Delayed selfing ensures reproductive assurance in Utricularia praeterita and Utricularia babui in Western Ghats

Numerous bladderwort (Utricularia) species are distributed worldwide, but their reproductive biology is rarely investigated. Bladderworts are known to depend on tiny organisms to meet a significant proportion of their energy requirement by trapping them in bladders. However, information on the extent of their reliance on insects for pollination success is limited. We examined the reproductive strategy of two Utricularia species viz. Utricularia praeterita and U. babui, endemic to Western Ghats, India. The main aspects of the investigation involved floral biology, breeding system, pollination mechanism, and reproductive success. Flowers of both the species are structured for outbreeding through entomophilous floral suites, herkogamy, protandrous dichogamy and sensitive lobes of the stigma. With nearly 65% natural fruit-set, both the species appeared to be sufficiently open-pollinated. However, pollinators failed to show in plants of U. praeterita while in U. babui there was an apparent mismatch between the extent of fruit-set and pollinator visits. The study demonstrated that in the absence/insufficient visits of pollinators, the two species resort to autonomous selfing. In U. babui, denser patches of plants appeared to be crucial for attracting the pollinators. Both species are self-compatible, and reproductive success is predominantly achieved by delayed autonomous selfing. The sensitive stigma in the species fails to prevent selfing due to diminished herkogamy during the late anthetic stages. It is inferred that in the pollinator-limited environment, delayed selfing contributes to absolute natural fecundity in U. praeterita, while it produces a mixed progeny in U. babui.