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Assessing source-sink dynamics in invaded habitat using dietary metabarcoding
  • Anna Holmquist,
  • Seira Adams,
  • Rosemary Gillespie
Anna Holmquist
University of California Berkeley
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Seira Adams
University of California Berkeley
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Rosemary Gillespie
University of California Berkeley
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Abstract

Earth systems are nearing a global tipping point, beyond which the dynamics of biological systems will become unstable. One major driver of instability is species invasion, especially by organisms that act as “ecosystem engineers” through their modification of abiotic and biotic factors. In a mosaic landscape of non-invaded and invaded habitat, ecosystems modified through invasion may serve as “sink” habitat. To understand how native organisms respond to habitat that is becoming increasingly modified, it is essential to examine biological communities within invaded and non-invaded habitat, identifying compositional shifts between native and non-native taxa as well as measuring how modification has affected interactions among community members. Using dietary metabarcoding, our study examines the response of a native Hawaiian generalist predator to habitat modification by comparing biotic interactions across metapopulations of spiders collected in native forest and sites invaded by kahili ginger. Our study shows that, although there are shared components of the dietary community, spiders in invaded habitat are eating a less consistent and more diverse diet consisting of more non-native arthropods which are rarely or entirely undetected in spiders collected from native forest. Additionally, the frequency of novel interactions with parasites was significantly higher in invaded sites, reflected by the frequency and diversity of non-native Hymenoptera parasites and entomopathogenic fungi. The study highlights the role of habitat modification driven by an invasive plant in altering community structure and biotic interactions, appearing to serve as a “sink” for native arthropods and thereby threatening the stability of the ecosystem.