Temporal variation in sex allocation in hermaphrodites of gynodioecious Thymus vulgaris L.

Summary1 Theory predicts that hermaphrodites adjust sex allocation in relation to the relative fitness contributions of male and female functions. Few studies have, however, focused on temporal variation in sex allocation within individuals. 2 We quantified temporal variation in allocation to male and female function of hermaphrodites of gynodioecious Thymus vulgaris across a single flowering season, in families from four natural populations grown in an experimental garden. 3 Allocation to pollen production and to seed set and germination varied significantly among sample dates, with male function highest when female function was lowest, and a significant negative correlation between pollen production and seed set among families indicated a trade‐off between male and female function. 4 Females and hermaphrodites showed gender‐specific flowering phenology: female plants achieved peak flowering later and flowered for a significantly shorter period than hermaphrodites. 5 The number of open female flowers was significantly positively correlated with pollen production by hermaphrodites. Hermaphrodite male function was maximized at the time of peak flowering by females in all four populations. 6 These results fit theoretical predictions that across‐season variation in the mating environment could select for a temporal variation in hermaphrodite sex allocation, but other factors (e.g. variation in the selfing rate or resource levels) may also contribute to the observed pattern.