The ambiguity of "hybrid swarm": inconsistent definitions and applications in existing research

1Hybridization is common in wild taxa and often increases in frequency following anthropogenic disturbance to an environment. Next-generation sequencing techniques make genomic analysis of a large number of individuals feasible, vastly improving the analysis for and promoting a greater frequency of studies on hybridization. However, terminology surrounding hybridization can be inconsistent; in particular, the term "hybrid swarm" has been used extensively in the literature but lacks a consistent definition. In this paper, we conducted a comprehensive review of the literature that uses the term "hybrid swarm" in reference to hybridization between taxa and challenged putative definitions of the term. We found that the term "hybrid swarm" is used in a variety of contexts, including some contradictory to other literature, and that there is little consensus on what constitutes a hybrid swarm in terms of hybrid outcomes, frequency relative to disturbances, or duration of existence. We dissuade researchers from use of the term "hybrid swarm" and instead suggest more specific and clear terminology to describe aspects of hybridization. Consequently, we hope that this paper promotes consensus surrounding hybridization terminology and improves the quality of future research on hybridization.