Are there systematic differences in germination between rare and common species? A case study from central European mountains
Abstract
Understanding the factors responsible for species rarity is key for designing effective management strategies aimed at long-term conservation of species. Most such studies investigate plant size, competitive vigour or habitat requirements, but studies that explore more complex characteristics of species directly related to different stages of the plant life cycle are much less common.
Germination is the most critical stage in the life cycle of many plants and is the primary source of variation in the regeneration niche. However, only a few authors have studied differences in germination requirements between common and rare congeners, and none have studied these requirements for large sets of species.
The aim of this study was to compare seed mass, germination requirements and proportions of germinated seeds of rare and common congeners across a large set of species. We analysed seed mass, proportions of germinated seeds in specific conditions and total proportions of germinated seeds of 18 congeneric pairs of rare and common plant species.
We tested different lengths of cold stratification, constant or alternating temperatures, and different light conditions. Seed mass of rare and common congeners was not significantly different.
The results indicated that after cold stratification, the proportions of germinated seeds were higher in rare than in common species. In common species, the proportions of germinated seeds were significantly higher during cold stratification than those of rare species.
Rare species had higher proportions of germinated seeds than those of their common congeners, and total proportions of germinated seeds were influenced by seed mass and species rarity. Rare species were apparently well adapted to local conditions in the mountains and the inability to germinate was clearly not a cause for their rarity.
The study provides unique data on proportions of germinated seeds over a wide spectrum of species and conditions.