Species boundaries in the Himantura uarnak species complex (Myliobatiformes: Dasyatidae)

Samples of the 'Himantura uarnak' species complex (H. leoparda, H. uarnak, H. undulata under their current definitions), mostly from the Coral Triangle, were analyzed using nuclear markers and mitochondrial DNA sequences. Genotypes at five intron loci showed four reproductively isolated clusters of individuals. The COI sequences showed four major mitochondrial lineages, each diagnostic of a cluster as defined by nuclear markers. No mitochondrial introgression was detected. The average Kimura-2 parameter nucleotide distance separating clades was 0.061-0.120 (net: 0.055-0.114), while the distance separating individuals within a clade was 0.002-0.008. Additional, partial cytochrome-b gene sequences were used to link these samples with previously published sequences of reference specimens of the three nominal species. One of the clusters was identified as H. undulata and another one, as H. uarnak, while two cryptic species were uncovered within the recently-described H. leoparda, challenging the current morphology-based taxonomy of species within the H. uarnak species complex.