SUNScholar - Browsing by Author "Bellstedt, Dirk U."

Browsing by Author "Bellstedt, Dirk U."

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Conservation implications of avian malaria exposure for African penguins during rehabilitation
(Academy of Science of South Africa, 2017-02-15) Botes, Annelise; Thiart, Hanlie; Parsons, Nola J.; Bellstedt, Dirk U.
ENGLISH ABSTRACT: The African penguin (Spheniscus demersus) is the only penguin species that breeds on the African continent and it is currently classified as endangered. Its conservation is assisted by the Southern African Foundation for the Conservation of Coastal Birds (SANCCOB) which is a seabird rehabilitation facility based at the Rietvlei Wetland Reserve in Tableview, Cape Town. Despite the success of SANCCOB in rehabilitating diseased, injured or oiled penguins, significant mortalities have occurred at the facility as a result of avian malaria. Avian malaria can be contracted during rehabilitation during which penguins are inadvertently exposed to additional threats. An enzyme-linked immunosorbent assay (ELISA) was used to assess the anti-Plasmodium antibody levels of penguins to avian malaria on entry into the SANCCOB facility from 2001 to 2004 and during their rehabilitation process. Using blood smear data, avian malaria prevalence and malaria-related deaths were also monitored from 2002 to 2013. Significant increases in anti-Plasmodium antibody levels after admission were found during summer months. New infection and not parasite recrudescence was concluded to be the cause of this increase. This source was confirmed by a dramatic drop in penguin mortalities upon exclusion of mosquito vectors in 2008. Mortalities did not depend on the birds’ abilities to produce an anti-Plasmodium antibody response and oiling had no influence on immunity or prevalence of avian malaria infections. This study highlights the importance of mosquito vector control to control pathogen exposure in wild bird rehabilitation centres. Significance: • Efforts to assist with the conservation of endangered species can unintentionally add to the conservation burden. • Rehabilitation influences exposure of African penguins to avian malaria. • Avian malaria prevalence and mortality are not influenced by oiling or anti-Plasmodium antibody responses. • Vector control can limit avian malaria exposure in wild bird rehabilitation centres.
Consistent phenological shifts in the making of a biodiversity hotspot : the Cape flora
(BioMed Central, 2011-02) Warren, Ben H.; Bakker, Freek T.; Bellstedt, Dirk U.; Bytebier, Benny; Claszen-Bockhoff, Regine; Dreyer, Leanne L.; Edwards, Dawn; Forest, Felix; Galley, Chloe; Hardy, Christopher R.; Linder, H. Peter; Muasya, A. Muthama; Mummenhoff, Klaus; Oberlander, Kenneth C.; Quint, Marcus; Richardson, James E.; Savolainen, Vincent; Schrire, Brian D.; Van der Niet, Timotheus; Verboom, G. Anthony; Yesson, Christopher; Hawkins, Julie A.
ABSTRACT: Background: The best documented survival responses of organisms to past climate change on short (glacial-interglacial) timescales are distributional shifts. Despite ample evidence on such timescales for local adaptations of populations at specific sites, the long-term impacts of such changes on evolutionary significant units in response to past climatic change have been little documented. Here we use phylogenies to reconstruct changes in distribution and flowering ecology of the Cape flora - South Africa's biodiversity hotspot - through a period of past (Neogene and Quaternary) changes in the seasonality of rainfall over a timescale of several million years. Results: Forty-three distributional and phenological shifts consistent with past climatic change occur across the flora, and a comparable number of clades underwent adaptive changes in their flowering phenology (9 clades; half of the clades investigated) as underwent distributional shifts (12 clades; two thirds of the clades investigated). Of extant Cape angiosperm species, 14-41% have been contributed by lineages that show distributional shifts consistent with past climate change, yet a similar proportion (14-55%) arose from lineages that shifted flowering phenology. Conclusions: Adaptive changes in ecology at the scale we uncover in the Cape and consistent with past climatic change have not been documented for other floras. Shifts in climate tolerance appear to have been more important in this flora than is currently appreciated, and lineages that underwent such shifts went on to contribute a high proportion of the flora's extant species diversity. That shifts in phenology, on an evolutionary timescale and on such a scale, have not yet been detected for other floras is likely a result of the method used; shifts in flowering phenology cannot be detected in the fossil record.
