Fish mediate high food web connectivity in the lower reaches of a tropical floodplain river

High levels of hydrological connectivity during seasonal flooding provide significant opportunities for movements of fish between rivers and their floodplains, estuaries and the sea, possibly mediating food web subsidies among habitats. To determine the degree of utilisation of food sources from different habitats in a tropical river with a short floodplain inundation duration (similar to 2 months), stable isotope ratios in fishes and their available food were measured from three habitats (inundated floodplain, dry season freshwater, coastal marine) in the lower reaches of the Mitchell River, Queensland (Australia). Floodplain food sources constituted the majority of the diet of large-bodied fishes (barramundi Lates calcarifer, catfish Neoarius graeffei) captured on the floodplain in the wet season and for gonadal tissues of a common herbivorous fish (gizzard shad Nematalosa come), the latter suggesting that critical reproductive phases are fuelled by floodplain production. Floodplain food sources also subsidised barramundi from the recreational fishery in adjacent coastal and estuarine areas, and the broader fish community from a freshwater lagoon. These findings highlight the importance of the floodplain in supporting the production of large fishes in spite of the episodic nature and relatively short duration of inundation compared to large river floodplains of humid tropical regions. They also illustrate the high degree of food web connectivity mediated by mobile fish in this system in the absence of human modification, and point to the potential consequences of water resource development that may reduce or eliminate hydrological connectivity between the river and its floodplain.

Long-term variation of tropical rock lobster panulirus ornatus (decapoda, palinuridae) growth inTorres Strait, Australia

This analysis of all carapace length measurements collected between 1989 and 2009, during scientific surveys, describes the variation of tropical rock lobster, Panulirus ornatus, somatic growth in Torres Strait. Multiple models of carapace length frequency distributions were compared by maximum likelihood to determine which hypotheses were most supported by the data. The best model assumed sex and cohort-specific Von Bertalanffy's parameters. These estimates are consistent with results derived from tagging data collected in the 1980s and provide new information on parameters' uncertainty. In the past two decades, growth rates have fluctuated inter-annually without displaying any distinctive trend. Associated uncertainties are large, suggesting that sampling will need to be intensified in order to detect an effect of climate change.

Spatial and temporal effects of grazing management and rainfall on the vertebrate fauna of a tropical savanna

Grazing by domestic livestock is one of the most widespread uses of the rangelands of Australia. There is limited information on the effects of grazing by domestic livestock on the vertebrate fauna of Australia and the establishment of a long-term grazing experiment in north-eastern Queensland at Wambiana provided an opportunity to attempt an examination of the changes in vertebrate fauna as a consequence of the manipulation of stocking rates. The aim was to identify what the relative effects of vegetation type, stocking rate and other landscape-scale environmental factors were on the patterns recorded. Sixteen 1-ha sites were established within three replicated treatments (moderate, heavy and variable stocking rates). The sites were sampled in the wet and dry seasons in 1999-2000 (T-0) and again in 2003-04 (T-1). All paddocks of the treatments were burnt in 1999. Average annual rainfall declined markedly between the two sampling periods, which made interpretation of the data difficult. A total of 127 species of vertebrate fauna comprising five amphibian, 83 bird, 27 reptile and 12 mammal species were recorded. There was strong separation in faunal composition from T-0 to T-1 although changes in mean compositional dissimilarity between the grazing stocking rate treatments were less well defined. There was a relative change in abundance of 24 bird, four mammal and five reptile species from T-0 to T-1. The generalised linear modelling identified that, in the T-1 data, there was significant variation in the abundance of 16 species explained by the grazing and vegetation factors. This study demonstrated that vertebrate fauna assemblage did change and that these changes were attributable to the interplay between the stocking rates, the vegetation types on the sites surveyed, the burning of the experimental paddocks and the decrease in rainfall over the course of the two surveys. It is recommended that the experiment is sampled again but that the focus should be on a rapid survey of abundant taxa (i.e. birds and reptiles) to allow an increase in the frequency of sampling and replication of the data. This would help to articulate more clearly the trajectory of vertebrate change due to the relative effects of stocking rates compared with wider landscape environmental changes. Given the increasing focus on pastoral development in northern Australia, any opportunity to incorporate the collection of data on biodiversity into grazing manipulation experiments should be taken for the assessment of the effects of land management on faunal species.

