Local Adaptation of Trees at the Range Margins Slows Range Shifts in the Face of Climate Change


Project Abstract:

The inability of certain species to track their climatic niche at rates comparable to climate change is concerning, particularly if those species are constrained due to their adaptation to the local environment within their current species range. In long-lived, sessile organisms such as trees, genetic adaptation can be slow, and our knowledge of the relative contribution of the driving factors which control range shifts is lacking. Here, we conducted a species wide seed transplant experiment to investigate a series of contributing factors thought to be constraining species range expansion at the seedling establishment phase. We find a combination of provenance, climatic, and microsite factors all play important roles in the ability of a species to migrate northward in latitude, but where their relative contribution of each of these factors changes depending on the environment at the local scale. First, seed provenance from the northern portion of the range provides currently the best opportunity for establishment beyond the current range, where climatic conditions are more similar than those of the central or southern portions of the species range. Second, while we find seedling establishment was highest within the species range, survival rates were comparable to those introduced to sites at the range margin and beyond, regardless of seed provenance. Third, we find that the local climate was the most influential factor for establishment and survival within and at the species range margin; however, a lack of suitable microsites were also found to constrain recruitment. Ultimately, a significant decline in tree recruitment rates will occur if climatic changes continues to occur at a rate superior to the adaptive capacity of seedlings to novel climatic and site conditions beyond their current species range.

Predictions:

(1) We make the following predictions: (i) southern seed provenances will be the most maladapted to the environmental conditions occurring at and beyond the current northern range limit, as they are the furthest in proximity of their origins (provenance effect)

(2) Early seedling establishment will be best within sites which meet the species specific climatic requirements needed to ensure seed germination (climate effect)

(3) Upon seedling establishment, local microsite conditions more closely resembling those within the range limit will favour higher survival rates (microsite effect).

 

Experimental Design: 

6 x Sugar Maple Seed Origins

12x Transplant Sites

*4 sites within the Boreal Forest Biome – Beyond Current Species Range Limit,

*4 sites within the Mixedwood/Transition Biome – At the Current Species Range Limit

*4 sites within the Temperate Forest – Within the Current Species Range

18 Plots at each site  ( 3 replicates x 6 Seed Origins)

150 Seeds/Plot (32,400 Seeds In Total)

Seed Lots
150 seeds from each seed origin were used in each plot.

A total of 216 transplant plots were used.

*Curious how this study turned out? Send me a message.