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  • Open Access
    Authors: 
    Daniel Vázquez Pombo;
    Publisher: Elsevier BV
    Country: Denmark

    The COVID-19 pandemic and its countermeasures radically affected the energy sector. Within a matter of days, whole countries were into lockdown causing the largest energy impact of the last decades. This study explores the pandemic and its effects on the isolated power systems of Cape Verde, a small island-based developing state in Africa. Historical data from 2013 to 2021 is combined with ARIMA-based forecasting to estimate a COVID-free scenario. The results show how the country’s electricity demand suffered a 10% drop distributed among the islands proportionally to GDP per capita. The energy mix was unaffected, but the lower demand motivated 6% less emissions. The reliability of the system improved with respect previous years, but the transmission losses increased by 5% due to energy theft caused by the severe economic crisis suffered in the archipelago. In that sense, the impact on revenue and energy sector workers was quite limited. Furthermore, we also studied the effects of the pandemic in other energy related sectors such as water desalination and transport. The recovery started in the third quarter of 2020 as marked by the increased electricity demand, but also with the rapid growth of passengers and goods in the transport sector.

  • Open Access
    Authors: 
    Amar Aganovic; Guangyu Cao; Jarek Kurnitski; Arsen Melikov; Pawel Wargocki;
    Publisher: Elsevier BV
    Country: Denmark

    A widely used analytical model to quantitatively assess airborne infection risk is the Wells-Riley model which is limited to complete air mixing in a single zone. However, this assumption tends not to be feasible (or reality) for many situations. This study aimed to extend the Wells-Riley model so that the infection risk can be calculated in spaces where complete mixing is not present. Some more advanced ventilation concepts create either two horizontally divided air zones in spaces as displacement ventilation or the space may be divided into two vertical zones by downward plane jet as in protective-zone ventilation systems. This is done by evaluating the time-dependent distribution of infectious quanta in each zone and by solving the coupled system of differential equations based on the zonal quanta concentrations. This model introduces a novel approach by estimating the interzonal mixing factor based on previous experimental data for three types of ventilation systems: incomplete mixing ventilation, displacement ventilation, and protective zone ventilation. The modeling approach is applied to a room with one infected and one susceptible person present. The results show that using the Wells-Riley model based on the assumption of completely air mixing may considerably overestimate or underestimate the long-range airborne infection risk in rooms where air distribution is different than complete mixing, such as displacement ventilation, protected zone ventilation, warm air supplied from the ceiling, etc. Therefore, in spaces with non-uniform air distribution, a zonal modeling approach should be preferred in analytical models compared to the conventional single-zone Wells-Riley models when assessing long-range airborne transmission risk of infectious respiratory diseases.

  • Open Access English
    Authors: 
    Benjamin M. Scott; Vincent Lacasse; Ditte G. Blom; Peter D. Tonner; Nikolaj S. Blom;
    Country: Denmark

    Abstract Background The coronavirus nonstructural protein 5 (Nsp5) is a cysteine protease required for processing the viral polyprotein and is therefore crucial for viral replication. Nsp5 from several coronaviruses have also been found to cleave host proteins, disrupting molecular pathways involved in innate immunity. Nsp5 from the recently emerged SARS-CoV-2 virus interacts with and can cleave human proteins, which may be relevant to the pathogenesis of COVID-19. Based on the continuing global pandemic, and emerging understanding of coronavirus Nsp5-human protein interactions, we set out to predict what human proteins are cleaved by the coronavirus Nsp5 protease using a bioinformatics approach. Results Using a previously developed neural network trained on coronavirus Nsp5 cleavage sites (NetCorona), we made predictions of Nsp5 cleavage sites in all human proteins. Structures of human proteins in the Protein Data Bank containing a predicted Nsp5 cleavage site were then examined, generating a list of 92 human proteins with a highly predicted and accessible cleavage site. Of those, 48 are expected to be found in the same cellular compartment as Nsp5. Analysis of this targeted list of proteins revealed molecular pathways susceptible to Nsp5 cleavage and therefore relevant to coronavirus infection, including pathways involved in mRNA processing, cytokine response, cytoskeleton organization, and apoptosis. Conclusions This study combines predictions of Nsp5 cleavage sites in human proteins with protein structure information and protein network analysis. We predicted cleavage sites in proteins recently shown to be cleaved in vitro by SARS-CoV-2 Nsp5, and we discuss how other potentially cleaved proteins may be relevant to coronavirus mediated immune dysregulation. The data presented here will assist in the design of more targeted experiments, to determine the role of coronavirus Nsp5 cleavage of host proteins, which is relevant to understanding the molecular pathology of coronavirus infection.

  • Open Access
    Authors: 
    Robert Böhm; Cornelia Betsch; Yana Litovsky; Philipp Sprengholz; Noel Brewer; Gretchen B. Chapman; Julie Leask; George Loewenstein; Martha Scherzer; Cass R. Sunstein; +1 more
    Publisher: Center for Open Science
    Country: Denmark

    SummaryBackgroundCOVID-19 booster vaccine uptake rates are behind the rate of primary vaccination in many countries. Governments and non-governmental institutions rely on a range of interventions aiming to increase booster uptake. Yet, little is known how experts and the general public evaluate these interventions.MethodsWe applied a novel crowdsourcing approach to provide rapid insights on the most promising interventions to promote uptake of COVID-19 booster vaccines. In the first phase (December 2021), international experts (n = 78 from 17 countries) proposed 46 unique interventions. To reduce noise and potential bias, in the second phase (January 2022), experts (n = 307 from 34 countries) and representative general population samples from the UK (n = 299) and the US (n = 300) rated the proposed interventions on several evaluation criteria, including effectiveness and acceptability, on a 5-point Likert-type scale.FindingsSanctions were evaluated as potentially most effective but least accepted. Evaluations by expert and general population samples were considerably aligned. Interventions that received the most positive evaluations regarding both effectiveness and acceptability across evaluation groups were: a day off work after getting vaccinated, financial incentives, tax benefits, promotional campaigns, and mobile vaccination teams.InterpretationThe results provide useful insights to help governmental and non-governmental institutions in their decisions about which interventions to implement. Additionally, the applied crowdsourcing method may be used in future studies to retrieve rapid insights on the comparative evaluation of (health) policies.FundingThis study received funding from the Austrian Science Fund (SFB F63) and the University of Vienna.

