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Article ; Online: Cost-benefit evaluation of management strategies for an invasive amphibian with a stage-structured model

Giovanni Vimercati / Sarah J. Davies / Cang Hui / John Measey

NeoBiota, Vol 70, Iss , Pp 87-

2021 Volume 105

Abstract: Management strategies for invasive populations should be designed to maximise efficacy and efficiency, i.e. to accomplish their goals while operating with the least resource consumption. This optimisation is often difficult to achieve in stage-structured ...

Abstract	Management strategies for invasive populations should be designed to maximise efficacy and efficiency, i.e. to accomplish their goals while operating with the least resource consumption. This optimisation is often difficult to achieve in stage-structured populations, because costs, benefits and feasibility of removing individuals may vary with stage. We use a spatially-explicit stage-structured model to assess efficacy of past, present and alternative control strategies for invasive guttural toads, Sclerophrys gutturalis, in Cape Town. The strategies involve removal of variable proportions of individuals at different life-history stages and spatial scales. We also quantify the time necessary to implement each strategy as a proxy of financial resources and we correct strategy outcomes by implementation of time to estimate efficiency. We found that the strategy initially pursued in Cape Town, which did not target any specific stage, was less efficient than the present strategy, which prioritises adult removal. The initial strategy was particularly inefficient because it did not reduce the population size despite allocating consistent resources to remove eggs and tadpoles. We also found that such removal might be detrimental when applied at high levels. This counter-intuitive outcome is due to the ‘hydra effect’: an undesired increase in population size caused by removing individuals before overcompensatory density dependence. Strategies that exclusively remove adults ensure much greater management efficiency than those that also remove eggs and tadpoles. Available management resources should rather be allocated to increase the proportion of adult guttural toads that are removed or the spatial extent at which this removal is pursued.
Keywords	Biology (General) ; QH301-705.5
Language	English
Publishing date	2021-12-01T00:00:00Z
Publisher	Pensoft Publishers
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Opening the floor for discussion

Molly V. Czachur / Melvi Todd / Tainã Gonçalves Loureiro / James M. Azam / Siphokazi Nyeleka / Amanda Alblas / Sarah J. Davies

South African Journal of Science, Vol 117, Iss 1/

A perspective on how scholars perceive attitudes to science in policymaking in South Africa

2021 Volume 2

Keywords	science communication ; research communication ; policy development ; decision-making ; Science ; Q ; Science (General) ; Q1-390 ; Social Sciences ; H ; Social sciences (General) ; H1-99
Language	English
Publishing date	2021-01-01T00:00:00Z
Publisher	Academy of Science of South Africa
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Late Glacial and Holocene Palaeolake History of the Última Esperanza Region of Southern Patagonia

Stephen J. Roberts / Robert D. McCulloch / Joseph F. Emmings / Sarah J. Davies / Wim Van Nieuwenhuyze / Mieke Sterken / Katrien Heirman / Jeroen Van Wichelen / Carolina Diaz / Evelien Van de Vyver / Alex Whittle / Wim Vyverman / Dominic A. Hodgson / Elie Verleyen

Frontiers in Earth Science, Vol

2022 Volume 10

Abstract: We undertook multi-proxy analyses on two sediment cores from Lago Pato, a small lake basin at 51°S topographically separated from Lago del Toro in Torres del Paine (TdP), to provide insights into glacier dynamics and lake-level change in the TdP and ... ...

