Very little is known about the performance of non-agricultural plant species in monocultures, even though nearly all agricultural species have experienced the transition from multi-species environments to dense monospecific stands during the breeding process. In the light of recent work that highlighted the possibility that the weedy species Arabidopsis thaliana can offer novel insight into crop breeding, we aimed to test the effect of sowing density on group and individual performance in different photoperiod environments in A. thaliana.

We studied the performance of A. thaliana Cvi-0 ecotype. The choice of Cvi-0 was based on a preliminary experiment in which plants of Cvi-0 ecotype exhibited high competitive performance. Sowing densities used were 17.6, 8.8, 4.4, 2.2 and 1.1 cm² per plant and photoperiod environments 12 or 16 h of day light.

In this experiment, populations attained constant total seed yield for all densities. Some interaction effect occurred, as at high sowing density and at longer day length plants produced heavier seeds, whereas at shorter day length seed weight was negatively related to plant density. These results shed light on different strategies that annual plants can adopt when they face intense intraspecific competition, and could help to offer new perspectives for breeding crops with enhanced group performance.