DOI: 10.5061/dryad.hmgqnk9sg
title: Data from: Dispersal limits poleward expansion of mangroves on the west coast of North America

description: While much attention has been paid to the climatic controls of species’
 range limits, other factors such as dispersal limitation are also
 important. Temperature is an important control of the distribution of
 coastal mangrove forests, and mangrove expansion at multiple poleward
 range limits has been linked to increasing temperatures. However, mangrove
 abundances at other poleward range limits have been surprisingly
 insensitive to climate change, indicating other drivers of range
 limitation. For example, along the west coast of North America, the
 poleward mangrove range limits are found on the Baja California and
 mainland coasts of Mexico, between 26.8 - 30.3°N. Non-climatic factors may
 play an important role in setting these range limits as 1) the abundance
 of range limit populations has been relatively insensitive to climate
 variability and 2) an introduced population of mangroves has persisted
 hundreds of kilometers north of the natural range limits. We combined a
 species distribution model with a high-resolution oceanographic transport
 model to identify the roles of climate and dispersal limitation in
 controlling mangrove distributions. We identified estuarine habitat that
 is likely climatically suitable for mangroves north of the current range
 limits. However, propagules from current mangrove populations are unlikely
 to reach these suitable locations due to prevailing ocean currents and
 geomorphic factors that create a patchy distribution of estuarine habitat
 with large between-patch distances. Thus, although climate change is
 driving range shifts of mangroves in multiple regions around the world,
 dispersal is currently limiting poleward mangrove expansion at several
 range limits, including the west coast of North America.
description: <strong>Particle transport
 simulation</strong> Propagule trajectories were
 computed using surface-ocean current data from a mesoscale and
 tide-resolving configuration of the Massachusetts Institute of Technology
 general circulation model (MITgcm). The simulation was carried out in a
 latitude-longitude-polar cap (LLC) configuration with a polar cap that has
 4320 grid cells on each side (hereafter referred to as LLC4320). There are
 243 million horizontal grid cells and 90 vertical (depth) levels for a
 total grid count of 2.2 ^ 10<sup>10</sup>. The model has a
 nominal horizontal grid resolution of 1/48°, which ranges from 0.75 km
 near Antarctica to 2.2 km at the Equator, and a vertical grid spacing of 1
 m near the surface to better resolve surface currents and diurnal
 cycles. A Lagrangian approach was used to compute
 particle propagation by linearly interpolating the zonal and meridional
 LLC4320 surface-ocean velocities and using a first-order Euler
 time-stepping method. Vertical motion was neglected, which is a reasonable
 assumption for mangrove propagules that are buoyant and generally remain
 on the ocean surface. Release locations were generated from the mangrove
 extent data described above. Release locations were shifted to the closest
 ocean grid cell (hereafter called ‘coastal grid cells’) and potential
 duplicate locations removed. Particles were released hourly at 589 coastal
 grid cells from 13 September 2011 to 13 November 2011  (i.e., 1,448 time
 steps in total), which coincides with the period of reported propagule
 availability in the region. Simulated propagules were tracked over 12
 months, which was the maximum floating period considered.
 From the Lagrangian particle trajectories, dispersal trajectory
 density maps were generated by aggregating all modeled particle
 trajectories on a 1/48° resolution grid (i.e., the native grid
 resolution). We then tracked all the particles that stranded, i.e.,
 reached an ocean cell adjacent to a land grid cell within the respective
 floating period. To account for the role of habitat suitability in our
 assessment of mangrove range limit dynamics in the region, we combined
 dispersal simulations with our coastal wetland layer. More specifically,
 we susbetted the strandings that were in grid cells potentially suitable
 for mangrove establishment and growth, i.e., either a saltmarsh or
 mangrove cell.
description: # Data from: Dispersal limits poleward expansion of mangroves on the west
 coast of North America
 [https://doi.org/10.5061/dryad.hmgqnk9sg](https://doi.org/10.5061/dryad.hmgqnk9sg) This package provides results of a particle transport simulation to estimate dispersal of mangrove propagules. ## Description of the data and file structure **particleDensities.zip** This files contains particle densities from the particle transport simulation for four floating periods: 1 month, 3 months, 6 months, and 12 months. Particle densities are aggregated to a 1/48° resolution grid. Each floating period has a structure called 'densities' that contain the density of particle that stranded in each grid cell. We provide the latitude, longitude and density value for all cells with particle density values &gt; 0. Fields that begin with 'suitable' are cells that contain either saltmarsh or mangrove. Fields that begin with nonSuitable are cells with no mangroves or saltmarsh. ## Sharing/Access information Data was derived from the following sources: * MITgcm ([https://mitgcm.readthedocs.io/en/latest/](https://mitgcm.readthedocs.io/en/latest/))