Abstract	We undertook multi-proxy analyses on two sediment cores from Lago Pato, a small lake basin at 51°S topographically separated from Lago del Toro in Torres del Paine (TdP), to provide insights into glacier dynamics and lake-level change in the TdP and Última Esperanza region over the last ∼30,000 cal a BP (30 ka). Lago Pato is situated in a region overridden by the Southern Patagonian Ice Field during the Last Glacial and in a transitional climatic zone of Southern Patagonia sensitive to seasonal- to millennial-scale changes in the Southern Hemisphere Westerly Winds (SWW). Results show that a deep ice-dammed and enlarged palaeolake encompassed Lago del Toro and Lago Pato c. 30–20 ka after the ice had retreated from local-Last Glacial Maximum (l-LGM) limits at c. 48–34 ka and during the build-up to the global-Last Glacial Maximum (g-LGM), c. 26–19 ka. Gaps in both sediment records between c. 20–13.4 ka and c. 20–10 ka suggest hiatuses in sediment accumulation during the g-LGM and Antarctic Cold Reversal (ACR) readvances and/or removal by lake lowering or flushing during the Late Glacial–early Holocene. The palaeolake level dropped from >100 m a.s.l. to ∼40–50 m a.s.l. towards the end of the ACR c. 13.4–13.0 ka, creating a shallower glaciolacustrine environment dammed by an ice tongue in the Estancia Puerto Consuelo–Última Esperanza fjord. Further lowering of the enlarged palaeolake level occurred when the ice thinned to <40 m a.s.l., eventually isolating Lago Pato from Lago del Toro and glaciogenic sediment input at c. 11.7 ka. After isolation, the ecology and water levels in Lago Pato became sensitive to regional climate shifts. The shallow, stable, and highly anoxic environment that developed after c. 11.7 ka is associated with weaker (or poleward shifted) SWW at 51°S and was replaced at c. 10 ka by an increasingly productive shallow-littoral lake with a variable lake-level and periodic shifts in anoxic-oxic bottom water conditions and ratios of benthic-planktonic diatoms. A more open Nothofagus forest, ...
Keywords	Last Glacial Maximum (LGM) ; palaeoclimate ; palaeolimnology ; glaciation ; lake-level changes ; Patagonia ; Science ; Q
Subject code	550
Language	English
Publishing date	2022-03-01T00:00:00Z
Publisher	Frontiers Media S.A.
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: A Tournaisian (earliest Carboniferous) conglomerate-preserved non-marine faunal assemblage and its environmental and sedimentological context

Jennifer A. Clack / Carys E. Bennett / Sarah J. Davies / Andrew C. Scott / Janet E. Sherwin / Timothy R. Smithson

PeerJ, Vol 6, p e

2019 Volume 5972

Abstract: A conglomerate bed from the Tournaisian Ballagan Formation of Scotland preserves a rich array of vertebrate and other nonmarine fossils providing an insight into the wider ecosystem and paleoenvironment that existed during this pivotal stage of Earth ... ...

Abstract	A conglomerate bed from the Tournaisian Ballagan Formation of Scotland preserves a rich array of vertebrate and other nonmarine fossils providing an insight into the wider ecosystem and paleoenvironment that existed during this pivotal stage of Earth history. It challenges hypotheses of a long-lasting post-extinction trough following the end-Devonian extinction event. The fauna recovered includes a wide size range of tetrapods, rhizodonts, and dipnoans, from tiny juveniles or small-bodied taxa up to large adults, and more than one taxon of each group is likely. Some fauna, such as actinopterygians and chondrichthyans, are rare as macrofauna but are better represented in the microfossil assemblage. The fauna provides evidence of the largest Carboniferous lungfish ever found. The specimens are preserved in a localized, poorly-sorted conglomerate which was deposited in the deepest part of a river channel, the youngest of a group of channels. In addition to the fossils (micro- and macro-), the conglomerate includes locally-derived clasts of paleosols and other distinctive elements of the surrounding floodplains. Charcoal fragments represent small woody axes and possible larger trunk tissue from arborescent pteridosperms. Preservation of the fossils indicates some aerial exposure prior to transport, with abrasion from rolling. The findings presented here contrast with other published trends in vertebrate size that are used to interpret a reduction in maximum sizes during the Tournaisian. The richness of the fauna runs counter to the assumption of a depauperate nonmarine fauna following the end-Devonian Hangenberg event, and charcoal content highlights the occurrence of fire, with the requisite levels of atmospheric oxygen during that stage.
Keywords	Tetrapods ; Rhizodonts ; Dipnoans ; Chondrichthyans ; Charcoal ; Micropaleontology ; Medicine ; R ; Biology (General) ; QH301-705.5
Subject code	333
Language	English
Publishing date	2019-01-01T00:00:00Z
Publisher	PeerJ Inc.
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article: Does restricted access limit management of invasive urban frogs?

