The majority of climate change work has focused on how high latitude, high elevation plant communities will respond to changes in climate. Less emphasis has been placed on how low latitude, low elevation plant communities will respond to climate change, as future increases in temperature are predicted to be lower at low latitudes and low elevations and therefore less influenced by changes in climate. We tested this hypothesis using 238 pollen records of vascular woody plants across North and South America during periods of climate change throughout the Holocene (~ 10,000 – 150 ybp). We quantified community change using Bray-Curtis dissimilarity and Euclidean distance measures on pollen percentages.
Results/Conclusions
We identified a latitudinal unimodal response of plant community change from 5,000 – 150 ybp, with low latitudes having higher community change; however this relationship was not present from 10,000 - 5,000 ybp. Species richness was not correlated with plant community change, meaning that greater community changes at low latitudes were not spuriously caused by higher species richness in the tropics. We attribute these results to differences in climate change patterns between the Climatic Optimum (10,000 – 5,000 ybp) and post-Climatic Optimum (5,000 – 150 ybp) of the Holocene: 1) the retreat of glaciers from 10,000 – 6,000 ybp in the northern hemisphere lead to high rates of community change at high latitudes collapsing latitudinal gradients; 2) increased precipitation variability causing increased aridity over the past 5,000 years around the equator yielded higher levels of community change at lower latitudes. We also identified a positive relationship between elevation and community change across high elevation communities from 5,000 – 150 ybp, explained by greater decreases in temperature at extremely high elevations relative to high latitude areas with low elevations. Our results suggest that low latitude and high elevation plant communities may be greater affected by changes in climate, as predictions of increased aridity around the equator and increased temperatures at high elevations caused by changes in climate over the next 50 years may induce greater community change in these areas than previously thought.