  • Open Access English
    Authors: 
    Sarang S. Nath; John Villadsen;
    Country: Denmark

    Modeling complex chemical reaction networks has inspired a considerable body of research and a variety of approaches to modeling nonlinear pathways are being developed. Here, a general methodology is formulated to convert an arbitrary reaction network into its equivalent electrical analog. The topological equivalence of the electrical analog is mathematically established for unimolecular reactions using Kirchhoff's laws. The modular approach is generalized to bimolecular and nonlinear autocatalytic reactions. It is then applied to simulate the dynamics of nonlinear autocatalytic networks without making simplifying assumptions, such as use of the quasi-steady state/Bodenstein approximation or the absence of nonlinear steps in the intermediates. This is among the few papers that quantify the dynamics of a nonlinear chemical reaction network by generating and simulating an electrical network analog. As a realistic biological application, the early phase of the spread of COVID-19 is modeled as an autocatalytic process and the predicted dynamics are in good agreement with experimental data. The rate-limiting step of viral transmission is identified, leading to novel mechanistic insights.

  • Open Access English
    Authors: 
    G. Berg-Beckhoff; M. Bask; S.S. Jervelund; J.D. Guldager; A. Quickfall; F. Rabiee Khan; G. Oddsson; K.A. van der Wel; K.K. Sarasjärvi; S. Olafsdottir; +3 more
    Countries: Denmark, Sweden

    Understanding predictors of adherence to governmental measures to prevent the spread of the COVID-19 is fundamental to guide health communication. This study examined whether political stringency and infection rates during the first wave of the pandemic were associated with higher education students' adherence to COVID-19 government measures in the Nordic countries (Denmark, Finland, Norway, Iceland, and Sweden) and the United Kingdom. Both individual- and country-level data were used in present study. An international cross-sectional subsample (n = 10,345) of higher-education students was conducted in May–June 2020 to collect individual-level information on socio-demographics, study information, living arrangements, health behaviors, stress, and COVID-19-related concerns, including adherence to government measures. Country-level data on political stringency from the Oxford COVID-19 Government Response Tracker and national infection rates were added to individual-level data. Multiple linear regression analyses stratified by country were conducted. Around 66% of students reported adhering to government measures, with the highest adherence in the UK (73%) followed by Iceland (72%), Denmark (69%), Norway (67%), Finland (64%) and Sweden (49%). Main predictors for higher adherence were older age, being female and being worried about getting infected with COVID-19 (individual-level), an increase in number of days since lockdown, political stringency, and information about COVID-19 mortality rates (country-level). However, incidence rate was an inconsistent predictor, which may be explained by imperfect data quality during the onset of the pandemic. We conclude that shorter lockdown periods and political stringency are associated with adherence to government measures among higher education students at the outset of the COVID-19 pandemic.

  • Open Access English
    Authors: 
    J. Panovska-Griffiths; R.M. Stuart; C.C. Kerr; K. Rosenfield; D. Mistry; W. Waites; D.J. Klein; C. Bonell; R.M. Viner;
    Publisher: Elsevier Inc.
    Countries: Australia, United Kingdom, Denmark, Australia, Denmark

    Following the resurgence of the COVID-19 epidemic in the UK in late 2020 and the emergence of the alpha (also known as B117) variant of the SARS-CoV-2 virus, a third national lockdown was imposed from January 4, 2021. Following the decline of COVID-19 cases over the remainder of January 2021, the question of when and how to reopen schools became an increasingly pressing one in early 2021. This study models the impact of a partial national lockdown with social distancing measures enacted in communities and workplaces under different strategies of reopening schools from March 8, 2021 and compares it to the impact of continual full national lockdown remaining until April 19, 2021. We used our previously published agent-based model, Covasim, to model the emergence of the alpha variant over September 1, 2020 to January 31, 2021 in presence of Test, Trace and Isolate (TTI) strategies. We extended the model to incorporate the impacts of the roll-out of a two-dose vaccine against COVID-19, with 200,000 daily vaccine doses prioritised by age starting with people 75 years or older, assuming vaccination offers a 95% reduction in disease acquisition risk and a 30% reduction in transmission risk. We used the model, calibrated until January 25, 2021, to simulate the impact of a full national lockdown (FNL) with schools closed until April 19, 2021 versus four different partial national lockdown (PNL) scenarios with different elements of schooling open: 1) staggered PNL with primary schools and exam-entry years (years 11 and 13) returning on March 8, 2021 and the rest of the schools years on March 15, 2020; 2) full-return PNL with both primary and secondary schools returning on March 8, 2021; 3) primary-only PNL with primary schools and exam critical years (years 11 and 13) going back only on March 8, 2021 with the rest of the secondary schools back on April 19, 2021 and 4) part-rota PNL with both primary and secondary schools returning on March 8, 2021 with primary schools remaining open continuously but secondary schools on a two-weekly rota-system with years alternating between a fortnight of face-to-face and remote learning until April 19, 2021. Across all scenarios, we projected the number of new daily cases, cumulative deaths and effective reproduction number R until April 30, 2021. Our calibration across different scenarios is consistent with alpha variant being around 60% more transmissible than the wild type. We find that strict social distancing measures, i.e. national lockdowns, were essential in containing the spread of the virus and controlling hospitalisations and deaths during January and February 2021. We estimated that a national lockdown over January and February 2021 would reduce the number of cases by early March to levels similar to those seen in October 2020, with R also falling and remaining below 1 over this period. We estimated that infections would start to increase when schools reopened, but found that if other parts of society remain closed, this resurgence would not be sufficient to bring R above 1. Reopening primary schools and exam critical years only or having primary schools open continuously with secondary schools on rotas was estimated to lead to lower increases in cases and R than if all schools opened. Without an increase in vaccination above the levels seen in January and February, we estimate that R could have increased above 1 following the reopening of society, simulated here from April 19, 2021. Our findings suggest that stringent measures were integral in mitigating the increase in cases and bringing R below 1 over January and February 2021. We found that it was plausible that a PNL with schools partially open from March 8, 2021 and the rest of the society remaining closed until April 19, 2021 would keep R below 1, with some increase evident in infections compared to continual FNL until April 19, 2021. Reopening society in mid-April, without an increase in vaccination levels, could push R above 1 and induce a surge in infections, but the effect of vaccination may be able to control this in future depending on the transmission blocking properties of the vaccines.

