Influence of temperature, maternal source, and seed position in fruit on seed germination and ability to form soil seed banks in threatened species of Coincya (Cruciferae)

The influence of temperature, maternal source, and seed position in fruit on seed germination and ability to form soil seed banks was analyzed in four endemic species of Iberian Coincya (Cruciferae): C. rupestris subsp. rupestris, C. rupestris subsp. leptocarpa, C. longirostra, and C. monensis subsp. orophila, the first three being endangered. Highest germination percentages were recorded at fluctuating temperatures of 15-4 degreesC, followed closely by 20-7 degreesC and 15 degreesC. Geographical (interpopulation level) and maternal (intrapopulation level) sources of seeds, as well as position of seeds in fruit (intraindividual level) influenced the germination patterns decisively. Thus, significantly different final germination percentages between populations in the same taxa were achieved at certain temperature-incubation treatments. In 5 of the 7 populations investigated, a high intrapopulation variability in germination patterns was detected, depending on the maternal source. In two populations of C. rupestris subsp. rupestris and in one of C. rupestris subsp. leptocarpa, seeds from the beak of the fruit germinated to higher percentages than those from the valvar portion. The soil seed bank of all Coincya taxa studied had a persistent component, but also had a high nonviable-seed fraction in the soil, indicating the existence of short-term persistent seed banks. The importance of such a seed bank type in population maintenance of threatened species is discussed.