News post - Sam Wiles ms.

Author: IceAgeEcologist

_posts/2014-08-13-PalEON.md~

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+layout: post
+title:  "New Paper:  Are Ecotonal Communities more Sensitive to Climate Change?"
+date:   2025-07-03 12:00:00 -0700
+categories: media
+blurb:
+---
+Congratulations to Williams Lab alum Sam Wiles, for their recent paper just published in [Global Ecology and Biogeography](https://doi.org/10.1111/geb.70172).  This paper, based on Sam's Master's thesis, conducted a major new reanalysis and mapping of the shifting position of the Tension Zone in Michigan over the past 10,000 years.  (What's the Tension Zone, you ask?  It's the boundary between more warm-loving plant species in the central US and more cold-hardy species in the northern US and southern Canada.  It cuts across Minnesota, Wisconsin, Michigan, southern Ontario, and New England.  Position of the TZ affected by fire regime, soil characteristics, etc. etc.)  Prior work, notably (Hupy, 2012 and Webb, 1983) had shown that the Michigan TZ (MTZ) moved northward during the early Holocene in response to rising temperatures, then shifted southward during the middle to late Holocene.
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+Sam's new paper  reproduces this pattern, but thanks to roughly twice as many fossil pollen records in Michigan than previously analyzed, shows that the north-and-south movements of the MTZ weren't as dramatic as previously reported.  Sam's mapping of the MTZ is based on a very cool NMDS ordination analysis that showed four distinct axes of variation in the Michigan Holocene pollen assemblages, of which one is very clearly associated with the MTZ and a north-south gradient in forest composition in Michigan.    
+
+This paper also shows that communities close to the MTZ ecotone have a higher compositional variability over the ecotone than communities farther away.  This provides support for the often-asserted, rarely tested hypothesis that populations in ecotonal regions should be more sensitive to climate change than communities farther away.  
+
+Nice work Sam and congratulations!