Columnea florida (?)
Photos by Ron Myhr
Growing in nature in Rara Avis preserve, Costa Rica
There are a few species of Columnea which have these characteristic "windowpane" markings on the leaves. The light filters through the red spots, providing a colorful effect overhead in the jungle. The result is to attract pollinators to the plant, probably hummingbirds. Another example of the effect can be seen in C. consanguinea. Brightly colored red tips to the leaves likely serve the same function.
Unfortunately, I saw no flowers on these plants when I was in Costa Rica, so positive identification was impossible. It is likely, although not certain, that this species is C. florida. Note the extremely unequal nature of the leaves -- it is almost as if the leaves alternate along the stem, but each large leaf has a tiny mate at the same point on the stem, as can be seen more clearly here, in a photo of another species. In some cases, the smaller leaf of the pair is deciduous and disappears altogether. This pattern, where the appearance becomes one of alternate leaves, is referred to as anisophylly.