Bohley K.,Johannes Gutenberg University Mainz |
Winter P.J.D.,South African National Biodiversity Institute SANBI |
Kadereit G.,Johannes Gutenberg University Mainz
Systematic Botany | Year: 2017
Sesuvium and Cypselea are closely related succulent genera within the Sesuvioideae (Aizoaceae). Since Cypselea is nested in Sesuvium in molecular studies and both genera share traits separating them from other members of the subfamily, we propose to include Cypselea in Sesuvium. Sesuvium (incl. Cypselea) comprises 14 species and is distributed worldwide with centres of diversity in southern Africa and North and Central America. Sesuvium comprises erect to procumbent herbs with opposite leaves that often bear conspicuous sheath-like lateral appendages on the petioles (pseudostipules). These and the many-seeded capsules are diagnostic traits, separating Sesuvium from the closely related genera Trianthema and Zaleya. Sesuvium is usually found in coastal or otherwise saline areas and is phylogenetically divided into an African (5 spp.) and an American lineage (9 spp.). While all African species are C4 plants, the American lineage also comprises a derived C3 lineage, which includes the cosmopolitan species S. portulacastrum. Some floras provide descriptions and keys for locally relevant species, but currently no comprehensive taxonomic treatment is available for Sesuvium. In this paper, a key and descriptions for all species are provided. Furthermore, we compile information on the rare and poorly known species of the genus and address issues concerning species concepts in Sesuvium, which impede species identification. The inclusion of Cypselea in Sesuvium leads to three new combinations: Sesuvium humifusum, Sesuvium mezianum and Sesuvium rubriflorum. © Copyright 2017 by the American Society of Plant Taxonomists.
Van der Walt K.,South African National Biodiversity Institute SANBI |
Van der Walt K.,University of Witwatersrand |
Witkowski E.T.F.,University of Witwatersrand
South African Journal of Botany | Year: 2017
The regeneration ecology of many southern African threatened plant species is poorly understood. Temperature is considered the most important environmental factor governing seed germination. The germination temperature requirements of the critically endangered stem succulent, Adenium swazicum, were determined under controlled conditions, together with tetrazolium staining protocol tests to assess seed viability. The effects of soil medium, watering levels, depth of sowing and shading on germination/seedling emergence were also determined at the Lowveld National Botanical Garden (LNBG). Germination/seedling emergence was compared under nursery conditions within (Skukuza Nursery in Kruger National Park) and outside (LNBG) the natural distribution range of A. swazicum. The germination of viable seeds ranged 96.5-100% for a broad range of temperatures from 20 to 35. °C as well as for 30/20. °C (light/dark) alternating temperature. No germination was recorded at 5. °C and 10. °C, and relatively limited germination at 15. °C (42.9%) and 40. °C (15.4%). These results were modelled using a Generalized non-linear model, with a binomial error and a logit link function, best-fit models were second-order polynomials (i.e., quadratic). Mean Germination Time ranged from 2 to 6. days among temperature treatments. Tetrazolium together with germination results for the 20. -35. °C temperatures showed moderate to high seed viability across populations and between years within the same population. Seedlings readily emerged irrespective of soil media (3 types) or planting depth (surface, 5 and 10. mm) but higher emergence occurred under more frequent watering. Seedlings emerged equally well under sun or shade conditions, but only subsequently survived in the shade. Despite lower temperatures recorded during October/November 2010 at LNBG (outside range: 27.2. ±. 0.9. °C) compared to Skukuza (within range: 32.6. ±. 0.9. °C), final germination/seedling emergence was high at both locations (LNBG: 82%; Skukuza: 94%). Together with field observations, this study shows that (a) seed germination is rapid and with high percentages after being cued by warm to hot summer temperatures, a period when rainfall is also at its highest, and (b) that seedling recruitment depends on the availability of suitably shaded microsites. This is the first study on the regeneration ecology of an Adenium sp. and will aid both in situ and ex situ conservation of A. swazicum. © 2017 SAAB.
