No abstract

Foundation species are species that play important roles in structuring ecological communities. Therefore, conservation managers often aim to promote foundation species. However, it can be unclear which features of foundation species ought to be the focus of management. We studied hummock‐forming grasses in the genus Triodia. Triodia grasses are considered foundation species because they create complex structures used by many fauna species. Although conservation managers often aim to promote extent cover of Triodia, this is only likely to be optimal for species most strongly associated with extent cover or other structural features strongly correlated with extent cover. We tested (i) whether ‘extent cover’ is the most appropriate way to characterise Triodia as habitat and (ii) whether fauna are associated with any non‐Triodia structures. We studied the Triodia structure associations of one mammal, two birds and five reptiles associated with Triodia scariosa at 524 sites in the Murray‐Mallee, Australia (Ningaui yvonneae, Amytornis striatus, Stipiturus mallee, Ctenophorus fordi, Ctenotus atlas, Ctenotus inornatus, Delma australis and Delma butleri). We used site‐level presence–absence data and vegetation structure data to compare parsimony of models built using four Triodia structural features: extent cover, mean height, mean width and mean volume. We also included non‐Triodia vegetation structures in the model selection: extent cover of leaf litter, shrubs and trees. We divided structural features related to extent cover into categories according to their heights. One species was most closely associated with mean Triodia height; one species with mean Triodia width and six species with extent cover of Triodia, although here, Triodia height categories differed between species. Five species were also associated with shrubs or trees. Extent cover of Triodia was generally an appropriate measure of Triodia structure. Nevertheless, we found variation between species. When characterising the structure of foundation species, we recommend testing faunal associations with multiple structural features.

Conservation managers regularly burn vegetation to regenerate habitat for fire-dependent species. When determining the time since fire at which to burn, managers model change in a species' occurrence over time, post-fire (fire-response curve) and identify the time since fire associated with decline in occurrence. However, where species exhibit variability in their fire response across space, using a single fire-response curve to determine the timing of burns may lead to burning habitat at an inappropriate time since fire. We tested if elevation, local topography, soil properties, vegetation type or evapotranspiration affect the fire response of the endangered Mallee Emu-wren Stipiturus mallee and its hummock-grass habitat Triodia scariosa in southeastern Australia (n = 217). Previous work on the Mallee Emu-wren found a unimodal fire response with decline in occurrence at~30-50 yr since fire and a time window of occurrence of~30 yr. We found that time since fire and elevation interact to affect the Mallee Emu-wren fire response. At high elevations (55-98 m), Mallee Emuwrens declined in occurrence at~50 yr since fire, with a time window of occurrence of 20-40 yr. However, at low elevations (28-55 m), Mallee Emu-wrens showed no decline in occurrence with increasing time since fire with a time window of occurrence of up to 107 yr. Extent cover of Tall T. scariosa showed similar patterns to the Mallee Emu-wren, indicating that vegetation structure is a likely driver of variability in the Mallee Emu-wren fire response. We speculate that the effect of low elevation is mediated by increased soil nutrient and water availability for key plants. We used our findings to map the appropriate time since fire at which to burn to regenerate habitat for the Mallee Emu-wren across the study region. We recommend no burning for regeneration across one-third of potential habitat, because the Mallee Emu-wren showed no decline in occurrence in these areas. We recommend managers model variability in species' fire responses across space to improve the timing of burns for regeneration.

When key ecological information is lacking, conservation translocations should be conducted within an adaptive, experimental framework to maximise knowledge gained and to increase the probability of success. Here we investigated whether timing of release or composition of release groups influenced indices of success during a trial reintroduction of the mallee emu-wren, Stipiturus mallee, to Ngarkat Conservation Park, South Australia. We translocated cohorts of 40 and 38 birds in the Austral autumn and spring of 2018 respectively. We released individuals in small groups, comprising either familiar or unfamiliar birds, and intensively monitored all treatments for 2 weeks post-release to quantify short-term survival and dispersal. We used occupancy modelling to assess persistence of the translocated population for 2 years following releases. We also monitored source populations to assess the impact of removals. Mallee emu-wrens released in spring were more likely to remain at the release site and attempt breeding. Familiarity within a release group did not influence short-term survival. Mallee emu-wren occupancy at the release sites declined following releases and by July 2019 (12–15 months after release), we could no longer detect any emu-wrens. Density at source populations was lower 12 months after removal compared with pre-harvest levels, though these differences were not significant. Despite the failure to establish a population, we gained valuable management insights regarding both the focal species, and translocation practice more broadly. Timing of release can influence short-term indices of success. Spring releases should be considered priority actions in future mallee emu-wren translocations.

Species extinctions and declines are occurring globally and commonly have cascading effects on ecosystems. In Australia, mammal extinctions have been extensive, particularly in arid areas, where precipitation drives ecosystems. Many ecologically extinct mammals feed on soil-dwelling insects. However, how this topdown pressure affected their prey and how this contrasts with the bottom-up impacts of fluctuating precipitation remains unclear. We constructed a long-term exclusion experiment in a multi-species mammal reintroduction zone in semi-arid Australia to test how top-down (reintroduced mammals) and bottom-up (precipitation) factors affect root-feeding chafer beetles (Coleoptera: Melolonthinae). We used emergence traps in ten replicate 20 9 20 m plots of control, exclusion and procedural control treatments to trap chafers biannually from 2009 to 2015. Annual precipitation during this period varied from 173 to 481 mm. Mammal exclusion did not affect chafers, indicating that top-down regulation was not important. Instead, chafer abundance, species density and biomass increased with precipitation. Chafer body size and assemblage composition were best predicted by sampling year, suggesting that random drift determined species abundances. Increased resource availability therefore favoured all species similarly. We thus found no evidence that mammal predation alters chafer populations and conclude that they may be driven primarily by bottom-up processes. Further research should determine if the cascading effects of species loss are less important for herbivores generally than for higher level trophic groups and the role of ecosystem stability in mediating these patterns.