Phylogenetic patterns of extinction risk in the Eastern Arc Ecosystems, an African biodiversity hotspot
- Yessoufou, Kowiyou, Daru, Barnabas H., Davies, T. Jonathan
- Authors: Yessoufou, Kowiyou , Daru, Barnabas H. , Davies, T. Jonathan
- Date: 2012
- Subjects: African biodiversity , Biodiversity , Ecosystems , Climate change , Phylogenetics , Eatern Arc Mountains
- Type: Article
- Identifier: uj:5853 , ISSN 1932-6203 , http://hdl.handle.net/10210/7950
- Description: There is an urgent need to reduce drastically the rate at which biodiversity is declining worldwide. Phylogenetic methods are increasingly being recognised as providing a useful framework for predicting future losses, and guiding efforts for preemptive conservation actions. In this study, we used a reconstructed phylogenetic tree of angiosperm species of the Eastern Arc Mountains – an important African biodiversity hotspot – and described the distribution of extinction risk across taxonomic ranks and phylogeny. We provide evidence for both taxonomic and phylogenetic selectivity in extinction risk. However, we found that selectivity varies with IUCN extinction risk category. Vulnerable species are more closely related than expected by chance, whereas endangered and critically endangered species are not significantly clustered on the phylogeny. We suggest that the general observation for taxonomic and phylogenetic selectivity (i.e. phylogenetic signal, the tendency of closely related species to share similar traits) in extinction risks is therefore largely driven by vulnerable species, and not necessarily the most highly threatened. We also used information on altitudinal distribution and climate to generate a predictive model of at-risk species richness, and found that greater threatened species richness is found at higher altitude, allowing for more informed conservation decision making. Our results indicate that evolutionary history can help predict plant susceptibility to extinction threats in the hyper-diverse but woefully-understudied Eastern Arc Mountains, and illustrate the contribution of phylogenetic approaches in conserving African floristic biodiversity where detailed ecological and evolutionary data are often lacking.
- Full Text:
- Authors: Yessoufou, Kowiyou , Daru, Barnabas H. , Davies, T. Jonathan
- Date: 2012
- Subjects: African biodiversity , Biodiversity , Ecosystems , Climate change , Phylogenetics , Eatern Arc Mountains
- Type: Article
- Identifier: uj:5853 , ISSN 1932-6203 , http://hdl.handle.net/10210/7950
- Description: There is an urgent need to reduce drastically the rate at which biodiversity is declining worldwide. Phylogenetic methods are increasingly being recognised as providing a useful framework for predicting future losses, and guiding efforts for preemptive conservation actions. In this study, we used a reconstructed phylogenetic tree of angiosperm species of the Eastern Arc Mountains – an important African biodiversity hotspot – and described the distribution of extinction risk across taxonomic ranks and phylogeny. We provide evidence for both taxonomic and phylogenetic selectivity in extinction risk. However, we found that selectivity varies with IUCN extinction risk category. Vulnerable species are more closely related than expected by chance, whereas endangered and critically endangered species are not significantly clustered on the phylogeny. We suggest that the general observation for taxonomic and phylogenetic selectivity (i.e. phylogenetic signal, the tendency of closely related species to share similar traits) in extinction risks is therefore largely driven by vulnerable species, and not necessarily the most highly threatened. We also used information on altitudinal distribution and climate to generate a predictive model of at-risk species richness, and found that greater threatened species richness is found at higher altitude, allowing for more informed conservation decision making. Our results indicate that evolutionary history can help predict plant susceptibility to extinction threats in the hyper-diverse but woefully-understudied Eastern Arc Mountains, and illustrate the contribution of phylogenetic approaches in conserving African floristic biodiversity where detailed ecological and evolutionary data are often lacking.
