Probably just a weed - but it caught my eye because of it's bright color. Everything in the rainforest is some shade of green and the tiniest spots of color stand out.

I have been trying to identify this plant since I posted it. With the help of my friends on the Dave's Garden plant identification forum I now know that it is a senecio.
But since there are so many species I am not going to attempt any further research.

Senecio is a genus of the daisy family (Family Asteraceae) that includes ragworts and groundsels.
The flower heads are normally rayed, completely yellow, and the heads are borne in branched clusters.
Though of late the genus has been reviewed and split up, it still contains a vast number of species (about 1,500)
of extremely wide form including leaf succulents, stem and tuber succulents, annuals, perennials, aquatic forms, climbers, shrubs and small trees.
Some species produce natural pesticides (especially alkaloids) to deter or even kill animals that would eat them.

Wikipedia

This photograph was taken beside the road in the Soberanía National Park.