When Bigger Is not Better: Corolla Length Increases Nectar Robbing in Aloe secundiflora Engl. (Asphodelaceae)

Nectar robbing is a widespread but unevenly documented component of plant–pollinator interactions, and quantitative assessments from African savanna systems remain limited. Based on a short field survey conducted over two consecutive days, this study quantified the frequency and reproductive consequences of nectar robbing in a population of Aloe secundiflora in northern Tanzania and tested whether robbing probability was associated with floral morphology and plant‐level traits. A total of 385 flowers from 10 plants were examined. Nectar robbing affected 34% of flowers, whereas 21% initiated fruit. Robbing was performed not only by insects but also by the collared sunbird ( Hedydipna collaris ), whereas the scarlet‐chested sunbird ( Chalcomitra senegalensis ) acted as the dominant legitimate visitor. The probability of robbing increased strongly with corolla tube length but was unrelated to corolla diameter, floral display or nearest‐neighbour distance. Nectar robbing had a pronounced negative effect on fruit initiation: robbed flowers showed substantially lower probability of fruit initiation than non‐robbed flowers. In contrast, fruit initiation was positively associated with corolla diameter, whereas corolla tube length had no independent effect once robbing status was included in the model. These results indicate that floral morphology influences susceptibility to nectar robbing and that robbing can impose short‐term fitness costs even in bird‐pollinated African succulents. By providing quantitative evidence from an understudied African system, this study highlights the importance of illegitimate floral interactions in shaping reproductive outcomes in bird‐pollinated succulents.