Aims. The study of the adaptive potential of the germination patterns of invading species enables us to identify some traits linked with their capacity to colonize new sites, and to better understand their area of distribution. The aim of the present study is to determine the germination pattern of Ulex europaeus, a cosmopolitan invasive species, in relation to temperature and to explore its potential evolution in a tropical invaded region since its introduction from Europe. Methods. We studied the germination pattern of U. europaeus (the common gorse) to test both physical dormancy and germination capacity within the range of temperatures found in the native and invasive regions. To comprehend its germination pattern and its evolution, the rate and the speed of germination, as well as the percentage of seeds that mold during the experiment, have been compared between a native habitat, France and a habitat to which it has been introduced, the tropical island of La Reunion. Important findings. The results show that the gorse seeds possess a very high power of germination, the ability to germinate under a wide range of temperatures and confirm the physical dormancy of the seeds (caused by seed coat impermeability).The decrease in germination from 25ºC upwards, coupled with an increase in the rate of moulding help to explain its restricted distribution at altitude in tropical environments. For scarified seeds, we have not detected any difference between the two regions, neither in the percentage of germinated seeds, nor in the percentage of mould seeds. However, seeds from Réunion germinate faster at 20ºC than seeds from France. For unscarified seeds … and a greater number of seeds from Réunion are able to germinate without scarification (10-60 % for Reunion vs 0-10 % for France). These results suggest that whilst preserving the advantages of the native habitat, in Réunion gorse develops a strategy which favours the rapid occupation of new sites.

Species presently considered as invasive were often deliberately introduced. Which factors led them from being desired to being denounced and what trajectory did such a transition follow? Using the case of common gorse (Ulex europaeus) on Reunion Island, the aims of this study were first, to identify and describe the different status that were attributed to this species since its introduction; and second, to discern the factors that influenced their emergence and decline in the public sphere. Five types of status were identified for common gorse in Reunion (useful, nationalistic, indigenized, noxious weed, and invasive), each peaking at a certain time, and then reverting to a low-key presence. The emergence and dissemination of each status in the public sphere depends on how well the various narratives proposed about the plant by networks of legitimate actors match the socio-technical landscape, as well as on how these narratives appear within legal and institutional frameworks. In addition, translating a status into actions of management can bolster its trajectory in the public sphere. Lastly, the decline of a status can be explained by a gradual desynchronization between its cognitive, normative and/or instrumental dimensions and the local socio-technical landscape.

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This study analyzes the natural and social factors influencing the emergence and publicization of the invasive status of a fast-growing bush, gorse (Ulex europaeus), by comparison between countries on a global scale. We used documents collected on the web in a standardized way. The results show that in all the countries studied, there are several public statuses attributed to gorse. The invasive status is the one that is most shared. The other most frequently encountered status are those of noxious weed, and those of which are economically useful. The invasive status is publicized in nearly all countries, including those where gorse is almost absent. We quantified the publicization of the invasive gorse status of gorse by an indicator with 5 levels, and then performed a multivariate analysis that combines natural and social explanatory variables. The results lead us to propose the concept of invasive niche, which is the set of natural and social parameters that allow a species to be considered invasive in a given socio-ecosystem

Histoire humaine et naturelle d'une invasion biologique L'ajonc d'Europe sur l'île de La Réunion Human and natural history of a biological invasion: Gorse on Reunion Island

