Positive interaction between shrubs and native orchids in a Mediterranean ecosystem

Abstract

In the Mediterranean portion of Central Chile, where anthropic disturbances are common and severe, precipitations could drastically decrease and temperatures increase due to climate change. In this ecological context, positive interactions between plants could increase in relevance since they can increase growth and survival in stressful conditions. In this area, natural populations also suffer herbivore damage, mainly by cattle and other introduced species. The orchid family is represented in Chile by terrestrial species only that grow in natural and disturbed sites where native shrubs are common. These species have been poorly studied in terms of their ecology, and some species are currently severely threatened. In this study, we tested if native shrubs can facilitate Chilean orchids, reducing abiotic stress and herbivory. We evaluated this positive interaction in three sites with different orchid and shrub species. We found that in all sites, there are more orchid individuals growing inside the canopy of shrubs compared to open areas. Additionally, abiotic conditions were milder and herbivory was reduced inside shrubs in all sites. Our results suggest that there is a positive interaction between native shrubs and native orchids that could result in increased survival in orchid individuals growing inside the canopy of such shrubs. This result could be essential for future conservation and restoration initiatives that should take into account the need for shrubs before re-introduction of individuals in the field, especially for endangered orchid species present in Central Chile.