Gynodioecy, the co-occurrence of female and hermaphrodite plants in the same population is relatively common in the genus Thymus, where a high and variable female frequency has been reported in several species, populations and years. In most gynodioecious species, female plants produce more and/or better seeds than hermaphrodite plants, facilitating female maintenance in natural populations. Thymus × arundanus and T. granatensis are two sympatric gynodioecious species that inhabit the region of Andalucia, Spain. Here we studied reproductive components in two different years (1987 and 2016) as flower number, fruit-set, seed number and seed mass, and their possible relation to female frequencies in those years in natural populations of both species. In T. × arundanus, mean female frequency (59%) was ten times higher than that of T. granatensis (5%). Female frequency was relatively constant in T. × arundanus after almost 15 years (1987–2016), and in T. granatensis low female frequencies were observed (0–5%) with the exception of one population (18%). However, reproductive components were variable among species, years and genders, showing no consistent female fertility advantage. High female frequencies in T. × arundanus are not likely to be maintained by female fertility advantage but stochastic and pleiotropic effects on sex determination may play a relevant role in sex ratio variation in the studied populations of both species.

雌，雌雄同体植物在同一种群中并存，在雌性胸腺中相对普遍，而在几种物种，种群和年份中，雌性的发生率却很高且可变。在大多数雌雄同体物种中，雌性植物比雌雄同体的植物产生更多和/或更好的种子，从而有利于自然种群中的雌性维持。百里香×阿伦达努斯和T. granatensis是居住在西班牙安达卢西亚地区的两个同胞雌雄同体物种。在这里，我们研究了两种不同年份（1987年和2016年）的生殖成分，如花数，坐果，种子数和种子质量，以及它们在这两个物种的自然种群中当年的雌性频率的可能关系。在T中。× arundanus，平均雌性频率（59％）比T. granatensis（5％）高十倍。女性频率在T中相对恒定。× arundanus经过近15年（1987-2016年）以及T. granatensis除了一个人群（18％）外，观察到女性的频率很低（0-5％）。但是，生殖成分在物种，年龄和性别之间是可变的，没有显示出一致的女性生育优势。T中的雌性频率高。×阿伦丹犬不太可能通过女性的生育力优势而维持，但是在性别决定中，随机和多效性可能在这两个物种的性别比变化中发挥了相关作用。