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In comparison with drylands elsewhere, the unpredictability of rainfall in central Australia is globally distinctive. The transformative rhythms of arid Australia reflect extremes of climatic conditions rather than seasons, and are characterized by irregular pulses of productivity that punctuate long periods of drought. These decadal-scale dynamics are only now beginning to be understood. Further complications in predicting and managing the biological processes within these landscapes arise from the vast spatial extent of arid and semi-arid communities, and increasing recognition of the heterogeneities that drive the formation of patterns across multiple scales. In 2010 and 2011 flooding rains broke long-standing rainfall records and triggered an anticipated greening of the typically dry red landscapes of central Australia. These unusual climatic events provided an unparalleled opportunity to test ideas about productivity and function, bottom-up versus top-down effects, and differential responses of biota that reflect landscape connections and heterogeneity. Migrations of species outside their known ranges, irruptions of rodents and redistribution of resources are just a few of the novel observations that were reported. The transformation of the landscape also presented land managers with challenges stemming from the influx of invasive species that trigger novel ecological interactions and processes. The papers presented in this special issue describe how ecologists and managers responded to the unprecedented rainfall events, key lessons that we have learnt, and practical recommendations on how to improve conservation outcomes for the fragile inland environment into the future. [ABSTRACT FROM AUTHOR]

Arid zone catchments experience extreme hydrological variability and some rivers are entirely ephemeral, replenished only by intermittent flooding. The ecological roles of ephemeral systems are rarely studied. This paper describes movement patterns of fish in the Mulligan River, an ephemeral system in the Lake Eyre Basin, central Australia. Several sites were sampled along a temporal gradient encompassing floods and dry periods. After a single major flood in 2007 up to seven fish species were found at sites up to 300 km from the closest permanent waterhole. Following a series of floods (when waterholes were replenished and remained wet between 2009 and 2011) a further five species were recorded including the first records for the Lake Eyre hardyhead, Craterocephalus eyresii, from the rivers of far western Queensland. The presence of all species known from the parent catchment (the Georgina, where permanent waterholes occur) in the ephemeral catchment (the Mulligan) suggests that many fish species present in the river systems of central Australia are capable of dispersing long distances following the opening of movement pathways during flooding. However, two distinct groups of species were identified: extreme dispersing species, that move as far as possible into intermittently wetted habitats, and conservative dispersing species, that do not move as far, tending to inhabit deeper waterholes within mid-reaches of the river that are more likely to hold water for longer. Preservation of the natural flow regime of Australia's arid-zone rivers is important for maintaining these fish communities and facilitating study of their adaptations to ephemerality. [ABSTRACT FROM AUTHOR]

In the Canidae family, cases of infanticide have been recorded in populations of dingoes, wolves and red foxes. The consumption of individuals from the same species has not been recorded yet for the crab‐eating fox (Cerdocyon thous), a medium‐sized South American canid with generalist eating habits; however, in a semi‐arid region in north‐eastern Brazil, two C. thous faecal samples were found in August and October 2018 with fur and fragments of paws from young individuals of this species. Cases of offspring consumption have also been reported in other carnivore species from semi‐arid regions, and it is a phenomenon that might be related to the scarcity of resources and a mechanism for obtaining food. Competition for resources is also hypothesized to explain these natural events in nature, as the death of a pup results in greater access to resources for the parent and its offspring. Thus, infanticide can increase the chances of survival of the mother or the other pups. [ABSTRACT FROM AUTHOR]

