Search

Habitat loss and fragmentation are likely to seriously impact parasites, a less studied but critical component of ecosystems, yet we lack long‐term experimental evidence. Parasites structure communities, increase connectivity in food webs, and account for a large proportion of an ecosystem's total biomass. Food web models predict that parasites with multiple obligate hosts are at greater risk of extinction because the local extinction, or reduction in abundance, of any host will result in a life‐cycle bottleneck for the parasite. We examine the response of a parasite and its multiple hosts to forest fragmentation over 26 years in the Wog Wog Habitat Fragmentation Experiment in southeastern Australia. The parasite is the nematode Hedruris wogwogensis, its intermediate host is the amphipod, Arcitalitrus sylvaticus, and its definitive host is the skink, Lampropholis guichenoti. In the first decade after fragmentation, nematodes completely disappeared from the matrix (plantation forestry) and all but disappeared from their definitive host (skinks) in fragments, and by the third decade after fragmentation had not appreciably recovered anywhere in the fragmented landscape compared to continuous forest. The low prevalence of the nematode in the fragmented landscape was associated with the low abundance of one or the other host in different decades: low abundance of the intermediate host (amphipod) in the first decade and low abundance of the definitive host (skink) in the third decade. In turn, the low abundance of each host was associated with changes to the abiotic environment over time due largely to the dynamically changing matrix as the plantation trees grew. Our study provides rare long‐term experimental evidence of how disturbance can cause local extinction in parasites with life cycles dependent on more than one host species through population bottlenecks at any life stage. Mismatches in the abundance of multiple hosts over time are likely to be common following disturbance, thus causing parasites with complex life cycles to be particularly susceptible to habitat fragmentation and other disturbances. The integrity of food webs, communities, and ecosystems in fragmented landscapes may be more compromised than presently appreciated due to the sensitivity of parasites to habitat fragmentation. [ABSTRACT FROM AUTHOR]

The kelp, Ecklonia radiata, is an abundant subtidal ecosystem engineer in southern Australia. Density‐dependent changes in the abiotic environment engineered by Ecklonia may feedback to affect reproduction and subsequent recruitment. Here, we examined: 1) how the reproductive capacity of Ecklonia individuals in the field (zoospores released · mm−2 reproductive tissue) varied with adult density and time, and 2) how the recruitment of microscopic gametophytes and sporophytes was influenced by zoospore density at two times. Zoospore production did not vary with adult density, with only one month out of ten sampled over a 2‐y period showing a significant effect of density. However, zoospore production varied hugely over time, being generally highest in mid‐autumn and lowest in mid‐late summer. There were strong effects of initial zoospore density on gametophyte and sporophyte recruitment with both a minimum and an optimum zoospore density for sporophyte recruitment, but these varied in time. Almost no sporophytes developed when initial zoospore density was <6.5 · mm−2 in spring or <0.5 · mm−2 in winter with optimum densities of 90‐355 · mm−2 in spring and 21‐261 · mm−2 in winter, which resulted in relatively high recruitment of 4‐7 sporophytes · mm−2. Sporophyte recruitment declined at initial zoospore densities >335 · mm−2 in spring and >261 · mm−2 in winter and was zero at very high zoospore densities. These findings suggest that although adult Ecklonia density does not affect per‐capita zoospore production, because there is a minimum zoospore density for sporophyte production, a decline in population‐level output could feedback to impact recruitment. [ABSTRACT FROM AUTHOR]

In arid environments, shade provided by vegetation forms the crux of many facilitation pathways by providing other organisms with relief from high levels of solar radiation and extreme temperatures. Shade is an important determinant that structures arid ecosystem processes and functioning. While shade is considered an essential refuge for many organisms in arid environments, few studies have assessed how parasitic plants such as aerial mistletoes can influence the quality of shade provided by its host, and how this can subsequently influence species interactions. Here, we investigate how mistletoe influences the microclimate and daytime use of sub-canopy habitat by a large herbivore that seeks out shady micro-habitats to avoid daytime heat in Australia's Strzelecki Desert. We experimentally removed the pale-leaved mistletoe (Amyema maidenii) from mulga trees (Acacia aneura) and monitored sub-canopy ambient temperatures and the daytime use of sub-canopy habitat by red kangaroos (Osphranter rufus). Results showed that average hourly temperature during the daytime and daily maximum temperature were cooler and that kangaroos were approximately three times more likely to shelter beneath trees where mistletoe was present (control) compared to where mistletoes had been removed (treatment). By showing that mistletoe can improve the quality of shade provided by their host trees, our study offers a novel insight into how mistletoes can facilitate the surrounding biota through modifying the abiotic environment beyond its physical structure. More broadly, the results of our study emphasise the prevalence of positive interactions within ecological communities and how they can occur in unexpected ways and indirectly between organisms that never come into direct contact. [ABSTRACT FROM AUTHOR]