Effect of monensin inclusion in supplements for cattle consuming low quality tropical forage

A pen feeding study was carried out over 70 days to determine the effects of monensin (M) inclusion in two commercial supplements designed to provide different planes of nutrition to recently weaned steers. Thirty Bos indicus crossbred steers (191.4 +/- s.d. 7.1 kg) were individually fed a low quality pangola grass hay (57 g crude protein/kg DM; 497 g/kg DM digestibility) ad libitum (Control) with either a urea/molasses-based supplement of Rumevite Maxi-graze 60 Block (B), fed at 100 g/day, or grain-based Rumevite Weaner Pellets (WP), fed at 7.5 g/kg liveweight (W).day, both with and without M, viz. B, B+M, WP and WP+M, respectively. There were no significant interactions between supplement type and M inclusion for any measurement. Growth rates (main effects) averaged 0.17, 0.35 and 0.58 kg/day for the Control, B and WP supplements, respectively, with all means different (P < 0.05), while the response (P < 0.05) to M across supplement type was 0.11 kg/day. Hay DM intake was similar for the Control and B treatments (18.6 and 19.6 g/kg W.day) but was reduced (P < 0.05) with the WP supplement (16.8 g/kg W.day) while corresponding total DM intakes increased from 18.6 to 20.0 to 23.5 g/kg W.day (all differences P < 0.05), respectively. Monensin inclusion in the supplements did not affect supplement, hay or total DM intake. Inclusion of of M in supplements for grazing weaners in northern Australia may increase survival rates although the effect of M with cattle at liveweight maintenance or below requires further investigation.

Major Australian tropical fruits biodiversity: Bioactive compounds and their bioactivities

The plant kingdom harbours many diverse bioactive molecules of pharmacological relevance. Temperate fruits and vegetables have been highly studied in this regard, but there have been fewer studies of fruits and vegetables from the tropics. As global consumers demand and are prepared to pay for new appealing and exotic foods, tropical fruits are now being more intensively investigated. Polyphenols and major classes of compounds like flavonoids or carotenoids are ubiquitously present in these fruits, as they are in the temperate ones, but particular classes of compounds are unique to tropical fruits and other plant parts. Bioactivity studies of compounds specific to tropical fruit plants may lead to new drug discoveries, while the synergistic action of the wide range of diverse compounds contained in plant extracts underlies nutritional and health properties of tropical fruits and vegetables. The evidence for in vitro and animal bioactivities is a strong indicator of the pharmacological promise shown in tropical fruit plant biodiversity. In this review, we will discuss both the occurrence of potential bioactive compounds isolated and identified from a selection of tropical fruit plants of importance in Australia, as well as recent studies of bioactivity associated with such fruits and other fruit plant parts.

How weed control and fertilisation influence tree physiological processes and growth at early establishment in an exotic F1 hybrid pine plantation of subtropical Australia