Carrion is an ubiquitous resource that drives the dynamics of scavenger populations and shapes the structure and composition of their communities. Corvids (Family: Corvidae) are among the most common scavengers globally, facilitating carcass discovery by other species and contributing to carcass biomass removal. Here, we examine how environmental factors influence corvid scavenging dynamics in an arid region of Central Australia. Specifically, we investigate how habitat, season and a major flood event affect corvid discovery and visitation time, and group size around carcass sites. To do so, we used data collected from camera traps monitoring 80 experimentally positioned red kangaroo (Osphranter rufus) carcasses stratified across closed and open habitats, spring and winter seasons, and before and after a flood event. Corvids took longer to discover carcasses in closed compared to open habitats, but habitat did not affect how long corvids spent visiting carcasses, or corvid group size. Corvids discovered carcasses faster in winter compared to spring and in post‐flood compared with the pre‐flood periods, and season and flood interacted to influence both corvid visitation time and group size. Our results reflect a complex interplay between temperature, the extreme boom and bust cyclicity of the study region and changing corvid activity and abundance in the local study area. We identify environmental factors as key determinants of corvid scavenging dynamics and provide the first detailed description of scavenging by corvids in the arid zone of Australia. [ABSTRACT FROM AUTHOR]

Fertile islands are an important determinant of ecosystem functioning in drylands. These resource‐rich patches are maintained by complex interactions among biotic and abiotic factors. Soil microorganisms are responsible for essential ecosystem processes and could affect the ability of fertile islands to capture and cycle nutrients, both directly and indirectly enhancing the fertile island effect. In this context, we aimed to evaluate the attributes of soil microbial communities (abundance and activity), elucidate key drivers of the fertile island effect and analyze relationships with a range of soil parameters (physicochemical). The soils under shrub canopies had higher values of microbial biomass carbon (MBC) and soil basal respiration (SBR) rates than soils from intercanopy spaces. However, no differences were observed in Soil Organic Carbon (SOC) or in fungal and bacterial abundances between the microhabitats. Soil nutrient stocks (NPK) and pH values had a positive correlation with MBC and SBR. Also, a positive correlation was observed for fungi abundance and the K content of the soil. We also observed a positive correlation between the bacterial abundance and soil N content. This study suggests that M. tridens can be considered a keystone species that generates fertility islands, critical for biodiversity and ecosystem functioning. The keystone role that M. tridens plays in this system underscores the importance of improving our understanding of these interactions (plant–soil‐microorganisms), especially important as drylands expand and aridity increases due to climate change in the second half of this century. [ABSTRACT FROM AUTHOR]

Long‐term studies are required to reveal responses by long‐lived, top‐order predator populations to ongoing seasonal fluctuations. However, such investigations are rare in the Australian context. Between 2009 and 2019, the breeding density and productivity of an arid and a mesic wedge‐tailed eagle Aquila audax population, each occupying an area of 2800 km2, were compared (11–98 pairs monitored annually). Breeding pairs spaced themselves evenly in both study areas, with no significant difference between the average arid zone nearest‐neighbour distance of 5.32 ± 1.98 km (n = 44) and that determined for the mesic zone (4.88 ± 2.32 km, n = 54). This similarity in spacing suggests a maximum average density is tolerated by these territorial raptors. By contrast, annual breeding success (proportion of pairs fledging young) and productivity (fledged young per pair) differed significantly between the two populations, with rainfall (but not temperature) influencing reproduction. In the arid zone, the proportion of successful pairs per occupied breeding home range was consistently low each year (mean = 12 ± 7% fledged broods per pair, range 0–26%) and positively correlated with annual rainfall. In the mesic zone, it was consistently high each year (mean = 69 ± 9%, range 57–91%) and not significantly correlated with annual rainfall. Overall productivity figures showed similar differences, with 0.13 and 0.77 fledglings per pair per year for arid (n = 9 years) and mesic (n = 11 years) eagles, respectively. Such low arid zone productivity, the lowest ever recorded for the species, could have long‐term implications in the face of the increased frequency of extreme weather events. That breeding density can be independent of climatic factors provides new insight into the way a large Aquila species integrates with Australia's predominantly arid environment. This study provides an important baseline data set for continued research on long‐term occupancy and productivity trends. [ABSTRACT FROM AUTHOR]

