An Odyssey of Integrative Taxonomy Unveils Marine Fish Diversity, New Records and Cryptic Species in Malaysian Waters.

This study elucidates the species diversity of marine fishes in the Exclusive Economic Zone (EEZ) of Peninsular Malaysia (PM) using an integrative approach combining DNA barcoding and morphological identification. Our focus was on demersal surveys conducted on the east coast of PM in the South China Sea. We re-evaluated the diversity of 475 specimens across 93 putative species (92 barcoded morphospecies), from 16 orders and 41 families, including two IUCN vulnerable species. A total of two species - and - are presented as new record, and three species - , and - as the first specimen-based records in Malaysian waters. Cytochrome oxidase subunit I () sequence analyses delineated 95 consensus Molecular Operational Taxonomic Units (MOTUs), exceeding morphological diversity. Interestingly, the barcode analysis revealed several MOTUs delimited within one morphologically identified fish species, with both intraspecific and interspecific genetic divergences exceeding 2%, indicating substantial intraspecific genetic divergence within species groups or the existence of morphologically cryptic species within our dataset. These findings highlight the complexity of species delimitation and the value of genetic methods. Our study provides valuable insights into marine fish diversity from the east coast of Peninsular Malaysia and enhances our understanding of genetic diversity, distribution, and conservation needs of ecosystems through DNA barcoding. By integrating DNA barcoding with morphology, we present a comprehensive framework for future research to develop conservation and management strategies for Malaysia's marine biodiversity. The expansion of the genetic barcode database generated in this study will facilitate future molecular taxonomy research.