Cryptic spatial aggregation of the cushion plant Azorella selago (Apiaceae) revealed by a multilocus molecular approach suggests frequent intraspecific facilitation under sub-Antarctic conditions

Premise of the study: In abiotically severe habitats, intraspecific aggregations can increase species' fitness by ameliorating stressful environmental factors. However, the difficulty of identifying individual plants in some growth forms makes the measurements of intraspecific aggregation, and therefore the assessment of intraspecific facilitation, problematic. In this study, we examined the genotype composition within cushions of Azorella selago, a sub-Antarctic cushion plant, to investigate the potential extent of intraspecific facilitation. Methods: The study was performed on Marion Island, South Africa. Two to eight samples were collected from 42 A. selago cushions, comprising eight different growth forms. Samples were genotyped using seven microsatellite markers. Key results: We showed that all cushion shapes, with the exception of small cushions, may be comprised of more than one genetically distinct individual. Conclusions: Under harsh sub-Antarctic conditions, intraspecific aggregation between A. selago individuals appears common and may be driven by the positive impacts of environmental amelioration.