Resting egg production is considered the most common form of dormancy in aquatic invertebrates. Given that many taxa at least partially terminate resting egg state using environmental cues, knowledge on environmental drivers of hatching success is important, particularly within the context of climate change and environmental degradation. Fairy shrimp (anostracans) are temporary wetland specialists that are reliant on resting egg production for population persistence. Temporary wetlands are common in many arid regions projected to experience increases in temperature, and in areas often compromised by human‐mediated activities. In this study, we assessed the combined effects of light and temperature on the hatching success of Streptocephalus cafer (Anostraca) dormant eggs from temporary wetlands in an arid environment. Both temperature and light altered hatching success, with emergent effects evident. Light caused a significant threefold increase in hatching success overall, while temperature effects were non‐linear, with hatching optimised at 27°C, and especially under light conditions. These results are discussed within the context of shifting climates and disturbances to temporary wetland ecosystems. [ABSTRACT FROM AUTHOR]

Understanding the conditions under which small native Australian mammals can persist in the presence of introduced predators remains a key challenge to conservation ecologists. Bettong‐specific one‐way gates were used at a predator‐free reserve in South Australia to allow the burrowing bettong (Bettongia lesueur) – a small potoroid, listed as 'vulnerable' nationally – to disperse out of the reserve. We conducted a field experiment to explore the conditions affecting residence time of bettongs that left the reserve. We monitored bettong and mammalian predator activity outside the fence using track surveys across 18 sites over two seasons. We examined the effect of supplementary feeding as a strategy for increasing residence time, as well as the influence of predator presence and habitat quality, using linear mixed models. Bettong activity was positively associated with supplementary feeding, midstorey vegetation cover and shelter availability. After gates were closed, bettong activity near gates declined to almost zero the following weeks, likely either due to death from predation or due to movement away from the sites. To a small extent, mammalian predators were more likely to be present at sites with high bettong activity. Further research on conditions to support persistence of burrowing bettongs and other small mammals, including understanding minimum necessary predator control effort, is required before successful establishment of populations outside of fences can occur. [ABSTRACT FROM AUTHOR]

High levels of sub‐speciation in Australian mesic zone taxa have been attributed to the creation of biogeographic barriers by Pleistocene expansion of the arid zone. However, several of these barriers also align with major floodplains. The Carpentarian Barrier in the Gulf Plains (GUP) – one of Australia's most significant biogeographic barriers – experiences extreme floods on a sub‐decadal timescale. These floods rise suddenly, cover thousands of square kilometres to a depth of several metres and can take weeks to subside. We investigated whether these floods have shaped community composition. If this is the case, species that are particularly vulnerable to extreme flooding – understorey animals and woody plants, particularly shrubs – should be under‐represented, and grasslands should be over‐represented on GUP floodplains. We used Akaike selection of logistic models to assess influence of floodplains and other potential drivers on grassland distribution and shrub abundance, and on representation of understorey fauna. We also compared post‐flood faunal records with the bioregional data set to assess influence of the 2009 flood on representation of understorey reptiles. Grasslands and shrub‐free vegetation were significantly over‐represented and understorey fauna significantly under‐represented on floodplains, even when the influences of other factors were taken into account. Understorey Gekkota were absent from – and understorey skinks under‐represented in – recently flooded areas. Hence, floods appear to have shaped community composition on GUP floodplains by selectively displacing and/or destroying woody plants – particularly shrubs – and understorey animals. Our findings demonstrate association rather than causality, but show that further examination of the ecological and biogeographic impacts of extreme flooding is warranted. Influence of floods on the Australian biota should be considered an ongoing ecological and evolutionary driver, and one that is likely to intensify as extreme floods are expected to become more frequent under climate change. [ABSTRACT FROM AUTHOR]

