Background:

Floral biology influences the plant reproductive systems and allows identify factors that affect the survival and dynamics of plant populations.

Questions:

What are the floral attributes, the floral display, the reproductive system, reproductive performance, and the main floral visitors of N. gracilis? Can intrapopulation crossings lead to inbreeding depression?

Study species:

Nymphaea gracilis an emerging rooted hydrophyte endemic to central Mexico and threatened with extinction.

Site and years of studies:

The study was carried out in two bodies of water in the municipality of Toluca, State of Mexico. From August to December 2017 and 2018.

Methods:

The floral morphology and the male and female function were evaluated throughout the anthesis. The production and biomass of fruits and seeds, the floral visitors and the pollen: ovule relationship were analyzed. The reproductive strategy was evaluated by pollinator exclusion experiments and artificial pollinations.

Results:

Nymphaea gracilis presents diurnal anthesis for 4-6 days, stigmatic receptivity first two days, incomplete protogyny and facultative xenogamy. Apis mellifera made the largest contribution of pollination. Artificial crosses indicated that the species is not agamosperm and that it maintains a mixed crossing system, autocompatibility, autogamy, pollinator-mediated pollen limitation, and relatively low levels of inbreeding depression.

Conclusions:

The mixed reproductive system in N. gracilis could be favoring the permanence of the population and guarantee the offspring in an environment where the availability of pollinators is low.