Interpreting molecular evidence for biosecurity decision-making: Lessons from coconut rhinoceros beetle incursions in the Pacific.

Molecular and genomic tools are increasingly used in biosecurity to support early detection, diagnostics and reconstruction of invasion pathways. However, selecting an appropriate marker for the question being addressed is critical, and translating molecular evidence into operational decisions can be challenging. Over-interpretation of commonly used markers may lead to misleading conclusions about population structure, invasion history and management priorities. DNA barcoding remains valuable for species identification and initial haplotype assignment, but questions concerning invasion pathways, admixture and phenotypic variation require additional molecular and ecological evidence. Here, we use coconut rhinoceros beetle (Oryctes rhinoceros) incursions in the Pacific as a case study to highlight interpretive pitfalls and lessons for applying molecular and genomic tools in biosecurity and biological control. We synthesise evidence on the strengths and limitations of mitochondrial markers, particularly CoxI, for haplotyping and inference of population relationships, and show how incomplete sampling and simplified assays can obscure cryptic diversity and bias interpretation. We then examine factors that complicate interpretation of OrNV-based biocontrol outcomes, including diagnostic sensitivity, study design and environmental modulation of host-pathogen interactions. Overall, these examples show that molecular evidence is most informative when marker choice, biological validation and phenotypic data are aligned with the biosecurity question.