employed. Results obtained from the phylogenetic analyses show an increase in resolution at both species and higher levels compared to previous work and as such several new groupings are delimitated. Each species grouping is characterised by shared, derived morphological, ecological, and geographic characters and when compared to previous phylogenetic studies are supported to some extent. The current study provides the first step towards a much-needed monograph and revision of the entire genus Encephalartos.
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Phylogenetic analysis of plant community assemblages in the Kruger National Park, South Africa
- Authors: Yessoufou, Kowiyou
- Date: 2012-08-16
- Subjects: Plant communities , Kruger National Park (South Africa) , Cladistic analysis , Savanna ecology , Herbivores
- Type: Thesis
- Identifier: uj:9574 , http://hdl.handle.net/10210/5998
- Description: D.Phil. , What underlies species distribution and species coexistence has long been of key interest in community ecology. Several methods and theories have been used to address this question. However, it still remains a controversial debate. The recent development of plant DNA barcodes with possibility of merging phylogeny with ecology brings high expectation in uncovering the processes underlying community assemblages. Previous works that used molecular approach in community ecology focused mainly on rainforests. Using a phylogenetic approach, this study brings novel understandings about savanna ecology, especially regarding how megaherbivores impact plant community composition. The Kruger National Park (KNP) is one of the world’s largest reserves, but less studied from a phylogenetic perspective. A DNA database of 445 DNA sequences (plant DNA barcodes, rbcLa + matK) was generated for the woody plants of the KNP. This database proves reliable in reconstructing the phylogeny of Angiosperms of the park. Based on this phylogeny, the present study characterised plant community composition, and investigated how megaherbivores influence this composition. Results indicate that plant communities in the KNP are not neutral, i.e. they are more clustered than expected under various null models. This suggests that ecological forces, most likely habitat filtering may be playing key role in dictating community structure in the KNP. The KNP is well-known for its richness in megaherbivores. The contribution of these animals to the current shape of plant community structures was therefore further investigated. Where megaherbivores have been excluded, plant diversity decreases, but shifts in plant community structure are contingent upon the initial community composition, suggesting that herbivory might be important filter that drives the clustering pattern observed.
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