Summary• The absence of co-evolved mutualists of plants invading a novel habitat is the logical corollary of the more widely recognized 'enemy escape'. To avoid or overcome the loss of mutualists, plants may co-invade with nonnative mutualists, form novel associations with native mutualists or form associations with native cosmopolitan mutualists, which are native but not novel to the invading plant.• We tested these hypotheses by contrasting the ectomycorrhizal fungal communities associated with invasive Pinus contorta in New Zealand with co-occurring endemic Nothofagus solandri var. cliffortioides.• Fungal communities on Pinus were species poor (14 ectomycorrhizal species) and dominated by nonnative (93%) and cosmopolitan fungi (7%). Nothofagus had a species-rich (98 species) fungal community dominated by native Cortinarius and two cosmopolitan fungi.• These results support co-invasion by mutualists rather than novel associations as an important mechanism by which plants avoid or overcome the loss of mutualists, consistent with invasional meltdown.

Abstract. Understanding the responses of biodiversity to different land use regimes is critical for managing biodiversity in the face of future land use change. However, there is still significant uncertainty around how consistent the responses of different taxonomic groups to land use change are. Here, we use a combination of high-throughput environmental DNA sequencing and traditional field-based survey methods to examine how patterns of richness and community composition correlate among four domains/kingdoms (bacteria, fungi, plants, and metazoans) and the four most-abundant animal taxonomic groups (arachnids, Collembola, insects, and nematodes) across five different land use types (natural forest, planted forest, unimproved grassland, improved grassland, and vineyards). Richness for each taxonomic group varied between land use types, yet different taxa showed inconsistent responses to land use, and their richness was rarely correlated. This contrasted with community composition of taxonomic groups, for which there was relatively good discrimination of land use types and there was strong correlation between group responses. We found little evidence for consistent drivers of taxonomic richness, yet identified several significant drivers of community composition that were shared across many groups. Drivers of composition were not the same as the drivers of diversity, suggesting diversity and composition are independently controlled. While land use intensification has been viewed as having generally negative effects on biodiversity, our results provide evidence that different taxa respond divergently across different land uses. Further, our study demonstrates the power of high-throughput sequencing of environmental DNA as a tool for addressing broad ecological patterns relating to landscape biodiversity.

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Threatened animal taxa are often absent from most of their original habitats, meaning their ecological niche cannot be fully captured by contemporary data alone. Although DNA metabarcoding of scats and coprolites (palaeofaeces) can identify the past and present species interactions of their depositors, the usefulness of coprolites in conservation biology is untested as few endangered taxa have known coprolite records. Here, we perform multilocus metabarcoding sequencing and palynological analysis of dietary plants of >100 coprolites (estimated to date from c. 400–1900 A.D.) and > 100 frozen scats (dating c. 1950 A.D. to present) of the critically endangered, flightless, herbivorous kākāpō (Strigops habroptilus), a species that disappeared from its natural range in Aotearoa-New Zealand (NZ) after the 13th C. A.D. We identify 24 orders, 56 families and 67 native plant genera unrecorded in modern kākāpō diets (increases of 69, 108 and 75% respectively). We found that southern beeches (Nothofagaceae), which are important canopy-forming trees and not an important kākāpō food today, dominated kākāpō diets in upland (c. >900 m elevation) habitats. We also found that kākāpō frequently consumed hemiparasitic mistletoes (Loranthaceae) and the holoparasitic wood rose (Dactylanthus taylorii), taxa which are nutrient rich, and now threatened by mammalian herbivory and a paucity of dispersers and pollinators. No single dataset or gene identified all taxa in our dataset, demonstrating the value of multiproxy or multigene datasets in studies of animal diets. Our results highlight how contemporary data may considerably underestimate the full dietary breadth of threatened species and demonstrate the potential value of coprolite analysis in conservation biology.