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Globally, the cultivation area of genetically modified (GM) crops is increasing dramatically. Despite their well-known benefits, they may also pose many risks to agriculture and the environment. Among the various GM crops, GM rapeseed (Brassica napus L.) is widely cultivated, mainly for oil production. At the same time, B. napus possesses a number of characteristics, including the ability to form feral populations and act as small-seeded weeds, and has a high potential for hybridization with other species. In this review, we provide an overview of the commercialization, approval status, and cultivation of GM rapeseed, as well as the status of the feral rapeseed populations. In addition, we highlight the case studies on the unintentional environmental release of GM rapeseed during transportation in several countries. Previous studies suggest that the main reason for the unintentional release is seed spillage during transport/importing of rapeseed in both GM rapeseed-cultivating and -non-cultivating countries. Despite the fact that incidents of unintentional release have been recorded often, there have been no reports of serious detrimental consequences. However, since rapeseed has a high potential for hybridization, the possibilities of gene flow within the genus, especially with B. rapa, are relatively significant, and considering their weedy properties, effective management methods are needed. Hence, we recommend that specific programs be used for the effective monitoring of environmental releases of GM rapeseed as well as management to avoid environmental and agricultural perturbations.

Mink farming has seen a resurgence in Bulgaria since 2013, and this has led to a high risk of American mink escaping and establishing feral populations. The largest active commercial farm in the country has a capacity of nearly 130,000 animals. The aims of this study were to gather first-hand evidence of the presence of mink in the wild around the farm, assess their level of establishment, and document the native species and local communities for future impact assessment. Surveys were conducted using camera traps within a 3.7 km radius around the farm in the period 2020–2021 at ten stations with 1943 realised trap-nights. Some early signs of the establishment of the American mink in Bulgaria were documented. A large number of registrations was made, as frequently as the Eurasian otter and golden jackal and more frequently than other mustelids in the study area. Mink were observed throughout the two-year study, and escaped mink have been registered in the region as early as 2017. These factors are interpreted as signs of the early stages of establishment. When considering environmental, economic, public health, and social factors, we recommend that mink farming should be banned in Bulgaria and further monitoring and management actions must be undertaken for the individuals in the wild.

Introduced species, those dispersed outside their natural ranges by humans, now cause almost all biological invasions, i.e., entry of organisms into habitats with negative effects on organisms already there. Knowing whether introduction tends to give organisms specific ecological advantages or disadvantages in their new habitats could help understand and control invasions. Even if no specific species traits are associated with introduction, introduced species might out-compete native ones just because the pool of introduced species is very large (“global competition hypothesis”). Especially in the case of intentional introduction, high initial propagule pressure might further increase the chance of establishment, and repeated introductions from different source populations might increase the fitness of introduced species through hybridization. Intentional introduction screens species for usefulness to humans and so might select for rapid growth and reproduction or carry species to suitable habitats, all which could promote invasiveness. However, trade offs between growth and tolerance might make introduced species vulnerable to extreme climatic events and cause some invasions to be transient (“reckless invader hypothesis”). Unintentional introduction may screen for species associated with human-disturbed habitats, and human disturbance of their new habitats may make these species more invasive. Introduction and natural long-distance dispersal both imply that species have neither undergone adaptation in their new habitats nor been adapted to by other species there. These two characteristics are the basis for many well-known hypotheses about invasion, including the “biotic resistance”, “enemy release”, “evolution of increased competitive ability” and “novel weapon” hypotheses, each of which has been shown to help explain some invasions. To the extent that biotic resistance depends upon local adaption by native species, altering selection pressures could reduce resistance and promote invasion (“local adaptation hypothesis”), and restoring natural regimes could reverse this effect.