  • Open Access
    Authors: 
    Marie Stender; Lene Wiell Nordberg;
    Country: Denmark

    The Danish post-war housing areas originally epitomised the dawn of the welfare state, with modern housing blocks organised as enclaves surrounded by open green spaces, promoting ideals like hygiene, light, fresh air, equity, and community. Often, these housing areas were developed in vacant lots in suburban areas, and social infrastructure planning was an essential part of stimulating the sense of community with centrally located community centres and other common facilities. Due to segregation, some of these housing areas have become disadvantaged neighbourhoods, and the Danish state has recently introduced new measures including demolitions and evictions to transform the areas and increase their social and functional mix. The social infrastructure of these areas has traditionally been a physical framework for organised social activities and social support for socially disadvantaged citizens, facilitated by professionals. However, during the pandemic lockdown, shared physical facilities were temporarily closed and all organised social activities cancelled, thus rendering visible critical aspects of social infrastructure that may normally be taken for granted or remain unnoticed. Yet the pandemic also activated communities in new ways, making visible more informal and ad hoc social infrastructure with new communication channels, practical help among neighbours and community singing from balconies. Based on recent architectural-anthropological field studies in a range of disadvantaged housing areas in Denmark, this article locates social infrastructure during the time of Covid-19. It discusses the potential of mapping existing social networks and suggests a more differentiated view through three levels of social infrastructure learning from the pandemic's emergency period. The Danish post-war housing areas originally epitomised the dawn of the welfare state, with modern housing blocks organised as enclaves surrounded by open green spaces, promoting ideals like hygiene, light, fresh air, equity, and community. Often, these housing areas were developed in vacant lots in suburban areas, and social infrastructure planning was an essential part of stimulating the sense of community with centrally located community centres and other common facilities. Due to segregation, some of these housing areas have become disadvantaged neighbourhoods, and the Danish state has recently introduced new measures, including demolitions and evictions, to transform the areas and increase their social and functional mix. The social infrastructure of these areas has traditionally been a physical framework for organised social activities and social support for socially disadvantaged citizens, facilitated by professionals. However, during the pandemic lockdown, shared physical facilities were temporarily closed and all organised social activities cancelled, thus rendering visible critical aspects of social infrastructure that may normally be taken for granted or remain unnoticed. Yet the pandemic also activated communities in new ways, making visible more informal and ad hoc social infrastructure with new communication channels, practical help among neighbours, and community singing from balconies. Based on recent architectural-anthropological field studies in a range of disadvantaged housing areas in Denmark, this article locates social infrastructure during the time of Covid-19. It discusses the potential of mapping existing social networks and suggests a more differentiated view through three levels of social infrastructure learning from the pandemic’s emergency period.

  • Open Access English
    Authors: 
    César Fernández-de-las-Peñas; Jo Nijs; Randy Neblett; Andrea Polli; Maarten Moens; Lisa Goudman; Madhura Shekhar Patil; Roger D. Knaggs; Gisele Pickering; Lars Arendt-Nielsen;
    Country: Denmark

    Pain after an acute Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection and coronavirus disease 2019 (COVID-19) condition (post-COVID pain) is becoming a new healthcare emergency. Precision medicine refers to an evidence-based method of grouping patients based on their diagnostic/symptom presentation and then tailoring specific treatments accordingly. Evidence suggests that post-COVID pain can be categorized as nociceptive (i.e., pain attributable to the activation of the peripheral receptive terminals of primary afferent neurons in response to noxious chemical, mechanical, or thermal stimuli), neuropathic (i.e., pain associated with a lesion or disease of the somatosensory nervous system and limited to a “neuroanatomically plausible” distribution of the system), nociplastic (i.e., pain arising from altered nociception despite no clear evidence of actual or threatened tissue damage causing the activation of peripheral nociceptors or evidence for disease or lesion of the somatosensory system causing the pain), or mixed type (when two pain phenotypes co-exist). Each of these pain phenotypes may require a different treatment approach to maximize treatment effectiveness. Accordingly, the ability to classify post-COVID pain patients into one of these phenotypes would likely be critical for producing successful treatment outcomes. The 2021 International Association for the Study of Pain (IASP) clinical criteria and grading system provide a framework for classifying pain within a precision pain medicine approach. Here we present data supporting the possibility of grouping patients with post-COVID pain into pain phenotypes, using the 2021 IASP classification criteria, with a specific focus on nociplastic pain, which is probably the primary mechanism involved in post-COVID pain. Nociplastic pain, which is usually associated with comorbid symptomology (e.g., poor sleep quality, fatigue, cognitive–emotional disturbances, etc.) and is considered to be more difficult to treat than other pain types, may require a more nuanced multimodal treatment approach to achieve better treatment outcomes.

