干旱区生态环境知识资源中心

Identifying and determining the magnitude of plant fitness limitations is important in designing effective management and recovery plans for threatened and endangered plant species. In this study we investigate the extent to which seed abortion and pre-dispersal seed predation by weevils affect reproductive output in Sidalcea nelsoniana, a legally protected species occurring in northwestern Oregon. In addition, we also examine the relationship between host population size and seed predation rates, the relative amounts of weevil infestations on other local Sidalcea species, and the potential significance these factors may have regarding the conservation and recovery of S. nelsoniana. Results showed that recorded seed output in nature was far less than the sum of ovules available for fertilization, primarily due to seed loss from pre-dispersal predation. Production of undamaged seeds averaged 14.6 percent of total ovules, and did not exceed six percent at three of eleven populations. There was no significant correlation between seed predation and population size, suggesting that the latter may not be useful in predicting seed predation rates, and that, in relation to seed predation, neither large nor small populations are inordinately more important from a conservation standpoint. Preliminary results also suggest that weevils prefer S. nelsoniana over other, more common congeners, stressing further the potentially important role seed predation may play in the rarity of this threatened species. Given the limitations to sexual reproductive output in S. nelsoniana, controlling weevils to bolster plant fitness and population recruitment should be considered in future recovery plans for the species.