Phylogeography of Sepioteuthis lessoniana (the bigfin reef squid) and Uroteuthis duvauceli (the Indian squid).

摘要

Sepioteuthis lessoniana (the bigfin reef squid) and Uroteuthis duvauceli (the Indian squid) are two squid species found in largely overlapping regions in the Indian and Pacific Oceans. While both squids are important to fisheries throughout their ranges, very little taxonomic work has been done on either of them. Previous studies have led scientists to believe that S. lessoniana is actually a species complex (for example, there appear to be three species of “S. cf. lessoniana” in Japanese waters alone). The similarly broad geographic range of U. duvauceli suggests that this species could also harbor substantial cryptic genetic diversity. In order to evaluate genetic variation within these two species, regions of two mitochondrial genes—the large subunit ribosomal RNA gene (16S) and the cytochrome oxidase I gene (COI)—from specimens caught in regions throughout the northern Indian and western Pacific Oceans were sequenced and compared. Sequences were obtained by extracting the DNA from tissue samples of both species, amplifying the DNA using the polymerase chain reaction (PCR), determining the sequences of both DNA strands using a automated DNA sequencer, and comparing sequences to one another to establish similarities and differences between geographic locations. To expand the significance of this study, we compared our sequences to data contributed by a collaborator (Samantha H. Cheng, Department of Ecology and Evolutionary Biology, UCLA) and data downloaded from GenBank (an online genetic database). Phylogeographic analyses showed that Sepioteuthis lessoniana from southern India represent two very distinct genetic lineages, suggesting that “S. cf. lessoniana” comprises at least two cryptic species in south Indian waters. For Uroteuthis duvauceli, specimens from Iran are genetically distinct from those in Thailand and Japan, which may support the hypothesis of several undescribed species within “U. cf. duvauceli”. This study is the first attempt to assess genetic diversity across the ranges of these two species; future work will require additional genetic markers and (most importantly) additional sampling from other geographic regions.