Évolution des usages de l'ajonc dans ses régions d'origine ou envahies : quels impacts sur sa dynamique et sa gestion ?-L'introduction et l'expansion géographique des espèces invasives, comme leur régression, suivent souvent des processus où le rôle de l'Homme est central. C'est le cas de l'Ajonc d'Europe (Ulex europaeus) qui a été introduit volontairement dans plus de 30 pays différents, et est considéré comme l'une des « 100 of the world's worst invasive species » par l'UICN. Dans sa zone d'origine (principalement Grande-Bretagne, Bretagne, et Galice), il n'est pas perçu comme problématique car il fait l'objet d'une gestion régulière et efficace. L'ajonc y a longtemps servi d'auxiliaire agricole, fournissant notamment du fourrage, et les pratiques de gestion se sont développées parallèlement à ces usages. Cependant, la plupart de ces pratiques et usages n'ont pas été transposés dans les zones introduites. Notre étude a pour but de décrire l'évolution des usages et pratiques de gestion traditionnels et contemporains des ajoncs dans les zones d'origine comme dans les zones envahies, afin d'une part de retracer l'histoire et les motivations de son introduction de par le monde, d'autre part de proposer des pratiques de gestion novatrices et durables. Pour cela, nous avons été amenés à reparcourir les représentations et usages de la plante en zones d'origine comme en zones envahies. Les données historiques et contemporaines ont été recueillies par des recherches bibliographiques et documentaires. Nous avons également effectué un focus sur une zone d'origine (la Bretagne), et une zone envahie (l'île de La Réunion), à l'aide d'enquêtes par entretiens. Nous avons ainsi pu retracer le panorama des usages agricoles des ajoncs, les motivations de son introduction dans l'empire colonial européen, la perte progressive de ces usages, et les techniques contemporaines de contrôle. Nous avons également montré que les usages traditionnels de la plante et ses vertus demeurent connus dans la zone d'origine : les agriculteurs témoignent d'un intérêt pour tenter de recycler ses qualités fourragères, et les partenaires institutionnels et industriels pour en faire une ressource commercialisable (combustible, fourrage, fertilisant). On observe également des essais pour des innovations de gestion, dans les espaces naturels, comme dans les espaces agricoles. Ces travaux suggèrent des innovations possibles, ainsi que leurs limites, pour les zones envahies.SUMMARY.-The introduction and geographic expansion of invasive species, as well as their possible decline, often follow processes in which humans play a central role. This is the case for gorse (Ulex europaeus), which was intentionally introduced into more than 30 countries and is considered as one of the "100 of the world's worst invasive species" by the IUCN. Within its native range (Western Europe), it is very widespread in Great Britain, Brittany and Galicia, but it is not seen as a problem there as it is routinely and effectively managed. Gorse has long been used for agricultural pu...

Background and aims-Large, persistent seed banks contribute to the invasiveness of non-native plants, and maternal plant size is an important contributory factor. We explored the relationships between plant vegetative size (V) and soil seed bank size (S) for the invasive shrub (Ulex europaeus) in its native range and in non-native populations, and identified which other factors may contribute to seed bank variation between native and invaded regions.  Methods-We compared the native region (France) with two regions where Ulex is invasive, one with seed predators introduced for biological control (New Zealand) and another where seed predators are absent (La Réunion). We quantified seed bank size, plant dimensions, seed predation, and soil fertility for six stands in each of the three regions.  Key results-Seed banks were 9 to 14 times larger in the two invaded regions compared to native France. We found a positive relationship between current seed bank size and actual plant size, and that any deviation from this relationship was probably due to large differences in seed predation and/or soil fertility. We further identified three possible factors explaining larger seed banks in non-native environments: larger maternal plant size, lower activity of seed predators and higher soil fertility.  Conclusions-In highlighting a positive relationship between maternal plant size and seed bank size, and identifying additional factors that regulate soil seed bank dynamics in non-native ranges, our data offer a number of opportunities for invasive weed control. For non-native Ulex populations specifically, management focusing on 'S' (i.e. the reduction of the seed bank by stimulating germination, or the introduction of seed predators as biological control agents), and/or 'V' (i.e. by cutting mature stands to reduce maternal plant biomass) offers the most probable combination of effective control options.

The incessant pollution of land and water by crude oil and petroleum products in the Niger Delta region of Nigeria poses significant threats to its ecosystem. This region is known for its increasing oil spills because of its large oil deposits and growing oil and gas related industrial activities. Cases of unattended oil spills are also prevalent in these regions which have resulted in the persistence of large amounts of oil in the affected soils thus requiring effective ways of oil removal. It has been reported that these sites are poorly and most often never investigated to know the extent of contamination and as a result there is high possibility of accumulation of these pollutants in these affected areas. This paper, however, seeks to address this problem by giving an insight into some of the major causes of oil spill occurrences within NPDC Operational areas in Edo, Delta, Bayelsa and Port-Harcourt regions of the Niger Delta. Oil Spill data analysis done for the past 6 years (2011 to 2016) revealed that third party interferences which include sabotage, vandalism and crude oil theft accounted for 74.4% of the spillages within these regions. While 25.3% of spillages occurred due to corrosion, equipment failure and human error, less than 1% was ascribed to unknown and unidentifiable causes. Out of the estimated 44, 034.35 barrels of oil involved during these periods, about 37,279.84 barrels (approximately 85%) constituted the amount spilled through vandalism ranging from activities such as the use of hacksaw, dynamites and explosives on pipelines; and crude oil theft through hot tapping and illegal oil bunkering. The most prevalent vandalism occurrence was recorded along the Trans Forcados export pipeline axis within (OML 30) Delta State, a marine and seasonal swamp terrain.