Differential Tolerance to Increasing Heterospecific Pollen Deposition in Two Sympatric Species of Burmeistera (Campanulaceae: Lobelioideae)

Premise of research. Heterospecific pollen deposition on stigmas can impact plant reproduction by decreasing seed set or inducing fruit abortion. Pollinating bats often carry pollen from many species on their fur, and thus bat-pollinated flowers may exhibit tolerance to heterospecific pollen deposition, but to our knowledge this has never been studied. We investigated the relative impact of increasing heterospecific pollen deposition on female reproduction of two sympatric species of Burmeistera that experience pollen transfer between them by their shared bat pollinators.Methodology. We simulated heterospecific pollen deposition by applying pollen mixtures that differed in the ratio of heterospecific to conspecific flowers used to make them (3∶1; 2∶2, and 1∶3) and measured female reproduction by quantifying fruit abortion, seed number, and seed mass.Pivotal results. For Burmeistera borjensis, applying a higher relative amount of heterospecific pollen led to decreased seed production and lighter seed mass,...