For all researches, please visit our "Peer-reviewed publications" page.
Cheek M, Semple J (2016)
First official record of naturalised populations of Solidago altissima L. var. pluricephala M.C. Johnst. (Asteraceae: Astereae) in Africa
South African Journal of Botany 105 333-336.
Solidago altissima var. pluricephala is recorded for the first time as naturalised in Africa, with two populations detected in South Africa. One 0.5ha population has been found near Harding and another of 403 shoots near Hilton, both in KwaZulu-Natal. A projected species distribution model for South Africa indicates that the grassland biome is the most at risk from invasion by this species. These plants are most likely garden escapees although we are uncertain how widely they are cultivated in South Africa.
Keywords: Distribution model, Golden rods, Grasslands, Invasive species, Ornamental plants
Congrains C, Carvalho A, Miranda E, Cumming G, Henry D, Manu S et al. (2016)
Genetic and paleomodelling evidence of the population expansion of the cattle egret Bubulcus ibis in Africa during the climatic oscillations of the Late Pleistocene
Journal of Avian Biology.
Increasing aridity during glacial periods produced the retraction of forests and the expansion of arid and semi-arid environments in Africa, with consequences for birds. Cattle egret (Bubulcus ibis) is a dispersive species that prefers semiarid environments and requires proximity to bodies of water. We expected that climatic oscillations led to the expansion of the range of the cattle egret during arid periods, such as the Last Maximum Glacial (LGM) and contraction of distribution during the Last Interglacial (LIG) period, resulting in contact of populations previously isolated. We investigated this hypothesis by evaluating the genetic structure and population history of 15 cattle egret breeding colonies located in West and South Africa using the mitochondrial DNA (mtDNA) control region, mtDNA ATPase 8 and 6, and an intron of nuclear gene transforming growth factor beta-2. Occurrence data and bioclimatic information were used to generate ecological niche models of three periods (present, LGM and LIG). We used the genetic and paleomodelling data to assess the responses of the cattle egret from Africa to the climatic oscillations during the late Pleistocene. Genetic data revealed low levels of genetic differentiation, signs of isolation-by-distance, as well as recent increases in effective population size that started during the LGM. The observed low genetic structure may be explained by recent colonization events due to the demographic expansion following the last glacial period and by dispersal capacity of this species. The paleomodels corroborated the expansion during the LGM, and a more restricted potential distribution during the LIG. Our findinds supports the hypothesis that the species range of the cattle egret expanded during arid periods and contracted during wet periods.
Keywords: Distribution model, Golden rods, Grasslands, Invasive species, Ornamental plants
Geerts S, Mashele B, Visser V, Wilson J (2016)
Lack of human-assisted dispersal means Pueraria montana var. lobata (kudzu vine) could still be eradicated from South Africa
Biological Invasions 1-8.
The legume, Pueraria montana var. lobata (kudzu vine) is one of the worst plant invaders globally. Here we present the first study of P. montana in South Africa. We found only seven P. montana populations covering an estimated condensed area of 74 hectares during the height of the growing season. Based on a species distribution model, it appears that large parts of the globe are suitable, including parts of the eastern escarpment of South Africa (where most populations occur). South African populations of P. montana appear to have a similar ecology to populations in the USA: high growth rates, low seed germination, no natural long-distance dispersal, little herbivory and vigorous post-fire resprouting. In contrast to the USA, most South African populations do flower and flowers are capable of producing seed in the absence of pollinators. However, P. montana appears to have never been widely planted in South Africa, and the incursion was for many years restricted to a single introduction site. The comparison between the invasions of P. montana in the USA and South Africa highlights the often overriding importance of human-assisted dispersal and cultivation in creating widespread invasions, and should serve as a warning to people who have proposed to utilize the species in Africa.
Keywords: Africa, Alien invasive weed, Climate models, FabaceaeLegume, Pollination
Greve M, Lykke A, Fagg C, Gereau R, Lewis G, Marchant R et al. (2016)
South African Journal of Botany 105 317-323.
One of the major challenges in ecosystem conservation is obtaining baseline data, particularly for regions that have been poorly inventoried, such as regions of the African continent. Here we use a database of African herbarium records and examples from the literature to show that, although herbarium records have traditionally been collected to build botanical reference “libraries” for taxonomic and inventory purposes, they provide valuable and useful information regarding species, their distribution in time and space, their traits, phenological characteristics, associated species and their physical environment. These data have the potential to provide invaluable information to feed into evidence-based conservation decisions.
