COMPLEXITY vs COMPLICATION OK, now it comes the challenge..If two decades after Complexity as an already established science we still don't get the point that's because the definition of Complexity is still one of the not-yet-answered premises. Papers in lots of journals and big projects are today taking advantage of the "fashion" of complexity by working with complicated studies. Thus the main difference between both concepts lies on how its nature counteracts when patterns are seen through different scales. Usually a complicated system is that with a large array of agents that interact. In a complex one large-scale patterns are to be seen from the simple interactions between its many components: that is, the so-called emergence (Drake et al., 2007). Thus, structure appears on scales above that of the components: a complicated system may not be complex, while a complex system may not be complicated or composed by many agents. ECOLOGICAL COMPLEXITY Ecological systems have been subject of many studies studying some typical properties of complex systems, such as emergence, strong nonlinear outcomes and even phase transitions. The many degrees of freedom associated to ecological components of interaction are accounted by species in communities and food webs, delayed responses in species interactions, and even spatial domains or scales of foraging. Percolation, predators meltdown, prey switching, species diversity, species-area relationships, habitat fragmentation, assembly of communities, productivity-diversity or the disturbance-heterogeneity hypothesis have been explained through a complex systems approach. Thus, although most of them have not been yet experimentally explored, the field opens a very interesting theoretical basis for future experimental protocols and reveals lots of questions to track on ecological grounds. The figure of the left is a clear example. It stands on graph-theoretic approaches to reveal how habitat patches (nodes) are connected in a landscape through dispersal by a species. The resulting (reorganized through certain sorting algorithm) graph shows a hierarchical system of patches where the most connected nodes may not necessarily be those larger patches, but those keystone patches that may avoid extinction of a species through rescue effects. RESEARCH FIELDS Click on each picture to check Javier's interests