Moussab/ORKG-training-evaluation-set huggingface dataset:
Research field: Ecology and Evolutionary Biology
Title: The vulnerability of habitats to plant invasion: disentangling the roles of propagule pressure, time and sampling effort
Abstract: Aim To quantify the vulnerability of habitats to invasion by alien plants having accounted for the effects of propagule pressure, time and sampling effort. Location New Zealand. Methods We used spatial, temporal and habitat information taken from 9297 herbarium records of 301 alien plant species to examine the vulnerability of 11 terrestrial habitats to plant invasions. A null model that randomized species records across habitats was used to account for variation in sampling effort and to derive a relative measure of invasion based either on all records for a species or only its first record. The relative level of invasion was related to the average distance of each habitat from the nearest conurbation, which was used as a proxy for propagule pressure. The habitat in which a species was first recorded was compared to the habitats encountered for all records of that species to determine whether the initial habitat could predict subsequent habitat occupancy. Results Variation in sampling effort in space and time significantly masked the underlying vulnerability of habitats to plant invasions. Distance from the nearest conurbation had little effect on the relative level of invasion in each habitat, but the number of first records of each species significantly declined with increasing distance. While Urban, Streamside and Coastal habitats were over-represented as sites of initial invasion, there was no evidence of major invasion hotspots from which alien plants might subsequently spread. Rather, the data suggest that certain habitats (especially Roadsides) readily accumulate alien plants from other habitats. Main conclusions Herbarium records combined with a suitable null model provide a powerful tool for assessing the relative vulnerability of habitats to plant invasion. The first records of alien plants tend to be found near conurbations, but this pattern disappears with subsequent spread. Regardless of the habitat where a species was first recorded, ultimately most alien plants spread to Roadside and Sparse habitats. This information suggests that such habitats may be useful targets for weed surveillance and monitoring.
Extracted statement — hypothesis: Propagule pressure
Research field: Ecology and Evolutionary Biology
Title: Quarantine arthropod invasions in Europe: the role of climate, hosts and propagule pressure
Abstract: To quantify the relative importance of propagule pressure, climate‐matching and host availability for the invasion of agricultural pest arthropods in Europe and to forecast newly emerging pest species and European areas with the highest risk of arthropod invasion under current climate and a future climate scenario (A1F1).
Extracted statement — hypothesis: Propagule pressure
Research field: Ecology and Evolutionary Biology
Title: Propagule pressure and stream characteristics influence introgression: cutthroat and rainbow trout in British Columbia
Abstract: Hybridization and introgression between introduced and native salmonids threaten the continued persistence of many inland cutthroat trout species. Environmental models have been developed to predict the spread of introgression, but few studies have assessed the role of propagule pressure. We used an extensive set of fish Stocking records and geographic information system (GIS) data to produce a spatially explicit index of potential propagule pressure exerted by introduced rainbow trout in the Upper Kootenay River, British Columbia, Canada. We then used logistic regression and the information-theoretic approach to test the ability of a set of environmental and spatial variables to predict the level of introgression between native westslope cutthroat trout and introduced rainbow trout. Introgression was assessed using between four and seven co-dominant, diagnostic nuclear markers at 45 sites in 31 different streams. The best model for predicting introgression included our GIS propagule pressure index and an environmental variable that accounted for the biogeoclimatic zone of the site (r2=0.62). This model was 1.4 times more likely to explain introgression than the next-best model, which consisted of only the propagule pressure index variable. We created a composite model based on the model-averaged results of the seven top models that included environmental, spatial, and propagule pressure variables. The propagule pressure index had the highest importance weight (0.995) of all variables tested and was negatively related to sites with no introgression. This study used an index of propagule pressure and demonstrated that propagule pressure had the greatest influence on the level of introgression between a native and introduced trout in a human-induced hybrid zone.
Extracted statement — hypothesis: Propagule pressure
Research field: Ecology and Evolutionary Biology
Title: How many founders for a biological invasion? Predicting introduction outcomes from propagule pressure
Abstract: Ecological theory on biological invasions attempts to characterize the predictors of invasion success and the relative importance of the different drivers of population establishment. An outstanding question is how propagule pressure determines the probability of population establishment, where propagule pressure is the number of individuals of a species introduced into a specific location (propagule size) and their frequency of introduction (propagule number). Here, we used large-scale replicated mesocosm ponds over three reproductive seasons to identify how propagule size and number predict the probability of establishment of one of world's most invasive fish, Pseudorasbora parva, as well as its effect on the somatic growth of individuals during establishment. We demonstrated that, although a threshold of 11 introduced pairs of fish (a pair is 1 male, 1 female) was required for establishment probability to exceed 95%, establishment also occurred at low propagule size (1-5 pairs). Although single introduction events were as effective as multiple events at enabling establishment, the propagule sizes used in the multiple introductions were above the detected threshold for establishment. After three reproductive seasons, population abundance was also a function of propagule size, with rapid increases in abundance only apparent when propagule size exceeded 25 pairs. This was initially assisted by adapted biological traits, including rapid individual somatic growth that helped to overcome demographic bottlenecks.
