Abstract
Woody plant invasions, such as Pinus in the Southern Hemisphere, often occur into anthropogenic grass and shrubland ecosystems that were historically forest. These invasions drive profound changes in soil nutrient cycling, in part by influencing soil predators. Nonetheless, woody invasions can also result in an ecosystem state more functionally similar to the original forest than to the indigenous species dominated but anthropogenic ecosystems they replace. Here we investigated the impacts of Pinus invasion on soil micro-eukaryote (protist) communities, comparing pine invaded shrublands to uninvaded shrublands and to indigenous forest. Using meta-barcoding, we found that pine invasion reduced the richness of soil micro-eukaryote communities when compared to shrubland soils. Micro-eukaryote communities in shrubland soils were more varied than the communities present in both the indigenous forest and pine-invaded soils, and pine invaded soils showed more compositional overlap with indigenous forest. We detected that the Cercozoa were the dominant micro-eukaryote group in all three vegetation types, with pine invasion increasing their abundance compared to the indigenous forest. The results support the concept of invasive plants having strong impacts on soil biota, but also suggest that the impacts of woody plant invasions should be compared not only to uninvaded but anthropogenic ecosystems, but also to intact indigenous woody vegetation.