Evidence for reproductive philopatry in the bull shark, Carcharhinus leucas in northern Australia.

Journal of Fish Biology

Vol. 80, pages 2140-2158, 2012

Authors

Tillett, B.J.
Meekan, M. G.
Field, I.C.
Thorburn, D.C.
Ovenden, J. R.

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Abstract

Adult bull sharks (Carcharhinus leucas) are ubiquitous in near- and off-shore habitats across northern Australia. Females give birth in freshwater / estuarine nurseries and juveniles mature in these environments. If females return to the same pupping areas, then this reproductive philopatry could drive patterns of genetic diversity among nurseries. To test this hypothesis we compared the evolution of mitochondrial (NADH dehydrogenase subunit 4, 797 base pairs and control region genes 837, base pairs) and nuclear (three microsatellite loci) DNA of juveniles sampled from thirteen river systems across northern Australia. Populations in this region are arguably the least subject to anthropogenic disturbance within the species’ global distribution and thus represent the best approximation of the behaviour of the species in its natural state. High genetic diversity among juveniles sampled from different rivers (mitochondrial FST = 0.0839, p < 0.0002; microsatellite FST = 0.0056, p < 0.988) supported the hypothesis of female reproductive philopatry. Genetic structure was not further influenced by geographic distance (p < 0.8623) or long-shore barriers to movement. Additionally, we show that the species in northern Australia has an effective population size of 11 - 13 000 females and has undergone population bottlenecks and expansions that coincide with the timing of the last ice ages. [/two_third]