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.
Cousins S.R.,University of Witwatersrand |
Witkowski E.T.F.,University of Witwatersrand |
Pfab M.F.,University of Witwatersrand |
Pfab M.F.,South African National Biodiversity Institute SANBI
South African Journal of Botany | Year: 2014
Studies on plant population size structure provide important baseline information for monitoring and conservation. Traditionally, inverse J-shaped size class distributions (SCD) were considered indicative of 'healthy', stable plant populations; however, this may not hold true for long-lived, slow-growing species. This study assessed the population size structure of 19 populations of Aloe plicatilis, a Cape fynbos endemic tree aloe, and quantified population size and density. A strong positive linear relationship between stem diameter (SDr) and height was used to align SDr and height SCD bins, and to harmonize stage and size classes. Onset of reproduction occurs at ~. 15. cm SDr and ~. 0.8. m in height. Some A. plicatilis individuals appear to display a 'bonsai effect' whereby the growth of individuals in very rocky sites is suppressed. Stunted plants may be non-reproductive 'suppressed juveniles' or 'reproductive dwarfs'. The short, shrub-like growth form of many individuals may also result from height restrictions imposed by persistent strong winds. Population size, extent and density ranged from 31 to >. 110 000 individuals, 0.05-103. ha and 75-3000 plants/ha respectively. Bell-shaped SCDs were the most common (50% of populations). The SDr and height SCDs for all populations combined were also bell-shaped. Seven populations displayed irregular SCDs, but were similar in structure to the bell-shaped SCDs, both of which were attributed to an adult-persistence population survival strategy. This study challenges the suitability of the inverse J as the only SCD indicative of healthy, stable populations for long-lived, slow-growing species. The study provides baseline demographic data on A. plicatilis across its distribution for long-term monitoring, and provides insights useful for examining trends in the demographics of other long-lived, slow-growing species. © 2013 South African Association of Botanists.
Cousins S.R.,University of Witwatersrand |
Witkowski E.T.F.,University of Witwatersrand |
Pfab M.F.,University of Witwatersrand |
Pfab M.F.,South African National Biodiversity Institute SANBI |
And 2 more authors.
South African Journal of Botany | Year: 2013
While the pollination ecology of many Aloe species is well-documented, knowledge on aloe seed ecology, and hence aloe reproductive ecology in its entirety is limited. The aim of this study was to investigate the reproductive ecology of Aloe plicatilis, a Cape fynbos tree aloe endemic to the Cape Winelands, South Africa. Results from a pollinator exclusion experiment conducted at an A. plicatilis population on Paarl mountain suggests pollination primarily by insects, although bird visitation significantly increased seed set/fruit indicating possible co-pollination with insects. The species' long-tubed flowers and production of concentrated nectar, with observations of malachite sunbirds as the most common avian visitors to A. plicatilis flowers indicate the importance of long-billed specialist avian nectarivores as floral visitors. Analysis of the relationship between plant size and inflorescence production for five populations combined revealed a significant, positive linear relationship between plant size and the logarithm of the number of inflorescences/plant. Natural fruit and seed set determined for three populations (1325, 27,930 and 251,616 seeds/population) suggests low reproductive output compared to several other Aloe species. The smallest (31 individuals) and least dense (75. plants/ha) A. plicatilis population produced the lowest seed set/plant (128 seeds) and per population (1325 seeds), suggesting an Allee effect. Evaluation of seed dispersal potential showed that potential dispersal distances were approximately three times the canopy height; however, the occurrence of A. plicatilis on mountains isolated from more continuous mountain ranges on which the species also occurs suggests the possibility of long-distance dispersal by strong, gusty, summer winds. Soil seed bank samples collected from 13 populations yielded close to zero seedling emergence, indicating the absence of persistent seed banks. A. plicatilis seeds stored under ambient laboratory conditions for 3, 18 and 24. months were germinated in an environmental control chamber and a laboratory. High percentage germination was recorded for 18- and 24-month-seed (86 and 80%, respectively), while germination of 3-month-old seeds was three times lower, suggesting the need for after-ripening. Germination of fresh and one-year-old seed under ambient nursery conditions at the Karoo Desert National Botanical Garden in Worcester yielded emergence percentages of 67 and 44%, respectively, and were therefore less successful than germination under more controlled conditions. This is the first known study to investigate the reproductive ecology of a tree aloe species and that of a Cape fynbos aloe. The study highlights the importance of further studies on aloe seed ecology, particularly for rare and threatened species. © 2013 South African Association of Botanists.
