Carrying capacity and species diversity in the Pleistocene

Abstract

Carrying capacity (CC) is the maximum biomass that an ecosystem can sustain over the long term. Since CC is ultimately determined by Primary Productivity, it can be predicted from Mean Annual Temperature and Annual Rainfall, the two main determinants of Primary Productivity. In addition to be one of the main determinants of biodiversity, CC strongly conditions several ecological processes. Thus, analyzing the variation in the CC of ecosystems along the Pleistocene, and its relationship with species diversity provides information on how the biological communities of the past were structured. We illustrate here how maps of inferred maximum CC in the past may help us to understand the functioning of palaeoecosystems with an ecological structure without recent analogues. We show that, when compared with recent ecosystems, the mammalian communities of southern Europe were characterized during the late Early Pleistocene by a high carnivore species richness and a moderate, or relatively low, herbivore species richness. Carnivore species richness was as high as it is in the richer recent African communities, but carnivore CC was much lower. Consequently carnivores necessarily occurred in the late Early Pleistocene ecosystems of Europe at low population densities, and this undoubtedly affected ecosystem functioning.