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Evidence of constant diversification punctuated by a mass extinction in the African cycads
- Yessoufou, Kowiyou, Bamigboye, Samuel O., Daru, Barnabas H., Van der Bank, Michelle
- Authors: Yessoufou, Kowiyou , Bamigboye, Samuel O. , Daru, Barnabas H. , Van der Bank, Michelle
- Date: 2013
- Subjects: Encephalartos , Cycads - Africa , Extinction (Biology)
- Type: Article
- Identifier: uj:5410 , ISSN 2045-8827 , http://hdl.handle.net/10210/10051
- Description: The recent evidence that extant cycads are not living fossils triggered a renewed search for a better understanding of their evolutionary history. In this study, we investigated the evolutionary diversification history of the genus Encephalartos, a monophyletic cycad endemic to Africa. We found an antisigmoidal pattern with a plateau and punctual explosive radiation. This pattern is typical of a constant radiation with mass extinction. The rate shift that we found may therefore be a result of a rapid recolonization of niches that have been emptied owing to mass extinction. Because the explosive radiation occurred during the transition Pliocene–Pleistocene, we argued that the processes might have been climatically mediated.
- Full Text:
- Authors: Yessoufou, Kowiyou , Bamigboye, Samuel O. , Daru, Barnabas H. , Van der Bank, Michelle
- Date: 2013
- Subjects: Encephalartos , Cycads - Africa , Extinction (Biology)
- Type: Article
- Identifier: uj:5410 , ISSN 2045-8827 , http://hdl.handle.net/10210/10051
- Description: The recent evidence that extant cycads are not living fossils triggered a renewed search for a better understanding of their evolutionary history. In this study, we investigated the evolutionary diversification history of the genus Encephalartos, a monophyletic cycad endemic to Africa. We found an antisigmoidal pattern with a plateau and punctual explosive radiation. This pattern is typical of a constant radiation with mass extinction. The rate shift that we found may therefore be a result of a rapid recolonization of niches that have been emptied owing to mass extinction. Because the explosive radiation occurred during the transition Pliocene–Pleistocene, we argued that the processes might have been climatically mediated.
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A global trend towards the loss of evolutionarily unique species in mangrove ecosystems
- Daru, Barnabas H., Yessoufou, Kowiyou, Mankga, Ledile T., Davies, T. Jonathan
- Authors: Daru, Barnabas H. , Yessoufou, Kowiyou , Mankga, Ledile T. , Davies, T. Jonathan
- Date: 2013
- Subjects: Mangrove ecology , Threatened species , Biodiversity conservation
- Type: Article
- Identifier: uj:5984 , http://hdl.handle.net/10210/8604
- Description: The mangrove biome stands out as a distinct forest type at the interface between terrestrial, estuarine, and near-shore marine ecosystems. However, mangrove species are increasingly threatened and experiencing range contraction across the globe that requires urgent conservation action. Here, we assess the spatial distribution of mangrove species richness and evolutionary diversity, and evaluate potential predictors of global declines and risk of extinction. We found that human pressure, measured as the number of different uses associated with mangroves, correlated strongly, but negatively, with extinction probability, whereas species ages were the best predictor of global decline, explaining 15% of variation in extinction risk. Although the majority of mangrove species are categorised by the IUCN as Least Concern, our finding that the more threatened species also tend to be those that are more evolutionarily unique is of concern because their extinction would result in a greater loss of phylogenetic diversity. Finally, we identified biogeographic regions that are relatively species-poor but rich in evolutionary history, and suggest these regions deserve greater conservation priority. Our study provides phylogenetic information that is important for developing a unified management plan for mangrove ecosystems worldwide.
- Full Text:
- Authors: Daru, Barnabas H. , Yessoufou, Kowiyou , Mankga, Ledile T. , Davies, T. Jonathan
- Date: 2013
- Subjects: Mangrove ecology , Threatened species , Biodiversity conservation
- Type: Article
- Identifier: uj:5984 , http://hdl.handle.net/10210/8604
- Description: The mangrove biome stands out as a distinct forest type at the interface between terrestrial, estuarine, and near-shore marine ecosystems. However, mangrove species are increasingly threatened and experiencing range contraction across the globe that requires urgent conservation action. Here, we assess the spatial distribution of mangrove species richness and evolutionary diversity, and evaluate potential predictors of global declines and risk of extinction. We found that human pressure, measured as the number of different uses associated with mangroves, correlated strongly, but negatively, with extinction probability, whereas species ages were the best predictor of global decline, explaining 15% of variation in extinction risk. Although the majority of mangrove species are categorised by the IUCN as Least Concern, our finding that the more threatened species also tend to be those that are more evolutionarily unique is of concern because their extinction would result in a greater loss of phylogenetic diversity. Finally, we identified biogeographic regions that are relatively species-poor but rich in evolutionary history, and suggest these regions deserve greater conservation priority. Our study provides phylogenetic information that is important for developing a unified management plan for mangrove ecosystems worldwide.
