These biogeographic breaks act as barriers for species with low dispersal 20, 21 and promote non-random spatial movements of larvae in plankton, such as unidirectional movement 22 or asymmetric dispersal among populations 23. The biogeographic break at 42°S is caused by the collision of the West Wind Drift Currents (Antarctic Circumpolar Current) with the Chilean coast, producing the northward Humboldt (Peru) Current and southward Cape Horn Current 18, 19. The biogeographic break at 30°S is likely caused by differences in eddy kinetic energy (high south of and low north of 30°S) and equatorward wind (strong and variable south of and weak but persistent north of 30°S) 17. Examples include Cape Cod in the Atlantic Ocean 14, Point Conception in North America 15, and latitudes 30°S and 42°S in Chile 16. Small-scale processes (e.g., turbulence, small eddies, and stagnant zones) combine with nearshore physical processes (e.g., waves, winds, and tides) to affect the degree of larval retention in each system 12, while mesoscale behaviors (e.g., meanders) and global-scale physical processes (e.g., the main oceanographic currents) affect the degree of larval dispersal and population connectivity at a large scale 5, 13.Īt large scales, the hydrographic regime and bottom topography affect biogeographic breaks. Finally, all scales of oceanic water movement affect larval dispersal. This behavior could regulate larval engagement with physical forcing and circulation, which would prevent them from straying from the coast 11. One of the most important larval behaviors described in the water column is active vertical migration 10. In addition, larval behavior contributes to changes in magnitude and direction of larval movement, enabling offshore transport or residence near the coast 9. Planktonic larval duration is positively correlated with dispersal distance 6 and depends on the species, ranging from merely hours among corals 7 to a year among lobsters 8. Although the larval period only represents approximately 1–5% of the total life cycle of these species, it is important for population connectivity 2 because it is fundamental to maintaining the cohesiveness of benthic populations, enabling them to persist through ecological and evolutionary time 3.įactors influencing marine population connectivity and larval dispersal include planktonic larval duration, larval behavior, and oceanographic currents 4, 5. Most adult benthic marine invertebrates have limited mobility or are sessile, as the larval stage is the period that enables dispersion 1. edwardsii comprises a single large population with high levels of gene flow among sites separated by over 1700 km and demonstrate temporal stability in its genetic structure. Moreover, migration analyses supported gene flow among all sites but at different rates for different pairs of sites. Similarly, we found no evidence of an effect on gene flow of the biogeographic break caused by the the West Wind Drift Current. Using population genetic approaches, we found no evidence of geographic or temporal population differentiation. Specimens were collected at eight sites within its geographic distribution, with collection at four of these sites was performed twice. Based on variability at 4209 single-nucleotide polymorphisms in 234 individuals, we determine the genetic structure, temporal genetic stability, and gene flow among populations of the commercially important mola rock crab Metacarcinus edwardsii in a system in southern Chile with a biogeographic break at latitude 42°S. Understanding these processes becomes particularly important in areas with a biogeographic break and unidirectional water movement along the sides of the break. Elucidating the processes responsible for maintaining the population connectivity of marine benthic species mediated by larval dispersal remains a fundamental question in marine ecology and fishery management.
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