Taxonomic review, phylogeny, and geographical population structure of the sawfishes (Chondrichthyes, Pristiformes)

Sawfishes (Pristidae) are considered endangered species worldwide, but their conservation and management have been undermined due to poor understanding of the group's natural taxonomy. The main purpose of this work was to review the taxonomy of sawfishes based on historical taxonomic literature supplemented with empirical observations on morphology, genetics, and geographic distribution. A molecular phylogenetics study based on both mitochondrial and nuclear genes was carried out to estimate the evolutionary interrelationships among the different species of sawfishes. Seven distinct living species are recognized based on external morphology and DNA sequence comparisons. Four are distributed in the Indo-West Pacific, two in the Atlantic, and one in the East Pacific. The phylogeny obtained suggests Anoxypristis cuspidata (Latham 1794) is sister to monophyletic Pristis. The later is further divided into two clades: (1) P. clavata Garman 1906 basal to sister species P. zijsron Bleeker 1851 and P. pectinata Latham 1794, and (2) P. zephyreus Jordan & Starks 1895 basal to sister species P. microdon Latham 1794 and P. perotteti Muller & Henle 1841. Population structure within species was investigated based on mitochondrial DNA sequence data. Results indicate that Western and Eastern Atlantic populations of P. pectinata and P. perotteti should be viewed as separate units for conservation purposes. The pattern for the Indo-West Pacific was less clear. It is not possible to invoke a mechanism of isolation that applies to all species. Nevertheless, a sub-division of sawfish populations into Indian and West Pacific conservation units is consistent with both the patterns of nucleotide variation and variation in rostral tooth count.; Pristis pristis (Linneaus 1758) cannot be assigned to a single species. The nominal species P. pristis has historically been associated with features from several different species and as such is a chimaeric taxon that does not exist in nature. This has caused confusion in the past and in the present time. Herein, I propose the name P. pristis be suppressed.