Persistent diversity-climate disequilibria due to Quaternary and pre-Quaternary climate change

Background/Question/Methods

Earth has experienced dramatic and sometimes rapid climate changes in the past in both near time (Quaternary, last 2.6 million years) and deep time (earlier). The extent to which current species diversity patterns are still shaped by these past changes offer key insights into what to expect in terms of biotic responses to future rapid climate change, both in terms of constraints on these responses and in terms of the time frames over which their effects may persist afterwards. Geographic patterns in distributions, species richness, or functional community structure is typically understood as primarily determined by the contemporary environment, notably climate, sometimes via an interplay with evolutionary niche dynamics. However, past climate change may cause these patterns to not be in equilibrium with climate due to lagged responses, e.g., due to dispersal limitation. Here, I present results from a suite of macroecological studies that have addressed this issue.

Results/Conclusions

Analyses of plant species distributions across Europe show that many have distributions that are not in equilibrium with contemporary climate, but are still constrained by limited postglacial recolonization from their glacial refugia. Studies of plant and animal species richness patterns similarly show constraints imposed by limited postglacial recolonization, not just in Europe, but also worldwide and even within tropical regions such as Madagascar. These constraints are strongest for poorly dispersed groups and for small-ranged species, while of little or no importance for wide-ranging species. Studies of palms globally and across Africa furthermore illustrate how deep-time pre-Quaternary climate may also still constrain diversity patterns. Several plant studies show that past climate-change legacies may penetrate across scales to affect diversity patterns at landscape and local scales. While yet little studied, a few studies indicate that past climate change constraints on distribution and diversity patterns may also have consequences for community and ecosystem functioning. In conclusion, these studies show that distribution and diversity responses to climate change can exhibit lags lasting many millennia to even millions of years.