When relationships aren't what they seem

February is all about relationships. But isn't it sad that we need a special month to dedicate ourselves to our relationships? In biological sciences, almost everything is about relationships. All year round. With the difference that we do not call them romantic or platonic, but instead phylogenetic or evolutionary. The most basic question in biology is how organisms are related to each other. This can be done by studying all kinds of features or by just analyzing DNA sequences.

Analyzing evolutionary relationships often gives surprising results. We now know that besides crocodiles, the closest living relatives of dinosaurs are birds, not lizards or snakes. Thus, look-alikes are not necessarily close to each other, and often completely unrelated organisms have acquired strikingly similar features through convergent evolution. A well-known example are dolphins and sharks. One of the best cases among lichens are beard lichens (Usnea and Ramalina) and the Spanish moss (Tillandsia usneoides). The latter is neither a lichen nor a moss, but a flowering plant related to the pineapple! The most similar lichen is Ramalina usnea. Both the Tillandsia (left, from Venezuela) and the Ramalina (right, from Mexico and Galapagos) form curtains of long beard in tree canopies, well-adapted to capture moisture and nutrients from the air. Both are widely distributed in the Americas, dispersed by wind and probably also by birds that use them as nesting material. Yet, one is a plant from the pineapple family and the other is a fungus and hence, believe it or not, more closely related to dinosaurs!