Counting the bodies: Estimating the numbers and spatial variation of Australian reptiles, birds and mammals killed by two invasive mesopredators

Aim Introduced predators negatively impact biodiversity globally, with insular fauna often most severely affected. Here, we assess spatial variation in the number of terrestrial vertebrates (excluding amphibians) killed by two mammalian mesopredators introduced to Australia, the red fox (Vulpes vulpes) and feral cat (Felis catus). We aim to identify prey groups that suffer especially high rates of predation, and regions where losses to foxes and/or cats are most substantial. Location Australia. Methods We draw information on the spatial variation in tallies of reptiles, birds and mammals killed by cats in Australia from published studies. We derive tallies for fox predation by (i) modelling continental-scale spatial variation in fox density, (ii) modelling spatial variation in the frequency of occurrence of prey groups in fox diet, (iii) analysing the number of prey individuals within dietary samples and (iv) discounting animals taken as carrion. We derive point estimates of the numbers of individuals killed annually by foxes and by cats and map spatial variation in these tallies. Results Foxes kill more reptiles, birds and mammals (peaking at 1071 km−2 year−1) than cats (55 km−2 year−1) across most of the unmodified temperate and forested areas of mainland Australia, reflecting the generally higher density of foxes than cats in these environments. However, across most of the continent – mainly the arid central and tropical northern regions (and on most Australian islands) – cats kill more animals than foxes. We estimate that foxes and cats together kill 697 million reptiles annually in Australia, 510 million birds and 1435 million mammals. Main conclusions This continental-scale analysis demonstrates that predation by two introduced species takes a substantial and ongoing toll on Australian reptiles, birds and mammals. Continuing population declines and potential extinctions of some of these species threatens to further compound Australia's poor contemporary conservation record

What role do plant-fungal mutualisms play in restoration ecology? Assessing the impacts of coastal dune modification on mycorrhizae, and whether reconnecting mycorrhizal networks can facilitate restoration of dune vegetation.

Background - Anthropogenic landscape modification, through such processes as deforestation, agricultural and urban expansion, significantly threatens biodiversity and ecosystem function by disrupting species interactions, particularly mutualisms. Whilst the effects of landscape change on other mutualisms, such as pollination, have been well studied, relatively little is known about impacts on the mutualistic association between plants and mycorrhizal fungi within the soil. Plant-mycorrhizal associations occur in all terrestrial ecosystems, for approximately 80 % of all known terrestrial plant species, and are fundamental to the ecological function and diversity of vegetation communities. Disruption of plant-mycorrhizal mutualisms could thus drive a reduction in biodiversity across modified landscapes, and prevent the recovery of plant communities in response to restoration intervention by land managers. Aims - The first aim of this study was to determine whether the abundance and functional identity of fungi within native plant roots vary between reconstructed and remnant coastal dune habitats, using a comparative field-based study within the Illawarra region of southern New South Wales. The second aim was to assess whether the application of a mycorrhizal inoculate (obtained from remnant dunes) to nurserygrown plants prior to their introduction to reconstructed dunes facilitates their establishment and enhances vegetation recovery, through both field and mesocosmbased experiments. Study system – Since European colonisation of the Illawarra region approximately 200 years ago, the landscape has been extensively modified through removal of coastal vegetation for agriculture and urbanisation. Since the 1980s and early 1990s, many of the coastal dunes were reconstructed by local land managers through the deposition of sand from nearby mines and reintroduction of native vegetation, in order to limit coastal erosion, protect urban assets from destructive storms and wave surges, and restore the native coastal ecosystems. The ecological function of these reconstructed dunes relative to those in which the native vegetation was not destroyed by European settlement is not known. Results - For the field-based study I found that there were no significant differences in the abundance and composition of fungal structures between plants on reconstructed and remnant coastal dune habitats. Rates of mycorrhizal colonisation of plant roots varies substantially across the coastal landscapes, but was not influenced by the history of disturbance of the dune vegetation. In the mesocom experiment, there was a non-significant trend towards increased growth of native plant seedlings in response to mycorrhizal inoculation. However, in the field experiments, I detected significant positive effects of inoculate addition on survivorship of native seedlings, although this depended upon the identity of the plant species. Inoculation had no effect on Lomandra longifolia survival, with all plants surviving, whilst inoculation moderately improved survival rates of the grass Poa labillardieri. Study outcomes and implications – My study has demonstrated that mycorrhizal associations between plants and their fungal mutualists may not always be adversely affected by habitat disturbance and subsequent reconstruction. Furthermore, inoculating seedlings with additional mycorrhizae is unlikely to significantly increase rates of vegetation restoration at reconstructed dunes in the short-term. It is probable that mycorrhizae were either not impacted by the original deforestation of the coastal dunes or were able to rapidly recolonise the dune when it was rehabilitated and reform functional networks with the reintroduced plants. I observed, however, that coastal plant communities are still highly fragmented and degraded by a variety of disturbance processes, including alien plant invasion, vandalism and attack by vertebrate pests, such as rabbits. It is suggested that future research investigate the incidence and magnitude of these disturbances between remnant and reconstructed dunes, what their impacts are on native vegetation restoration, and the mechanisms by which these impacts can be reduced