Vimercati, Giovanni / Sarah J. Davies / Cang Hui / John Measey

Biological invasions. 2017 Dec., v. 19, no. 12

2017

Abstract: Management recommendations that target urban invaders should consider environmental and socio-economic aspects peculiar to the urban landscape. Urbanization often leads to the fragmentation of the invaded landscape into subunits inaccessible to managers ( ...

Abstract	Management recommendations that target urban invaders should consider environmental and socio-economic aspects peculiar to the urban landscape. Urbanization often leads to the fragmentation of the invaded landscape into subunits inaccessible to managers (restricted access) or for which detailed information is lacking. Using models to explore impact of these limitations on management success provides a useful approach to propose effective countermeasures. Here we deploy a spatially explicit age-structured model applied to a pond network to investigate how restricted access and lack of detailed information may affect management of three invasive anuran species across a peri-urban landscape. The target species, the guttural toad Sclerophrys gutturalis, the African clawed frog Xenopus laevis and the painted reed frog Hyperolius marmoratus, belong to different ecotypes (terrestrial, aquatic and arboreal, respectively) and have different life history traits. We show that restricted property access significantly constrains management success in two of the three species (the guttural toad and the painted reed frog), while lack of detailed information around the invaded landscape impedes successful management in only one species (the guttural toad). The species-dependent response we detected is due to contrasting demographic and spatial invasion dynamics linked to the different anuran ecotypes. Our work highlights the necessity to adopt a context-dependent approach when proposing management recommendations in urban environment.
Keywords	Xenopus laevis ; ecological invasion ; ecotypes ; frogs ; landscapes ; life history ; managers ; models ; socioeconomics ; toads ; urban areas ; urbanization
Language	English
Dates of publication	2017-12
Size	p. 3659-3674.
Publishing place	Springer International Publishing
Document type	Article
ZDB-ID	1438729-3
ISSN	1573-1464 ; 1387-3547
ISSN (online)	1573-1464
ISSN	1387-3547
DOI	10.1007/s10530-017-1599-6
Database	NAL-Catalogue (AGRICOLA)

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Article: Integrating age structured and landscape resistance models to disentangle invasion dynamics of a pond-breeding anuran

Vimercati, Giovanni / Cang Hui / G. John Measey / Sarah J. Davies

Ecological modelling. 2017 July 24, v. 356

2017

Abstract: Modelling population dynamics of invasive species may help to propose effective management countermeasures. Invasion dynamics generally show recursive patterns across species and regions, where initial lag is followed by spread and eventual dominance ... ...

Abstract	Modelling population dynamics of invasive species may help to propose effective management countermeasures. Invasion dynamics generally show recursive patterns across species and regions, where initial lag is followed by spread and eventual dominance phases. However, timing and modes of these phases are highly variable, emerging from the interplay between traits of the invader and characteristics of the invaded landscape. Disentangling this interplay is particularly arduous in species with complex life-histories, where an individual passes through different life stages that alter physiology, behaviour and interactions with the environment. Here, we describe an age structured model that can be utilized to simulate population dynamics of invasive pond-breeding anurans. The model follows a spatially structured population approach, each pond representing a discrete habitat patch that exchanges individuals with other similar patches, and simulates change in survival and dispersal behaviour as a function of age. It also integrates dispersal with landscape complexity through landscape resistance modelling to depict functional connectivity across the pond network. Then we apply the model to a case study, the invasion of the guttural toad Sclerophrys gutturalis in Cape Town, first detected in 2000. Age-structured demographic and spatial dynamics of the focal population are reconstructed in a network of 415 ponds embedded in a heterogeneous landscape. Parameterization is conducted through field and laboratory surveys, a literature review and data collected during an ongoing extirpation from 2010. We use the model to explore: i) occurrence and duration of lag phase; ii) whether the spatial spread fits an accelerating or a linear trend; iii) how simulated dynamics match field observations. Additionally we test model sensitivity to demographic and behavioural traits. We found a lag phase in both demographic and spatial dynamics; however the lag duration of these dynamics does not coincide, where invaders start to spread across the pond network five years before the demographic explosion. Also, we found that the spatial spread fits an accelerating trend that causes complete invasion of the network in six years. Such dynamics noticeably match field observations and confirmed patterns previously detected in other invaders characterized by high dispersal abilities. Sensitivity analysis suggests that it would have been preferable to quantify initial propagule size and post-metamorphic survival in the field; both timing and modes of invasion are particularly sensitive to these parameters. We conclude that the model has potential to forecast amphibian invasion dynamics and test management countermeasures.
Keywords	Anura ; case studies ; data collection ; dispersal behavior ; habitats ; invasive species ; landscapes ; models ; physiology ; ponds ; population dynamics ; surveys ; toads
Language	English
Dates of publication	2017-0724
Size	p. 104-116.
Publishing place	Elsevier B.V.
Document type	Article
ZDB-ID	191971-4
ISSN	0304-3800
ISSN	0304-3800
DOI	10.1016/j.ecolmodel.2017.03.017
Database	NAL-Catalogue (AGRICOLA)