  • Open Access English
    Authors: 
    Maximilian G. R. Vollstädt; Mauro Galetti; Christopher N. Kaiser‐Bunbury; Benno I. Simmons; Fernando Gonçalves; Alcides L. Morales‐Pérez; Luis Navarro; Fabio L. Tarazona‐Tubens; Spencer Schubert; Tomas Carlo; +6 more
    Countries: Denmark, Netherlands

    AimMutualistic interactions between plants and animals are fundamental for the maintenance of natural communities and the ecosystem services they provide. However, particularly in human-dominated island ecosystems, introduced species may alter mutualistic interactions. Based on an extensive dataset of plant–frugivore interactions, we mapped and analysed a meta-network across the Caribbean archipelago. Specifically, we searched for subcommunity structure (modularity) and identified the types of species facilitating the integration of introduced species in the Caribbean meta-network.LocationCaribbean archipelago (Lucayan archipelago, Greater Antilles, Lesser Antilles).MethodsWe reviewed published scientific literature, unpublished theses and other nonpeer-reviewed sources to compile an extensive dataset of plant–frugivore interactions. We visualized spatial patterns and conducted a modularity analysis of the cross-island meta-network. We also examined which species were most likely to interact with introduced species: (1) endemic, nonendemic native or introduced species, and (2) generalized or specialized species.ResultsWe reported 3060 records of interactions between 486 plant and 178 frugivore species. The Caribbean meta-network was organized in 13 modules, driven by a combination of functional or taxonomic (modules dominated by certain groups of frugivores) and biogeographical (island-specific modules) mechanisms. Few introduced species or interaction pairs were shared across islands, suggesting little homogenization of the plant–frugivore meta-network at the regional scale. However, we found evidence of “invader complexes,” as introduced frugivores were more likely to interact with introduced plants than expected at random. Moreover, we found generalist species more likely to interact with introduced species than were specialized species.Main conclusionsThese results demonstrate that generalist species and “invader complexes” may facilitate the incorporation of introduced species into plant–frugivore communities. Despite the influx of introduced species, the meta-network was structured into modules related to biogeographical and functional or taxonomic affinities. These findings reveal how introduced species become an integral part of mutualistic systems on tropical islands.1 INTRODUCTIONMutualistic interactions between plants and animals, such as pollinators and frugivores, are critically important for maintaining the functionality of natural communities (Jordano, 1987;Ollerton et al., 2011; Rech et al., 2016). While most flowering plants are dependent on animals for pollination and seed-set (Ollerton et al., 2011; Rech et al., 2016), animal frugivores may ingest or otherwise manipulate and consequently disperse millions of seeds annually (Bueno et al., 2013). Frugivory is thereby crucial for the maintenance of plant diversity (Harms et al., 2000), as it allows plants to populate new sites, maintains gene flow between distinct populations and decreases density-dependent mortality in proximity of the parent individuals (Rogers et al., 2021). In some tropical systems, approximately 90% of all woody plants depend on frugivores for seed dispersal (Almeida-Neto et al., 2008; Howe & Smallwood, 1982). In addition to providing direct dispersal to specific, favourable sites for the plant (Wenny & Levey, 1998), frugivores can enhance the probability of successful germination, for example through the passage of seeds in the intestinal system (e.g. Traveset et al., 2001). The most important frugivore groups are birds, mammals and reptiles with birds and reptiles being particularly important in tropical island ecosystems (Kaiser-Bunbury et al., 2010; Valido & Olesen, 2007).Globally, co-evolved plant–frugivore communities are suffering from an array of drivers associated with global change, such as the introduction of species into new environments, where they become integrated into local communities through species interactions (Gallardo et al., 2016; Vilà et al., 2011). Species communities are thus being altered, which in turn may have consequences for biotic interactions and ecosystem functions, such as seed dispersal (Aslan et al., 2013; Lugo et al., 2012; Traveset & Richardson, 2006; Vizentin-Bugoni et al., 2021). Island ecosystems are particularly vulnerable to the disruption of native plant–frugivore interactions as island mutualists have evolved in isolation, and frequently developed specific traits, such as altered dispersal, or loss of defence traits in plants (Burns, 2019). Furthermore, as islands harbour many endemic species found nowhere else on Earth (Kier et al., 2009; Paulay, 1994), and have experienced disproportionally high extinction rates and numerous extant island species are threatened with extinctions (Blackburn et al., 2004; Fernández-Palacios et al., 2021; Groombridge, 1992), it is especially important to understand how introduced species integrate into island communities (Wood et al., 2017).Introduced species may integrate into existing communities and establish themselves in different ways. For instance, the concept of “invader complexes” suggests that introduced species facilitate the establishment of other introduced species, resulting in groups of introduced species interacting strongly with each other and less with the remaining community (D'Antonio & Dudley, 1993). Alternatively, endemic species that have become superabundant and highly generalized species due to ecological release and density compensation may readily include new arrivals into their interactions and thereby facilitate the establishment of introduced species on islands (Olesen et al., 2002). Furthermore, a growing number of studies show that species with many mutualistic partners (i.e. generalized species irrespectively of being nonendemic native or endemic) are more likely to incorporate new partners into their networks (Bascompte & Stouffer, 2009; Maruyama et al., 2016). In network theory, this is called “preferential attachment” (Newman, 2001), and thus, most generalized species would be expected to interact with introduced species.In addition to understanding which species are responsible for incorporating introduced species into native communities, we have little quantitative understanding of how introduced species affect the structure of native interaction networks and how this varies biogeographically (Fricke & Svenning, 2020). As for other mutualistic networks, plants and frugivores form complex interaction networks with reccurring structural properties (Bascompte & Jordano, 2007). One such property of interaction networks is modularity, which describes how interacting species aggregate into modules consisting of species that interact strongly within the respective module but much less with species of other modules (Thébault, 2013). The