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Plant secondary metabolites (PSMs) can influence the consumption of particular plants by herbivores. Unsubstituted B-ring flavanones (UBFs), which are compounds found in the leaves of Eucalyptus species from the Eucalyptus subgenus (common name monocalypt), deter feeding by common brushtail possums (Trichosurus vulpecula ) when added to artificial diets at concentrations that reflect those found naturally in foliage. We hypothesised that common ringtail possums (Pseudocheirus peregrinus ) would tolerate higher UBF concentrations, because, unlike brushtail possums, they regularly eat monocalypt foliage. This proved to be the case; ringtail possums were not deterred by two different UBFs, pinocembrin and flavanone, at concentrations up to 4.7% dry matter, which is substantially higher than the concentrations that deter brushtail possums. These results extend and refine our understanding of how variation in tolerance or susceptibility to eucalypt PSMs affects the diets of sympatric marsupial folivores, potentially reducing competition for food. [ABSTRACT FROM AUTHOR]

In food-productive river basins, ecosystems reliant on natural flows are affected by climate change and water removal. One such example is Australia's Murray-Darling Basin (MDB), to which the ecologically important black box tree Eucalyptus largiflorens (Myrtaceae) is unique. Little is known about its mineral nutrition and response to flooding. A field study conducted at Hattah Kulkyne National Park on the MDB examined nutrient and Al distribution in mature and young foliage of trees whose status varied with respect to the presence of surface floodwaters. Black box is also of interest due to emerging evidence of its capacity to accumulate high foliar salt concentrations. Here, cryo scanning electron microscopy alone (SEM), combined with energy dispersive spectroscopy (SEM-EDS) and X-ray fluorescence (XRF) spectroscopy were applied to evaluate leaf anatomy and elemental patterns at the cellular and whole-leaf levels. Variation in whole-leaf elemental levels across flooded and dry trees aligned with known nutritional fluctuations in this drought-tolerant species reliant on occasional infrequent flooding. The microprobe data provide evidence of drought tolerance by demonstrating that extended conditions of lack of water to trees do not elicit leaf anatomical changes nor changes to leaf cellular storage of these elements. Foliar Na concentrations of ~2000-6000 mg kg-1 DW were found co-localised with Cl in mesophyll and dermal cells of young and mature leaves, suggesting vacuolar salt disposal as a detoxification strategy. Black box, the iconic floodplain eucalypt unique to Australia's Murray-Darling Basin, is affected by anthropogenic activities, yet knowledge about its environmental interactions is limited. Little is understood of its adaptation to drier conditions well away from watercourses. This study revealed similar leaf structure and nutrient distribution in both flooded trees and those that received very little water, with indication of possible species-wide salt tolerance. Insights were gained into key aspects of black box tolerance of dry and saline conditions. [ABSTRACT FROM AUTHOR]

Understanding intraspecific variation in the vulnerability of the xylem to hydraulic failure during drought is critical in predicting the response of forest tree species to climate change. However, few studies have assessed intraspecific variation in this trait, and a likely limitation is the large number of measurements required to generate the standard 'vulnerability curve' used to assess hydraulic failure. Here we explore an alternative approach that requires fewer measurements, and assess within species variation in leaf xylem vulnerability in Eucalyptus globulus Labill., an ecologically and economically important species with known genetic variation in drought tolerance. Using this approach we demonstrate significant phenotypic differences and evidence of plasticity among two provenances with contrasting drought tolerance. Few studies assess the range in drought tolerance that exists among individuals of the same species, yet this is critical in accurately predicting the effect of climate change on plants. This may be the result of the labour intensive process of assessing drought tolerance, which typically requires multiple measurements per individual. Here we present an alternative approach for large-scale analysis that reduces the number of measurements, thereby improving efficiency and increasing our ability to assess a broader range of individuals. [ABSTRACT FROM AUTHOR]

Bell miner–associated dieback (BMAD) is a form of canopy decline involving bell miner (Manorina melanophrys) colonies on the eastern coast of Australia. The association can include an understorey of lantana (Lantana camara) preventing eucalypt regeneration. To date, comparatively little is known about the effects of these processes on mammal diversity and abundance. We therefore considered the effects of BMAD and lantana presence on ground mammals and insectivorous bats in four forest sites within New South Wales. These were monitored in association with a restoration project for the treatment of lantana that used glyphosate spraying to kill lantana in half of six 50 m × 50 m quadrats per site (three control and three treated). Passive bioacoustic recorders, infrared cameras and Elliott traps were used to survey understorey fauna over four consecutive nights during each season. We found a greater number of small ground-dwelling and large mammals in control areas with an intact understorey of lantana relative to areas where lantana had been treated. However, insectivorous bats were not influenced by lantana presence. Our results suggest that ground-dwelling mammals benefit from the presence of lantana, as it may provide structural complexity that reduces predation risk and/or provides a food resource. [ABSTRACT FROM AUTHOR]