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Article ; Online: Invasion science for society

Brian W. van Wilgen / Sarah J. Davies / David M. Richardson

South African Journal of Science, Vol 110, Iss 7/8, Pp 12-

A decade of contributions from the Centre for Invasion Biology

2014 Volume 12

Abstract: Biological invasions are a growing problem worldwide. In 2004, the South African Department of Science and Technology, through the National Research Foundation, established a Centre of Excellence for Invasion Biology, with the primary goal of providing ... ...

Abstract	Biological invasions are a growing problem worldwide. In 2004, the South African Department of Science and Technology, through the National Research Foundation, established a Centre of Excellence for Invasion Biology, with the primary goal of providing scientific understanding and building capacity in the field of biological invasions. South Africa is an extraordinary natural laboratory for the study of biological invasions, and the Centre for Invasion Biology (C·I·B) has capitalised on this situation. During its first decade, the C·I·B generated over 800 publications, and produced almost 200 graduates at honours, master’s and doctoral levels. The C·I·B has therefore made a considerable contribution to building human capacity in the field of biological invasions. Substantial advances have been made in all aspects of invasion science, which is not limited to biology and ecology, but includes history, sociology, economics and management. The knowledge generated by the C·I·B has been used to inform policy and improve management practices at national and local levels. The C·I·B has emerged as a leading institute in the global field of invasion biology, with several unique features that differentiate it from similar research institutes elsewhere. These features include a broad research focus that embraces environmental, social and economic facets, leading to a diverse research programme that has produced many integrated products; an extensive network of researchers with diverse interests, spread over a wide geographical range; and the production of policy- and management-relevant research products arising from the engaged nature of research conducted by the C∙I∙B.
Keywords	invasive alien species ; capacity building ; biological invasions ; Centres of Excellence ; research strategy ; Science ; Q ; Science (General) ; Q1-390 ; Social Sciences ; H ; Social sciences (General) ; H1-99
Language	English
Publishing date	2014-07-01T00:00:00Z
Publisher	Academy of Science of South Africa
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Author Correction

Stephen J. Roberts / Patrick Monien / Louise C. Foster / Julia Loftfield / Emma P. Hocking / Bernhard Schnetger / Emma J. Pearson / Steve Juggins / Peter Fretwell / Louise Ireland / Ryszard Ochyra / Anna R. Haworth / Claire S. Allen / Steven G. Moreton / Sarah J. Davies / Hans-Jürgen Brumsack / Michael J. Bentley / Dominic A. Hodgson

Nature Communications, Vol 13, Iss 1, Pp 1-

Past penguin colony responses to explosive volcanism on the Antarctic Peninsula

2022 Volume 1

Keywords	Science ; Q
Language	English
Publishing date	2022-06-01T00:00:00Z
Publisher	Nature Portfolio
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Emerging infectious diseases and biological invasions

Nick H. Ogden / John R. U. Wilson / David M. Richardson / Cang Hui / Sarah J. Davies / Sabrina Kumschick / Johannes J. Le Roux / John Measey / Wolf-Christian Saul / Juliet R. C. Pulliam

Royal Society Open Science, Vol 6, Iss

a call for a One Health collaboration in science and management

2019 Volume 3

Abstract: The study and management of emerging infectious diseases (EIDs) and of biological invasions both address the ecology of human-associated biological phenomena in a rapidly changing world. However, the two fields work mostly in parallel rather than in ... ...

