The contribution of phenotypically plastic traits to evolution depends on the degree of environmental influence on the target of selection (the phenotype) as well as the underlying genetic structure of the trait and plastic response. Likewise, maternal effects can help or hinder evolution through affects to the response to selection. The sacoglossan sea slug Alderia willowi exhibits intraspecific variation for developmental mode (= poecilogony) that is environmentally modulated with populations producing more yolk-feeding (lecithotrophic) larvae during the summer, and more planktonic-feeding (planktotrophic) larvae in the winter. I found significant family level variation in the reaction norms between 17 maternal families of A. willowi when reared in a split-brood design in low (16 ppt) versus high (32 ppt) salinity; conditions which mimic seasonal variation in salinity of natural populations. I documented a significant response to selection for lecithotrophic larvae in high and low salinity. The slope of the reaction norm was maintained following one generation of selection for lecithotrophy. When the maternal environment was controlled in the lab, I found significant maternal effects, which reduced the response to selection. These results suggest there is standing genetic variation for egg-mass type in A. willowi, but the ability of selection to act on that variation may depend on the environment in which the phenotype is expressed in preceding generations.

This paper presents data from two experiments, one designed to evaluate the response to selection in high and low salinity, and the other to determine the role of maternal effects and effect of selection on phenotypic plasticity.

For both experiments adult slugs were collected from the field. They laid eggs in the lab, the offspring from which were reared in low (16ppt) and high (32ppt) salinity. The data stored here consists of egg-capule diameter and egg diameter measurements from slugs reared in the lab.

Raw data and R scripts are included to perform all analyses and make all data figures.

There are 4 data files which contain the raw data, described as follows:

TomalesBay_capsuledata.csv contains the egg capsule measurements for slugs from Tomales Bay reared in low and high salinity. Column headers and their descriptions are, date, order, capsule (egg capsule diameter in mm), gen (generation), Family, ID (individual slug ID), eggmass (egg mass number according to date laid), original (environment)

EggDiameterMeasurements.csv. contains the egg diameter measurements and has columns: date, EggDi (in mm), Family, ID, eggmass, original

SoCalvNorCal_Data.csv contains the egg capsule measurements for slugs from Mill Valley and Long Beach reared in low and high salinity. Column headers and their descptions are: date, order, capsule, Family, ID, eggmass, original, region.

F1_capsule_data.csv contains the egg capsule measurements for slugs from the F1 treatment evaluating maternal effects and the effect of selection to the reaction norm. column headers are: date, order, Capsule, mom_id (maternal id), mom_env (maternal environment), off_id (offspring id), offspring_env (offspring environment), Family. 

Scripts in R are provided for each figure in an R markdown document which is also presented in a pdf. 

Scripts for performing the quantitive genetics models are provided in the R file: Gibbs_sample_threshold_bays.R