Local climate modulates the development of soil biodiversity after glacier retreat

Background/Question/Methods

: The world’s mountain glaciers are retreating at an unprecedented rate due to ongoing climate change, and the pace of glacier retreat is accelerating across the globe. Deglaciated areas undergo quick colonization by multiple lifeforms and develop into new ecosystems. Climatic differences between regions of the world could modulate the emergence of biodiversity and functionality after glacier retreat but global tests of this hypothesis are lacking. Thus, we urgently need to understand the dynamics of these environments to predict the consequences of climate change. Nematodes are the most abundant soil animals, with keystone roles in ecosystem functioning. Understanding the factors affecting nematodes colonization of deglaciated areas at global scale will provide key information on the formation of soil, on the biotic communities that will follow, and on their long-term responses to climate change. We used a global dataset representing 240 sites in 48 deglaciated areas, comprising five continents from the equator to the polar regions, to evaluate how taxonomic and functional diversity of nematodes emerges in ecosystems developing after the retreat of glaciers. We produced taxonomic inventories using environmental DNA metabarcoding from 1,197 soil samples and combined taxonomic data with available databases on functional traits to obtain estimates of functional diversity.

Results/Conclusions

: We show that some nematode taxa colonize deglaciated areas almost immediately. While both taxonomic and functional diversities quickly increase over time, this patter is modulated by climate so that colonization starts earlier in forelands with mild summer temperatures. Colder forelands initially host poor communities, but the colonization rate then accelerates, eventually levelling biodiversity differences between climatic regimes after 150 years. Communities showed functional shifts during colonization, indicating a major role of environmental filtering in succession patterns. Soon after glacier retreat, communities were dominated by small colonizer species with r ecological strategy. At later stages, we found more species with longer generation times and larger body size. The effects of local climate on biotic colonization led to heterogeneous but predictable patterns around the world, likely affecting soil evolutions, which are vital for the development of ecosystems. Recognizing the complexity of biotic responses will allow to understand how these environments develop and to predict cascading effects at multiple scales.