Van Rooy J.,University of Pretoria |
Van Rooy J.,South African National Biodiversity Institute |
Van Rooy J.,South African National Biodiversity Institute SANBI |
Van Wyk A.E.,University of Pretoria
Journal of Bryology | Year: 2010
A TWINSPAN classification divides southern Africa (South Africa, Namibia, Botswana, Swaziland and Lesotho) into two main bryofloristic regions: (1) a subtropical or palaeotropical region in the northern, eastern and southern parts, characterised by a predominantly mesophytic moss flora; and (2) a temperate or austral region in the central and western parts of the study area with a xerophytic moss flora. The subtropical region is subdivided into the Zambezian and Afromontane Regions, and the temperate region into the Karoo-Namib and Highlands Regions. The four regions are further subdivided into eight domains: (1) the Zambezian Region into the Caprivi and Bushveld Domains; (2) the Afromontane Region into the Drakensberg and Cape Domains; (3) the Karoo-Namib Region into the Western Cape and Namaqua Domains; and (4) the Highlands Region into the Drakensberg Alpine and Upper Karoo Domains. Meaningful phytogeographical classification of the arid and semi-arid central and northwestern sectors of the study area is dependent on future plant collecting or sampling efforts. © 2010 British Bryological Society.
Thorson J.T.,National Oceanic and Atmospheric Administration |
Rindorf A.,Technical University of Denmark |
Gao J.,National Oceanic and Atmospheric Administration |
Gao J.,University of Washington |
And 3 more authors.
Proceedings of the Royal Society B: Biological Sciences | Year: 2016
The spatial distribution of marine fishes can change for many reasons, including density-dependent distributional shifts. Previous studies show mixed support for either the proportional-density model (PDM; no relationship between abundance and area occupied, supported by ideal-free distribution theory) or the basin model (BM; positive abundance-area relationship, supported by density-dependent habitat selection theory). The BM implies that fishes move towards preferred habitat as the population declines. We estimate the average relationship using bottom trawl data for 92 fish species from six marine regions, to determine whether the BM or PDM provides a better description for sea-bottom-associated fishes. We fit a spatio-temporal model and estimate changes in effective area occupied and abundance, and combine results to estimate the average abundance-area relationship as well as variability among taxa and regions. The average relationship is weak but significant (0.6% increase in area for a 10% increase in abundance), whereas only a small proportion of species-region combinations show a negative relationship (i.e. shrinking area when abundance increases). Approximately one-third of combinations (34.6%) are predicted to increase in area more than 1% for every 10% increase in abundance. We therefore infer that population density generally changes faster than effective area occupied during abundance changes. Gadiformes have the strongest estimated relationship (average 1.0% area increase for every 10% abundance increase) followed by Pleuronectiformes and Scorpaeniformes, and the Eastern Bering Sea shows a strong relationship between abundance and area occupied relative to other regions. We conclude that the BM explains a small but important portion of spatial dynamics for sea-bottom-associated fishes, and that many individual populations merit cautious management during population declines, because a compressed range may increase the efficiency of harvest. © 2016 The Author(s) Published by the Royal Society. All rights reserved.
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) Jamesâ€™ Rule and 2) the Sensory Drive Hypothesis. According to Jamesâ€™ 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 Jamesâ€™ 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.
PubMed | South African National Biodiversity Institute SANBI and University of Cape Town
Type: Journal Article | Journal: 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.
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.