Keywords: Biological collections, Database, Historical records, Label information, Long-term data collections, Trait
Keet J, Cindi D, du Preez P (2016)
Assessing the invasiveness of Berberis aristata and B. julianae (Berberidaceae) in South Africa: Management options and legal recommendations
South African Journal of Botany 105 288-298.
The detection of two alien species spreading in natural ecosystems, namely Berberis julianae and Berberis aristata, prompted investigation into the risk that they pose as invasive plants to South Africa. Here we determined their distribution in South Africa, assessed population structure and reproductive size, determined seed germinability, evaluated the risks posed by the species by conducting weed risk assessments, and provide recommendations for control. We also assessed the extent of current and historic cultivation. B. julianae was found to be widely cultivated while but B. aristata was not found in cultivation. Only a single naturalized population was found for each species, with B. julianae occupying an area of 14ha (0.02ha condensed canopy) and B. aristata occupying an area 180ha (1.58ha condensed canopy). Given its very limited known distribution, there is an opportunity to eradicate B. aristata, although this would need to be reviewed if further surveys find new populations; we recommend that it be classified as category 1a invasive according to the National Environmental Management: Biodiversity Act. We do not yet recommend that B. julianae be regulated particularly given its horticultural popularity. However, it is clearly a species that needs to be monitored.
Keywords: Berberis, Biological invasion, Early detection, Management, Weed risk
Langejans G, Dusseldorp G, Thackeray J (2016)
Pleistocene molluscs from Klasies River (South Africa): Reconstructing the local coastal environment
We explore if taxonomic analysis of archaeological mollusc assemblages can be used to reconstruct Late Pleistocene (MIS 5–3) coastal environments at Klasies River in South Africa. To obtain a balanced reconstruction, we analyse the large molluscs separately from the so-called incidentals, the small mollusc species. Based on modern mollusc habitat preferences and tolerances we identify four different eco-profiles to help characterise sea surface temperatures and the character of the shore: temperature profile; geographical distribution; substrate; wave interaction. We hypothesise that changes in the Klasies River mollusc community/eco-profiles can be linked to global glacial and interglacial events and we define several testable assumptions. We found that in response to global warming and cooling events, the Klasies River mollusc communities change slightly, yet significantly. Other sources of marine environmental data confirm that average sea surface temperatures gradually decreased, but probably remained within the modern southern east coast range of variation. It appears that coastal sea surface temperatures of the warm Agulhas current were not particularly depressed during the occupation sequence. The character of the coastal topography does change more apparently during the occupation sequence of the sites and with it the mollusc assemblages: from an interglacial rocky shore in the Klasies and two Mossel Bay phases to a more glacial sandy environment during the Howiesons Poort and the MSA III. In conclusion, the temperature tolerance levels of many Klasies River mollusc species are too broad to reflect small changes in sea surface temperatures. However, in conjunction with other eco-profiles and environmental proxies, such as substrate requirements and oxygen isotopes, the temperature approximations are useful, particularly when evaluating large scale sea surface temperature fluctuations. For the characterisation of the shore and substrate we found the eco-profile approach very useful.
Keywords: Climatic and environmental change, Klasies River, Late Pleistocene, Middle Stone Age, Molluscs, South Africa
Lens F, Vos R, Charrier G, van der Niet T, Merckx V, Baas P et al. (2016)
Scalariform-to-simple transition in vessel perforation plates triggered by differences in climate during the evolution of Adoxaceae
Annals of Botany mcw151.
Background and Aims Angiosperms with simple vessel perforations have evolved many times independently of species having scalariform perforations, but detailed studies to understand why these transitions in wood evolution have happened are lacking. We focus on the striking difference in wood anatomy between two closely related genera of Adoxaceae, Viburnum and Sambucus, and link the anatomical divergence with climatic and physiological insights. Methods After performing wood anatomical observations, we used a molecular phylogenetic framework to estimate divergence times for 127 Adoxaceae species. The conditions under which the genera diversified were estimated using ancestral area reconstruction and optimization of ancestral climates, and xylem-specific conductivity measurements were performed. Key Results Viburnum, characterized by scalariform vessel perforations (ancestral), diversified earlier than Sambucus, having simple perforations (derived). Ancestral climate reconstruction analyses point to cold temperate preference for Viburnum and warm temperate for Sambucus. This is reflected in the xylem-specific conductivity rates of the co-occurring species investigated, showing that Viburnum lantana has rates much lower than Sambucus nigra. Conclusions The lack of selective pressure for high conductive efficiency during early diversification of Viburnum and the potentially adaptive value of scalariform perforations in frost-prone cold temperate climates have led to retention of the ancestral vessel perforation type, while higher temperatures during early diversification of Sambucus have triggered the evolution of simple vessel perforations, allowing more efficient long-distance water transport.
