Some thoughts on the evolution and ecology of recalcitrant seeds

Abstract There are substantial scientific reports on the basic physiology and desiccation sensitivity of recalcitrant seeds, but ecological and evolutionary aspects of their biology have received scant attention. Recalcitrant seeds are shed hydrated, are desiccation sensitive and have a short lifespan. In vegetative tissue, desiccation sensitivity is probably the ancestral state, but tolerance is thought to have evolved early and a number of times independently. It is difficult to see evolutionary relationships among species producing recalcitrant seeds. However, it is suggested that early evolved seeds were desiccation sensitive and that desiccation tolerance is a derived characteristic. Desiccation sensitivity and short lifespan of recalcitrant seeds places constraints on the range of environmental conditions in which reproductive success can occur. Species producing recalcitrant seeds are common in humid tropical forests, where the seeds of climax species germinate and form a seedling bank, rather than contributing to the soil seed bank. However, there is a wide range in post‐shedding physiology among recalcitrant seed species, and recalcitrant seeds do occur in habitats with seasonal climates. Here, regeneration strategies may be more specialized.