Plant species with differing flowering periods tend to co-occur more in patchy vegetation of a semi-arid environment.

Stressful environments can lead to patchy vegetation patterns, bringing plants into close spatial proximity, which may intensify plant-plant interactions. These interactions are influenced by functional variation among co-occurring species, and increased variation can reduce niche overlap. One such trait, phenology, has been shown to influence both competitive and facilitative interactions. Phenological differences may reduce competition for resources and enhance facilitation between neighbouring plants during high-demand periods (e.g. flowering). We therefore hypothesized that species with more distinct phenologies would co-occur more frequently across vegetation patches. Plant data were collected from gypsum outcrops in Spain, where the phenology of plant species was recorded over 2 years and co-occurrence over 4 years. Indices of phenological difference and co-occurrence were correlated to test for a statistical relationship. Phenological and co-occurrence data from six species, of 166 and 1560 individuals, respectively, were used in the analyses. The species generally flowered during the same season but differed in flowering duration and intrinsic occurrence. The correlated indices showed a significant positive relationship, indicating that a species pair with more dissimilar flowering periods is more likely to co-occur within the same vegetation patch. Temporal niche partitioning can thus reduce competition for nutrients and pollinators and enhance nitrogen transfer between species. Complementary species can reduce the negative impacts of peak resource demand. The study suggests that phenological relationships between species should be considered during conservation and restoration efforts targeting patchy vegetation in semi-arid environments.