From flowering to dispersal: Reproductive ecology of an endemic plant, Astragalus australis var. olympicus (Fabaceae)

Astragalus australis var. olympicus is an endemic plant of the Olympic Moun tains, Washington. It is considered a Species of Concern by the U.S. Fish a nd Wildlife Service. This study focused on the reproductive biology of the plant from Rower production through seed germination to identify possible w eak points that might contribute to its rarity and impede its conservation. Most plants produced a large mean number of flowers and ovules (314.8 and 4106, respectively), but relatively few of these formed fruits and seeds (2 5.8 and 3.8%, respectively). In decreasing importance, ovules in fruits wer e lost to predation, seed abortion, and lack of fertilization. The percenta ges of these fates differed among sites and years. Excluding pollinators by bagging flowers reduced fruit set by similar to 50%, but seed set per frui t and seed mass were unaffected. Germination was affected by scarification, temperature, and moisture availability. About 11% of seeds damaged by pred ispersal seed predators (weevil larvae) remained viable and were released f rom dormancy. I hypothesize that predispersal seed predation (over 80% at o ne site) has a negative effect on population growth. Conservation of this s pecies could benefit from improved fruit set and decreased seed predation.