Community ecology: diversity and dynamics over time

Abstract

This paper aims to show the relevance of past ecological records, at centennial to millennial timescales, for community ecological principles and theory, mainly in relation to temporal dynamics and the origin of present-day community patterns. The underlying assumption is that ecological time is a continuum and the ecological understanding of the present biosphere needs inputs from multilevel timescales. In particular, the so-called Q-time, embracing the Quaternary (the last 2.6 million years), is proposed as a key time period to understand present-day patterns and the underlying causal processes, as for example the latitudinal diversity gradient, the relationship between species richness and stability, the equilibrium/non-equilibrium conditions between communities and the environment, the main trends and clues on the origin of present-day species and the communities they form, the community succession under changing environmental conditions, or the nature (individual vs collective) of such biotic responses, among others. In this temporal context, neoecological studies and modeling, based on short-term evidence and calibration/validation data sets, are viewed as an important source for hypotheses to be tested with long-term ecological (i.e., palaeoecological) and molecular phylogenetic studies. The considerations around these topics provide valuable insights to address the potential future state of modern communities under the predicted global change, which would be useful to propose suitable conservation strategies. It is hoped that this paper will promote constructive discussions leading to a more close collaboration between neoecologists and palaeoecologists, in the way towards the natural convergence of both into one single, time-independent, discipline as is (or should be) ecology. As this paper has been conceived for both neo- and palaeoecologists, the message is twofold: to neoecologists, care about time; to palaeoecologists, care about ecology.