Dataset: Aggregation kin vs nonkin

Reproductive colonies of B. neritina were collected from the seagrass at Dog Island near the Florida State University Coastal and Marine Laboratory (FSUCML) in St. Teresa, Florida, USA (29° 54' N, 84° 30' W) from a depth of more than 1 meter on 17th June 2017. Colonies were kept in dark, aerated aquaria for two days. Each colony was then placed in its own glass bowl filled with 250 milliliters (mL) of seawater and then exposed to bright light to induce larval release. Larvae were then pipetted into new bowls with a 6 centimeter x 6 centimeter roughened acetate sheet floated on the surface so larvae would settle on the roughened underside. Roughened acetate sheets were held in aerated unfiltered seawater for 2 days prior to developing a biofilm to provide settlement cues. Glass bowls were randomly allocated to one of two treatments. One treatment consisted of larvae from the same maternal sibship (‘Sibs’, n = 13). The other treatment consisted of larvae where each larva was from a different maternal sibship (‘Non-sibs’, n = 13). The number of larvae placed in each glass bowl was haphazardly chosen, and settlement density ranged from 4 to 20 settlers per sheet in both treatments.