Phosphorus (P) limitation is known to have substantial impacts on leaf metabolism. However, uncertainty remains around whether P deficiency alters scaling functions linking leaf metabolism to associated traits.Weinvestigated the effect of P deficiency on leaf gas exchange and related leaf traits in 17 contrasting Eucalyptus species that exhibit inherent differences in leaf traits. Saplings were grown under controlled-environment conditions in a glasshouse, where they were subjected to minus and plus P treatments for 15 weeks. P deficiency decreased P concentrations and increased leaf mass per area (LMA) of newly-developed leaves. Rates of photosynthesis (A) and respiration (R) were also reduced in P-deficient plants compared with P-fertilised plants. By contrast, P deficiency had little effect on the temperature sensitivity of R. Irrespective of P treatment, on a log-log basis A and R scaled positively with increasing leaf nitrogen concentration [N] and negatively with increasing LMA. Although P deficiency had limited impact on A-R-LMA relationships, rates of CO2 exchange per unit N were consistently lower in P-deficient plants. Our results highlight the importance of P supply for leaf carbon metabolism and show howP deficiencies (i.e. when excluding confounding genotypic and environmental effects) can have a direct effect on commonly used leaf trait scaling relationships. [ABSTRACT FROM AUTHOR]

Leaves that develop on seedlings, young saplings or regenerative shoots of many eucalypt species are strikingly different in morphology from the typical leaves of more mature plants; a developmental pattern known as heteroblasty. We measured dimorphism between juvenile and adult leaves in shape and size, leaf mass per unit area, and vein frequency in a continent-wide sample of Angophora, Corymbia and Eucalyptus species. We tested whether heteroblasty in this group is an adaptation to shading by comparing the degree of juvenile-adult leaf dimorphism with the canopy closure (measured by the leaf area index) of the habitat in which species occurred. No pattern emerged for heteroblasty in leaf shape and size or leaf mass per unit area, but there was a significant relationship (accounting for phylogenetic relationships) between the degree of juvenile-adult dimorphism in vein frequency and habitat leaf area index. Juvenile leaves tended to have more widely spaced veins than adult leaves of the same species, in regions with more closed vegetative canopies. This evidence suggests that eucalypt heteroblasty is, at least in part, a hydraulic adaptation to the different conditions faced by younger and older plants in higher productivity regions with denser vegetation. [ABSTRACT FROM AUTHOR]

Tall eucalypt old-growth forests are notable for their large, old (i.e. venerable) trees and have both significant conservation value and high carbon stores. We investigated whether canopy height and biomass had recovered in an oldgrowth red tingle (Eucalyptus jacksonii) forest 78 years after a high-intensity fire. We recorded species, diameter, hollow butting and height of all 596 trees .10-cm diameter at breast height, as well as fine and coarse woody debris, in a 3.55-ha plot near Nornalup, south-western Australia. Pre-fire canopy height was estimated by allometrics derived from tree height and diameter, and diameter and length of recently fallen branches. Of the basal area (75.0 m2 ha -11), 92.7% was eucalypt (chiefly E. jacksonii), with regeneration accounting for only 8.5% of the total. Although canopy species composition apparently did not change following fire, stand height and biomass had not recovered to pre-1937 levels by 2015. Canopy height remained 5.06 m (11%) less and biomass 25% less, 78 years after the fire. The combination of intense fire and a warmer, drier climate appears to have prevented recovery of forest height and structure at this site. These findings indicate that ecologically important, venerable trees are increasingly vulnerable to canopy fire and climate change. [ABSTRACT FROM AUTHOR]

Wetland forests home to the last remaining wild populations of the helmeted honeyeater and lowland Leadbeater's possum are under threat from tree dieback and a lack of natural regeneration, putatively the result of an altered hydrological regime. To restore these critical wetland forests, a better understanding of the flooding tolerance of the seedlings of the dominant tree species, Eucalyptus camphora subsp. humeana L.A.S.Johnson & K.D.Hill, is essential. I tested the effect of flooding on the establishment and growth of E. camphora seedlings in three nursery-based experiments. These experiments involved E. camphora seedlings of different ages (1, 3, and 8 months old) being subjected to different depths and durations (up to 12 months) of flooding. Eucalyptus camphora seedlings were able to survive and grow while flooded for 12 months as long as they were emergent. However, flooding negatively affected the growth of E. camphora seedlings, with these effects increasing with increasing depth and duration of flooding, and decreasing seedling age. The ability of E. camphora seedlings to survive prolonged shallow flooding is considerable, an ability enabled by its rapid and extensive production of aerenchyma tissue and stem-borne adventitious roots under flooded conditions. Nonetheless, conditions for E. camphora seedling establishment and growth are likely to improve with reduced flooding, with an absence of flooding during its growth period (early spring-late summer) most favourable. [ABSTRACT FROM AUTHOR]

