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Stohlgren T.J.,U.S. Geological Survey | Pysek P.,Academy of Sciences of the Czech Republic | Pysek P.,Charles University | Kartesz J.,Biota of North America Program | And 12 more authors.
Biological Invasions | Year: 2011

Estimates of the level of invasion for a region are traditionally based on relative numbers of native and alien species. However, alien species differ dramatically in the size of their invasive ranges. Here we present the first study to quantify the level of invasion for several regions of the world in terms of the most widely distributed plant species (natives vs. aliens). Aliens accounted for 51.3% of the 120 most widely distributed plant species in North America, 43.3% in New South Wales (Australia), 34.2% in Chile, 29.7% in Argentina, and 22.5% in the Republic of South Africa. However, Europe had only 1% of alien species among the most widespread species of the flora. Across regions, alien species relative to native species were either as well-distributed (10 comparisons) or more widely distributed (5 comparisons). These striking patterns highlight the profound contribution that widespread invasive alien plants make to floristic dominance patterns across different regions. Many of the most widespread species are alien plants, and, in particular, Europe and Asia appear as major contributors to the homogenization of the floras in the Americas. We recommend that spatial extent of invasion should be explicitly incorporated in assessments of invasibility, globalization, and risk assessments. © 2011 Springer Science+Business Media B.V. Source


Bentley J.,University of Cape Town | Klaassen E.S.,National Botanical Research Institute NBRI | Bergh N.G.,South African National Biodiversity Institute SANBI | Bergh N.G.,University of Cape Town
Taxon | Year: 2015

The small southern African genus Philyrophyllum (Asteraceae) has t raditionally been placed amongst t he basal lineages of tribe Gnaphalieae, close to the Namibian-centred genus Pentatrichia. However, a recent plastid phylogeny placed Philyrophyllum distant from Pentatrichia within the Gnaphalieae crown radiation, a finding that is strongly contradicted by a suite of morphological synapormorphies that are otherwise unvarying within the crown radiation. In the present study, two linked nuclear loci (ITS, ETS) and one plastid region (trnL-trnF) are sequenced to determine the phylogenetic position of Philyrophyllum, with the addition of available plastid psbA-trnH spacer and ndhF sequences for outgroup taxa. Maximum likelihood bootstrap and Bayesian analysis is used to assess support for phylogenetic relationships. Individual plastid and nuclear, as well as combined data, strongly support a close relationship between Philyrophyllum and the African-centred, morphologically diverse genus Anisopappus, currently placed in subtribe Anisopappinae of the anomalous tribal assemblage Athroismeae. Athroismeae is the sister group of Feddeeae and the “Heliantheae tribal alliance”, a large mainly northern hemisphere grouping that is phylogenetically distant from Gnaphalieae. © International Association for Plant Taxonomy (IAPT) 2015. Source


Ernstson H.,University of Stockholm | Leeuw S.E.V.D.,Arizona State University | Redman C.L.,Arizona State University | Meffert D.J.,Tulane University | And 3 more authors.
Ambio | Year: 2010

Urbanization is a global multidimensional process paired with increasing uncertainty due to climate change, migration of people, and changes in the capacity to sustain ecosystem services. This article lays a foundation for discussing transitions in urban governance, which enable cities to navigate change, build capacity to withstand shocks, and use experimentation and innovation in face of uncertainty. Using the three concrete case cities New Orleans, Cape Town, and Phoenixthe article analyzes thresholds and cross-scale interactions, and expands the scale at which urban resilience has been discussed by integrating the idea from geography that cities form part of "system of cities" (i.e., they cannot be seen as single entities). Based on this, the article argues that urban governance need to harness social networks of urban innovation to sustain ecosystem services, while nurturing discourses that situate the city as part of regional ecosystems. The article broadens the discussion on urban resilience while challenging resilience theory when addressing human-dominated ecosystems. Practical examples of harnessing urban innovation are presented, paired with an agenda for research and policy. © 2010 Royal Swedish Academy of Sciences. Source


Mutumi G.L.,University of Cape Town | Jacobs D.S.,University of Cape Town | Winker H.,South African National Biodiversity Institute SANBI
PLoS ONE | Year: 2016

Geographic variation can be an indicator of still poorly understood evolutionary processes such as adaptation and drift. Sensory systems used in communication play a key role in mate choice and species recognition. Habitat-mediated (i.e. adaptive) differences in communication signals may therefore lead to diversification.We investigated geographic variation in echolocation calls of African horseshoe bats, Rhinolophus simulator and R. swinnyi in the context of two adaptive hypotheses: 1) James’ Rule and 2) the Sensory Drive Hypothesis. According to James’ Rule body-size should vary in response to relative humidity and temperature so that divergence in call frequency may therefore be the result of climate-mediated variation in body size because of the correlation between body size and call frequency. The Sensory Drive Hypothesis proposes that call frequency is a response to climate-induced differences in atmospheric attenuation and predicts that increases in atmospheric attenuation selects for calls of lower frequency. We measured the morphology and resting call frequency (RF) of 111 R. simulator and 126 R. swinnyi individuals across their distributional range to test the above hypotheses. Contrary to the prediction of James’ Rule, divergence in body size could not explain the variation in RF. Instead, acoustic divergence in RF was best predicted by latitude, geography and climate-induced differences in atmospheric attenuation, as predicted by the Sensory Drive Hypothesis. Although variation in RF was strongly influenced by temperature and humidity, other climatic variables (associated with latitude and altitude) as well as drift (as suggested by a positive correlation between call variation and geographic distance, especially in R. simulator) may also play an important role. © 2016 Mutumi et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Source


Beukes C.W.,University of Pretoria | Stepkowski T.,Warsaw University of Life Sciences | Venter S.N.,University of Pretoria | Clapa T.,University of Life Sciences in Poznan | And 4 more authors.
Molecular Phylogenetics and Evolution | Year: 2016

The genus Bradyrhizobium contains predominantly nitrogen-fixing legume symbionts. Phylogenetic analysis of the genes responsible for their symbiotic abilities (i.e., those encoded on the nodulation [nod] and nitrogen-fixation [nif] loci) has facilitated the development of an extensive phylogeographic framework for the genus. This framework however contains only a few nodulating isolates from Africa. Here we focused on nodulating Bradyrhizobium isolates associated with native southern African legumes in the tribes Genisteae and Crotalarieae found along the Great Escarpment in the Mpumalanga Province of South Africa. The aims of this study were to: (1) obtain rhizobial isolates from legumes in the Genisteae and Crotalarieae; (2) verify their nodulation ability; (3) characterize them to species level based on phylogenetic analyses of several protein coding gene regions (atpD, dnaK, glnII, recA, rpoB and gyrB) and (4) determine their placement in the phylogeographic framework inferred from the sequences of the symbiotic loci nodA and nifD. Twenty of the 21 Bradyrhizobium isolates belonged to six novel species, while one was conspecific with the recently described B. arachidis. Among these isolates, the nodA phylogeny revealed several new clades, with 18 of our isolates found in Clades XIV and XV, and only three forming part of the cosmopolitan Clade III. These strains formed predominantly the same groups in the nifD phylogeny although with slight differences; indicating that both vertical and horizontal inheritance of the symbiotic loci occurred. These findings suggest that the largely unexplored diversity of indigenous African rhizobia are characterized by unique ancestries that might mirror the distribution of their hosts and the environmental factors driving their evolution. © 2016 Elsevier Inc. Source

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