Keywords: Adoxaceae, Baileyan wood trends, Sambucus, Viburnum, ancestral area and climate reconstruction, molecular dating, vessel perforation plate transition, wood anatomy
Nxumalo MM, Lalla R R (2016)
Hydrocleys nymphoides (Humb. & Bonpl. ex Willd.) Buchenau: first record of naturalisation in South Africa
BioInvasions Records 5.
Hydrocleys nymphoides (water poppy), an aquatic plant native to South America, has been recorded as invasive on several continents (Europe, Australia and Asia). Here we report on the first known natura lized population in South Africa, in a dam in the KwaZulu-Natal (K ZN) Midlands region, near the town of Howick. This popu lation, first detected and identified in 2009, had by the end of the 2013 summer seas on occupied 1.8ha (30% of the dam). Surveys of 34 surrounding water bodies during the period between 2012 and 2013 did not result in detection of any new populations. The only other population (0.1 ha) was recorded growin g in cultivation at the Durban Botanic Gardens. This note re ports on the history of H. nymphoides in South Africa, details its current and potential distribution, looks at the risk it poses, and outlines plans for nation-wid e eradication.
Keywords: South, invasive alien aquatic plant, water poppy
Oberlander K, Dreyer L, Goldblatt P, Suda J, Linder H (2016)
Species-rich and polyploid-poor: Insights into the evolutionary role of whole-genome duplication from the Cape flora biodiversity hotspot
American Journal of Botany 103(7) 1336-1347.
PREMISE OF THE STUDY: Whole-genome duplication (WGD) in angiosperms has been hypothesized to be advantageous in unstable environments and/or to increase diversification rates, leading to radiations. Under the first hypothesis, floras in stable environments are predicted to have lower proportions of polyploids than highly, recently disturbed floras, whereas species-rich floras would be expected to have higher than expected proportions of polyploids under the second. The South African Cape flora is used to discriminate between these two hypotheses because it features a hyperdiverse flora predominantly generated by a limited number of radiations (Cape clades), against a backdrop of climatic and geological stability. METHODS: We compiled all known chromosome counts for species in 21 clades present in the Cape (1653 species, including 24 Cape clades), inferred ploidy levels for these species by inspection or derived from the primary literature, and compared Cape to non-Cape ploidy levels in these clades (17,520 species) using G tests. KEY RESULTS: The Cape flora has anomalously low proportions of polyploids compared with global levels. This pattern is consistently observed across nearly half the clades and across global latitudinal gradients, although individual lineages seem to be following different paths to low levels of WGD and to differing degrees. CONCLUSIONS: This pattern shows that the diversity of the Cape flora is the outcome of primarily diploid radiations and supports the hypothesis that WGD may be rare in stable environments.
Keywords: Cape flora, diversification, environmental stability, evolutionary radiation, polyploidy, whole-genome duplication
Tolley K, Alexander G, Branch W, Bowles P, Maritz B (2016)
The assimilation of information on taxonomy, distribution, basic ecology and conservation status of Africa's reptiles lags far behind that for most other continents. Many regions of mainland Africa are rarely surveyed, resulting in severe knowledge gaps that currently limit effective conservation of African reptiles. Here, we provide a précis on the knowledge gaps and conservation status of mainland African reptiles, and quantify the main threats based on IUCN Red List of Threatened Species assessments using publicly available distribution data. Our results show that these data are insufficient to confidently identify areas of high biodiversity, with large gaps in knowledge in the Horn of Africa, central Africa and West Africa. There is a strong overall taxonomic bias in extinction risk with 45% of families more threatened than expected by chance. Furthermore, Amphisbaenidae, Chameleonidae, Gerrhosauridae, Testudinidae, Viperidae all have a high percentage of their constituent species at risk. Overall, land transformation for agriculture, particularly subsistence farming, constitutes the primary threat to African reptiles, and our derived Threat Index based on socio-economic traits of African countries show that risk is high in Burundi, Ethiopia, Liberia, Malawi, Rwanda and Sierra Leone. These findings highlight important challenges facing the conservation of African reptiles, and we suggest that conservation priorities in mainland Africa be focussed on areas where the potential for overall loss of biodiversity is high, particularly in regions where knowledge is inadequate.
Keywords: Biodiversity, Conservation, Global Reptile Assessment, Habitat loss, Species richness