A framework for predicting which non-native individuals and species will enter, survive, and exit human-mediated transport

Determining which non-natives are likely to be introduced is integral for understanding and predicting biological invasions. However, the hypotheses and research regarding invasive species have largely focused on processes occurring post-introduction. Improving predictions of non-native transport and generating new hypotheses about the drivers of species invasion requires a better understanding of the ‘pre-introduction’ mechanisms that determine whether propagules successfully enter, survive, and exit human vectors. We propose that the subset of non-natives successfully introduced are determined by two primary filtering mechanisms: (1) the characteristics of organisms, and the way in which these characteristics are shaped by and interact with their environment; and (2) the attributes, movement, and behavior of human vectors. We review how species distribution, individual phenotype, environmental conditions, and ecological interactions filter organisms between each pre-introduction stage of non-native transport. Additionally, we apply a modified version of the vector science framework to elucidate mechanisms driving patterns in human movements, which also determine the subset of individuals transported and introduced as non-natives. Our framework distills the human-mediated transport process to its most critical components, providing a simple approach for creating new hypotheses of the drivers of biological invasions.