TRANSECT - the geographical area in which sampling was conducted, as indicated in main manuscript Fig. 1 REGION - each transect consisted of a region dominated by populations with or without unisexual plants; this column indicates the sexual system (androdioecy or dioecy = with males, monoecy = regions in which males are largely absent) Ploidy - the ploidy level of the populations in each region YEAR - the year in which data were collected SITE - the site number; survey sites were each divided into four plots; sowing sites comprised only a single plot (where seeds were sown) SOWING - whether the site was used for an experimental sowing LATITUDE - decimal degrees N LONGITUDE - decimal degrees E SIZE_A - the size of plot A in m^2 SIZE_B - the size of plot B in m^2 SIZE_C - the size of plot C in m^2 SIZE_D - the size of plot D in m^2 A_PERC_COV - the % cover of Mercurialis annua in plot A A_N - the number of Mercurialis annua plants in plot A A_N_MALES - the number of males in plot A A_PERC_MAL - the percentage of male plants in plot A B_PERC_COV - the % cover of Mercurialis annua in plot B B_N - the number of Mercurialis annua plants in plot B B_N_MALES - the number of males in plot B B_PERC_MAL - the percentage of male plants in plot B C_PERC_COV - the % cover of Mercurialis annua in plot C C_N - the number of Mercurialis annua plants in plot C C_N_MALES - the number of males in plot C C_PERC_MAL - the percentage of male plants in plot C D_PERC_COV - the % cover of Mercurialis annua in plot D D_N - the number of Mercurialis annua plants in plot D D_N_MALES - the number of males in plot D D_PERC_MAL - the percentage of male plants in plot D --- Columns with census data are followed by columns indicating the percent cover of other types of vegetation (V) using the following scale 0: plant type is absent from the plot 1: P ~ 0% but present 2: V < 1% 3: 1% < V < 5% 4: 5% < V < 20% 5: 20% V < 50% 6: V > 50% There are four sets of columns indicating the cover data collected in the study, one for each of plots A, B, C, and D. These are the percent cover of: SOIL; GRASS; LAWN; OXALIS (Oxalis pes-caprae); NETTLES (Urtica dioica); PARIET (Parietaria judaica); LITTER (leaf litter); THORN_AN (thorny annuals); ERECT_AN (erect annuals); ROSET_AN (rosette-forming annuals); PROST_AN (prostrate annuals); HERBPER (herbaceous perennials).