Cities alter body size of animal communities

Introduction: A large and international team of ecologists reports in the renowned journal Nature that urbanization is driving body-size shifts in animal communities. Three authors of the Global Change Ecology Centre , Erik Matthysen , Lisa Baardsen and Thierry Backeljau (all belonging to the research group Evolutionary Ecology ), contributed to the study. Thomas Merckx (Université Catholique de Louvain-la-Neuve) -the lead author of the paper- says: "We are the first to show that urbanization is causing bi-directional shifts in body size. What our concerted sampling effort across ten animal groups demonstrates, is that the majority of animal groups shows a pattern of dominance of smaller species with increasing urbanization. This finding is fully in line with the increased ambient temperatures which we recorded for ponds, grasslands and woodlots in urban settings, well-known as the urban-heat-island effect. This urban-heat-island effects selects for smaller body sizes as it increases metabolic costs." However, Thomas Merckx goes on to say that "For three groups -butterflies, moths and grasshoppers- we discovered that the pattern was completely reversed. For these groups, body size is positively linked to mobility, and we concluded that must have overruled the general pattern towards smaller size.