modular structure of mutualistic networks may reflect “co-evolutionary units” (Olesen et al., 2007) determined by an array of factors, such as phenological overlap, morphological traits, taxonomic relatedness and biogeography (Araujo et al., 2018; Dalsgaard et al., 2013; Donatti et al., 2011; Martín González et al., 2018; Maruyama et al., 2014; Schleuning et al., 2014). However, it is poorly understood whether introduced species influence the modular structure of mutualistic systems.Here, we present an extensive dataset on plant–frugivore interactions compiled from published and unpublished resources across the islands of the Caribbean archipelago: Lucayan archipelago, Greater Antilles and Lesser Antilles. We use the data to (i) explore the distribution of frugivory records across the Caribbean islands; (ii) assess island connectivity through shared species and interactions; (iii) evaluate the modular structure of the regional plant–frugivore meta-network and (iv) determine whether generalized vs. specialized species and introduced vs. endemic species are more likely to integrate introduced plants and frugivores into native plant–frugivore communities in island systems.2 METHODS2.1 Data collection and study regionAll our data were collected on the Caribbean islands, that is the Lucayan archipelago (The Bahamas and Turks and Caicos), the Greater Antilles (Cuba, Cayman Islands, Jamaica, Hispaniola and Puerto Rico) and the Lesser Antilles (a series of islands from the US and British Virgin Islands in the north to Grenada in the south). We did not include plant–frugivore interactions from islands such as Trinidad and Tobago, Curaçao, and Bonaire just north of South America, as these are continental islands with biotas with strong affinities to the South American mainland (Carstensen et al., 2012; Ricklefs & Bermingham, 2008). The low-lying sedimentary islands of the Lucayan Archipelago are part of the North American platform (Iturralde-Vinent & MacPhee, 1999; Trejo-Torres & Ackerman, 2001), and some of the islands have been interconnected in the Pleistocene (Murphy et al., 2004; Trejo-Torres & Ackerman, 2001). The mostly large and mountainous islands of the Greater Antilles are old with different geological origins (Graham, 2003; Iturralde-Vinent & MacPhee, 1999). The Greater Antilles emerged as fragments in the Eocene about 49 Ma; the geological history of the region has been highly dynamic with some parts connected in the past (Buskirk, 1985; Graham, 2003; Iturralde-Vinent & MacPhee, 1999; Ricklefs & Bermingham, 2008). The current biota of the Greater Antilles was only in small parts formed by vicariance, with dispersal facilitated by the Aves Ridge about 32–35 Ma (Iturralde-Vinent & MacPhee, 1999) or a more likely overwater dispersal at least for the avifauna (Buskirk, 1985; Graham, 2003; Ricklefs & Bermingham, 2008). The Lesser Antilles form a volcanic arc where the North and South American plates subduct under the Caribbean plate and likely originated at least 20 Ma (Ricklefs & Bermingham, 2008). To the east of the volcanic arc are some younger and low-lying islands such as Antigua and Barbuda, which consist of uplifted marine sediments (Ricklefs & Bermingham, 2008; Ricklefs & Lovette, 1999). Some islands were interconnected during the last glacial maximum, but most Lesser Antilles islands have never been interconnected (Ricklefs & Bermingham, 2004, 2008). The isolation of the Caribbean islands from the mainland differs greatly (Carstensen et al., 2012). Bimini in the Bahamas, for instance, is only approx. 87 km from the North American continent and Grenada in the Lesser Antilles is only 137 km from the continental landmass of South America. By contrast, islands such as Grand Turk (993 km) and South Caicos (999 km) are much more isolated from the mainland. On average, the isolation from any continental landmass in the Caribbean is over 500 km (Mean: 593 km ± 248 km SD; see details in Supporting Information Table S1). The distances between single islands are much smaller, for example the distance between Martinique and Dominica and Martinique and Saint Lucia is approx. 40 km. An island size threshold of 10,000 km2 has previously been suggested to be important for islands to be considered sources for colonization (Weigelt & Kreft, 2013), and on average, the islands of the Caribbean are approx. 304 km (±174 km SD) from the nearest island that exceeds 10,000 km2 (Table S1). Given the geological history and isolation of the Caribbean, the biota is characterized by being depauperate with high levels of endemism.To collect data on interactions between plants and frugivores in the Caribbean, we screened the Web of Science (WoS) and Google Scholar search engines. We used the combination of the following search terms: (“frugivory” OR “seed dispersal” OR “seed removal” OR “mutualism”) AND (“Caribbean” OR “Lesser Antilles” OR “Greater Antilles” OR “West Indies” OR “Bahamas” OR “Turks and Caicos” OR “Cayman Islands” OR “Jamaica” OR “Cuba” OR “Hispaniola” OR “Haiti” OR “Dominican Republic” OR “República Dominicana” OR “Puerto Rico” OR “Mona” OR “Virgin Islands” OR “Saint Martin” OR “Anguilla” OR “St. Kitts and Nevis” OR “Antigua” OR “Barbuda” OR “Montserrat” OR “Guadeloupe” OR “Dominica” OR “Martinique” OR “St. Lucia” OR “St. Vincent” OR “Grenadines” OR “Barbados” OR “Grenada”). To also include the grey literature, we contacted local ornithologists and ecologists working in the Caribbean region. This approach allowed us to obtain non-English publications, such as theses and dissertations not available online. We screened each of the studies manually, discarding studies where no appropriate data were presented (e.g. mutualistic interactions in marine environments). Interactions were only included when the respective authors presented original evidence for interaction events, that is evidence of fruits and/or seeds being ingested by frugivores. Thus, we discarded records where interactions between species were speculative (e.g. observation of frugivores on fruiting plant species without any evidence of fruit ingestion).We standardized the species names of plants and frugivores using the R-package taxize (Chamberlain & Szocs, 2013; Global Names Resolver, 2021) and data from the Integrated Taxonomic Information System (ITIS, 2021). We also retrieved information about species taxonomies (i.e. class, order and family) from ITIS. Finally, we compiled information about the native status of species and classified them into nonendemic native (species native to the Caribbean, but also naturally occurring elsewhere), endemic (only occurring within the Caribbean) and introduced (not naturally occurring within Caribbean) species (see details in Supporting Information Text S1). Of the original records, 95 plant (approx. 