The extent of population genetic subdivision differs among four co-distributed shark species in the Indo-Australian archipelago - PubMed (original) (raw)

The extent of population genetic subdivision differs among four co-distributed shark species in the Indo-Australian archipelago

Jenny R Ovenden et al. BMC Evol Biol. 2009.

Abstract

Background: The territorial fishing zones of Australia and Indonesia are contiguous to the north of Australia in the Timor and Arafura Seas and in the Indian Ocean to the north of Christmas Island. The area surrounding the shared boundary consists of a variety of bio-diverse marine habitats including shallow continental shelf waters, oceanic trenches and numerous offshore islands. Both countries exploit a variety of fisheries species, including whaler (Carcharhinus spp.) and hammerhead sharks (Sphyrna spp.). Despite their differences in social and financial arrangements, the two countries are motivated to develop complementary co-management practices to achieve resource sustainability. An essential starting point is knowledge of the degree of population subdivision, and hence fisheries stock status, in exploited species.

Results: Populations of four commercially harvested shark species (Carcharhinus obscurus, Carcharhinus sorrah, Prionace glauca, Sphyrna lewini) were sampled from northern Australia and central Indonesia. Neutral genetic markers (mitochondrial DNA control region sequence and allelic variation at co-dominant microsatellite loci) revealed genetic subdivision between Australian and Indonesian populations of C. sorrah. Further research is needed to address the possibility of genetic subdivision among C. obscurus populations. There was no evidence of genetic subdivision for P. glauca and S. lewini populations, but the sampling represented a relatively small part of their distributional range. For these species, more detailed analyses of population genetic structure is recommended in the future.

Conclusion: Cooperative management between Australia and Indonesia is the best option at present for P. glauca and S. lewini, while C. sorrah and C. obscurus should be managed independently. On-going research on these and other exploited shark and ray species is strongly recommended. Biological and ecological similarity between species may not be a predictor of population genetic structure, so species-specific studies are recommended to provide new data to assist with sustainable fisheries management.

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Figures

Figure 1

Figure 1

Circles encompass collection locations for four shark species from East Australia (1), West Australia (2), Indonesia (3), Gulf of Carpentaria (4) and mid-north Pacific (5).

Figure 2

Figure 2

Inferred phylogeny (A) and statistical parsimony network (B) among haplotypes of C. obscurus. The phylogeny was rooted with C. sorrah and C. dussumieri and nodal support is given as Bayesian posterior probabilities/ML boostrap support. Dash (-) indicates support of less than 50%. In the network, each indicated step (circle) represents a single nucleotide difference in the mtDNA control region sequence. The area of circles is scaled to represent the relative frequency of that haplotype and the smallest circle represent inferred haplotypes that were not sampled. The collection location of sampled haplotypes is numbered (in italics) according to Fig. 1.

Figure 3

Figure 3

Inferred phylogeny (A) and statistical parsimony network (B) among haplotypes of C. sorrah collected in Indonesia (Ind) and Australia (Aust). The phylogeny was rooted with C. obscurus and C. dussumieri and nodal support is given as Bayesian posterior probabilities/ML boostrap support. Dash (-) indicates support of less than 50%. In the network, each indicated step (circle) represents a single nucleotide difference in the mtDNA control region sequence. The area of circles is scaled to represent the relative frequency of that haplotype and the smallest circle represent inferred haplotypes that were not sampled. The collection location of sampled haplotypes is numbered (in italics) according to Fig. 1.

Figure 4

Figure 4

Inferred phylogeny (A) and statistical parsimony network (B) among haplotypes of P. glauca collected in Indonesia (Ind) and Australia (Aust). The phylogeny was rooted with C. falciformis and C. amblyrhynchos and nodal support is given as Bayesian posterior probabilities/ML boostrap support. Dash (-) indicates support of less than 50%. In the network, each indicated step (circle) represents a single nucleotide difference in the mtDNA control region sequence. The area of circles is scaled to represent the relative frequency of that haplotype and the smallest circle represent inferred haplotypes that were not sampled. The collection location of sampled haplotypes is numbered (in italics) according to Fig. 1.

Figure 5

Figure 5

Inferred phylogeny (A) and statistical parsimony network (B) among haplotypes of S. lewini. The phylogeny was rooted with S. mokarran and E. blochi and nodal support is given as Bayesian posterior probabilities/ML boostrap support. Dash (-) indicates support of less than 50%. In the network, each indicated step (circle) represents a single nucleotide difference in the mtDNA control region sequence. The area of circles is scaled to represent the relative frequency of that haplotype and the smallest circle represent inferred haplotypes that were not sampled. Haplotype SL09 from the North Atlantic (Atl) is equivalent to Duncan et al [15] haplotype number 16. The collection location of sampled haplotypes is numbered (in italics) according to Fig. 1.

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