Variation in seed longevity among different populations, species and genera found in collections from wild Australian plants

Natural variation in longevity among populations of the same species, and between species and genera was investigated to inform seed-collection strategies. Seed longevity for 30 wild Australian populations was measured with a controlled ageing test. The populations were represented by eight species from three genera, namely Minuria (Asteraceae), Wahlenbergia (Campanulaceae) and Plantago (Plantaginaceae), each collected from up to eight different locations. Seed-survival curves were fitted by using the equation v = Ki + p/s, which allowed comparison of the initial population viability (Ki), the population distribution of seed life spans (s), and mean seed longevity (P50, calculated as Ki × s). At a genus level, the average P50 indicated that M. integerrima (DC) Benth. is the longest-lived, Wahlenbergia is intermediate and Plantago is the shortest-lived. However, there was also variation in P50 values among populations of most species. Some species had the same s value for all populations, e.g. all eight populations of W. communis Carolin had the same s value, with the differences in Ki causing the variation in P50. This consistency in s existed even though seedlots were collected from diverse locations, with mean annual rainfall ranging from 180 to 840 mm. In comparison, for the six seedlots of W. gracilis (G.Forst.) A.DC., a large difference in s as well as Ki led to the variability in P50, with some indication of a possible correlation between annual rainfall and P50 or s in some species. A relationship between variation in s and the breeding system is proposed for Wahlenbergia. The data show that it can be risky to expect accurate prediction of seed longevity for a wild species on the basis of survival data from a single collection.