16% of all reported plants) and one frugivore record were not identified to species level (e.g. only genus name reported) and were thus excluded from data analyses. The final data used in statistical analyses consisted of interactions between 486 plant and 178 frugivore species.2.2 Data analysis2.2.1 Cross-island patterns of shared species and interactionsWe summarized patterns of shared species and interaction pairs across the Caribbean by calculating the proportion of shared species and interaction pairs across all islands. We calculated this proportion as the number of species/interaction pairs found on any two islands, divided by the total number of species/interaction pairs found on the given islands (Fricke & Svenning, 2020). We summarized these patterns separately for all reported records, for endemic, nonendemic native and for introduced plant and frugivore species and interaction pairs, respectively.2.2.2 Modularity of the Caribbean plant–frugivore meta-networkTo detect a modular structure of the meta-network, that is the network of plant–frugivore interactions across all islands, we employed Beckett's DIRT-LPA algorithm in the computeModules function of the R-package “bipartite” (Dormann et al., 2008, 2009). We ran 10 independent runs of the algorithm on the binary meta-network containing interactions between all identified species and identified the run with the single best division into modules, that is the highest degree of modularity Q. For the run with the highest Q value, we recorded the Q value, the number of modules as well as the respective plant and frugivore species in each module (Schleuning et al., 2014) and the islands on which they were recorded. To test whether the identified modular structure of the meta-network differed from random, we compared our results to 100 null models. To this end, we used an algorithm proposed by Patefield (1981) to randomize the interactions between species, using fixed marginal totals to produce networks with randomly associated species without constraining the degree of specialization (Blüthgen et al., 2008; Schleuning et al., 2014). For each of the null models, we applied the same approach as with the original matrix, that is we identified the single best configuration from 10 independent runs (Schleuning et al., 2014). We then tested whether modularity of the original matrix was significantly different from the best 100 null models by looking at the proportion of null modularity values that were greater than the empirical one, that is if  .05; Figure S2c) and the frugivore perspective (slope = 0.003, p > .05; Figure S2d).4 DISCUSSIONHere, we present a comprehensive review of published plant–frugivore interactions across the Caribbean archipelago, including the Lucayan archipelago, the Greater and Lesser Antilles. All islands shared species and unique interaction pairs with neighbouring islands and archipelagos, thereby forming a cohesive meta-network. We show that the meta-network of plant–frugivore interactions across the Caribbean was structured into modules, with at least some modules determined by a combination of functional or taxonomic (i.e. certain groups of frugivores) and biogeographical (i.e. island-specific modules) mechanisms. While relatively few species in the dataset were introduced to the Caribbean (16% plant and 8% frugivore species), we found support for the “invader complexes” theory, whereby introduced species facilitate the establishment of other introduced species (D'Antonio & Dudley, 1993; Olesen et al., 2002). Moreover, we found that generalized species were more likely to incorporate introduced species into their interactions, giving support for the “preferential attachment” theory (Newman, 2001). Below, we first discuss the available data on frugivory in the Caribbean, whereafter we discuss how species and interactions are shared across islands. We end by discussing the drivers of modularity and the integration of introduced species into plant–frugivore communities across the Caribbean.4.1 Data on frugivores and their plants in the Caribbean archipelagoAcross all islands, the vast majority of reported frugivores were birds (79%), followed by reptiles (13%) and mammals (8%), of which in turn the majority were bats (71%). These data thus reflect patterns that are typical for oceanic islands, as there is generally a lack of nonvolant, large-bodied, frugivorous mammals which may be ecologically replaced by birds and reptiles (Kaiser-Bunbury et al., 2010). The low number of mammal species in the dataset could also reflect past mammal extinctions particularly on the islands of the Greater Antilles (Turvey et al., 2021), potentially leaving some plants without their main seed dispersers.A large proportion of the plant species (28%) and the majority of frugivore species in the dataset (65%) were classified as endemic to the Caribbean. High degrees of endemism in local species communities are characteristic of island ecosystems (Kier et al., 2009; Paulay, 1994). In a review of plant–frugivore interactions on the Galapagos archipelago, Heleno et al. (2011) found similarly high proportions of endemic frugivores in the species pool (71%), underlining the importance of endemic frugivores for island communities. By contrast, only a few species in the dataset were classified as introduced to the Caribbean (16% plants and 8% frugivores), which was lower than other studies on island ecosystems. Notably on Hawai'i, the proportion of introduced seed disperser species ranged from 50% to 100% for plants and from 60% to 100% for birds (Vizentin-Bugoni et al., 2019). On the Galapagos, the proportion of introduced plants and frugivores was 28% and 23%, respectively (Heleno et al., 2011). However, on the Galapagos, all introduced frugivore species were mammals, whereas in our data, the vast majority of introduced species were birds (86%) and only two species (14%) were mammals (a primate: Chlorocebus pygerythrus and a carnivore: Herpestes javonicus).4.2 Cross-island patterns of shared species and interactionsWhen examining the role of different groups of plants and frugivores in connecting islands and archipelagos, we found that nonendemic native species and interaction pairs were shared most widely across islands (Figure 2), which is expected, as these species are widespread species occurring throughout the Caribbean and the Neotropical mainland. They are thus supposedly good dispersers, and their ranges often occur across multiple islands and cross-borders of archipelagos (Dalsgaard et al., 2014). Although endemic frugivores made up more than 60% of the frugivore species, generally they overlapped much less between islands compared to nonendemic natives, which only accounted for less than 30% of the frugivores in the data (Table 2). This pattern is not surprising, since the distributional ranges of endemic species are per definition confined within limited geographical areas (Kricher, 2011), many species being single-island endemics or occurring on few islands within each of the archipelagoes, that is the Lucayan archipelago, the Greater and Lesser Antilles (Dalsgaard et al., 2014). In the Caribbean, for instance, there is a high number of single-island endemic frugivorous birds, such as various species of parrots like the Saint Vincent Parrot Amazona guildingii (Birds Caribbean, 2021). Introduced plant species were shared widely across the Caribbean (Figure 2), which was expected, as most were agricultural