Background
The genus Lates occurs both in African freshwaters and broadly across the Indo-Pacific. Lates calcarifer (Bloch 1790) was long-considered to be the sole Indo-Pacific representative of the genus, with a type locality of Tamil Nadu, India. Katayama & Taki 1984 added a second species, L. japonicus, from the western North Pacific. More recently, two species were described from the Indian Ocean in Sri Lanka – L. lakdiva Pethiyagoda & Gill 2012 – and Myanmar – L. uwisara Pethiyagoda & Gill 2012. These newer species are indicated to be regional endemics closely related to L. calcarifer. Molecular techniques have strongly supported the recognition of L. japonicus and shown a clear division Indian Ocean and Pacific Ocean fishes within a L. calcarifer species complex. First evidenced by mitochondrial barcoding, subsequent genomic analyses have clearly substantiated the separation of Indian Ocean and Pacific Ocean fish.
Methods
Our ongoing taxonomic studies are aimed at addressing the observed separation of the Indian Ocean and Pacific Ocean lineages in the L. calcarifer species complex, including associated nomenclatural issues. The oldest available name for the Pacific Ocean lineage is Pseudolates cavifrons Alleyne & Macleay 1877, but Pethiyagoda & Gill (2012) were unable to find the holotype of the species, which was collected from either the Torres Strait or the southeast coast of New Guinea. A comprehensive molecular data set that addresses all nominal species has also been lacking.
Results
We have recently rediscovered the holotype of Pseudolates cavifrons, which will allow proper consideration of the nominal species as the potential name for the Pacific Ocean lineage. We present genomic sequence data from a broad representation of fishes within the L. calcarifer species complex including L. lakdiva and the type specimens of L. uwisara.
Conclusions
Genomic sequence data from the L. calcarifer species complex indicate a western Indian subcontinent genetic grouping within the broader Indian Ocean lineage. Within the Pacific Ocean lineage, Southeast Asian, Wallacean, and Australasian phylogroups are evident. Chromosomal inversions on three chromosomes may be important sources of adaptive variation or have roles in the maintenance of species boundaries within the L. calcarifer species complex.