Purpose This study investigated how nitrogen (N) nutrition and key physiological processes varied under changed water and nitrogen competition resulting from different weed control and fertilisation treatments in a 2-year-old F1 hybrid (Pinus elliottii Engelm var. elliottii × P. caribaea var. hondurensis Barr. ex Golf.) plantation on a grey podzolic soil type, in Southeast Queensland. Materials and methods The study integrated a range of measures including growth variables (diameter at ground level (DGL), diameter at breast height (DBH) and height (H)), foliar variables (including foliar N concentration, foliar δ13C and δ15N) and physiological variables (including photosynthesis (An), stomatal conductance (gs), transpiration (E), intrinsic water use efficiency (WUEi) (A/gs) and xylem pressure potential (ΨXPP)) to better understand the mechanisms influencing growth under different weed control and fertilisation treatments. Five levels of weed control were applied: standard (routine), luxury, intermediate, mechanical and nil weed control, all with routine fertilisation plus an additional treatment, routine weed control and luxury fertilisation. Relative weed cover was assessed at 0.8, 1.1 and 1.6 years after plantation establishment to monitor the effectiveness of weed control treatments. Soil investigation included soil ammonium (NH4 +-N), nitrate (NO3 −-N), potentially mineralizable N (PMN), gravimetric soil moisture content (MC), hot water extractable organic carbon (HWETC), hot water extractable total N (HWETN), total C, total N, stable C isotope composition (δ13C), stable N isotope composition (δ15N), total P and extractable K. Results and discussion There were significant relationships between foliar N concentrations and relative weed cover and between tree growth and foliar N concentration or foliar δ15N, but initial site preparation practices also increased soil N transformations in the planting rows reducing the observable effects of weed control on foliar δ15N. A positive relationship between foliar N concentration and foliar δ13C or photosynthesis indicated that increased N availability to trees positively influenced non-stomatal limitations to photosynthesis. However, trees with increased foliar N concentrations and photosynthesis were negatively related to xylem pressure potential in the afternoons which enhanced stomatal limitations to photosynthesis and WUEi. Conclusions Luxury and intermediate weed control and luxury fertilisation positively influenced growth at early establishment by reducing the competition for water and N resources. This influenced fundamental key physiological processes such as the relationships between foliar N concentration, A n, E, gs and ΨXPP. Results also confirmed that time from cultivation is an important factor influencing the effectiveness of using foliar δ15N as an indicator of soil N transformations.

Genetics of early and lifetime annual reproductive performance in cows of two tropical beef genotypes in northern Australia

Reproduction records from 2137 cows first mated at 2 years of age and recorded through to 8.5 years of age were used to study the genetics of early and lifetime reproductive performance from two genotypes (1020 Brahman and 1117 Tropical Composite) in tropical Australian production systems. Regular ultrasound scanning of the reproductive tract, coupled with full recording of mating, calving and weaning histories, allowed a comprehensive evaluation of a range of reproductive traits. Results showed components traits of early reproductive performance had moderate to high heritabilities, especially in Brahmans. The heritability of lactation anoestrous interval in 3-year-old cows was 0.51 +/- 0.18 and 0.26 +/- 0.11 for Brahman and Tropical Composite, respectively. Heritabilities of binary reproductive output traits (conception rate, pregnancy rate, calving rate and weaning rate) from first and second matings were generally moderate to high on the underlying scale. Estimates ranged from 0.15 to 0.69 in Brahman and 0.15 to 0.34 in Tropical Composite, but were considerably lower when expressed on the observed scale, particularly for those traits with high mean levels. Heritabilities of lifetime reproduction traits were low, with estimates of 0.11 +/- 0.06 and 0.07 +/- 0.06 for lifetime annual weaning rate in Brahman and Tropical Composite, respectively. Significant differences in mean reproductive performance were observed between the two genotypes, especially for traits associated with anoestrus in first-lactation cows. Genetic correlations between early-in-life reproductive measures and lifetime reproduction traits were moderate to high. Genetic correlations between lactation anoestrous interval and lifetime annual weaning rate were -0.62 +/- 0.24 in Brahman and -0.87 +/- 0.32 in Tropical Composite. The results emphasise the substantial opportunity that exists to genetically improve weaning rates in tropical beef cattle breeds by focusing recording and selection on early-in-life female reproduction traits, particularly in Brahman for traits associated with lactation anoestrus.

