SUNScholar - Browsing by Author "Novoa, Ana"

Browsing by Author "Novoa, Ana"

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Biodiversity assessments : origin matters
(Public Library of Science, 2018-11-13) Pauchard, Anibal; Meyerson, Laura A.; Bacher, Sven; Blackburn, Tim M.; Brundu, Giuseppe; Cadotte, Marc W.; Courchamp, Franck; Essl, Franz; Genovesi, Piero; Haider, Sylvia; Holmes, Nick D.; Hulme, Philip E.; Jeschke, Jonathan M.; Lockwood, Julie L.; Novoa, Ana; Nunez, Martin A.; Peltzer, Duane A.; Pysek, Petr; Richardson, David M.; Simberloff, Daniel; Smith, Kevin; Van Wilgen, Brian W.; Vila, Montserrat; Wilson, John R. U.; Winter, Marten; Zenni, Rafael D.
Recent global efforts in biodiversity accounting, such as those undertaken through the Convention on Biological Diversity (CBD) and Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES), are vital if we are to track conservation progress, ensure that we can address the challenges of global change, and develop powerful and scientifically sound indicators. Schlaepfer [1] proposes that we should work toward inventories of biodiversity that account for native and non-native species regardless of species origin and ecological context. We strongly disagree with the approach of combining counts of native and non-native species because this will reduce our capacity to detect the effects of non-native species on native biodiversity with potentially devastating consequences. Compelling and abundant evidence demonstrates that some non-native species can become invasive and produce major ecosystem disruptions and even native species extinction. Unfortunately, we still cannot be certain which non-native species will be the most detrimental (e.g., [2]). Combining native and non-native species together into a single biodiversity index would not only inflate biodiversity estimates and risk promoting the spread of invasive non-native species but would also ignore the fundamental ecological differences between the two groups.
Biogeographical comparison of terrestrial invertebrates and trophic feeding guilds in the native and invasive ranges of Carpobrotus edulis
(Pensoft, 2020-05-14) Rodriguez, Jonatan; Novoa, Ana; Cordero-Rivera, Adolfo; Richardson, David M.; Gonzalez, Luis
ENGLISH ABSTRACT: Plant invasions impact on biodiversity by altering the composition of native communities by disrupting taxonomic and functional diversity. Non-native plants are often released from their natural enemies, which might result in a reduction of the attack of primary consumers. However, they can also be exposed to the attack of new herbivores that they might not be able to tolerate. Hence, invertebrate communities can be influenced by invasive non-native plants, which in turn modify interactions and change environmental conditions. In this study, we examined the compositional and trophic diversity of invertebrate species, comparing ecosystems with and without the plant species Carpobrotus edulis in coastal areas in its native (South Africa) and introduced (Iberian Peninsula) ranges. Results show that C. edulis has a clear impact on invertebrate communities in its non-native range, reducing their abundance in invaded areas, and particularly affecting certain trophic groups. Invasive C. edulis also alters the invertebrate diversity by not only reducing abundance but also by altering species composition. Overall, the physical dominance of C. edulis modifies the co-occurrence of invertebrate assemblages, reducing the number of trophic groups and leading to substantial effects on primary consumers. Results suggest that the lack of natural enemies might be an important driver of the expansion of C. edulis in its introduced range. Further work is needed to examine long-term changes caused by non-native plants on invertebrate assemblages and the subsequent modification of biological interactions.
A conceptual map of invasion biology : integrating hypotheses into a consensus network
(Wiley, 2020-03-25) Enders, Martin; Havemann, Frank; Ruland, Florian; Bernard-Verdier, Maud; Catford, Jane A.; Gomez-Aparicio, Lorena; Haider, Sylvia; Heger, Tina; Kueffer, Christoph; Kuh, Ingolf; Meyerson, Laura A.; Musseau, Camille; Novoa, Ana; Ricciardi, Anthony; Sagouis, Alban; Schittko, Conrad; Strayer, David L.; Vilà, Montserrat; Essl, Franz; Hulme, Philip E.; Van Kleunen, Mark; Kumschick, Sabrina; Lockwood, Julie L.; Mabey, Abigail L.; McGeoch, Melodie A.; Estibaliz, Palma; Pysek, Petr; Saul, Wolf-Christian; Yannelli, Florencia A.; Jeschke, Jonathan M.