Abstract	The study and management of emerging infectious diseases (EIDs) and of biological invasions both address the ecology of human-associated biological phenomena in a rapidly changing world. However, the two fields work mostly in parallel rather than in concert. This review explores how the general phenomenon of an organism rapidly increasing in range or abundance is caused, highlights the similarities and differences between research on EIDs and invasions, and discusses shared management insights and approaches. EIDs can arise by: (i) crossing geographical barriers due to human-mediated dispersal, (ii) crossing compatibility barriers due to evolution, and (iii) lifting of environmental barriers due to environmental change. All these processes can be implicated in biological invasions, but only the first defines them. Research on EIDs is embedded within the One Health concept—the notion that human, animal and ecosystem health are interrelated and that holistic approaches encompassing all three components are needed to respond to threats to human well-being. We argue that for sustainable development, biological invasions should be explicitly considered within One Health. Management goals for the fields are the same, and direct collaborations between invasion scientists, disease ecologists and epidemiologists on modelling, risk assessment, monitoring and management would be mutually beneficial.
Keywords	biological invasion ; emerging infectious disease ; one health ; Science ; Q
Subject code	333
Language	English
Publishing date	2019-03-01T00:00:00Z
Publisher	The Royal Society
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article: Significance of sedimentary organic matter input for shale gas generation potential of Mississippian Mudstones, Widmerpool Gulf, UK

Könitzer, Sven F / Christopher H. Vane / Melanie J. Leng / Michael H. Stephenson / Sarah J. Davies

Review of palaeobotany and palynology. 2016 Jan., v. 224

2016

Abstract: Carboniferous mudstones in central and northern England are shale gas prospects but the controls on the amount and composition of organic matter are not well understood, even though these parameters define the volumes of gas generated in fine-grained ... ...

Abstract	Carboniferous mudstones in central and northern England are shale gas prospects but the controls on the amount and composition of organic matter are not well understood, even though these parameters define the volumes of gas generated in fine-grained sediments. Organic matter in samples from basinal late Mississippian (Arnsbergian) mudstones in the Widmerpool Gulf was characterised by using semi-quantitative (n=58) and quantitative palynofacies (n=16) analyses, sporomorph counts and bulk rock geochemistry (total organic carbon, δ13C of bulk organic matter, Rock-Eval Pyrolysis).The results of this study suggest that most organic matter at this location was delivered to the sediment–water interface as aggregates of a granular translucent type of amorphous organic matter (AOMGr, mean=66.7%±19.3%) via hemipelagic suspension settling. AOMGr represents fragments of algal material with subordinate inclusions of small plant fragments and pyrite framboids held together by microbial colonies. AOMBr (brown granular amorphous organic matter) is the second most abundant group (mean=15.6%±8.5%) comprising similar microbial colonies that grew on suspended land plant-derived fragments in the water column. Palynofacies components representing clearly terrestrial organic matter are much less abundant and include gelified organic matter (G, mean=9.6%±12.6%), black phytoclasts (PhBl mean=2.7%±4.7%), brown phytoclasts (PhBr, mean=3.3%±3.6%) and sporomorphs (mean=1.4%±1.3%). Sediment delivery processes influence the balance between terrestrial organic matter and AOMGr. During low sea-level times, turbidity currents and debris flows delivered terrestrial organic matter (representing 12% to 40% of the palynofacies). Kerogen composition varies between Type II and III. In contrast, thin-bedded carbonate-bearing mudstones deposited during rising and high sea-level contain up to 95% AOMGr and these high abundances correspond to higher total organic carbon. Carbonate and AOMGr were generated by high bioproductivity in the water column. Type II (oil- and gas-prone) kerogens are dominant in these mudstones and therefore these intervals represent the best potential targets for thermogenic shale gas.
Keywords	algae ; carbonates ; geochemistry ; Late Mississippian epoch ; mass movement ; organic carbon ; pyrite ; pyrolysis ; sea level ; sediments ; sediment-water interface ; shale gas ; stable isotopes ; turbidity ; England
Language	English
Dates of publication	2016-01
Size	p. 146-168.
Publishing place	Elsevier B.V.
Document type	Article
ISSN	0034-6667
DOI	10.1016/j.revpalbo.2015.10.003
Database	NAL-Catalogue (AGRICOLA)

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