Is It a "Hybrid Swarm"? Opportunities for More Informative Terminology in Conservation Genomics

Hybridization is common in wild taxa, which may cause conservation concerns if hybridization occurs following disturbance or species introductions. High throughput DNA sequencing makes genomic analysis of many individuals feasible, vastly improving and promoting more studies on hybridization. However, more precise genomic identification of hybrids has not always extended to more precise use of terminology to describe hybrid ancestry. For hybridizing species of conservation concern, it is critical to understand hybridization dynamics precisely in order to effectively manage imperiled taxa. We conducted a review of 67 representative journal articles that use the term "hybrid swarm" in reference to hybridization, as variation in the usage of the term makes it difficult to understand which biological processes are being described. We found that "hybrid swarm" is used in several contexts across studies using various methods and numbers of genetic markers, reflecting vastly different statistical power and degrees of evidence for extensive hybridization. We encourage researchers working with genomic datasets to use clearer terminology when describing hybridization outcomes. We elaborate on scenario-specific terminology to strengthen uniformity in hybridization language, which we hope will promote more precise descriptions of hybridization and improve the clarity of future research on hybridization.