Background and aims: Since its emergence in the mid-20th century, invasion biology has matured into a productive research field addressing questions of fundamental and applied importance. Not only has the number of empirical studies increased through time, but also has the number of competing, overlapping and, in some cases, contradictory hypotheses about biological invasions. To make these contradictions and redundancies explicit, and to gain insight into the field’s current theoretical structure, we developed and applied a Delphi approach to create a consensus network of 39 existing invasion hypotheses. Results: The resulting network was analysed with a link-clustering algorithm that revealed five concept clusters (resource availability, biotic interaction, propagule, trait and Darwin’s clusters) representing complementary areas in the theory of invasion biology. The network also displays hypotheses that link two or more clusters, called connecting hypotheses, which are important in determining network structure. The network indicates hypotheses that are logically linked either positively (77 connections of support) or negatively (that is, they contradict each other; 6 connections). Significance: The network visually synthesizes how invasion biology’s predominant hypotheses are conceptually related to each other, and thus, reveals an emergent structure – a conceptual map – that can serve as a navigation tool for scholars, practitioners and students, both inside and outside of the field of invasion biology, and guide the development of a more coherent foundation of theory. Additionally, the outlined approach can be more widely applied to create a conceptual map for the larger fields of ecology and biogeography.
Division of labor brings greater benefits to clones of carpobrotus edulis in the non-native range : evidence for rapid adaptive evolution
(Frontiers Media, 2016) Roiloa, Sergio R.; Retuerto, Ruben; Campoy, Josefina G.; Novoa, Ana; Barreiro, Rodolfo
Why some species become invasive while others do not is a central research request in biological invasions. Clonality has been suggested as an attribute that could contribute to plant invasiveness. Division of labor is an important advantage of clonal growth, and it seems reasonable to anticipate that clonal plants may intensify this clonal attribute in an invaded range because of positive selection on beneficial traits. To test this hypothesis, we collected clones of Carpobrotus edulis from native and invasive populations, grew pairs of connected and severed ramets in a common garden and under negative spatial covariance of nutrients and light to induce division of labor, and measured biomass allocation ratios, final biomass, and photochemical efficiency. Our results showed that both clones from the native and invaded range develop a division of labor at morphological and physiological level. However, the benefit from the division of labor was significantly higher in apical ramets from the invaded range than in ramets from the native area. This is a novel and outstanding result because it provides the first evidence that the benefit of a key clonal trait such as division of labor may have been subjected to evolutionary adaptation in the invaded range. The division of labor can therefore be considered an important trait in the invasiveness of C. edulis. An appropriate assessment of the influence of clonal traits in plant invasions seems key for understanding the underlying mechanisms behind biological invasions of new environments.
Global actions for managing cactus invasions
(MDPI, 2019-10-16) Novoa, Ana; Brundu, Giuseppe; Day, Michael D.; Deltoro, Vicente; Essl, Franz; Foxcroft, Llewellyn C.; Fried, Guillaume; Kaplan, Haylee; Kumschick, Sabrina; Lloyd, Sandy; Marchante, Elizabete; Marchante, Helia; Paterson, Iain D.; Pysek, Petr; Richardson, David M.; Witt, Arne; Zimmermann, Helmuth G.; Wilson, John R. U.
The family Cactaceae Juss. contains some of the most widespread and damaging invasive alien plant species in the world, with Australia (39 species), South Africa (35) and Spain (24) being the main hotspots of invasion. The Global Cactus Working Group (IOBC GCWG) was launched in 2015 to improve international collaboration and identify key actions that can be taken to limit the impacts caused by cactus invasions worldwide. Based on the results of an on-line survey, information collated from a review of the scientific and grey literature, expertise of the authors, and because invasiveness appears to vary predictably across the family, we (the IOBC GCWG): (1) recommend that invasive and potentially invasive cacti are regulated, and to assist with this, propose five risk categories; (2) recommend that cactus invasions are treated physically or chemically before they become widespread; (3) advocate the use of biological control to manage widespread invasive species; and (4) encourage the development of public awareness and engagement initiatives to integrate all available knowledge and perspectives in the development and implementation of management actions, and address conflicts of interest, especially with the agricultural and ornamental sectors. Implementing these recommendations will require global co-operation. The IOBC GCWG aims to assist with this process through the dissemination of information and experience.
Introduced and invasive cactus species : a global review
(Oxford University Press, 2014-12-03) Novoa, Ana; Le Roux, Johannes J.; Robertson, Mark P.; Wilson, John R. U.; Richardson, David M.
