The short and unseasonal fruiting of plants: Competition escape

Background/Question/Methods

Anemochorous species tend to fruit in the dry season. The synchronization between seed dispersal and some climatic factors may increase the seed chances for reaching safe sites to germinate. However, the wind, as a dispersal resource, may be an object of competition for plants and when more species fruit in a period it means negative interactions for the dispersal agent. Field data showed that the majority of species dispersed by wind spend the year fruiting, reflecting the seasonal unpredictability or scarcity of resources needed for fruit development. So, if long period species frutification is distributed through the year, short period species may determine the seasonality of all anemochorous species. In opposition, fruiting of short period species may alternate and there is not seasonality. Then, we tried to answer if short period species fruit all long the year and how much the wind can interact them. The qualitative phenological observations were carried out monthly, from September 1995 to February 1997, in the Pé-de-Gigante Reserve, southeast Brazil. We classified the plants in short period (three months) and long period (four to twelve months), evaluated the fruiting time overlap and constructed an interaction matrix.

Results/Conclusions

We found fruits in 46 short period anemochorous species. There was not any seasonality in fruiting, on the contrary the species highly changed. This would be explained by many factors: the interval between pollination and fruit maturation, the responsiveness to the drought, the decrease in competition between seedlings or attack by pathogens, the wind blowing during the whole year, the needless of wind by plants, or the escape from wind competition. Consequently, the lack of seasonality of long period species could not be compensated by short period species. Species with less interactions were Eupatorium laevigatum e Pterocaulon virgatum (two interactions each one) and Vernonia herbacea was the species with more relations (18 interactions). Species that fruited only one month competed fewer than species that fruited three months. The habit and diaspore morphology may help to escape from competition. The plants rely on several strategies to increase their maintenance probabilities, and the asynchronized and short fruiting may be one of them.