CARCHARHINIDAE (REQUIEM SHARKS)

Henderson, Aaron C., Reeve, Alan J., Jabado, Rima W. & Naylor, Gavin J. P., 2016, Taxonomic assessment of sharks, rays and guitarfishes (Chondrichthyes: Elasmobranchii) from south-eastern Arabia, using the NADH dehydrogenase subunit 2 (NADH 2) gene, Zoological Journal of the Linnean Society 176 (2), pp. 399-442 : 421-423

CARCHARHINIDAE (REQUIEM SHARKS)

Sixteen carcharhinid species were assessed. They yielded a between-group mean distance of 10.17 ± 0.62%. Two species exhibited notable sub-clustering, namely Carcharhinus leucas and Loxodon macrorhinus , but although there was strong branch support for these divisions, between-group mean distances were relatively low in both cases ( Table 1). Naylor et al. (2012) noted three sub-clusters within their C. leucas samples, one consisting of samples from the Atlantic ( C. leucas ), one consisting of samples from Malaysia ( C. cf. leucas 1) and one consisting of samples from South Africa ( C. cf. leucas 2). Each of the two sub-clusters from the present study grouped separately with C. cf. leucas 1 and C. cf. leucas 2. Two sub-clusters were reported by Naylor et al. (2012) within L. macrorhinus , which they designated L. macrorhinus (specimens from India, Borneo and Philippines) and L. cf. macrorhinus (specimens from India and Madagascar). The majority of specimens from the present study clustered with the latter, while the remaining specimens clustered with the former. A sub-cluster with strong branch support was also evident within this cluster, but the mean 1, Carcharhinus altimus ; 2, Carcharhinus amboinensis ; 3, Carcharhinus sorrah ; 4, Carcharhinus brevipinna ; 5, Carcharhinus macloti ; 6, Carcharhinus cf. limbatus ; 7, Carcharhinus cf. leucas 1; 8, Carcharhinus cf. leucas 2; 9, Carcharhinus cf. melanopterus ; 10, Carcharhinus falciformis ; 11, Carcharhinus leiodon ; 12, Carcharhinus longimanus ; 13, Carcharhinus plumbeus ; 14, Galeocerdo cuvier ; 15, Loxodon macrorhinus (cluster A); 16, Loxodon cf. macrorhinus ; 17, Loxodon macrorhinus (cluster B); 18, Negaprion acutidens ; 19, Rhizoprionodon acutus .

erally showing greatest similarity to geographically proximate specimens. The exception to this is Carcharhinus leiodon , which was not included in the Naylor et al. (2012) study. This species clustered between their Carcharhinus amblyrhynchoides and Carcharhinus tilstoni specimens.

distance between this sub-cluster and the remainder of the L. macrorhinus cluster was low ( Table 1).

Although C. plumbeus and C. altimus are morphologically distinct ( Fig. 3 ), they formed a single cluster and exhibited a very low between-group mean distance ( Table 1). Naylor et al. (2012) also reported a single cluster containing Atlantic specimens of C. plumbeus and Atlantic/Pacific specimens of C. altimus , with a second cluster consisting of Pacific specimens of C. plumbeus designated C. cf. plumbeus . The specimens of both C. plumbeus and C. altimus from the present study clustered with the former.

A distinct genetic separation of western Atlantic and eastern Atlantic/Indo-Pacific specimens of C. limbatus was noted by Naylor et al. (2012), leading them to designate the latter C. cf. limbatus . The same authors also noted geographically separated divisions within C. melanopterus ( C. melanopterus in the Pacific and C. cf. melanopterus from Egypt) and Galeocerdo cuvier ( G. cuvier in the Indo-Pacific and G. cf. cuvier in the Atlantic). Specimens from the present study clustered with C. cf. limbatus , C. cf. melanopterus and G. cuvier , respectively. Similarly, Naylor et al. (2012) noted four subclusters within Rhizoprionodon acutus from across this species range. Based on the type locality, northern Indian Ocean specimens were designated R. acutus , those from western Africa R. cf. acutus 1, those from Australia R. cf. acutus 2 and those from Malaysia / Philippines R. cf. acutus 3 ( Naylor et al., 2012). Specimens from the present study all clustered with R. acutus . The remaining carcharhinid species clustered with the relevant taxa from Naylor et al. (2012), gen-

Figures

Figure 3. Specimens of Carcharhinus plumbeus (top) and Carcharhinus altimus (bottom) from south-eastern Arabia. Despite the fact that these species display a high level of genetic similarity, they are morphologically distinguishable from each other.