The stress‐gradient hypothesis (SGH) predicts that, although facilitation and competition occur together, facilitative interactions will be more prevalent with increasing abiotic stress. In water‐limited ecosystems, support for the SGH has been controversial. Because of the relevance of ecotones to local and regional diversity and the susceptibility to disturbance of the species inhabiting them, these systems represent interesting opportunities to test the SGH. Our aim was to determine whether the spatial pattern of species distribution along an arid ecotone is consistent with the SGH. Vegetation surveys were performed along topographical gradients found between several palaeochannels and bars where two communities dominated by Chuquiraga avellanedae and Larrea divaricata coexist. Daily precipitation and soil water potential at three depths were measured at a palaeochannel and a bar. Univariate and bivariate distribution patterns were investigated by second‐order spatial analysis based on Ripley's K function in order to evaluate the possible existence of positive or negative interactions among plants. Soil water potential was higher at palaeochannels, indicating that a gradient of water stress exists between the palaeochannels and the bars. Whereas palaeochannels showed regularity among C. avellanedae individuals, bars showed aggregation among L. divaricata individuals and among both species. These results suggest a change in dominant interactions along the gradient from facilitative at the more xeric bars to more competitive at the relatively wetter palaeochannels in accordance with the stress‐gradient hypothesis. [ABSTRACT FROM AUTHOR]

Abstract: Murundus are earth mounds widespread in most landscapes in the semi‐arid region of Brazil. Evidence obtained from predictive modelling has suggested a termite origin for these structures, opening up new opportunities for further research. Distribution of densely packed murundus at larger spatial scales is most related to climatic regime and soil nutrient availability. However, factors and processes underlying their distribution and density at smaller spatial scales are not yet fully understood. In this study, we adopted an approach based on mapping point data using high‐resolution satellite imagery, multi‐scale second‐order analysis and general linear models to examine the fine‐scale spatial distribution and density of murundus. Our results suggest that the distribution of those structures within densely packed areas is regulated by more than one process acting or interacting across multiple spatial scales. All densely packed murundus showed a significant regular distribution at the distance scale of up to 50 m radially and a completely random distribution across all other upper distance scales. We interpret the regular pattern as a result of competition for foraging territories between different termite colonies during the process formation of densely packed murundus. The random pattern at larger distance scales (above 50 m radially) can be attributed to habitat selection preferences by termite species builders of murundus mediated by local environmental resources and conditions (i.e. availability of food resources and nesting and open habitat), which would be randomly distributed in space. Thus, at finer spatial scales murundus distributions are associated with biotic interactions acting on an abiotic template. On the basis of significant linear correlations, we suggest that the density of murundus is strongly related to local temperature regime with soil‐type influencing its effect on the murundus densities. Our findings provide novel evidences that mound‐building termites are involved in the formation of murundus in the semi‐arid region of Brazil. [ABSTRACT FROM AUTHOR]

Savanna vegetation is controlled by bottom-up (e.g. soil and rainfall) and top-down (e.g. fire and herbivory) factors, all of which have an effect on biodiversity. Little is known about the relative contribution of these factors to biodiversity, particularly the long-term effects of top-down disturbance on patterns of woody plant composition. The aim of this study was to identify if various degrees of disturbance regimes create distinct woody species community assemblages. Data were collected over 1820 plots across Kruger National Park, South Africa. Woody species were identified and categorized into one of three height classes: shrub (0.75-2.5 m), brush (2.5-5.5 m), and tree (>5.5 m). Species richness and composition were calculated for each site and height class. A combination of long-term fire and elephant density data were used to delineate areas with varying degrees of top-down disturbance (i.e. low, medium and high). Using these degrees of disturbance, species composition was identified and community assemblages constructed according to each disturbance regime. Our results suggest that areas with similar disturbance regimes have similar species composition. Shrub composition was mainly responsive to the number of fires between the years 1941-1990, while tree composition was more responsive to elephant disturbance. A few dominant species were found equally under all degrees of disturbance at all height classes, while others were more regularly found under specific disturbance regimes at particular height classes. This study highlights that while species richness does not appear to be influenced by long-term, top-down disturbance regimes, species community composition may be responsive to these disturbances. Most species and structural classes persisted across all disturbance regimes, but the long-term effects of top-down disturbances can influence compositional and structural biodiversity. This information provides context for management policies related to artificial water provision, elephants and fire. [ABSTRACT FROM AUTHOR]