and widely cultivated plants, reflecting that the Caribbean is historically heavily impacted by humans (Kemp et al., 2020; Walters & Hansen, 2013). By contrast, introduced frugivores were reported on few islands only (Table 2), and these islands shared mostly low proportions of introduced frugivores (Table S4); introduced interaction pairs were almost not shared between islands. Globally, a recent study showed how introduced species caused an increase in the proportion of regions sharing species and interactions (Fricke & Svenning, 2020), demonstrating that species introductions led to increasing similarity and homogenization in plant–frugivore communities across the world (Fricke & Svenning, 2020). In the Caribbean, however, given our data, especially nonendemic natives played a bigger role in interconnecting islands.4.3 Modularity of the Caribbean plant–frugivore meta-networkThe Caribbean plant–frugivore meta-network was organized in modules, as are most mutualistic plant–animal interaction networks, both local networks (e.g. Dalsgaard et al., 2013; Dupont & Olesen, 2009; Mello et al., 2011a, 2011b; Olesen et al., 2007) and meta-networks (Araujo et al., 2018; Emer et al., 2018; Martín González et al., 2018). The separation of the meta-network into modules was at least partly driven by functional or taxonomic (i.e. modules dominated by certain species groups) and biogeographical (i.e. island-specific modules) mechanisms. For instance, one module consisted of small- to medium-sized bird species recorded in Jamaica (100% birds; 88% of frugivores recorded in Jamaica; module nine in Figure 4). Another module consisted mostly of various bat species (63% bats) recorded in Cuba (88% of frugivores recorded in Cuba; module one in Figure 4), whereas another module consisted almost exclusively of rock iguanas (Cychlura spp.) found in the Bahamas only (88% Iguanas; 88% of frugivores were recorded on the Bahamas only; module 13 in Figure 4). These modules associated with specific functional/taxonomic groups or specific islands were thus positioned in the periphery of the Caribbean meta-network (Figure 3). The separation into modules according to biogeographical affinities, such as single islands, was expected given that interactions between plants and frugivores are inherently spatial as species must be in the same place to interact (Morales & Vázquez, 2008) and many species are restricted to specific islands. Spatial patterns that correspond to insularity in the broad sense have previously been shown to partially explain the modular structure of mutualistic plant–animal networks in landscape matrices, where species are restricted to different types of patchily distributed habitats (Maruyama et al., 2014). Patterns of modularity have also previously been suggested to be explained by behavioural or functional traits of species (Dicks et al., 2002; Donatti et al., 2011; Maruyama et al., 2014). In plant–frugivore interactions, although plants typically aim to attract functionally diverse seed dispersers (Plein et al., 2013), there is evidence of functional matching between interaction partners, especially with birds (Vollstädt et al., 2017). Morphologically different frugivore species tend to forage on morphologically distinct sets of plant species (Dehling et al., 2016; Gautier-Hion et al., 1985; Lomáscolo et al., 2010; Mello et al., 2011b), which might be reflected in the modules composed primarily of specific frugivore groups with characteristic morphological and functional traits. Bats, for instance, consume different types of fruits than birds and may show a clear separation in their dietary composition (Gorchov et al., 1995). The patterns of modularity we detected were therefore in line with expectations of functional/taxonomic and biogeographical mechanisms as drivers of modularity. However, there were also modules consisting of a mix of species from various islands. One module consisted of about 50% of large parrot species (Amazona spp.), but the frugivores were recorded in the entire Caribbean (module six in Figure 4) and, notably, the module in the centre of the Caribbean meta-network consisted of various types of frugivores occurring throughout the Caribbean, thereby interconnecting islands and archipelagos in the Caribbean meta-network (module seven; Figure 3 and Table S5).4.4 Interactions with introduced speciesRegarding how introduced species were integrated into the meta-network, we found that nonendemic native and endemic plants and frugivores interacted significantly less with introduced frugivore species than expected at random (Figure 4a,b). Among Caribbean frugivores and their fruiting plants, there is therefore no support for the idea that endemic super-generalists are the main facilitators of introduced species, as suggested for pollination networks on tropical islands (Olesen et al., 2002). On the contrary, introduced frugivores were recorded interacting with introduced plants significantly more often than expected at random (Figure 4c). This pattern suggests that introduced frugivores “prefer” to feed on introduced plants, which in turn suggests the presence of “invader complexes,” that is introduced species interacting more among themselves than expected at random, thus facilitating their establishment (D'Antonio & Dudley, 1993). Such facilitation processes between introduced species can lead to “invasional meltdowns,” as large groups of introduced species may have increasingly negative impacts on native communities (Jeschke et al., 2012; Simberloff & von Holle, 1999). Other island ecosystems have been found to be even more dominated by introduced frugivores, notably Hawai'i is almost exclusively dominated by introduced frugivores, as most of the endemic species have gone extinct (Vizentin-Bugoni et al., 2019; Vizentin-Bugoni et al., 2021). These findings from various archipelagos are concerning, regarding the potential impact of introduced species on native ecosystems. Such findings are particularly worrying when considering that on other island ecosystems, introduced species were also more often involved in seed-dispersal interactions (rather than seed/pulp predation) than native species (Heleno et al., 2011; Vizentin-Bugoni et al., 2019, 2021). For many of the interaction records, our data do not distinguish between seed-dispersal interactions or seed/pulp predation events; thus, it is not possible to estimate the effect of introduced species on local native and endemic plant communities in the Caribbean. Nevertheless, in Hawai'i, it was shown that introduced frugivores do not sufficiently replace the species roles of lost seed dispersers, since they preferentially disperse seeds of introduced rather than native plants (Vizentin-Bugoni et al., 2019). This raises the question why introduced plant species seem so attractive. One reason could be that introduced plants may have specific traits, such as longer fruiting duration, which increase the probability of encounters and are therefore more likely to be consumed by frugivores (Heleno et al., 2011; Sperry et al., 2021). In the Caribbean meta-network, many of the