Evolution and ecology of fast seed germination in Amaranthaceae s. I.

摘要

Some of the fastest germinating seeds can germinate within a few hours after imbibition. From the scarce literature available it is clear that such very fast germination is typically found in species growing in stressful, highly dynamic or pioneer habitats (Parsons 2012). In such habitats, fast germination and establishment of seedlings might considerably reduce seedling mortality. Since the majority of examples for fast and very fast germination are species of Chenopodiaceae (now included in the Amaranthaceae s. I.), we chose the Chenopodiaceae/Amaranthaceae complex to study evolution and adaptive nature of germination speed. The main hypotheses we tested are the following: (1) Fast germination is an adaptation to stressful habitat conditions withshort and/or irregular phases of favourable conditions. (2) Fast germination is advantageous for short-lived species and pioneer species, which generally form a soil seed bank to reduce the impact of environmental variability. (3) Bet-hedging strategieshave evolved to reduce competition between offspring and to reduce the impact of environmental variability. (4) Higher germination rates have co-evolved with a C,,photosynthesis.