This study aimed to identify the optimal flowering times to maximise yield of lentil in current growing regions and areas of potential expansion of this crop in Australia. We used the validated APSIM-lentil model and identified critical reproductive periods matching minimum risk of abiotic stresses and then applied an ideotype breeding approach coupled with improved agronomic practices that maximise yield of lentils. Sowing windows defined between early-April and early-May were matched with optimal flowering periods (OFP). Optimum yield varied within the environments (2.64–4.64 t/ha) and was associated with OFP. Based on cumulative frost, heat, and water stress, 1750 environments were clustered into low-risk, medium-risk and high-risk categories corresponding to pre- and post-OFP. Overall, sowing later than the optimal sowing window significantly reduced yield of lentils across environments in all regions. For each week delay in sowing beyond the optimal window, yield was predicted to reduce by up to 49 kg/ha across the environments. Based on the association between phenological traits and seed yield, we developed fourteen new lentil ideotypes to target abiotic production constraints. In most cases, the predicted peak mean yields for the ideotypes were greater than that of a high yielding commercial variety across a wide range of production environments. The early-sown ideotypes provided maximum optimal yield advantage of 12–29% over a commercial variety across the three clusters. These results show that by coupling phenological traits with agronomic practices, a significant advantage in yield of lentils for specific environments under abiotic production constraints can be achieved. This model therefore can be used as a decision-making tool by growers, breeders, and agronomists to select improved varieties of lentils in combination with sets of critical phenological traits and suitable sowing times that minimise the impacts of frost, heat, and water stress. • Parameterised and validated APSIM-lentil model quantified the impact of frost, heat and water stress. • Based on risk related to abiotic stress, 1750 environments of lentil production in Australia were clustered. • Critical yield determinant periods matching minimum risk of abiotic stress were identified using APSIM-lentil model. • Coupling lentil phenology with agronomic practices can optimise abiotic stress limited flowering time and seed yield. [ABSTRACT FROM AUTHOR]

Ecosystem engineers are species that influence the abiotic and biotic environment around them and may assist the restoration of associated species, including other habitat‐forming species. We deployed an array of 28 artificial reefs with transplanted Ecklonia radiata, the dominant canopy‐forming kelp species across southern Australia, to investigate how the patch size and density of E. radiata influenced the establishment of the associated communities of plants and animals. Many of the reefs were rapidly colonized by Ostrea angasi, a critically depleted reef‐forming oyster. Over the 24‐month deployment of the reefs, thick oyster mats formed across the entire surface of many of the reefs with estimated biomass densities exceeding 5 kg of live oysters/m2; however, oyster density was dependent on E. radiata patch size and density. Increasing patch size and the presence of kelp resulted in significantly higher densities of oysters 5 months after the reefs were deployed and at the end of the experiment, where oysters were approximately three times more numerous on reefs with kelp compared to those without kelp. E. radiata appeared to facilitate the establishment of O. angasi largely through its capacity to reduce benthic light and thus suppress competition from turfing algae. These results may inform the development of novel approaches to tackle recruitment bottlenecks affecting the restoration of O. angasi reefs. [ABSTRACT FROM AUTHOR]

Abstract: Aim: The ways in which abiotic factors contribute to parallel evolution—the evolution of similar, derived phenotypes in independent, closely related lineages—remain understudied. Australian cockroaches of the subfamilies Panesthiinae (“wood feeders”) and Geoscapheinae (“soil burrowers”) are two closely related groups that provide a striking example of parallel evolution of burrowing behaviour. The ancestral wood‐feeding panesthiines migrated from Asia ~20 million years ago before soil burrowing was independently acquired multiple times in the derived geoscapheines. Here, we investigate whether specific abiotic factors were associated with the parallel evolution of soil burrowing behaviour, and whether divergence events of geoscapheines from panesthiine ancestors are consistent with niche conservatism or divergence. Location: The Australian mainland, including the areas in which selected Australian Panesthiinae and Geoscapheinae cockroach species are distributed. Methods: We generated environmental niche models for members of the Australian Geoscapheinae and Panesthiinae using presence‐only data and abiotic variables related to temperature, precipitation, and soil composition from BioClim and the Australian Soil Resource Information System. We used an existing phylogenetic framework to compare environmental niche models and tested for niche conservatism versus divergence. Morphological convergence was assessed by a regression analysis and principal components analysis of leg segment and body dimensions in soil burrowers and wood feeders. Results: We found no relationship between niche similarity and time since divergence, and only limited evidence for phylogenetic signal with respect to the environmental variables examined. We found that soil burrowing behaviour is consistently correlated with thirteen abiotic factors associated with aridity, including a wider range of temperatures and lower precipitation levels. Evidence for convergence in leg morphology and body dimensions across soil burrowers was found. Main conclusions: Our results are consistent with soil burrowing behaviour evolving in response to ancient aridification events following the arrival of the Panesthiinae in Australia. Our results suggest a scenario of niche divergence between soil burrowers and each of their wood feeding sister taxa. There is evidence for morphological convergence on a “shovel‐like” protibiotarsus in the Geoscapheinae that would aid in burrowing into soil. [ABSTRACT FROM AUTHOR]