ENGLISH ABSTRACT: Understanding which species are introduced and become invasive, and why, are central questions in invasion science. Comparative studies on model taxa have provided important insights, but much more needs to be done to unravel the context dependencies of these findings. The cactus family (Cactaceae), one of the most popular horticultural plant groups, is an interesting case study. Hundreds of cactus species have been introduced outside their native ranges; a few of them are among the most damaging invasive plant species in the world. We reviewed the drivers of introductions and invasions in the family and seek insights that can be used to minimize future risks. We compiled a list of species in the family and determined which have been recorded as invasive. We also mapped current global distributions and modelled the potential global distributions based on distribution data of known invasive taxa. Finally, we identified whether invasiveness is phylogenetically clustered for cacti and whether particular traits are correlated with invasiveness. Only 57 of the 1922 cactus species recognized in this treatment have been recorded as invasive. There are three invasion hotspots: South Africa (35 invasive species recorded), Australia (26 species) and Spain (24 species). However, there are large areas of the world with climates suitable for cacti that are at risk of future invasion—in particular, parts of China, eastern Asia and central Africa. The invasive taxa represent an interesting subset of the total species pool. There is a significant phylogenetic signal: invasive species occur in 2 of the 3 major phylogenetic clades and in 13 of the 130 genera. This phylogenetic signal is not driven by human preference, i.e. horticultural trade, but all invasive species are from 5 of the 12 cactus growth forms. Finally, invasive species tend to have significantly larger native ranges than non-invasive species, and none of the invasive species are of conservation concern in their native range. These results suggest fairly robust correlates of invasiveness that can be used for proactive management and risk assessments.
Invasive alien species add to the uncertain future of protected areas
(Pensoft, 2020-05-20) Moodley, Desika; Foxcroft, Llewellyn C.; Novoa, Ana; Pyskova, Klara; Pergl, Jan; Pysek, Petr
The invasive cactus Opuntia stricta creates fertility islands in African savannas and benefits from those created by native trees
(2021-10-21) Novoa, Ana; Foxcroft, Llewellyn C.; Keet, Jan‑Hendrik; Pysek, Petr; Le Roux, Johannes J.
The patchy distribution of trees typical of savannas often results in a discontinuous distribution of water, nutrient resources, and microbial communities in soil, commonly referred to as “islands of fertility”. We assessed how this phenomenon may affect the establishment and impact of invasive plants, using the invasion of Opuntia stricta in South Africa’s Kruger National Park as case study. We established uninvaded and O. stricta-invaded plots under the most common woody tree species in the study area (Vachellia nilotica subsp. kraussiana and Spirostachys africana) and in open patches with no tree cover. We then compared soil characteristics, diversity and composition of the soil bacterial communities, and germination performance of O. stricta and native trees between soils collected in each of the established plots. We found that the presence of native trees and invasive O. stricta increases soil water content and nutrients, and the abundance and diversity of bacterial communities, and alters soil bacterial composition. Moreover, the percentage and speed of germination of O. stricta were higher in soils conditioned by native trees compared to soils collected from open patches. Finally, while S. africana and V. nilotica trees appear to germinate equally well in invaded and uninvaded soils, O. stricta had lower and slower germination in invaded soils, suggesting the potential release of phytochemicals by O. stricta to avoid intraspecific competition. These results suggest that the presence of any tree or shrub in savanna ecosystems, regardless of origin (i.e. native or alien), can create favourable conditions for the establishment and growth of other plants.
MAcroecological Framework for Invasive Aliens (MAFIA) : disentangling large-scale context dependence in biological invasions
(2020-10-15) Pysek, Petr; Bacher, Sven; Kuhn, Ingolf; Novoa, Ana; Catford, Jane A.; Hulme, Philip E.; Pergl, Jan; Richardson, David M.; Wilson, John R. U.; Blackburn, Tim M.
ENGLISH ABSTRACT: Macroecology is the study of patterns, and the processes that determine those patterns, in the distribution and abundance of organisms at large scales, whether they be spatial (from hundreds of kilometres to global), temporal (from decades to centuries), and organismal (numbers of species or higher taxa). In the context of invasion ecology, macroecological studies include, for example, analyses of the richness, diversity, distribution, and abundance of alien species in regional floras and faunas, spatio-temporal dynamics of alien species across regions, and cross-taxonomic analyses of species traits among comparable native and alien species pools. However, macroecological studies aiming to explain and predict plant and animal naturalisations and invasions, and the resulting impacts, have, to date, rarely considered the joint effects of species traits, environment, and socioeconomic characteristics. To address this, we present the MAcroecological Framework for Invasive Aliens (MAFIA). The MAFIA explains the invasion phenomenon using three interacting classes of factors – alien species traits, location characteristics, and factors related to introduction events – and explicitly maps these interactions onto the invasion sequence from transport to naturalisation to invasion. The framework therefore helps both to identify how anthropogenic effects interact with species traits and environmental characteristics to determine observed patterns in alien distribution, abundance, and richness; and to clarify why neglecting anthropogenic effects can generate spurious conclusions. Event-related factors include propagule pressure, colonisation pressure, and residence time that are important for mediating the outcome of invasion processes. However, because of context dependence, they can bias analyses, for example those that seek to elucidate the role of alien species traits. In the same vein, failure to recognise and explicitly incorporate interactions among the main factors impedes our understanding of which macroecological invasion patterns are shaped by the environment, and of the importance of interactions between the species and their environment. The MAFIA is based largely on insights from studies of plants and birds, but we believe it can be applied to all taxa, and hope that it will stimulate comparative research on other groups and environments. By making the biases in macroecological analyses of biological invasions explicit, the MAFIA offers an opportunity to guide assessments of the context dependence of invasions at broad geographical scales.
