Discussion
As in other species with gynodioecy (Demyanova 1985, Godin and Demaynova
2013, Godin 2019, 2020), O. vulgare ssp. vulgare is
characterized by two types of flower sizes: large perfect and small
pistillate. They form on different plants. The most significant
differences between the two types of flowers regard the androecium. In
pistillate flowers, the stamens are completely sterile and their anthers
are several times smaller than in perfect ones. The reduction of the
androecium in pistillate flowers is accompanied by a decrease in the
size of the other parts of the flower but to varying degrees. The
abortion of the stamens also affects the corolla and its parts while
affecting the calyx and gynoecium only to a lesser extent. Most likely,
such a different reaction of the elements of the flower is due to known
correlations in the development of its parts. Even before the emergence
of molecular biological models of the development of flowers, some
researchers (Baker 1948, Plack 1957) experimentally showed that corolla
growth is affected by hormones secreted by the stamens. The final
confirmation of the mutual influence of the developing elements of the
corolla and androecium in the flower was convincingly demonstrated by
the ABC and later ABCDE models of flower development (Haughn and
Somerville 1988, Theißen 2001). In O. vulgare ssp.vulgare , size differences and an influence of androecium
reduction in pistillate flowers on its other parts were previously
revealed (Vereshchagina and Malanina 1974, Anisimova and Demyanova 2007,
Godin and Evdokimova 2017a).
The sex ratios are similar in populations of Origanum vulgaressp. gracile and in O. vulgare ssp. vulgare(Ietswaart et al. 1984, Trosenko 1994, Demyanova 2012, Godin and
Evdokimova 2017b, Gordeeva and Komarevceva 2019). The proportion of
hermaphrodites varies widely, but they always predominate. It can be
assumed that the inheritance of gynodioecy in these two subspecies is
similar and is controlled by the same two genes. The dominant Fgene causes anther abortion, and the H gene is a dominant
suppressor of the F gene (Lewis and Crowe 1956, Jain 1968).
The frequency of females differed across populations of Origanum
vulgare ssp. gracile . We found that the proportion of females is
higher in habitats with more annual precipitation than in drier places.
Several abiotic factors (annual precipitation, aridity index, mean
annual temperature, and annual temperature range) are expected to cause
fluctuations in the frequency of females. Populations of O.
vulgare ssp. gracile showed a strong positive correlation of
female proportions with annual precipitation and an average negative
correlation with aridity index, mean annual temperature, and annual
temperature range. This indicates that wetter and cooler habitats may
contribute to the success of females in populations, directly or
indirectly through some other variable (for example, abundance and
behaviour of pollinator insects or higher seed production of female
forms). The partial correlation showed that the proportion of females is
more strongly correlated with annual precipitation than with mean annual
temperature. This suggests that annual precipitation may be the driving
force behind the higher female frequency in populations ofOriganum vulgare ssp. gracile .