Resource pulses are a key feature of semi-arid and arid ecosystems and are generally triggered by rainfall. While rainfall is an acknowledged driver of the abundance and distribution of larger animals, little is known about how invertebrate communities respond to rain events or to vegetative productivity. Here we investigate Ordinal-level patterns and drivers of ground-dwelling invertebrate abundance across 6 years of sampling in the Simpson Desert, central Australia. Between February 1999 and February 2005, a total of 174 381 invertebrates were sampled from 32 Orders. Ants were the most abundant taxon, comprising 83% of all invertebrates captured, while Collembola at 10.3%of total captures were a distant second over this period. Temporal patterns of the six invertebrate taxa specifically analysed (Acarina, ants, Araneae, Coleoptera, Collembola and Thysanura) were dynamic over the sampling period, and patterns of abundance were taxon-specific. Analyses indicate that all six taxa showed a positive relationship with the cover of non-Triodia vegetation. Other indicators of vegetative productivity (seeding and flowering) also showed positive relationships with certain taxa. Although the influence of rainfall was taxon-dependent, no taxon was affected by short-term rainfall (up to 18 days prior to survey). The abundance of Acarina, ants, and Coleoptera increased with greater long-term rainfall (up to 18months prior to survey), whilst Araneae showed the opposite effect. Temperature and dune zone (dune crest vs. swale) also had taxon-specific effects. These results show that invertebrates in arid ecosystems are influenced by a variety of abiotic factors, atmultiple scales, and that responses to rainfall are not as strong or as predictable as those seen for other taxa. Our results highlight the diversity of invertebrates in our study region and emphasize the need for targeted long-term sampling to enhance our understanding of the ecology of these taxa and the role they play in arid ecosystems. [ABSTRACT FROM AUTHOR]

In arid to semi-arid grasslands and savannas, plant growth, population dynamics, and productivity are consistently and strongly limited by soil water and nutrient availability. Adaptive traits of the root systems of grasses in these ecosystems are crucial to their ability to cope with strong water and/or nutrient limitation and the increasing drought stress associated with ecosystem degradation or projected climate change. We studied 18 grass species in semi-arid savanna of the Kalahari region of Botswana to quantify interspecific variation in three important root system traits including root system architecture, rhizosheath thickness and mycorrhizal colonization. Drought-tolerant species and shorter-lived species showed greater rhizosheath thickness and fine root development but lower mycorrhizal colonization compared to later successional climax grasses and those characteristic of wetter sites. In addition, there was a significant positive correlation between root fibrousness index and rhizosheath thickness among species and a weak negative correlation between root fibrousness index and mycorrhizal colonization. These patterns suggest that an extensive fine root system and rhizosheath development may be important complementary traits of grasses coping with drought conditions, the former aiding in the acquisition of water by the grass plant and the latter aiding in water uptake and retention, and reducing water loss in the rhizosphere. Within species, both rhizosheath development and mycorrhizal colonization were significantly greater in a wet year than in a year with below-average precipitation. The observed patterns suggest that the primary benefit of rhizosheath development in African savanna grasses is improved drought tolerance and that it is a plastic trait that can be adjusted annually to changing environmental conditions. The functioning of mycorrhizal symbiosis is likely to be relatively more important in infertile savannas where nutrient limitation is higher relative to water limitation. [ABSTRACT FROM AUTHOR]