Do native plant associations with arbuscular mycorrhizal fungi and dark septate endophytes differ between reconstructed and remnant coastal dunes?

Anthropogenic landscape modification can disrupt mutualistic interactions between native plants and soil microbes. Restoration of native vegetation in disturbed habitats may depend upon reconnecting plants with their fungal symbionts, such as arbuscular mycorrhizal fungi (AMF). We compared levels of root colonisation by AMF (arbuscules, vesicles, aseptate hyphae) and dark septate endophytes (DSE; septate hyphae, microsclerotia) between reconstructed and remnant dunes along the southern coastline of New South Wales (Australia) for two native plants: Lomandra longifolia and Carpobrotus glaucescens. Reconstruction was undertaken approximately 30 years ago to reinstate native vegetation and reduce erosion on dunes deforested by European settlers during the 1800s. Fungal colonisation was assessed using the point-intercept method on stained root sections under a light microscope. Root colonisation by AMF did not differ significantly between reconstructed and remnant dune habitats, but did vary significantly amongst sites. In contrast, DSE was two times lower for L. longifolia plants growing in reconstructed compared with remnant fore dunes. Our finding of reduced DSE colonisation in reconstructed dunes may indicate that impacts of land clearing on plant-fungal associations may persist over long time periods for some key plant species. Reduced DSE colonisation may be associated with limited restoration potential and functioning of reconstructed fore dune ecosystems. Future research will be needed to assess the scale of reduced DSE across reconstructed coastal habitats, the role of plant-DSE relationships in vegetation community function, and implications of reduced DSE for ecosystem restoration

Sharing meals: Predation on Australian mammals by the introduced European red fox compounds and complements predation by feral cats

Two introduced carnivores, the European red fox Vulpes vulpes and domestic cat Felis catus, have had, and continue to have, major impacts on wildlife, particularly mammals, across Australia. Based mainly on the contents of almost 50,000 fox dietary samples, we provide the first comprehensive inventory of Australian mammal species known to be consumed by foxes, and compare this with a similar assessment for cats. We recorded consumption by foxes of 114 species of Australian land mammal (40% of extant species), fewer than consumed by cats (173 species). Foxes are known to consume 42 threatened mammal species (50% of Australia's threatened land mammals and 66% of those within the fox's Australian range). Reflecting the importance of mammals in their diet, foxes are known to consume a far higher proportion of Australian mammal species (40%) than of Australian birds (24%) and reptiles (16%). Both foxes and cats were most likely to consume medium-sized mammals, with the likelihood of predation by foxes peaking for mammals of ca. 280 g and by cats at ca. 130 g. For non-flying mammals, threatened species had a higher relative likelihood of predation by foxes than non-threatened species. Using trait-based modelling, we estimate that many now-extinct Australian mammal species had very high likelihoods of predation by foxes and cats, although we note that for some of these species, extinction likely pre-dated the arrival of foxes. These two predators continue to have compounding and complementary impacts on Australian mammals. Targeted and integrated management of foxes and cats is required to help maintain and recover the Australian mammal fauna