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Friends or foes? Polyploidy and competition in a grassland geophyte
De Sousa, Damian Vaz; Greve, Michelle; Taylor, Nicolette Jane; Oberlander, Kenneth Carl (Wiley, 2026-02)
Previous studies have suggested polyploids may possess a competitive advantage over diploids, due to their larger size, increased vigour or ability to better respond to abiotic stress. However, few studies have tested the effect of polyploidy on competitive ability directly, and only relatively recently has this oversight begun to be addressed. Here we assessed potential differences in competitive ability between diploids and tetraploids of a widespread African grassland geophyte, Oxalis obliquifolia. Diploid and tetraploid plants were grown in identical environmental conditions under four different competition scenarios. As a control, diploids and tetraploids were grown under solitary conditions. For intra-cytotype competition, pairs of diploids and tetraploids were planted together. Inter-cytotype competition involved planting individual diploids and tetraploids with one another, and for interspecies competition individual diploids and tetraploids were planted with Themeda triandra seedlings. Thirty-seven morphological, physiological and phenological traits were recorded and assessed for associations between cytotype and competition treatment using ordinations and GLMs. Ordination showed diploids and tetraploids as distinct clusters, with very little separation based on competition treatment. Univariate analyses showed tetraploids have larger but fewer organ structures than diploids, suggesting a tradeoff between these traits. Tetraploids also produce larger seeds. Diploids showed reduced numbers of leaves and were more negatively impacted by interspecies competition than tetraploids, suggesting tetraploids may potentially be the better interspecies competitor. Tetraploids also extended their flowering season in response to inter-cytotype and interspecies competition. Cytotypes respond differently under different competition treatments, and tetraploids may have a competitive advantage over diploids. However, this potential competitive asymmetry does not explain observed cytotype sympatry. Tetraploids also appear to differentiate between intra-cytotype competition, and competition with diploids and other species. The potential for abiotic factors to impact these competition dynamics remains unexplored.
Advances and shortfalls in knowledge of Antarctic terrestrial and freshwater biodiversity
Pertierra, Luis R.; Convey, P.; Barbosa, A.; Biersma, E.M.; Cowan, Don A.; Diniz, J.A.F.; De los Rios, A.; Escribano-Alvarez, P.; Fraser, C.I.; Fontaneto, D.; Greve, Michelle; Griffiths, H.J.; Harris, Mathew Andrew; Hughes, K.A.; Lynch, H.J.; Ladle, R.J.; Liu, X.P.; Le Roux, Peter Christiaan; Majewska, R.; Molina-Montenegro, M.A.; Peck, L.S.; Quesada, A.; Ronquillo, C.; Ropert-Coudert, Y.; Sancho, L.G.; Terauds, A.; Varliero, Gilda; Vianna, J.A.; Wilmotte, A.; Chown, S.L.; Olalla-Tárraga, M.A.; Hortal, J. (American Association for the Advancement of Science, 2025-02)
Antarctica harbors many distinctive features of life, yet much about the diversity and functioning of Antarctica’s life remains unknown. Evolutionary histories and functional ecology are well understood only for vertebrates, whereas research on invertebrates is largely limited to species descriptions and some studies on environmental tolerances. Knowledge on Antarctic vegetation cover showcases the challenges of characterizing population trends for most groups. Recent community-level microbial studies have provided insights into the functioning of life at its limits. Overall, biotic interactions remain largely unknown across all groups, restricted to basic information on trophic level placement. Insufficient knowledge of many groups limits the understanding of ecological processes on the continent. Remedies for the current situation rely on identifying the caveats of each ecological discipline and finding targeted solutions. Such precise delimitation of knowledge gaps will enable a more aware, representative, and strategic systematic conservation planning of Antarctica.
