Pre-dispersal seed predation by the weevils Trichapion rostrum and Tychius sordidus limits reproductive output of Baptisia alba (Fabaceae)
2017
Hembrough, Ashley M. | Borowicz, Victoria A.
Baptisia alba (L.) Vent., an herbaceous, perennial legume, produces more flowers than will mature into pods. Single-year experiments on two reconstructed prairies tested the hypothesis that reproductive potential of B.alba depends on nutrients, but pollen limitation and pre-dispersal seed predation by weevils reduce final production. Ramets were assigned one of four treatments that were combinations of fertilizer (none/70 g fertilizer twice) and insect barrier (none/application of Tanglefoot). Within inflorescences, flowers were naturally pollinated or supplemented with pollen. Fertilizer produced no effects, suggesting that B.alba are unresponsive within a season to nutrient supplementation. Pollen supplementation increased pod initiation at the two sites by 6.7% and 2.3%, respectively, but did not affect the proportion of initiated pods that matured or seed number within pods. Where Tychius sordidus occurred, only 67 pods matured on 19 ramets and only four seeds survived. Where only Trichapion rostrum was present, insect barrier increased pod maturation almost three-fold, but did not affect seed number within pods. Barrier treatment increased the reproductive output of entire ramets by increasing seed production, from 3.6 seeds·ramet⁻¹ to 60.5 seeds·ramet⁻¹. Prairie restoration frequently uses fruit collected from other populations. Managers should be careful to avoid the unintended introduction of voracious seed predators.
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