Abstract
The study of biological invasions of ecological systems has much to offer research on within–host (WH) systems, particularly for understanding infections and developing therapies using biological agents. Thanks to the ground-work established in other fields, such as community ecology and evolutionary biology, and to modern methods of measurement and quantification, the study of microbiomes has quickly become a field at the forefront of modern systems biology. Investigations of host-associated microbiomes (e.g. for studying human health) are often centred on measuring and explaining the structure, functions and stability of these communities. This momentum promises to rapidly advance our understanding of ecological networks and their stability, resilience and resistance to invasions. However, intrinsic properties of host-associated microbiomes that differ from those of free-living systems present challenges to the development of a WH invasion ecology framework. The elucidation of principles underlying the invasibility of WH networks will ultimately help in the development of medical applications and help shape our understanding of human health and disease.