Co-occurrence of temperate and tropical Sinanodonta lineages in Iraq suggests converging invasion pathways in the Middle East
Freshwater mussels of the genus Sinanodonta , native to East Asia, are among the most successful invasive bivalves globally, known for their rapid reproduction and growth, broad environmental tolerances, and ability to disrupt aquatic ecosystems. Their arrival and subsequent spread in parts of the Middle East remains poorly documented. Here, we present new DNA-based evidence that confirms the invasion of Iraq’s freshwater ecosystems by two genetically distinct Sinanodonta lineages: Sinanodonta woodiana and Sinanodonta pacifica . Using COI DNA sequences, we confirm the co-occurrence of these lineages in southern Iraq, a pattern not previously reported in any Middle Eastern country. The two invasions appear to result from independent introduction pathways, both through their obligatory parasitic larvae on fish: aquaculture of East Asian carp ( S. woodiana ), and the ornamental fish trade or tilapia farming ( S. pacifica ). This discovery raises significant ecological concerns, as the dual invasion may further threaten Iraq’s already declining native mussel fauna, particularly the endemic and potentially extirpated Anodonta vescoiana . Our findings highlight Iraq as an emerging hotspot for freshwater biological invasions, likely driven by its growing and largely unregulated fish farming industry. This underscores the urgent need for targeted genetic monitoring, risk assessments, and biosecurity measures to prevent further spread and ecological impact.