MEPS 388:121-135 (2009)  -  DOI: https://doi.org/10.3354/meps08167

ABSTRACT: Satellite-derived measurements of ocean currents made since 1993 were used to examine whether present-day oceanic circulation can explain 2 observed genetic lineages of the intertidal limpet Cellana strigilis in the New Zealand region. The western lineage comprises the South Island of New Zealand, Auckland and Campbell Islands, and the eastern lineage comprises the Chatham, Antipodes and Bounty Islands. Satellite-derived currents were used to simulate potential larval trajectories and hence estimate dispersal times between the islands. A random walk was added to the model to account for missing high-frequency variance in the satellite-derived currents. Surface drifters were used to calibrate the model. Minimum simulated dispersal times between the islands can easily explain the separation of the 2 lineages, but are too long, except between Antipodes and Bounty Islands, to explain the observed homogeneity within the lineages. It is suggested that rare long-distance dispersal events in the ocean, occurring too infrequently to be observed in 15 yr of simulations, influence the gene flow, and the frequency of these events may be estimated by fitting analytical functions to histograms of simulated larval dispersal. For some island pairs that are genetically connected, the maximum 10 d larval duration of C. strigilis appears at the 10^–4 percentile. If this genetic connection occurs via larval dispersal, this suggests that connection may occur even when fewer than 1 in 1 million dispersal times is shorter than the larval duration.

KEY WORDS: Cellana · Connectivity · Modelling · Larval connections · Dispersal time