The genus Lasiodiplodia, a member of the family Botryosphaeriaceae, is an important fungal disease genus in agriculture. However, the Lasiodiplodia species survey and genetic diversity in Taiwan remain unclear. This study aimed to investigate the Lasiodiplodia species associated with various fruit species to explore the cryptic Lasiodiplodia species diversity, validate species delimitation, and unveil cryptic genetic diversity. Overall, six Lasiodiplodia species were identified, with several new records of infection identified. Additionally, phylogenetic analyses indicated that the relations of all isolates of L. theobromae might be paraphyletic. They were grouped with L. brasiliense based on Automatic Barcode Gap Discovery (ABGD), Automatic Partitioning (ASAP) and structure-based clustering analyses. These analyses did not provide conclusive evidence for L. brasiliensis as a stable species. It may be necessary to gather more information to clarify the species delineation. The multiple new records of Lasiodiplodia species with high genetic diversity and differentiation revealed that the diversity of Lasiodiplodia in Taiwan was underestimated in the past. We found that L. theobromae has the highest number of haplotypes but the lowest number of haplotype and nucleotide diversities, indicating a recent population expansion. This was supported by the significant negative Tajima's D and Fu and Li's D* tests. The high genetic diversity, low gene flow, and host-associated differentiation of Lasiodiplodia species indicate that they might harbour powerful evolutionary potential in Taiwan. This study provided critical insights into genetic variation, host-associated differentiation, and demography of Lasiodiplodia species, which would be helpful for disease management of related pathogens.
Keywords: Lasiodiplodia; genetic diversity; host-associated differentiation; phylogeny.