What happens when we let special places remain special places, without intervening, disrupting, leveling, developing, or otherwise disturbing such special habitats? Here is what I know about Ruellia macarenensis. Prior to our visit to Colombia in January 2015, this enigmatic, highly restricted-endemic species was known only from its type collection, which was made in dense forests along the banks of the Río Güejar near the confluence with Río Zanza at the northern edge of the Cordillera Macarena. It was flowering in August of 1950. The Serranía de la Macarena is a biodiversity-rich isolated massif that lies due east of the Cordillera Oriental of Colombia. It represents a unique ecological transition zone between Amazonian, Orinoco, and Andean biotas.
Fast forward 65 years and our field team revisited the type locality to find, all these years later, the population to still be extant, albeit in fruit only in January. If it weren’t for the flowering material available on the holotype and its duplicates, I would swear that Ruellia macarenensis was conspecific with Ruellia jussieuoides. But the type (and protologue) clearly indicate a very different floral morphology of R. macarenensis compared to R. jussieuoides, thus readily distinguishing the two morphologically as different species. I do however predict close relationship between them – both share a conspicuous presentation of primary and secondary veins raised far about the leaf blade surface. Whereas Ruellia macarenensis is highly restricted and endemic to this one small corner of Earth, Ruellia jussieuoides occupies a much broader range that includes large portions of the Amazon north to mesic southern Mexico. Sounds like a classic case of peripatric speciation to me.
Wild collected, Colombia, Godden et al. #254 (COLO) and Tripp et al. #5248 (COLO); Photo by Grant Godden