Testing the co-invasion hypothesis: ectomycorrhizal fungal communities on Alnus glutinosa

It has been proposed that co-invasion with ectomycorrhizal (EM) fungi is a common mechanism by which non-indigenous trees overcome symbiont limitation, yet virtually all prior evidence has come from a single plant family, the Pinaceae. We tested the co-invasion hypothesis by examining the EM fungal communities associated with a specialized host, Alnus glutinosa (black alder), and a generalist host, Salix fragilis (crack willow), in New Zealand, where both trees are invasive. We aimed to find out if these two hosts, which often co-occur on invaded riverbanks, (1) were forming novel EM fungal associations in New Zealand and (2) had potential to facilitate each other through shared EM fungi. Location: New Zealand. Methods: We collected root tip samples from both host plants at riparian sites on the North Island and South Island and used DNA sequence-based identification to characterize EM fungal communities. Results: Both trees relied upon exotic EM fungi from their indigenous ranges and did not associate with any known endemic New Zealand EM fungi. Alnus had highly similar communities on both islands, while the Salix communities were distinct. All EM fungi on South Island Alnus were also present on South Island Salix, while North Island Salix did not substantially share EM fungal associates with Alnus. Main conclusions: Overall, our study indicates that plant hosts with specialized and more generalist EM fungal communities can both successfully invade new habitats with non-indigenous EM fungi. While there may be some potential for facilitation between these two EM plants hosts via shared non-indigenous fungi, this outcome was context specific. Our findings suggest that the specificity of fungal mutualists is not a major barrier to the spread of invasive plants and cannot be taken as evidence an introduced plant will not become invasive

A lost link between a flightless parrot and a parasitic plant and the potential role of coprolites in conservation paleobiology

Late Quaternary extinctions and population fragmentations have severely disrupted animal-plant interactions globally. Detection of disrupted interactions often relies on anachronistic plant characteristics, such as spines in the absence of large herbivores or large fruit without dispersers. However, obvious anachronisms are relatively uncommon, and it can be difficult to prove a direct link between the anachronism and a particular faunal taxon. Analysis of coprolites (fossil feces) provides a novel way of exposing lost interactions between animals (depositors) and consumed organisms. We analyzed ancient DNA to show that a coprolite from the South Island of New Zealand was deposited by the rare and threatened kakapo (Strigops habroptilus), a large, nocturnal, flightless parrot. When we analyzed the pollen and spore content of the coprolite, we found pollen from the cryptic root-parasite Dactylanthus taylorii. The relatively high abundance (8.9% of total pollen and spores) of this zoophilous pollen type in the coprolite supports the hypothesis of a former direct feeding interaction between kakapo and D. taylorii. The ranges of both species have contracted substantially since human settlement, and their present distributions no longer overlap. Currently, the lesser short-tailed bat (Mystacina tuberculata) is the only known native pollinator of D. taylorii, but our finding raises the possibility that birds, and other small fauna, could have once fed on and pollinated the plant. If confirmed, through experimental work and observations, this finding may inform conservation of the plant. For example, it may be possible to translocate D. taylorii to predator-free offshore islands that lack bats but have thriving populations of endemic nectar-feeding birds. The study of coprolites of rare or extinct taxonomic groups provides a unique way forward to expand existing knowledge of lost plant and animal interactions and to identify pollination and dispersal syndromes. This approach of linking paleobiology with neoecology offers significant untapped potential to help inform conservation and restoration plans.Jamie R. Wood, Janet M. Wilmshurst, Trevor H. Worthy, Avi S. Holzapfel, and Alan Coope