Extinction risk and diversification are linked in a plant biodiversity hotspot
(Public Library of Science, 2011-05) Davies, T. Jonathan; Smith, Gideon F.; Bellstedt, Dirk U.; Boatwright, James S.; Bytebier, Benny; Cowling, Richard M.; Forest, Felix; Harmon, Luke J.; Muasya, A. Muthama; Schrire, Brian D.; Steenkamp, Yolande; Van der Bank, Michelle; Savolainen, Vincent
It is widely recognized that we are entering an extinction event on a scale approaching the mass extinctions seen in the fossil record. Present-day rates of extinction are estimated to be several orders of magnitude greater than background rates and are projected to increase further if current trends continue. In vertebrates, species traits, such as body size, fecundity, and geographic range, are important predictors of vulnerability. Although plants are the basis for life on Earth, our knowledge of plant extinctions and vulnerabilities is lagging. Here, we disentangle the underlying drivers of extinction risk in plants, focusing on the Cape of South Africa, a global biodiversity hotspot. By comparing Red List data for the British and South African floras, we demonstrate that the taxonomic distribution of extinction risk differs significantly between regions, inconsistent with a simple, trait-based model of extinction. Using a comprehensive phylogenetic tree for the Cape, we reveal a phylogenetic signal in the distribution of plant extinction risks but show that the most threatened species cluster within short branches at the tips of the phylogeny—opposite to trends in mammals. From analyzing the distribution of threatened species across 11 exemplar clades, we suggest that mode of speciation best explains the unusual phylogenetic structure of extinction risks in plants of the Cape. Our results demonstrate that explanations for elevated extinction risk in plants of the Cape flora differ dramatically from those recognized for vertebrates. In the Cape, extinction risk is higher for young and fast-evolving plant lineages and cannot be explained by correlations with simple biological traits. Critically, we find that the most vulnerable plant species are nonetheless marching towards extinction at a more rapid pace but, surprisingly, independently from anthropogenic effects. Our results have important implications for conservation priorities and cast doubts on the utility of current Red List criteria for plants in regions such as the Cape, where speciation has been rapid, if our aim is to maximize the preservation of the tree-of-life.
Floral color, anthocyanin synthesis gene expression and control in Cape Erica species
(Frontiers Media, 2019-11-28) Le Maitre, N. C.; Pirie, Michael David; Bellstedt, Dirk U.
Introduction: The Cape Floristic Region (CFR) is a biodiversity hotspot, recognized globally for its unusually high levels of endemism. The origins of this biodiversity are a long-standing topic of research. The largest “Cape clade,” Erica, radiated dramatically in the CFR, its ca. 690 species arising within 10–15 Ma. Notable between- and within-species flower color variation in Erica may have contributed to the origins of species diversity through its impact on pollinator efficiency and specificity. Methods: We investigate the expression and function of the genes of the anthocyanin biosynthesis pathway that controls floral color in 12 Erica species groups using RT-qPCR and UPLC-MS/MS. Results: Shifts from ancestral pink- or red- to white- and/or yellow flowers were associated with independent losses of single pathway gene expression, abrogation of the entire pathway due to loss of the expression of a transcription factor or loss of function mutations in pathway genes. Discussion: Striking floral color shifts are prevalent amongst the numerous species of Cape Erica. These results show independent origins of a palette of mutations leading to such shifts, revealing the diverse genetic basis for potentially rapid evolution of a speciation-relevant trait.
Leaps and bounds : geographical and ecological distance constrained the colonisation of the Afrotemperate by Erica
(BMC (part of Springer Nature), 2019-12-05) Pirie, Michael D.; Kandziora, Martha; Nürk, Nicolai M.; Le Maitre, Nicholas C.; Mugrabi De Kuppler, Ana; Gehrke, Berit; Oliver, Edward G. H.; Bellstedt, Dirk U.
