Recruitment pattern in an isolated small population of the Mediterranean dwarf shrub Satureja thymbra L. and implication for conservation

Abstract

The recruitment pattern of Satureja thymbra (Lamiaceae), in a single and isolated population in Sardinia, was experimentally investigated by human-mediated sowing in the field: 12 plants in two habitats (inside and outside of “phrygana” habitat) were randomly selected as the source of seeds and a total of 2160 seeds were buried in two microhabitats, under the canopy and in open areas (3 replicas × 30 seeds × 12 plants × 2 microhabitats). The experiment was monthly monitored over a 2-year period. Germination and recruitment of S. thymbra were extremely low. Significant differences in the interaction among habitat and cohorts in seedling emergence were found. Differences between cohorts are due to the early emergence, which protected seedlings from seasonal drought. Seedling emergence in both microhabitats was recorded, although no significant differences were found. Additionally, significant differences in survived seedlings for habitat and cohort and for the interaction among them were found. The phrygana habitat showed a positive effect on the persistence of S. thymbra, by protecting plants from human disturbance, hence its conservation is essential to increase the population size of S. thymbra. Our findings, increasing the knowledge of the recruitment pattern of S. thymbra, provide also useful information for its conservation.