Untangling the colonization history of the Australo-Pacific reed warblers, one of the world's great island radiations.

This article focuses on resolving the complex evolutionary history of the Australo-Pacific reed warblers (Acrocephalus luscinius species complex), a widespread island radiation spanning over 10,000 km across Oceania, including the Mariana, Micronesia, and Polynesia archipelagos. By integrating mitochondrial genomes (mitogenomes) and genome-wide single nucleotide polymorphisms (SNPs) from both historical museum specimens and modern samples, the study reveals significant mitonuclear discordance shaped by incomplete lineage sorting (ILS) and gene flow rather than secondary sympatry. Notably, gene flow involving extinct and extant Mariana Islands species explains conflicting mitochondrial and nuclear DNA patterns, challenging previous hypotheses based solely on mtDNA. These findings have important conservation implications, suggesting that hybridization may play a role in maintaining genetic diversity and could be considered in management strategies for several threatened reed warbler species across the Pacific.