Background: The coincidence of long distance dispersal (LDD) and biome shift is assumed to be the result of a multifaceted interplay between geographical distance and ecological suitability of source and sink areas. Here, we test the influence of these factors on the dispersal history of the flowering plant genus Erica (Ericaceae) across the Afrotemperate. We quantify similarity of Erica climate niches per biogeographic area using direct observations of species, and test various colonisation scenarios while estimating ancestral areas for the Erica clade using parametric biogeographic model testing. Results: We infer that the overall dispersal history of Erica across the Afrotemperate is the result of infrequent colonisation limited by geographic proximity and niche similarity. However, the Drakensberg Mountains represent a colonisation sink, rather than acting as a “stepping stone” between more distant and ecologically dissimilar Cape and Tropical African regions. Strikingly, the most dramatic examples of species radiations in Erica were the result of single unique dispersals over longer distances between ecologically dissimilar areas, contradicting the rule of phylogenetic biome conservatism. Conclusions: These results highlight the roles of geographical and ecological distance in limiting LDD, but also the importance of rare biome shifts, in which a unique dispersal event fuels evolutionary radiation.
A new species of Streptocarpus (Gesneriaceae) endemic to Madagascar
(Museum Nationale d'Histoire Naturelle Paris, 2005-03) MacMaster, Gwyneth; Moller, Michael; Hughes, Mark; Edwards, Trevor J.; Bellstedt, Dirk U.
A new species of Streptocarpus (S. lanatus MacMaster) is described from central Madagascar. Material referable to this new taxon was previously assigned to S. ibityensis Humbert, from which it can be distinguished by its densely woolly leaves, smaller corolla lobes with purple markings, and lack of staminodes. It is endemic to Mt Itremo, where it grows in the shelter of boulders and small caves. Evidence in the form of a molecular phylogeny is presented to highlight the distinctiveness of the new species from related taxa. Both S. lanatus and S. ibityensis are classified in the IUCN category “Vulnerable”.
Phylogeography and molecular evolution of potato virus Y
(Public Library of Science, 2012-05-24) Cuevas, Jose M.; Delaunay, Agnes; Visser, Johan C.; Bellstedt, Dirk U.; Jacquot, Emmanuel; Elena, Santiago F.
Potato virus Y (PVY) is an important plant pathogen, whose host range includes economically important crops such as potato, tobacco, tomato, and pepper. PVY presents three main strains (PVY O, PVY N and PVY C) and several recombinant forms. PVY has a worldwide distribution, yet the mechanisms that promote and maintain its population structure and genetic diversity are still unclear. In this study, we used a pool of 77 complete PVY genomes from isolates collected worldwide. After removing the effect of recombination in our data set, we used Bayesian techniques to study the influence of geography and host species in both PVY population structure and dynamics. We have also performed selection and covariation analyses to identify evolutionarily relevant amino acid residues. Our results show that both geographic and host-driven adaptations explain PVY diversification. Furthermore, purifying selection is the main force driving PVY evolution, although some indications of positive selection accounted for the diversification of the different strains. Interestingly, the analysis of P3N-PIPO, a recently described gene in potyviruses, seems to show a variable length among the isolates analyzed, and this variability is explained, in part, by host-driven adaptation.
Targeted NGS for species level phylogenomics : "made to measure'' or "one size fits all''?
(PeerJ, 2017) Kadlec, Malvina; Bellstedt, Dirk U.; Le Maitre, Nicholas C.; Pirie, Michael D.
Targeted high-throughput sequencing using hybrid-enrichment offers a promising source of data for inferring multiple, meaningfully resolved, independent gene trees suitable to address challenging phylogenetic problems in species complexes and rapid radiations. The targets in question can either be adopted directly from more or less universal tools, or custom made for particular clades at considerably greater effort. We applied custom made scripts to select sets of homologous sequence markers from transcriptome and WGS data for use in the flowering plant genus Erica (Ericaceae). We compared the resulting targets to those that would be selected both using different available tools (Hyb-Seq; MarkerMiner), and when optimising for broader clades of more distantly related taxa (Ericales; eudicots). Approaches comparing more divergent genomes (including MarkerMiner, irrespective of input data) delivered fewer and shorter potential markers than those targeted for Erica. The latter may nevertheless be effective for sequence capture across the wider family Ericaceae. We tested the targets delivered by our scripts by obtaining an empirical dataset. The resulting sequence variation was lower than that of standard nuclear ribosomal markers (that in Erica fail to deliver a well resolved gene tree), confirming the importance of maximising the lengths of individual markers. We conclude that rather than searching for "one size fits all'' universal markers, we should improve and make more accessible the tools necessary for developing "made to measure'' ones.

Browsing by Author "Bellstedt, Dirk U."

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