observations were from agricultural areas, where agricultural plants such as Mangifera indica (Mango) are often abundant with large crops, and although they are not dispersed by any native frugivore, they do overall attract many frugivores. Fruiting plant and thus resource abundance is in turn linked to increased fruit consumption, because frugivores often track available fruits in the landscape (Quitián et al., 2019), and consequently, the patterns we find may be partially driven by the high abundance of introduced agricultural plants and their crop sizes in human-dominated environments. Such patterns may be more pronounced on densely populated islands than on islands with few people and relatively more protected areas.In addition to “invader complexes,” we found that generalist species, that is species with many interaction partners, were more likely to interact with introduced species, which was consistent for both plants and frugivores (Figure S2a,b). These results are in line with previous findings, underlining the importance of highly generalized species for the establishment of introduced species, especially on islands (Maruyama et al., 2016). This gives support for the “preferential attachment” hypothesis (Newman, 2001), that is that species with wide ecological niches include and facilitate the establishment of new species, such as introduced species on islands. Our finding that generalized species do not have a higher proportion of interactions with introduced partners in their total set of interactions than specialized species (Figure S2c,d) reflects the overall low numbers of introduced species in the Caribbean data. Since only few of the potentially available interaction partners are introduced species, generalized species with many interaction partners would also be expected to have a decreasing proportion of their interactions with introduced species. Thus, although generalized species are likely to incorporate introduced species into their niche (Figure S2a,b), they do not have a specific preference for introduced species (Figure S2c,d).5 CONCLUSIONSBased on a comprehensive review of accessible data on plant–frugivore interactions, we showed that the Caribbean meta-network is structured into modules and demonstrate how introduced species are integrated into native communities in the Caribbean archipelago. These results provide valuable insight into plant–frugivore interactions in insular biodiversity hotspots, showing how insular plant–frugivore systems are susceptible to invasion. Future studies are needed to demonstrate the importance of introduced species as seed dispersers compared with seed/pulp predators (Nogales et al., 2017). Specifically, research quantifying the relative importance of different frugivore groups as seed dispersers and their respective effectiveness is lacking for most plant–frugivore interactions in the Caribbean. This would provide valuable information and could help with the conservation of endemic plants in the Caribbean archipelago. Moreover, we also in general lack information on frugivory in the Caribbean. Kim et al. (2022) reported 4336 species of plants with animal-dispersal syndromes in the Caribbean archipelago, and our dataset represents only 11% of those species with some regional variation (Table S6). For instance, whereas Puerto Rican plants were covered relatively well (31% of the species), plants in Hispaniola (approx. 7%), Jamaica (approx. 8%) and the Lesser Antilles (approx. 9%) were less well represented. There may also be taxonomical differences in sampling completeness. Palms (Arecaceae) are highly diverse in the Caribbean representing 135 species (Roncal et al., 2008), and our dataset had only 23 palm species (17%). Several endemic and highly threatened fleshy-fruited plants do not have any information on the main seed dispersers (e.g. Catesbea spinosa, Brunfelsia portoricensis, Diospyros spp. and many cactus species). We also have limited and incomplete information on the fruit diet of several endemic frugivores (e.g. pigeons, thrashers and thrushes) that could play an important role for seed dispersal of Caribbean plants. There is therefore an urgent need to increment more scientific information on plant–frugivore interactions in the Caribbean, one of the world's insular biodiversity hotspots.ACKNOWLEDGEMENTSThis work is dedicated to our colleague and coauthor Michel Faife-Cabrera who passed away due to Covid-19 complications. M. Galetti thanks CNPq and University of Miami for financial support. M.G.R. Vollstädt, C. N. Kaiser-Bunbury, B. I. Simmons, F. Gonçalves, and B. Dalsgaard thank the Independent Research Fund Denmark (grant no. 0135-00333B). Funding for A. Strong's work was provided by an NSF grant to T. W. Sherry (Tulane University) and R. T. Holmes (Dartmouth College), the Chicago Zoological Society, Sigma Xi Grants-in-Aid-of Research, the World Nature Association, and The Louisiana Educational Quality Support Fund. A. Strong's work benefitted from collaborations with M. Johnson, T. Sherry, A. Sutton and the late R. Sutton. Funding for S. Schubert's work was provided by Rufford Foundation Small Grants 1, 2, & Booster, in addition to the Old Dominion University Paul W. Kirk Jr Student Research Award, a British Ornithologists' Union Student Research Award, and the BirdsCaribbean David S. Lee Fund. J. Salazar's work was funded by FONDOCyT. (Ministerio de Educaciòn Superior, Ciencia y Tecnología), Project 1B4-9. F. L. Tarazona-Tubens is supported by McKight Fellowship. B. I. Simmons was supported by a Royal Commission for the Exhibition of 1851 Research Fellowship. We also thank all researchers who have worked intensively in the Caribbean.CONFLICT OF INTERESTThe authors declare that there is no conflict of interest to report.Open ResearchSupporting InformationREFERENCESBIOSKETCHMaximilian Vollstädt is an ecologist, and a researcher at the University of Copenhagen, Denmark. His research interests include mutualistic interactions in plant-pollinator and plant-seed disperser communities in tropical island ecosystems.Author contributions: M.G.R.V., M.G., B.D. Conceptualization, Methodology; M.G.R.V., B.I.S. Formal analysis, Visualization; M.G.R.V., M.G., C.N.K.B., B.D. Original draft preparation, Writing; All Authors: Writing, Review & Editing.Volume28, Issue11November 2022Pages 2361-2374FiguresReferencesRelatedInformationRecommendedNatural mixing of species: novel plant–animal communities on Caribbean IslandsA. E. Lugo, T. A. Carlo, J. M. WunderleAnimal ConservationFrugivore distributions are associated with plant dispersal syndrome diversity in the Caribbean archipelagosSeokmin Kim, Lilian Sales, Daiane Carreira, Mauro GalettiDiversity and DistributionsInteractions between resource availability and enemy release in plant invasionDana M. BlumenthalEcology LettersHuman disturbances affect the topology of food websFrederico Mestre, Alejandro Rozenfeld, Miguel B. AraújoEcology LettersA general framework for species-abundance distributions: Linking traits and dispersal to explain commonness and rarityThomas Koffel, Kaito Umemura, Elena Litchman, Christopher A. Klausmeier