Coastal talitrids and connectivity between beaches: A behavioural test

Beach-hoppers and sandhoppers in the family Talitridae are strongly linked to the supralittoral environment. They are semi-terrestrial animals and because they are direct developers there is potentially no mobility between populations on adjacent beaches. In the case of coastlines fragmented by natural or artificial structures, the assumed lack of inter-connectivity between beaches may represent a severe threat for the resident populations: in case of impacts, they might not be able to recover and the habitat might not be re-colonised. Unless we consider another possible scenario: the potential connectivity of populations via water currents, from individuals swashed accidentally into the sea. We therefore tested two different species, the sandhopper Notorchestia quadrimana and the beach-hopper Platorchestia smithi for features relevant to dispersal and connectivity among beaches: 1) survival in sea-water; 2) orientation (baseline and scototaxis) in sea-water and 3) behaviour in a current. Talitrid populations were sampled from a sheltered beach and an exposed beach along the New South Wales coast. On the sheltered beach both species were found, co-occurring within the same distance from the shoreline. On the exposed beach only P. smithi was found, in a dune slack far away from the shoreline. All individuals tested survived 96. h in immersion, and when subjected to a current they were clinging on the edge of the flume apparatus for most of the duration of the test. Differences emerged when comparing orientation, with the sharpest precision towards a dark pattern (positive scototaxis) in P. smithi from the sheltered beach and bimodal orientation (partly scototactic and partly sun compass) in N. quadrimana. The behavioural differences observed are likely developed as risk-related: sandhoppers burrow in the substrate and are less exposed to occasional swash, while beach-hoppers living in cast wrack displayed the ability of swimming quickly towards a floating object, increasing the likelihood of being passively carried from one beach to another. Different ecological groups such "sandhoppers" and "beach-hoppers" showed different behavioural patterns. The consideration of behavioural answers to swash risk highlighted the possibility of the connectivity of talitrid populations across fragmented beaches. © 2014 Elsevier B.V.