Dataset: Dispersal distance

To estimate dispersal kernels, we quantified the number of settlers at a range of distances from a known source of reproductive colonies. We deployed 172 poles in seven concentric rings in a shallow area (more than 1 meter maximum depth, consistent across the study area) immediately east of the Florida State University Coastal and Marine Laboratory (FSUCML). Each pole was 1.9 centimeter diameter plastic pipe, extending 40 centimeters vertically from the ground, onto which settlement plates were attached. The seven rings had radiuses of 0.25, 0.5, 1, 2, 4, 8, and 12 meters. To ensure a relatively similar sampling effort at each dispersal distance, poles within each radius were placed approximately 1 meter apart (except for the 0.25 meter distance where poles were approximately 40 centimeters apart), resulting in 2, 4, 4, 8, 12, 23, 46, and 73 poles at radiuses of 0, 0.25, 0.5, 1, 2, 4, 8, and 12 meters, respectively. The area consisted mostly of sand, with small patches of short seagrass (mostly Halodule wrightii and Thalassia testudinum). Prior to deploying the poles, the area was thoroughly checked to ensure the absence of B. neritina colonies within a roughly 30 x 30 meter area.

Over a period of two months (between 17^th October and 14^th December 2017), we deployed settlement plates (roughened acetate sheets wrapped around the pole) on five occasions. On two ‘trial’ occasions, we placed seven adult reproductive colonies of B. nertina in the center of the array. Seven colonies, rather than one, were used to ensure high enough larval production to ensure adequate sampling of the dispersal kernel. On three ‘control’ occasions (before the first trial, between the first and second trial, and after the second trial), we did not place colonies of B. nertina in the center of the array but still estimated settlement. The function of the control deployments was to estimate any background settlement of larvae originating from unknown colonies outside the array in order to provide greater confidence that settlers during the trial deployments originated from the colonies placed in the center of the array. In each trial deployment, settlement plates were deployed for 3 days. In the three control deployments, settlement plates were deployed for 7, 4, and 3 days, respectively. Settlers were counted within hours of retrieving the settlement plates. On each settlement plate, all settlers within a pre-defined 21.5 centimeter x 7 centimeter area (150.5 cm²) were counted under a dissecting microscope. Settlement density was standardized as the number of B. neritina per cm² per day per colony (cm^-2 d^-1 colony^-1), which assumes that the seven colonies each contributed an equal number of larvae.