Towards global dominance of invasive alien plants in freshwater ecosystems: the dawn of the Exocene?

The global and seemingly unstoppable spread of invasive alien plants emerges as one of the main topics of current science. This is due to the multiple repercussions of invasive plants on biodiversity and ecosystem functioning, plus huge consequences on human existence. In freshwaters, lots of invaders are extremely competitive by virtue of their idiosyncratic reproductive and adaptive strategies. As "inland islands", freshwaters seem particularly prone to changes when invaded, such as reorganisation of food webs and biotic interactions. Together, these events are self-reinforcing, implying hardly reversible hysteric phenomena. The intention of this paper is to point out: invasion pathways, driving factors, invasion mechanisms, and noticeable effects mediated by plant invaders in freshwaters through an extensive knowledge review. The growing evidence suggests the dawn of a new epochal phase: a globally alien-dominated "bio-historical horizon", tentatively called "Exocene", where invaders play predominant roles that drive freshwaters functioning and successional unexpected stages. In the context of invasion science, Exocene reinforces the need for an ecosystem-based perspective to properly understand the implications of plant invaders in freshwaters. Seven challenging issues emerge to be addressed to better outline the global paths of biodiversity and functioning between biomes when faced with biological invasion.