Dataset: Postsettlement performance in kin groups from shallow seagrass habitats in St. Teresa, Florida, USA in November and December 2017

To test the consequences of spreading sibling larvae to progeny survival after dispersal, we established three treatments designed to mimic three possible patterns of larval dispersal for a fixed number of larvae released: 1) siblings each disperse to different vacant locations resulting in more sites being colonized at lower density and lower relatedness, 2) siblings each disperse to different locations but each location also has settlement of individuals from other families resulting in more sites being colonized at higher density but lower relatedness, and 3) siblings settle in aggregations resulting in fewer sites being colonized at higher density, but also higher relatedness. Therefore, the three treatments were: 1) 10 groups of one sib alone (low density, low relatedness), 2) 10 groups of one sib with four unrelated neighbors (high density, low relatedness), and 3) two groups of five sibs (high density, high relatedness). The distance to the nearest neighbor in the high-density treatments was approximately 1 centimeter, as commonly occurs in the field. There were four maternal families, each with 10 siblings per treatment, resulting in a total of 120 focal individuals. Siblings within a maternal family are likely to be both full and half sibs (Burgess, unpubublished data). Non-focal individuals, that acted as unrelated competitors, within each group all came from different maternal colonies. Note that our experiment was designed to measure the fitness of maternal broods in different contexts, rather than the average fitness of the whole group of unrelated individuals.

To establish the treatments, we collected approximately 30 reproductive colonies from the field on November 6th 2017, and returned them to the lab, where they were kept in the dark in unfiltered aerated seawater. After two days, each colony was placed into a different glass bowl with 250 milliliters (mL) of seawater and exposed to bright light. A roughened, biofilmed acetate sheet (approximately 6 centimeters in diameter) was floated on the surface of the water, onto which larvae readily attached. Acetate sheets, with all settlers from a known mother, were removed from the dish after approximately 3 hours and floated in new dishes of fresh unfiltered seawater with the attached settlers facing downwards. The following day, the acetate sheet around individual settlers was cut with a hollow punch tool resulting in a 5 millimeter (mm) diameter piece of acetate sheet with a single settler attached. Treatments were established by attaching acetate sheets with individual settlers to a 40 x 40 mm acetate sheet (=1 group) using non-toxic super glue. The 40 x 40 mm acetate was then glued to the end of a zip-tie. The base of the zip-tie was attached to the tip of a 760 millimeter (mm) length of food-grade bamboo stick (~7 mm diameter). In the field, experimental groups were held in place by pushing the bamboo stick into the sediment, leaving the experimental individuals at about the same height from the substratum as the height of the surrounding seagrass. A total of 280 individuals in 88 groups were outplanted to the field in a shallow area approximately 0.8 to 1.5 meters) immediately east of the FSUCML. The experimental groups were outplanted in two rows parallel to the shore, covering a distance of approximately 50 meters. Each randomly chosen group was separated by approximately 1 meter.

We monitored the size and survival of all 280 individuals, of which 120 were the focal individuals from the four maternal families. The size was measured 24 days after settlement as the number of bifurcations, which is monotonically related to the number of zooids. Post-settlement survival was measured at 10, 24, and 38 days after settlement by recording whether colonies were alive or dead (absent colonies were recorded as dead). By approximately 21 days after settlement, colonies are usually reproductive (indicated by the appearance of ovicells).