University of Greenwich

About: University of Greenwich is a education organization based out in London, United Kingdom. It is known for research contribution in the topics: Population & Context (language use). The organization has 3749 authors who have published 9958 publications receiving 234340 citations.

Genetic monitoring detects an overlooked cryptic species and reveals the diversity and distribution of three invasive Rattus congeners in south Africa

Abstract: South Africa's long and extensive trade activity has ensured ample opportunities for exotic species introduction. Whereas the rich biodiversity of endemic southern African fauna has been the focus of many studies, invasive vertebrates are generally overlooked despite potential impacts on biodiversity, health and agriculture. Genetic monitoring of commensal rodents in South Africa which uncovered the presence of Rattus tanezumi, a South-East Asian endemic not previously known to occur in Africa, provided the impetus for expanded studies on all invasive Rattus species present. To this end, intensified sampling at 28 South African localities and at one site in Swaziland, identified 149 Rattus specimens. Cytochrome b gene sequencing revealed the presence of two R. tanezumi, seven Rattus rattus and five Rattus norvegicus haplotypes in south Africa. Phylogenetic results were consistent with a single, recent R. tanezumi introduction and indicated that R. norvegicus and R. rattus probably became established following at least two and three independent introductions, respectively. Intra- and inter-specific diversity was highest in informal human settlements, with all three species occurring at a single metropolitan township site. Rattus norvegicus and R. rattus each occurred sympatrically with Rattus tanezumi at one and five sites, respectively. Karyotyping of selected R. rattus and R. tanezumi individuals identified diploid numbers consistent with those reported previously for these cryptic species. Ordination of bioclimatic variables and MaxEnt ecological niche modelling confirmed that the bioclimatic niche occupied by R. tanezumi in south Africa was distinct from that occupied in its naturalised range in south-east Asia suggesting that factors other than climate may influence the distribution of this species. This study has highlighted the value of genetic typing for detecting cryptic invasive species, providing historical insights into introductions and for directing future sampling. The apparent ease with which a cryptic species can become established signals the need for broader implementation of genetic monitoring programmes. In addition to providing baseline data and potentially identifying high-risk introduction routes, the predictive power of ecological niche modelling is enhanced when species records are genetically verified.

Rice yield gaps in irrigated systems along an agro‐ecological gradient in West Africa

Abstract: Irrigated rice (Oryza sativa L.) in West Africa covers about 12 % of the regional rice-growing area, and is produced all along the agro-ecological gradient from the forest zone to the Sahara desert margins. Spatial and temporal variability of yield gaps (i.e., difference between actual and potential yield) were determined to set priorities for research and target technologies. On-farm trials were conducted on 191 irrigated lowland fields in the humid forest, the savanna and the Sahel. Farmers' yields were compared with those of super-imposed treatments of improved fertilization and weed management. Farmers' yields varied between 0.2 and 8.7 Mg ha-1, with average yields of 3.4 Mg ha-1 (Guinea savanna), 3.6 Mg ha-1 (humid forest), 3.9 Mg ha-1 (Sahel), and 5.1 Mg ha-1 (Sudan savanna). Simulated potential yields increased from 7 Mg ha-1 in the forest to about 10 Mg ha-1 in the Sahel. Accordingly, yield gaps were large, ranging from 3.2 to 5.9 Mg ha-1. Researcher weed control in the Sahel gave grain yield increases of about 1.0 Mg ha-1. Improved weed and N fertilization management increased yields by 1 to 2 Mg ha-1 in the forest and Guinea savanna sites. A share of 57-80 % of the yield gap could not be accounted for. Improving weed control is likely to have the highest pay-off in the Sahel while improved management of fertilizer N will be most beneficial in the forest and savanna environments. Potenzielle und aktuelle Ertrage von bewassertem Reis in unterschiedlichen agrarokologischen Zonen Westafrikas Etwa 12 % der Reisanbauflache Westafrikas istmit bewassertem Nassreis (Oryza sativa L.) bestellt, der in allen agrarokologischen Zonen zwischen der Sahara und dem Regenwald angebaut wird. Die raumliche und zeitliche Variabilitat der Ertrage und die Differenzen, die zwischen den tatsachlichen, den von Forschern erzielten und den potenziellen (mit ORYZAS simulierten) Ertragen bestehen, wurden in 191 Nassreisfeldern der Regenwald-, der Feuchtsavanne-, der Trockensavanne- und der Sahelzone bestimmt. Ertrage in den Feldern der Reisbauern variierten zwischen 0.2 and 8.7 Mg ha-1, mit durchschnittlich 3.4 Mg ha-1 (Feuchtsavanne), 3.6 Mg ha-1 (Regenwald), 3.9 Mg ha-1 (Sahel) und 5.1 Mg ha-1 (Trockensavanne). Das simulierte Ertragspotential stieg von 7 Mg ha-1 in der Regenwaldzone auf etwa 10 Mg ha-1 im Sahel an. Die daraus resultierenden Ertragsdifferenzen lagen zwischen 3.2 und 5.9 Mg ha-1. Verbesserte Unkrautkontrolle vermochte den Reisertrag im Sahel um etwa 1.0 Mg ha-1 zu erhohen. Ein verbessertes Management der N-Dungung erhohte die Reisertrage in den Regenwald- und Savannenzonen um 1 bis 2 Mg ha-1, was 20-40 % der beobachteten Ertragsdifferenzen zu erklaren vermochte. Die Unkrautkontrolle sollte vorrangig in den Anbausystemen im Sahel verbessert werden. Bei derzeitigen Applikationsmengen durfte ein verbessertes Dungungsmanagement speziell in der Regenwald- und Savannenzone die Nutzungseffizienz von mineralischem N und somit die Reisertrage erhohen.

Enhancing resilience in the Covid-19 crisis: lessons from human resource management practices in Vietnam

Abstract: This study establishes how tourism and hospitality businesses in Vietnam developed organizational resilience to survive the first wave of the Covid-19 crises. With employees acknowledged as a criti...

Electrosynthesis Using Carboxylic Acid Derivatives: New Tricks for Old Reactions

Abstract: ConspectusElectrosynthetic organic chemistry is an old discipline that takes its root in Faraday’s seminal works. The field has a rich history and is in the midst of a renaissance, due to the growi...