Conservatism of ecological niche characteristics in North American plant species over the Pleistocene-to-Recent transition

Aim To provide a test of the conservatism of a species' niche over the last 20,000 years by tracking the distribution of eight pollen taxa relative to climate type as they migrated across eastern North America following the Last Glacial Maximum (LGM). Location North America. Methods We drew taxon occurrence data from the North American pollen records in the Global Pollen Database, representing eight pollen types -all taxa for which 5 distinct geographic occurrences were available in both the present day and at the LGM (21,000 years ago +/- 3000 years). These data were incorporated into ecological niche models based on present-day and LGM climatological summaries available from the Palaeoclimate Modelling Intercomparison Project to produce predicted potential geographic distributions for each species at present and at the LGM. The output for each time period was projected onto the 'other' time period, and tested using independent known occurrence information from that period. Results The result of our analyses was that all species tested showed general conservatism in ecological characteristics over the climate changes associated with the Pleistocene-to-Recent transition. Main conclusions This analysis constitutes a further demonstration of general and pervasive conservatism in ecological niche characteristics over moderate periods of time despite profound changes in climate and environmental conditions. As such, our results reinforce the application of ecological niche modelling techniques to the reconstruction of Pleistocene biodiversity distribution patterns, and to project the future potential distribution range of species in the face of global-scale climatic changes.