Flowering phenology, fruit set and seed mass and number of five coexisting Gymnocalycium (Cactaceae) species from Cordoba Mountain, Argentina

Flowering phenology may play a critical role in plant coexistence, allowing not only a temporal partitioning of resources but also conditioning the relationship between seed mass and number in these species. We analyzed how flowering phenology was related to seed mass and number, and how these seed traits were related in five coexisting Gymnocalycium (Cactaceae) species in two consecutive flowering seasons. The flowering phenology of each species was characterized in terms of timing (onset and peak), duration, and flowering synchronicity. Although species showed differences in duration and synchronicity, the earliest flowering species tend to have higher reproductive success than species flowering later. However, we did not find a clear relationship between the flowering time and seed traits. A trade-off between seed mass and number in these species was highlighted, as species with higher seed mass were those producing a lower number of seeds per fruit and individual, whereas species with lower seed mass had a higher number of seeds. Our results showed a temporal resource partitioning associated with differences in flowering timing among species, which may lead to differences in reproductive success (number of mature fruits and fruit set) and highlight the importance of the trade-off between colonization vs competitive ability in promoting plant coexistence.