Extracted statement — hypothesis: Propagule pressure
Research field: Ecology and Evolutionary Biology
Title: Short- and long-term effects of disturbance and propagule pressure on a biological invasion
Abstract: 1 Invading species typically need to overcome multiple limiting factors simultaneously in order to become established, and understanding how such factors interact to regulate the invasion process remains a major challenge in ecology. 2 We used the invasion of marine algal communities by the seaweed Sargassum muticum as a study system to experimentally investigate the independent and interactive effects of disturbance and propagule pressure in the short term. Based on our experimental results, we parameterized an integrodifference equation model, which we used to examine how disturbances created by different benthic herbivores influence the longer term invasion success of S. muticum. 3 Our experimental results demonstrate that in this system neither disturbance nor propagule input alone was sufficient to maximize invasion success. Rather, the interaction between these processes was critical for understanding how the S. muticum invasion is regulated in the short term. 4 The model showed that both the size and spatial arrangement of herbivore disturbances had a major impact on how disturbance facilitated the invasion, by jointly determining how much space‐limitation was alleviated and how readily disturbed areas could be reached by dispersing propagules. 5 Synthesis. Both the short‐term experiment and the long‐term model show that S. muticum invasion success is co‐regulated by disturbance and propagule pressure. Our results underscore the importance of considering interactive effects when making predictions about invasion success.
Extracted statement — hypothesis: Propagule pressure
Research field: Ecology and Evolutionary Biology
Title: Introduction history and species characteristics partly explain naturalization success of North American woody species in Europe
Abstract: 1 The search for general characteristics of invasive species has not been very successful yet. A reason for this could be that current invasion patterns are mainly reflecting the introduction history (i.e. time since introduction and propagule pressure) of the species. Accurate data on the introduction history are, however, rare, particularly for introduced alien species that have not established. As a consequence, few studies that tested for the effects of species characteristics on invasiveness corrected for introduction history. 2 We tested whether the naturalization success of 582 North American woody species in Europe, measured as the proportion of European geographic regions in which each species is established, can be explained by their introduction history. For 278 of these species we had data on characteristics related to growth form, life cycle, growth, fecundity and environmental tolerance. We tested whether naturalization success can be further explained by these characteristics. In addition, we tested whether the effects of species characteristics differ between growth forms. 3 Both planting frequency in European gardens and time since introduction significantly increased naturalization success, but the effect of the latter was relatively weak. After correction for introduction history and taxonomy, six of the 26 species characteristics had significant effects on naturalization success. Leaf retention and precipitation tolerance increased naturalization success. Tree species were only 56% as likely to naturalize as non‐tree species (vines, shrubs and subshrubs), and the effect of planting frequency on naturalization success was much stronger for non‐trees than for trees. On the other hand, the naturalization success of trees, but not for non‐trees, increased with native range size, maximum plant height and seed spread rate. 4 Synthesis. Our results suggest that introduction history, particularly planting frequency, is an important determinant of current naturalization success of North American woody species (particularly of non‐trees) in Europe. Therefore, studies comparing naturalization success among species should correct for introduction history. Species characteristics are also significant determinants of naturalization success, but their effects may differ between growth forms.