Browsing cascades have strong implications for biodiversity conservation and fire management. The associational resistance and associational susceptibility hypotheses suggest different mechanisms. We tested the veracity of these two hypotheses by using small dry eucalypt forest and woodland trees. At 67 sites, we measured the height of the browse line and estimated the proportion of foliage remaining below it for all adult individuals of small trees within a 50 x 50 m area, recorded scat numbers, browsing damage to tree seedlings by species and environmental data. The 110-130-cm browse line, and strong relationships between macropod scat numbers and the remaining foliage below the browse line, suggested that Bennetts wallabies (Macropus rufogriseus Shaw) were the main cause of umbrella-shaped trees. The browsers preferred Exocarpos cupressiformis Labill. and Bursaria spinosa Cav. At the other extreme, adult Acacia dealbata Link suffered no browsing damage. All species were browsed as seedlings. Associational resistance occurred in some species and associational susceptibility in others, with the degree of difference in palatability between alternative sources of browse possibly resolving this apparent contradiction. Low browsing pressure is likely to cause woody thickening, an increase in fire hazard and a decrease in biodiversity. Extremely high browsing pressure had no such effects. Animal browsing can transform tree and forest. We found that wallabies and pademelons preferred to eat prickly box and native cherries, and avoided many wattles, but would eat all small trees as seedlings. Their browsing appeared to keep dry forests more open, and less prone to fire damage, than would otherwise have been the case. [ABSTRACT FROM AUTHOR]

Australia houses some unusual biota (insects included), much of which is undescribed. Cystococcus Fuller (Hemiptera : Sternorrhyncha : Coccoidea : Eriococcidae) currently comprises two species, both of which induce galls exclusively on bloodwoods (Myrtaceae: Corymbia Hill & Johnson). These insects display sexual dichronism, whereby females give birth first to sons and then to daughters. Wingless first-instar females cling to their winged adult brothers and are carried out of the maternal gall when the males fly to find mates – a behaviour called intersexual phoresy. Here, we use data from two gene regions, as well as morphology and host-use of the insects, to assess the status of a previously undescribed species. We describe this newly recognised species as Cystococcus campanidorsalis, sp. nov. Semple, Cook & Hodgson, redescribe the two existing species – C. echiniformis Fuller and C. pomiformis (Froggatt), designate a lectotype for C. echiniformis, and provide the first descriptions of adult males, and nymphal males and females for the genus. We have also reinterpreted a key morphological character of the adult females. This paper provides a foundation for further work on the genus, which is widespread across northern Australia and could prove to be useful for studies on biogeography and bloodwood ecosystems. [ABSTRACT FROM AUTHOR]

The anthropogenic movement of Eucalyptus species beyond their natural distributions is increasing the opportunity for interspecific hybridisation. The conservation implications arising from hybridisation between indigenous and introduced eucalypt species in modified urban landscapes is an increasingly important management issue that requires an assessment of risk. It has been claimed that much of the tuart (Eucalyptus gomphocephala DC., Myrtaceae) seed in Kings Park, a large urban bushland remnant in Perth, Western Australia, is of hybrid origin with introduced eastern Australian eucalypts, and especially with E. cladocalyx. Using molecular markers, we tested this claim and determined whether hybridisation in tuart is a conservation management issue in Kings Park, as well as the adjacent Bold Park. Eight microsatellite markers were used to genotype 220 open-pollinated tuart seedlings from 19 families. Allele frequency estimates for tuart were generated by genotyping 42 mature tuart trees. Forty-four trees of four alternative species thought to be capable of hybridising with tuart in these parks, including two non-indigenous species, E. cladocalyx and E. camaldulensis, and two indigenous species, E. decipiens and E. rudis, were also genotyped. Pairwise FST between tuart and each alternative species for these markers ranged from 0.105 to 0.204. A hybrid-index analysis of seedling genotypes showed no significant evidence for hybridisation, and no alternative species private alleles (n = 35) were found in any tuart offspring genotypes. A likelihood analysis showed that the maximum likelihood of observing no private alleles of the alternative species in the progeny occurred at a hybridisation frequency of zero for all four alternative species. We conclude that hybridisation between tuart and non-indigenous species is not currently a conservation management issue in Kings Park and Bold Park. Rather, the invasion of pure non-indigenous species, and in particular E. cladocalyx, as weeds into bushland is of greater management concern. The introduction of non-indigenous species into modified landscapes risks negative consequences for the genetic purity of indigenous species if they are capable of hybridising. Using molecular markers and a hybrid index on open-pollinated offspring of tuart (Eucalyptus gomphocephala) in urban bushland remnants in Perth, Western Australia, we found no evidence for hybridisation. Our results highlight that the ongoing invasion of introduced species, and in particular E. cladocalyx (sugar gum), is currently a greater risk than hybridisation for tuart conservation in these remnants. [ABSTRACT FROM AUTHOR]