A Global Meta-Analysis of the Impacts of Forest Fragmentation on Biotic Mutualisms and Antagonisms.

Forest fragmentation is a grave threat to biodiversity. Forests are becoming increasingly fragmented with more than 70% now < 1 km from forest edge. While much is known about the effects of forest fragmentation on individual species, much less is understood about its effects on species interactions. In 2014, a meta-analysis by Magrach et al. assessed the impacts of forest fragmentation on different species interactions, across 82 studies. We expand on their findings by pooling their original data with new data published in the last 10 years, yielding 104 studies and 168 effect sizes. We also compare the new set of publications to the old set to evaluate potential changes in species interactions over time given the global increase in fragmentation rates. Our results confirm the original findings that mutualisms are more negatively impacted by forest fragmentation than antagonisms (p < 0.0001). Additionally, we found that edge effects, fragment size, and degradation negatively impact mutualisms, but not antagonisms; a different finding from the original meta-analysis. We determined that parasitic interactions are stronger with decreasing fragment size (p < 0.0001) - an intriguing result at variance with earlier studies. When data from old and new publications were compared, we found a more negative mean effect size of forest fragmentation on mutualisms. While research is still limited for some interactions, we identified an important scientific trend: current research focuses more on antagonisms. We conclude that forest fragmentation disrupts important species interactions and that this disruption has increased over time. This article is protected by copyright. All rights reserved.