Populations varied for a number of plant traits, with a significant effect in eight of the 11 traits measured (non-significant traits were flower longevity, pollen/ovule ratio and size after 25 d; Table 1, Supplementary Data Figs S2–S5). The mean number of days to germination as well as nectar quality were significantly different between one SI population (ZAR) and all the other populations (Table 1, Fig. S2). However, no significant differences were consistently found among the other populations (Figs S2–S5). We found little evidence of trait variation consistent with evolution towards a selfing syndrome in the SC population, except that plants in the SC population showed a somewhat shorter time to flowering (Table 1, Fig. S4).