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Molecular and morphological analysis of subfamily Alooideae (Asphodelaceae) and the inclusion of chortolirion in aloe
- Daru, Barnabas H., Manning, John C., Boatwright, James S., Maurin, Olivier, Maclean, Norman, Schaefer, Hanno, Kuzmina, Maria, van der Bank, Michelle
- Authors: Daru, Barnabas H. , Manning, John C. , Boatwright, James S. , Maurin, Olivier , Maclean, Norman , Schaefer, Hanno , Kuzmina, Maria , van der Bank, Michelle
- Date: 2013
- Subjects: Asphodelaceae , Alooideae , Asparagales , Aloe , Chortolirion
- Type: Article
- Identifier: uj:5985 , http://hdl.handle.net/10210/8605
- Description: Asphodelaceae subfam. Alooideae (Asparagales) currently comprises five genera, four of which are endemic to southern Africa. Despite their importance in commercial horticulture the evolutionary relationships among the genera are still incompletely understood. This study examines phylogenetic relationships in the subfamily using an expanded molecular sequence dataset from three plastid regions (matK, rbcLa, trnH-psbA) and the first subunit of the nuclear ribosomal internal transcribed spacer (ITS1). Sequence data were analysed using maximum parsimony and Bayesian statistics, and selected morphological traits were mapped onto the molecular phylogeny. Haworthia is confirmed as being polyphyletic, comprising three main clades that largely correlate with current subgeneric circumscriptions. Astroloba and Gasteria are evidently each monophyletic and sister respectively to Astroloba and H. subg. Robustipedunculares. Chortolirion is shown to be deeply nested within Aloe and is formally included in that genus. Aloe itself is clearly polyphyletic, with the dwarf species A. aristata allied to Haworthia subg. Robustipedunculares. The taxonomic implications of these findings are examined but branch support at critical lower nodes is insufficient at this stage to justify implementing major taxonomic changes.
- Full Text:
- Authors: Daru, Barnabas H. , Manning, John C. , Boatwright, James S. , Maurin, Olivier , Maclean, Norman , Schaefer, Hanno , Kuzmina, Maria , van der Bank, Michelle
- Date: 2013
- Subjects: Asphodelaceae , Alooideae , Asparagales , Aloe , Chortolirion
- Type: Article
- Identifier: uj:5985 , http://hdl.handle.net/10210/8605
- Description: Asphodelaceae subfam. Alooideae (Asparagales) currently comprises five genera, four of which are endemic to southern Africa. Despite their importance in commercial horticulture the evolutionary relationships among the genera are still incompletely understood. This study examines phylogenetic relationships in the subfamily using an expanded molecular sequence dataset from three plastid regions (matK, rbcLa, trnH-psbA) and the first subunit of the nuclear ribosomal internal transcribed spacer (ITS1). Sequence data were analysed using maximum parsimony and Bayesian statistics, and selected morphological traits were mapped onto the molecular phylogeny. Haworthia is confirmed as being polyphyletic, comprising three main clades that largely correlate with current subgeneric circumscriptions. Astroloba and Gasteria are evidently each monophyletic and sister respectively to Astroloba and H. subg. Robustipedunculares. Chortolirion is shown to be deeply nested within Aloe and is formally included in that genus. Aloe itself is clearly polyphyletic, with the dwarf species A. aristata allied to Haworthia subg. Robustipedunculares. The taxonomic implications of these findings are examined but branch support at critical lower nodes is insufficient at this stage to justify implementing major taxonomic changes.
- Full Text:
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