Novel organisms: comparing invasive species, GMOs, and emerging pathogens

Abstract

Invasive species, range-expanding species, genetically modified organisms (GMOs), synthetic organisms, and emerging pathogens increasingly affect the human environment. We propose a framework that allows comparison of consecutive stages that such novel organisms go through. The framework provides a common terminology for novel organisms, facilitating knowledge exchange among researchers, managers, and policy makers that work on, or have to make effective decisions about, novel organisms. The framework also indicates that knowledge about the causes and consequences of stage transitions for the better studied novel organisms, such as invasive species, can be transferred to more poorly studied ones, such as GMOs and emerging pathogens. Finally, the framework advances understanding of how climate change can affect the establishment, spread, and impacts of novel organisms, and how biodiversity affects, and is affected by, novel organisms.

Fig. 1

Proposed framework for comparing novel organisms. Invasive species, range-expanding species, GMOs, synthetic organisms, and emerging pathogens go through consecutive stages drawn as framed boxes. For example, transport, release, establishment, and spread for invasive species. The process can be stopped at each transition between two stages (drawn as thick white arrows), for example, a pathogen that has jumped to and replicated within a novel host (stage 2) may not establish itself in the novel host (e.g., Lyme disease with humans as novel host species). Those species that are released or established, and especially those that have spread can have severe environmental and economic impacts (yellow arrows), for example, by influencing biodiversity. To improve clarity, range-expanding species are not depicted explicitly. They are similar to invasive species, except they are not transported to a non-native range and released there, but instead are naturally dispersing to a non-native range where climate change may facilitate their establishment and spread. Blue (for GMOs) and red (for pathogens) arrows starting from different stages and pointing to the transport stage of invasive species illustrate that both GMOs and pathogens can become invasive, too: they can be transported beyond the region where they were first produced (GMOs) or where they first jumped to and replicated within a novel host (emerging pathogens). The probability that they will be transported beyond this region increases with their abundance, so it is higher for later stages of their processes (establishment and spread). Arrows pointing at the jump-to-novel-host stage of emerging pathogens illustrate that GMOs can serve as novel hosts (blue arrows) and that emergent pathogens can be a source for further novel pathogens (red arrows), again with higher probabilities in later stages of the processes. Invasive species can serve as novel hosts as well (not illustrated to improve the figure’s clarity). The grey-shaded boxes illustrate that altered climate and biodiversity affect probabilities of species to establish, spread, and have impacts. The effect of climate change is therefore both direct (because the new climate can, for example, better match a species’ fundamental ecological niche) and indirect (e.g., by reducing biodiversity). Biodiversity itself is also changed by impacts of novel organisms