Aim: We assess the role of contemporary oceanography and species traits in shaping observed patterns of biogeography over broad spatial scales.

Location: Our study domain covers the east and west coasts of North America, from 30° to 73° on the east coast and 33° to 73° on the west coast.

Time Period: Hydrodynamic models use climatological fields from 1990 to 2015 on the east coast, and 1993 to 2018 on the west coast.

Major Taxa Studied: Model simulations represent larval dispersal for generalized benthic invertebrate species distributed in the subtidal zone from 10 m to 100 m depth, with planktonic larval durations ranging from 21–60 days.

Methods: We conducted a literature review to identify major biogeographic barriers along the east and west coasts of North America, and then assessed the permeability of these barriers to larval dispersal using Lagrangian Particle Tracking. We ran a series of simulations in which we varied the suitable habitat distribution, planktonic larval duration, and spawning seasonality of simulated larvae (i.e. particles) to assess the role of species traits on biogeography.

Results: Our results showed a strong alignment of observed biogeographic barriers with larval dispersal patterns, with high variation in barrier permeability depending on the traits of the species considered. The location of suitable habitat and the season during which particle release occurred were the biological traits that drove much of the variation in barrier permeability among simulations on both coasts.

Main Conclusions: Our results indicate an important role of contemporary oceanographic and geographic features in determining the biogeography of species whose primary dispersal is during larval stages, suggesting that climate change is likely to alter patterns of species biogeography. Our results also demonstrate that species traits play a strong role in determining the location and strength of biogeographic barriers.

Data are connectivity matricies between coastal zones defined from literature data identifying the location of biogeographic barriers. Connectivity matrices were generated from model simulations of larval dispersal of coastal benthic species using Lagrangian Particle Track modelling. Simulations include particles with three sets of generalized initial habitat distributions defined by bathymetric depth and distance from shore (10m and 5km, 30m 20km, and 100m 50km), and were run and processed for three planktonic larval durations (21, 30, and 60 days). Simulations were run for 6 months per year, with the seasonality of particle release in each zone defined by a generalized spawning seasonality assigned to each zone based on temperature conditions. See the manuscript for more detail on the methods used to generate matrices.