Patterns of connectivity and population structure of the southern calamary Sepioteuthis australis in southern Australia

The southern calamary, Sepioteuthis australis, is a commercially and recreationally important inshore cephalopod endemic to southern Australia and New Zealand. Typical of other cephalopods, S. australis has a short life span, form nearshore spawning aggregations and undergo direct development. Such life history traits may restrict connectivity between spawning grounds creating highly structured and genetically differentiated populations that are susceptible to population crashes. Here we use seven polymorphic microsatellite markers to assess connectivity and population structure of S. australis across a large part of its geographic range in Australia. Little genetic differentiation was found between sampling locations. Overall, FST was low (0.005, 95% CI≤<0.001-0.011) and we detected no significant genetic differentiation between any of the locations sampled. There was no strong relationship between genetic and geographical distance, and our neighbour joining analysis did not show clustering of clades based on geographical locations. Similarly, network analysis showed strong connectivity amongst most locations, in particular, Tasmania appears to be well connected with several other locations and may act as an important source population. High levels of gene flow and connectivity between S. australis sampling sites across Australia are important for this short-lived species, ensuring resilience against spatial and temporal mortality fluctuations.