Extracted statement — hypothesis: Propagule pressure
Research field: Ecology and Evolutionary Biology
Title: Dealing with scarce data to understand how environmental gradients and propagule pressure shape fine-scale alien distribution patterns on coastal dunes
Abstract: Questions: On sandy coastal habitats, factors related to substrate and to wind action vary along the sea–inland ecotone, forming a marked directional disturbance and stress gradient. Further, input of propagules of alien plant species associated to touristic exploitation and development is intense. This has contributed to establishment and spread of aliens in coastal systems. Records of alien species in databases of such heterogeneous landscapes remain scarce, posing a challenge for statistical modelling. We address this issue and attempt to shed light on the role of environmental stress/disturbance gradients and propagule pressure on invasibility of plant communities in these typical model systems. Location: Sandy coasts of Lazio (Central Italy). Methods: We proposed an innovative methodology to deal with low prevalence of alien occurrence in a data set and high cost of field-based sampling by taking advantage, through predictive modelling, of the strong interrelation between vegetation and abiotic features in coastal dunes. We fitted generalized additive models to analyse (1) overall patterns of alien occurrence and spread and (2) specific patterns of the most common alien species recorded. Conclusion: Even in the presence of strong propagule pressure, variation in local abiotic conditions can explain differences in invasibility within a local environment, and intermediate levels of natural disturbance and stress offer the best conditions for spread of alien species. However, in our model system, propagule pressure is actually the main determinant of alien species occurrence and spread. We demonstrated that extending the information of environmental features measured in a subsample of vegetation plots through predictive modelling allows complex questions in invasion biology to be addressed without requiring disproportionate funding and sampling effort.
Extracted statement — hypothesis: Propagule pressure
Research field: Ecology and Evolutionary Biology
Title: Global patterns of introduction effort and establishment success in birds
Abstract: Theory suggests that introduction effort (propagule size or number) should be a key determinant of establishment success for exotic species. Unfortunately, however, propagule pressure is not recorded for most introductions. Studies must therefore either use proxies whose efficacy must be largely assumed, or ignore effort altogether. The results of such studies will be flawed if effort is not distributed at random with respect to other characteristics that are predicted to influence success. We use global data for more than 600 introduction events for birds to show that introduction effort is both the strongest correlate of introduction success, and correlated with a large number of variables previously thought to influence success. Apart from effort, only habitat generalism relates to establishment success in birds.
Extracted statement — hypothesis: Propagule pressure
Research field: Ecology and Evolutionary Biology
Title: Hotspots of plant invasion predicted by propagule pressure and ecosystem characteristics
Abstract: Aim Biological invasions pose a major conservation threat and are occurring at an unprecedented rate. Disproportionate levels of invasion across the landscape indicate that propagule pressure and ecosystem characteristics can mediate invasion success. However, most invasion predictions relate to species’ characteristics (invasiveness) and habitat requirements. Given myriad invaders and the inability to generalize from single‐species studies, more general predictions about invasion are required. We present a simple new method for characterizing and predicting landscape susceptibility to invasion that is not species‐specific.
Extracted statement — hypothesis: Propagule pressure
Research field: Ecology and Evolutionary Biology
Title: Effects of pre-existing submersed vegetation and propagule pressure on the invasion success of Hydrilla verticillata
Abstract: Summary 1 With biological invasions causing widespread problems in ecosystems, methods to curb the colonization success of invasive species are needed. The effective management of invasive species will require an integrated approach that restores community structure and ecosystem processes while controlling propagule pressure of non-native species. 2 We tested the hypotheses that restoring native vegetation and minimizing propagule pressure of invasive species slows the establishment of an invader. In field and greenhouse experiments, we evaluated (i) the effects of a native submersed aquatic plant species, Vallisneria americana, on the colonization success of a non-native species, Hydrilla verticillata; and (ii) the effects of H. verticillata propagule density on its colonization success. 3 Results from the greenhouse experiment showed that V. americana decreased H. verticillata colonization through nutrient draw-down in the water column of closed mesocosms, although data from the field experiment, located in a tidal freshwater region of Chesapeake Bay that is open to nutrient fluxes, suggested that V. americana did not negatively impact H. verticillata colonization. However, H. verticillata colonization was greater in a treatment of plastic V. americana look-alikes, suggesting that the canopy of V. americana can physically capture H. verticillata fragments. Thus pre-emption effects may be less clear in the field experiment because of complex interactions between competitive and facilitative effects in combination with continuous nutrient inputs from tides and rivers that do not allow nutrient draw-down to levels experienced in the greenhouse. 4 Greenhouse and field tests differed in the timing, duration and density of propagule inputs. However, irrespective of these differences, propagule pressure of the invader affected colonization success except in situations when the native species could draw-down nutrients in closed greenhouse mesocosms. In that case, no propagules were able to colonize. 5 Synthesis and applications. We have shown that reducing propagule pressure through targeted management should be considered to slow the spread of invasive species. This, in combination with restoration of native species, may be the best defence against non-native species invasion. Thus a combined strategy of targeted control and promotion of native plant growth is likely to be the most sustainable and cost-effective form of invasive species management.
