Non-analogous community formation in response to climate change

Palaeoecological and current ecological evidence suggests that species will respond individualistically to future climate change. This is likely to lead to the formation of Non-Analogous Communities (NACs), which may be defined as communities that are different in species composition from any communities that can be recognised at a selected reference point in time. We explore the process of NAC formation, with reference to the key processes of immigration and extinction and the potential influence of landscape pattern, in the context of a metacommunity framework. NAC formation has considerable implications for the development and implementation of conservation policies, which frequently refer to the maintenance of current communities. The achievement of such an objective represents a substantial challenge in an era of rapid environmental change, and fails to accept the dynamic nature of communities. We suggest that conservation policies should identify potential responses to community change based on an understanding of the processes of NAC formation

Taxonomic homogenization of woodland plant communities over 70 years

Taxonomic homogenization (TH) is the increasing similarity of the species composition of ecological communities over time. Such homogenization represents a form of biodiversity loss and can result from local species turnover. Evidence for TH is limited, reflecting a lack of suitable historical datasets, and previous analyses have generated contrasting conclusions. We present an analysis of woodland patches across a southern English county (Dorset) in which we quantified 70 years of change in the composition of vascular plant communities. We tested the hypotheses that over this time patches decreased in species richness, homogenized, or shifted towards novel communities. Although mean species richness at the patch scale did not change, we found increased similarity in species composition among woodlands over time. We concluded that the woodlands have undergone TH without experiencing declines in local diversity or shifts towards novel communities. Analysis of species characteristics suggested that these changes were not driven by non-native species invasions or climate change, but instead reflected reorganization of the native plant communities in response to eutrophication and increasingly shaded conditions. These analyses provide, to our knowledge, the first direct evidence of TH in the UK and highlight the potential importance of this phenomenon as a contributor to biodiversity loss