Managing conflict-generating invasive species in South Africa : challenges and trade-offs
(AOSIS Publishing, 2017) Zengeya, Tsungai; Ivey, Philip; Woodford, Darragh J.; Weyl, Olaf; Novoa, Ana; Shackleton, Ross; Richardson, David M.; Van Wilgen, Brian
Background: This paper reviewed the benefits and negative impacts of alien species that are currently listed in the Alien and Invasive Species Regulations of the National Environmental Management: Biodiversity Act (Act no 10 of 2004) and certain alien species that are not yet listed in the regulations for which conflicts of interest complicate management. Objectives: Specifically, it identified conflict-generating species, evaluated the causes and driving forces of these conflicts and assessed how the conflicts have affected management. Method: A simple scoring system was used to classify the alien species according to their relative degree of benefits and negative impacts. Conflict-generating species were then identified and further evaluated using an integrated cognitive hierarchy theory and risk perception framework to identify the value systems (intrinsic and economic) and risk perceptions associated with each conflict. Results: A total of 552 alien species were assessed. Most of the species were classified as inconsequential (55%) or destructive (29%). Beneficial (10%) and conflict-generating (6%) species made a minor contribution. The majority (46%) of the conflict cases were associated with more than one value system or both values and risk perception. The other conflicts cases were based on intrinsic (40%) and utilitarian (14%) value systems. Conclusions: Conflicts based on value and risk perceptions are inherently difficult to resolve because authorities need to balance the needs of different stakeholders while meeting the mandate of conserving the environment, ecosystem services and human well-being. This paper uses the identified conflict-generating species to highlight the challenges and trade-offs of managing invasive species in South Africa.
Native range size and growth form in Cactaceae predict invasiveness and impact
(Pensoft, 2016) Novoa, Ana; Kumschick, Sabrina; Richardson, David M.; Rouget, Mathieu; Wilson, John R. U.
Many recent studies in invasion science have identified species traits that determine either invasiveness or impact. Such analyses underpin risk assessments and attempts to prioritise management actions. However, the factors that mediate the capacity of an introduced species to establish and spread (i.e. its invasiveness) can differ from those that affect the nature and severity of impacts. Here we compare those traits correlated with invasiveness with those correlated with impact for Cactaceae (“cacti”) in South Africa. To assess impact magnitude, we scored 70 cacti (35 invasive and 35 non-invasive species) using the Generic Impact Scoring System (GISS) and identified traits correlated with impact using a decision tree approach. We then compared the traits correlated with impact with those identified in a recent study as correlated with invasiveness (i.e. native range size and growth form). We found that there is a significant correlation between native range size and both invasiveness and impact. Cacti with larger native ranges were more likely to become invasive (p=0.001) and cause substantial impacts (p=0.01). These results are important for prioritising efforts on the management of cactus species. Understanding when and why impact and invasiveness are correlated (as they appear to be for Cactaceae) is likely to be an important area of future research in risk assessment.
A proposed national strategic framework for the management of Cactaceae in South Africa
(AOSIS Publishing, 2017) Kaplan, Haylee; Wilson, John R.U.; Klein, Hildegard; Henderson, Lesley; Zimmermann, Helmuth G.; Manyama, Phetole; Ivey, Philip; Richardson, David M.; Novoa, Ana
Background: South Africa has a long history of managing biological invasions. The rapid increase in the scale and complexity of problems associated with invasions calls for new, more strategic management approaches. This paper explores strategic management approaches for cactus invasions in South Africa. Cacti (Cactaceae) have had a long history of socio-economic benefits, considerable negative environmental and socio-economic impacts, and a wide range of management interventions in South Africa. Objectives: To guide the future management of cactus invasions, a national strategic framework was developed by the South African Cactus Working Group. The overarching aim of this framework is to reduce the negative impacts of cacti to a point where their benefits significantly outweigh the losses. Method: Four strategic objectives were proposed: (1) all invasive and potentially invasive cactus species should be prevented from entering the country, (2) new incursions of cactus species must be rapidly detected and eradicated, (3) the impacts of invasive cacti must be reduced and contained and (4) socio-economically useful cacti (both invasive and non-invasive species) must be utilised sustainably to minimise the risk of further negative impacts. Results: There are currently 35 listed invasive cactus species in the country; 10 species are targeted for eradication and 12 are under partial or complete biological control. We discuss approaches for the management of cactus species, their introduction and spread pathways and spatial prioritisation of control efforts. Conclusion: A thorough understanding of context-specific invasion processes and stakeholder support is needed when implementing strategies for a group of invasive species.

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