Population structure of Manta birostris (Chondrichthyes:Mobulidae) from the Pacific and Atlantic oceans

Abstract

Sequence variation was examined in the circumtropical and highly vagile manta ray, Manta birostris, from the western and eastern Pacific oceans and the Gulf of Mexico to investigate the systematics and population structure of Manta. The entire coding region of the mitochondrial (mt) DNA molecule was sequenced for a single individual from Yap, Micronesia, and was similar in size and gene order as most other vertebrates. The control region was amplified and was three times larger than reported in other elasmobranchs. Direct sequencing revealed repeats in the 3' and 5' ends of the control region. The 3' repeat was sequenced for fifty-five mantas and a single individual of Mobula kuhlii. Manta repeats ranged in size from 61 to 312 bp, while the Mobula had a 143 bp region homologous to the repeat location in Manta but which contained unique sequence. The 5' repeat was sequenced for five mantas and a single individual M. kuhlii and Mobula munkiana. All mantas had 31 bp perfect repeats that could not be completely sequenced. M. kuhlii had a long series of imperfect repeats, and M. munkiana had 20 units of a 13 bp perfect repeat. No variation was found in an 862 bp fragment of cyt b and tRNA[] among mantas collected from four locations over an area spanning most of the western Pacific. Sequence variation among samples using a 2626 bps of ND-5, ND-6, and cyt b revealed a lack of genetic divergence among mantas from the western Pacific, and significant population structure among mantas from the western Pacific, eastern Pacific, and Gulf of Mexico. The presence of two individuals in the Gulf of Mexico possessing haplotypes similar to the eastern Pacific suggests integration of eastern Pacific mantas into the western Atlantic prior to the closure of the Isthmus of Panama. The rate of molecular divergence was calculated and appears to be significantly slower than in other species.