Quantifying baseflow with radon, H and O isotopes and field parameters in the urbanized catchment of the little Jukskei River, Johannesburg
Diphofe, Khutjo; Diamond, Roger; Kotze, Francois (MDPI, 2025-08-02)
Understanding groundwater and surface water interaction is critical for managing water resources, particularly in water-stressed and rapidly urbanizing areas, such as many parts of Africa. A survey was conducted of borehole, spring, seep and river water radon, δ2H, δ18O and field parameters in the Jukskei River catchment, Johannesburg. Average values of electrical conductivity (EC) were 274 and 411 μS·cm−1 for groundwater and surface water, and similarly for radon, 37,000 and 1100 Bq·m−3, with a groundwater high of 196,000 Bq·m−3 associated with a structural lineament. High radon was a good indicator of baseflow, highest at the end of the rainy season (March) and lowest at the end of the dry season (September), with the FINIFLUX model computing groundwater inflow as 2.5–4.7 L·m−1s−1. High EC was a poorer indicator of baseflow, also considering the possibility of wastewater with high EC, typical in urban areas. Groundwater δ2H and δ18O values are spread widely, suggesting recharge from both normal and unusual rainfall periods. A slight shift from the local meteoric water line indicates light evaporation during recharge. Surface water δ2H and δ18O is clustered, pointing to regular groundwater input along the stream, supporting the findings from radon. Given the importance of groundwater, further study using the same parameters or additional analytes is advisable in the urban area of Johannesburg or other cities.
Hydrochemistry, stable isotopes, and radon in waters of the Greater Timbavati catchment, South Africa
Raible, Kirsten; Diamond, Roger; Dippenaar, Matthys Alois (Springer, 2025-12)
A baseline study was conducted to better understand the relationship between groundwater, geology, and geography in the Greater Timbavati area, South Africa. Samples of rainwater, surface water, and groundwater were collected across nature reserves and rural communities. Basic water chemistry parameters, nitrates, and ammonium were measured in the field using an Aquaread AP-5000 probe, and water samples were collected for radon determination and stable isotope analysis. Significant differences in chemistry and isotopic signatures between surface water and groundwater were observed. Groundwater exhibited a mean total dissolved solids (TDS) of 1217 mg/l and pH of 7.5, whereas surface water had mean TDS of 332 mg/l and pH of 8.3. Groundwater δ2H and δ18O means were – 20.5 and – 3.8‰, respectively, contrasting with + 12.2 and + 2.3‰ in surface water. Hydrochemistry correlated with bedrock type and a close correlation between land use and nitrate concentrations was evident, particularly in groundwater, exceeding 500 mg/l in areas with dense human and livestock presence, suggesting urban and agricultural contamination. Radon concentrations in groundwater ranged from 188 to 51,400 Bq/m3, showing no clear correlation with underlying geology, suggesting groundwater flow paths across bedrock types. Overall, a strong distinction between groundwater and surface water characteristics suggests limited interaction, caused by deep water tables, especially at the end of the dry season when streams stop flowing, warranting further research in quantifying sustainable levels of groundwater abstraction.
The framing of the informal oil economy in Nigeria : toward epistemic justice of the illegal artisanal oil refineries in the Niger Delta
Ayodele, Austin A. (Springer, 2025-08-23)
The Nigerian oil sector is profoundly challenged by inefficiency and intractable problems, including mismanagement and poor oil governance, which create gaps in the country’s oil industry. This resulted in systemic exclusion, marginalisation, and poverty in the country’s Niger-delta region. A social reality that influenced the development of localised knowledge of artisanal oil refineries in the region’s riverine communities. Previous research paid little attention to the epistemic justice of the oil economy in Nigeria. This study bridged gaps in research by exploring the epistemic discrimination of localised knowledge, which sustains the informal oil business in the Niger-delta. It also investigates how the country’s oil government framed the activity of illegal artisanal refiners to establish a narrative that criminalises the riverine community’s attempt to explore its bequeathed resources. Adopting an exploratory design and a qualitative research method, forty-two participants were purposefully sampled through in-depth and key informant interviews in the riverine communities of Warri Southwest and Nembe Local Government Areas of Delta and Bayelsa States, Nigeria. Data were thematically analysed to form themes and patterns. The study found that, despite the state’s aggressive approaches and the oil government’s criminalisation of localised knowledge, the illegal artisanal refineries of the informal oil industry provide the refined product needs of the Delta region, sustain enterprises, and employ young people in riverine communities. The study contributes to knowledge on the importance of inclusive and equitable acceptance of the roles of artisanal illegal refineries. The oil government must regulate them as a win-win approach to Nigeria’s oil crisis.