Plant invasions can affect soil properties in the invaded habitat by altering the biotic and abiotic nature of soils through positive or negative plant–soil feedback. Litter decomposition from many invasive species enhanced soil nutrients, thereby decreasing native plant diversity and leading to further plant invasions. Here, we examined the impact of litter decomposition from an invasive plant (Sphagneticola trilobata) in a range of soils at varying depths on growth and physiology of its native congener (Sphagneticola calendulacea). We added litter from S. trilobata to each soil type at different depths (0, 2, 4 and 6 cm). Plants of S. calendulacea were grown in each treatment, and morphological and physiological parameters were measured at the end of the growing period. All soils treated with litter displayed increases in soil nutrients at depths of 2 and 4 cm; while most growth traits, leaf chlorophyll and leaf nitrogen of S. calendulacea decreased at the same soil depths. Therefore, litter decomposition from invasive S. trilobata resulted in a positive plant–soil feedback for soil nutrients, and a negative plant–soil feedback for growth in native S. calendulacea. Our findings also suggest that the effects of litter decomposition from an invasive plant on soils and native species can vary significantly depending on the soil depth at which the litter is deposited. Future studies should focus on plant–soil feedback for more native and invasive species in invaded habitats, and the effects of invasive litter in more soil types and at greater soil depths.

Eucalyptus is a genus that occurs in a range of habitats in Australia, Papua New Guinea, Timor, Sulawesi and the Philippines, with several species being used as sources of timber and fibre. However, despite its ecological and commercial significance, understanding its evolutionary history remains a challenge. The focus of the present study is the green ashes (subgenus Eucalyptus section Eucalyptus). Although previous studies, based primarily on morphology, suggest that the green ashes form a monophyletic group, there has been disagreement concerning the divergence of taxa. The present study aims to estimate the phylogeny of the green ashes and closely related eucalypts (37 taxa from over 50 locations in south-eastern Australia), using genome-wide analyses based on Diversity Arrays Technology (DArT). Results of analyses were similar in topology and consistent with previous phylogenies based on sequence data. Many of the relationships supported those proposed by earlier workers. However, other relationships, particularly of taxa within the Sydney region and Blue Mountains, were not consistent with previous classifications. These findings raise important questions concerning how we define species and discern relationships in Eucalyptus and may have implications for other plant species, particularly those with a complex evolutionary history where hybridisation and recombination have occurred.

Editorial: Global Changes and Plant Invasions