Coping with stressful environments: An experimental study of seed germination and seedling survival of Mexican riverweeds under natural conditions

•We studied seed germination and seedling survival of two species of Podostemaceae.•Study was performed in rivers with different light incidence.•We found significant differences between species in final seed germination.•Final seed germination is higher at the river with higher light incidence.•Seedling survival for both species is considerably low.