Extracted statement — hypothesis: Propagule pressure
Research field: Ecology and Evolutionary Biology
Title: Propagule pressure and disturbance interact to overcome biotic resistance of marine invertebrate
Abstract: Propagule pressure is fundamental to invasion success, yet our understanding of its role in the marine domain is limited. Few studies have manipulated or controlled for propagule supply in the field, and consequently there is little empirical data to test for non-linearities or interactions with other processes. Supply of non-indigenous propagules is most likely to be elevated in urban estuaries, where vessels congregate and bring exotic species on fouled hulls and in ballast water. These same environments are also typically subject to elevated levels of disturbance from human activities, creating the potential for propagule pressure and disturbance to interact. By applying a controlled dose of free-swimming larvae to replicate assemblages, we were able to quantify a dose-response relationship at much finer spatial and temporal scales than previously achieved in the marine environment. We experimentally crossed controlled levels of propagule pressure and disturbance in the field, and found that both were required for invasion to occur. Only recruits that had settled onto bare space survived beyond three months, precluding invader persistence in undisturbed communities. In disturbed communities initial survival on bare space appeared stochastic, such that a critical density was required before the probability of at least one colony surviving reached a sufficient level. Those that persisted showed 75% survival over the following three months, signifying a threshold past which invaders were resilient to chance mortality. Urban estuaries subject to anthropogenic disturbance are common throughout the world, and similar interactions may be integral to invasion dynamics in these ecosystems.
Extracted statement — hypothesis: Propagule pressure
Research field: Ecology and Evolutionary Biology
Title: Propagule pressure and the invasion risks of non-native freshwater fishes: a case study in England
Abstract: European countries in general, and England in particular, have a long history of introducing non-native fish species, but there exist no detailed studies of the introduction pathways and propagules pressure for any European country. Using the nine regions of England as a preliminary case study, the potential relationship between the occurrence in the wild of non-native freshwater fishes (from a recent audit of non-native species) and the intensity (i.e. propagule pressure) and diversity of fish imports was investigated. The main pathways of introduction were via imports of fishes for ornamental use (e.g. aquaria and garden ponds) and sport fishing, with no reported or suspected cases of ballast water or hull fouling introductions. The recorded occurrence of non-native fishes in the wild was found to be related to the time (number of years) since the decade of introduction. A shift in the establishment rate, however, was observed in the 1970s after which the ratio of established-to-introduced species declined. The number of established non-native fish species observed in the wild was found to increase significantly (P < 0·05) with increasing import intensity (log10x + 1 of the numbers of fish imported for the years 2000–2004) and with increasing consignment diversity (log10x + 1 of the numbers of consignment types imported for the years 2000–2004). The implications for policy and management are discussed.
Extracted statement — hypothesis: Propagule pressure
Research field: Ecology and Evolutionary Biology
Title: The demography of introduction pathways, propagule pressure and occurrences of non-native freshwater fish in England
Abstract: 1. Biological invasion theory predicts that the introduction and establishment of non-native species is positively correlated with propagule pressure. Releases of pet and aquarium fishes to inland waters has a long history; however, few studies have examined the demographic basis of their importation and incidence in the wild. 2. For the 1500 grid squares (10×10 km) that make up England, data on human demographics (population density, numbers of pet shops, garden centres and fish farms), the numbers of non-native freshwater fishes (from consented licences) imported in those grid squares (i.e. propagule pressure), and the reported incidences (in a national database) of non-native fishes in the wild were used to examine spatial relationships between the occurrence of non-native fishes and the demographic factors associated with propagule pressure, as well as to test whether the demographic factors are statistically reliable predictors of the incidence of non-native fishes, and as such surrogate estimators of propagule pressure. 3. Principal coordinates of neighbour matrices analyses, used to generate spatially explicit models, and confirmatory factor analysis revealed that spatial distributions of non-native species in England were significantly related to human population density, garden centre density and fish farm density. Human population density and the number of fish imports were identified as the best predictors of propagule pressure. 4. Human population density is an effective surrogate estimator of non-native fish propagule pressure and can be used to predict likely areas of non-native fish introductions. In conjunction with fish movements, where available, human population densities can be used to support biological invasion monitoring programmes across Europe (and perhaps globally) and to inform management decisions as regards the prioritization of areas for the control of non-native fish introductions. © Crown copyright 2010. Reproduced with the permission of her Majesty's Stationery Office. Published by John Wiley & Sons, Ltd.
Extracted statement — hypothesis: Propagule pressure