We examine the role of the native fox, Pseudalopex culpaeus, as a frugivore and seed disperser in a semiarid thornscrub of Chile. We quantified the fruit and animal components in its diet versus the availability of fruits and small mammals in the field over a 2-year period (January 1998 through February 2000). We tested the legitimacy and effectiveness of foxes as dispersers by quantifying the percentages of seed viability and of germination of seeds that passed through fox gut versus those picked from plants. We also studied their efficiency as dispersers, monitoring the fate of seeds in faeces placed in the field. The highest frequencies of fruit consumption by foxes were observed when abundances of small mammal prey were <6 individuals per hectare, regardless of fruit abundance in the field. Thus, foxes consumed fruits as a supplementary food resource. Based on 326 faeces, the total number of fruits consumed was about 34 000 over the 2-year study period, and fruits from the alien shrub Schinus molle represented 98% of that total, with the native Porlieria chilensis a distant second. Germination and viability of defecated seeds of P. chilensis were reduced by 66% and 48%, respectively, in comparison to controls. In contrast, germination of seeds of S. molle increased by 50% and no effect on viability was observed. With regard to P. chilensis, foxes were legitimate (they defecated viable seeds), but ineffective (seeds in faeces had lower germination than those taken directly from parental plants and there was no seedling establishment in the field) and inefficient dispersers (seeds in faeces were deposited on microhabitats hostile to seed germination and seedling establishment). However, with regard to S. molle, foxes were legitimate, effective (seeds in faeces had higher germination than those taken directly from parental plants; there was germination but no establishment in the field), and efficient dispersers (over 41% of seeds were deposited on safe microsites). Thus, a native fox may be contributing to the spread of an alien shrub, co-opting existing community processes. [ABSTRACT FROM AUTHOR]

Abstract Ants are widely used as bioindicators in environmental assessment in Australia, partly because the responses of ant communities to disturbance are relatively well understood. In particular, the use of functional groups has provided a predictive framework for analysing ant community responses to disturbance in the absence of reliable information on the responses of individual species. Here we review 45 studies of the responses of Australian ant communities to disturbance, in order to: (i) identify individual species or species-groups that respond consistently to disturbance; and (ii) examine the usefulness of the functional group scheme as a framework for predicting ant community responses under different disturbance regimes in different biogeographical regions. The most common forms of disturbance in our studies were fire (17 studies), mining (12; mostly studies of minesite restoration) and grazing (7), with other disturbances including clearing, logging, flooding, recreation, urbanization and farming. Responses of individual species were inevitably variable because of differences in vegetation type, severity of disturbance and time since disturbance. However, we identified a range of widespread species that showed predictable responses, including species of the metallica group of Rhytidoponera in temperate Australia (‘increasers’ in relation to disturbance), species of the terebrans and denticulatus groups of Camponotus (increasers), the aeneovirens group of Melophorus (increasers) from the arid zone, and Iridomyrmex pallidus (increaser) from the monsoonal region. The functional group scheme assessed here was not designed specifically in the context of disturbance, but nevertheless in some situations provides a useful framework for analysing ant community responses. Three distinct syndromes of functional group responses can be recognized. First, Dominant Dolichoderinae and Hot Climate Specialists are groups that prefer open environments,... [ABSTRACT FROM AUTHOR]

Abstract The presence of shrubs in arid lands creates spatial heterogeneity that affects the distribution and performance of annual plants; several possible mechanisms have been implicated. A preliminary survey in a chenopod shrubland in South Australia showed differences in the distribution of annual plants under canopies of Atriplex vesicaria and Maireana sedifolia (the two dominant shrub species) and open spaces. A series of experiments were conducted to test the potential contribution to these patterns of nutrient enrichment under shrubs, differential seed accumulation, stress reduction by the canopy, competition by shrub roots, and protection against grazing. The germinable soil seed-bank under A. vesicaria and M. sedifolia was different from that in open spaces, but these differences can only explain a fraction of the differences observed in the growing annual plant community in different microsites. The soil under A. vesicaria had higher total nitrogen content than soil in open spaces, whereas soil under M. sedifolia had lower available phosphorus than open spaces. Although annual plant densities under A. vesicaria were higher than in open spaces, experimental removal of shrubs increased their density, suggesting that shrub canopies inhibit annual plants in this system. Surprisingly, trenching of open areas close to shrubs (severing lateral shrub roots) decreased annual plant density. We suggest that water moves laterally through shrub roots, in a process akin to a hydraulic lift, increasing water availability for the annual plants. Exclusion of vertebrate grazers had a stronger effect on annual plant biomass in open spaces than under M. sedifolia , suggesting that this shrub provides shelter against herbivory. Overall our results show that shrubs can have simultaneously facilitative and inhibitory effects on the annual plant community through different mechanisms, but more importantly that different shrub species have different effects. This is a... [ABSTRACT FROM AUTHOR]