The article discusses research on stream flow management through analyzing abiotic environmental factors that impact the spawning of fishes in Murray River, New South Wales and South Australia. An overview of the impact that the water temperature has on the fish spawning, including in regard to weekly changes in temperature, is provided.

Ecosystems across the world, and the biodiversity they support, are experiencing increasing anthropogenic pressure, and many will not persist without intervention. Given their complexity, the International Union for Conservation of Nature has adopted an international standard for ecosystem risk assessment that builds on the strengths of the species-based Red List criteria. We applied this protocol to the relatively understudied Georgina gidgee woodland ecosystem, which has a patchy but widespread distribution in central Australia. To address the extensive knowledge gaps, we gathered data to provide the first description of the characteristic biota, distribution of dominant species and the processes that support the ecosystem. Criteria evaluated include historical, current and future declines in spatial distribution, the extent and area of occupancy, and disruptions to abiotic and biotic processes. Future declines in suitable habitat were based on key climatic variables of rainfall, temperature and soil substrate. We also quantified the uncertainty in bioclimatic models and scenarios as part of predicting degradation of the abiotic environment. Overall, we assessed the risk status of Georgina gidgee woodlands as vulnerable based on the degradation of abiotic and biotic processes. Bioclimatically suitable habitat was predicted to decline by at least 30% in eight scenarios over the period 2000 to 2050. Predicted declines in overall suitable habitat varied substantially across all scenarios (7-95%). Pressures from grazing, weed encroachment and altered fire regimes further threaten the ecosystem; therefore, vulnerable status was also recorded for future declines based on altered biotic processes. Accurate mapping and monitoring of the study ecosystem should receive priority to inform conservation decisions, and sustainable grazing practices encouraged. Our findings focus attention on other patchily distributed ecosystems that may also have escaped attention despite their contribution to supporting unique biodiversity and ecosystem services. It is timely that environmental monitoring and policy account for these natural assets. [ABSTRACT FROM AUTHOR]

Aim To examine the potential of remotely sensed abiotic measures as surrogates for the abundance, diversity and community composition of temperate rocky reef fishes and sessile invertebrates. Location Batemans Marine Park, south-eastern Australia. Methods We used high-resolution bathymetric side-scan sonar imagery to quantify abiotic measures of rocky reef habitat, within a marine protected area ( MPA), and examine the relationship between abiotic measures and (1) sessile invertebrate abundance, (2) sessile invertebrate species richness, (3) total fish abundance, (4) fish species richness, and (5) Monacanthidae abundance using generalized additive mixed models ( GAMMs). We chose GAMMs as the preferred statistical analysis to account for the spatial autocorrelation present in our data. Results We found a strong positive relationship between abiotic measures and sessile invertebrate abundance and diversity ( r2 > 0.64). By far the most important predictor was vertical relief within a 75 m radii seascape surrounding the faunal survey. Overall, abiotic measures were poor predictors of total fish abundance ( r2 = 0.175) and fish species richness ( r2 = 0.276), with minimum adequate models producing low explanatory power. In contrast, Monacanthids exhibited a strong positive relationship with abiotic variables ( r2 = 0.385), with increased abundance associated with greater depth and distance from soft sediment. Main conclusions Remotely sensed abiotic measures are important predictors in describing the spatial patterns of sessile invertebrate abundance and diversity and Monacanthid abundance. In contrast, abiotic variables were poor predictors of total fish abundance and diversity. Habitat could be a useful cost-effective surrogate to determine areas of conservation value for certain temperate rocky reef assemblages. This information is valuable for future MPA development and design. [ABSTRACT FROM AUTHOR]