Species delimitation in sharpnose sharks (genus Rhizoprionodon) in the western Atlantic Ocean using mitochondrial DNA

Abstract

Despite Springer's (1964) revision of the sharpnose sharks (genus Rhizoprionodon), the taxonomic definition and ranges of Rhizoprionodon in the western Atlantic Ocean remains problematic. In particular, the distinction between Rhizoprionodon terraenovae and R. porosus, and the occurrence of R. terraenovae in South American waters are unresolved issues involving common and ecologically important species in need of fishery management in Caribbean and southwest Atlantic waters. In recent years, molecular markers have been used as efficient tools for the detection of cryptic species and to address controversial taxonomic issues. In this study 415 samples of the genus Rhizoprionodon captured in the western Atlantic Ocean from Florida to southern Brazil were examined for sequences of the COI gene and the D-loop and evaluated for nucleotide differences. The results on nucleotide composition, AMOVA tests, and relationship distances using Bayesian-likelihood method and haplotypes network, corroborates Springer's (1964) morphometric and meristic finding and provide strong evidence that supports consideration of R. terraenovae and R. porosus as distinct species.

Phylogeography and genetic population structure of Caribbean sharpnose shark Rhizoprionodon porosus

“…Small tissue samples from each specimen were stored in ethanol (95%) and kept in the fish collection of Laboratório de Biologia e Genética de Peixes (LBP) of the Universidade Estadual Paulista UNESP (São Paulo, Brazil). The species-specific identification of all samples used in this study was confirmed with molecular methods described by Mendonça et al (2011).…”

“…In general, the rates of genetic distance had a tendency to increase according to the geographic distance of the populations. The possibility of incorrect identifications between R. terraenovae and R. porosus, which would lead to deviation of the population structure index, was solved by the observation of genetic divergences applying the criteria of differentiation presented by Mendonça et al (2011). Marine biogeographic barriers have been recognized for decades, and early researchers used breaks in the faunal composition and levels of endemism to designate geographic units or ''faunal provinces''.…”

“…Using the genetic methods developed by Mendonça et al (2011) to distinguish between R. terraenovae and R. porosus, no haplotype characteristics of R. terraenovae were found in the samples collected between the coasts of the Caribbean and southern Brazil. Furthermore, haplotypes corresponding to R. porosus were not found in the areas sampled in the Gulf of Mexico and eastern Florida.…”

“…Some authors have suggested that these species may have some degree of sympatry with R. terraenovae also located in South America (Bigelow and Schroeder 1948;Compagno 1984;Gadig 2001). Mendonça et al (2011) studied 415 samples of the genus Rhizoprionodon captured in the western Atlantic Ocean from Florida to southern Brazil. The samples were examined for sequences of the COI gene and the D-loop, and they were also evaluated for nucleotide differences.…”

DNA barcoding reveals the diversity of sharks in Guyana coastal markets

“…Given the 'Vulnerable' status of R. lalandii in Brazil, this might suggest that this species needs to be monitored more carefully in Guyana as well, given its prevalence in our sample. Alternatively, if R. lalandii populations in the Guianas are both stable and contiguous with Brazilian Sharpnose Shark populations, over harvested Brazilian populations could theoretically be replenished through immigration by coastal Guyana individuals (Mendonça et al, 2011).…”