Genetic correlations of young bull reproductive traits and heifer puberty traits with female reproductive performance in two tropical beef genotypes in northern Australia

Genetic correlations of young bull and heifer puberty traits with measures of early and lifetime female reproductive performance were estimated in two tropical beef cattle genotypes. Heifer age at puberty was highly (r(g) = -0.71 +/- 0.11) and moderately (r(g) = -0.40 +/- 0.20) genetically correlated with pregnancy rate at first annual mating (mating 1) and lifetime annual calving rate, respectively in Brahman (BRAH). In Tropical Composite (TCOMP), heifer age at puberty was highly correlated with reproductive outcomes from the first re-breed (mating 2), mainly due to its association with lactation anoestrous interval (r(g) = 0.72 +/- 0.17). Scrotal circumference were correlated with heifer age at puberty (r(g) = -0.41 +/- 0.11 at 12 months in BRAH; -0.30 +/- 0.13 at 6 months in TCOMP) but correlations were lower with later female reproduction traits. Bull insulin-like growth factor-I was correlated with heifer age at puberty (r(g) = -0.56 +/- 0.11 in BRAH; -0.43 +/- 0.11 in TCOMP) and blood luteinising hormone concentration was moderately correlated with lactation anoestrous interval (r(g) = 0.59 +/- 0.23) in TCOMP. Semen quality traits, including mass activity, motility and percent normal sperm were genetically correlated with lactation anoestrus and female lifetime female reproductive traits in both genotypes, but the magnitudes of the relationships differed with bull age at measurement. Preputial eversion and sheath scores were genetically associated with lifetime calving and weaning rates in both genotypes. Several of the early-in-life male and female measures examined were moderately to highly genetically correlated with early and lifetime female reproduction traits and may be useful as indirect selection criteria for improving female reproduction in tropical breeds in northern Australia.

Abundance indices for long-lived tropical snappers: estimating standardized catch rates from spatially and temporally coarse logbook data

The Northern Demersal Scalefish Fishery has historically comprised a small fleet (≤10 vessels year−1) operating over a relatively large area off the northwest coast of Australia. This multispecies fishery primarily harvests two species of snapper: goldband snapper, Pristipomoides multidens and red emperor, Lutjanus sebae. A key input to age-structured assessments of these stocks has been the annual time-series of the catch rate. We used an approach that combined Generalized Linear Models, spatio-temporal imputation, and computer-intensive methods to standardize the fishery catch rates and report uncertainty in the indices. These analyses, which represent one of the first attempts to standardize fish trap catch rates, were also augmented to gain additional insights into the effects of targeting, historical effort creep, and spatio-temporal resolution of catch and effort data on trap fishery dynamics. Results from monthly reported catches (i.e. 1993 on) were compared with those reported daily from more recently (i.e. 2008 on) enhanced catch and effort logbooks. Model effects of catches of one species on the catch rates of another became more conspicuous when the daily data were analysed and produced estimates with greater precision. The rate of putative effort creep estimated for standardized catch rates was much lower than estimated for nominal catch rates. These results therefore demonstrate how important additional insights into fishery and fish population dynamics can be elucidated from such “pre-assessment” analyses.

Screening Corymbia populations for resistance to Puccinia psidii

The exotic rust pathogen Puccinia psidii is now widespread along the east coast of Australia from temperate Victoria to tropical far north Queensland, with a current host range exceeding 200 species from 37 myrtaceous genera. To determine the threat P. psidii poses to plantation and native eucalypts, artificial inoculation was used to screen germplasm of spotted gum (Corymbia spp.) for resistance to the biotype of P. psidii that has become established in Australia. The objective was to characterize resistance to P. psidii within the Corymbia species complex so that management strategies for the deployment of germplasm from existing breeding programmes of these spotted gum species could be developed. Symptom development initiated 7 days after inoculation, with resistant and susceptible seedlings identified within all species, provenances and families. Inter- and intraspecific variability in rust resistance was observed among spotted gum species. There was no apparent relationship between climatic conditions at the provenance origin and disease resistance. The heritability estimates for all assessments are moderate to high and indicate a significant level of additive genetic variance for rust resistance within the populations. The results of this study clearly identify potential to select for resistance at the family level within the tested populations. While the potential for P. psidii to detrimentally impact upon Corymbia in the nursery and in young plantations was demonstrated, estimations of the heritability of resistance suggest that efforts to enhance this trait through breeding have reasonable prospects for success.

Population dynamics of Thaumastocoris peregrinus in Eucalyptus plantations of South Africa

Thaumastocoris peregrinus is a sap-sucking insect that infests non-native Eucalyptus plantations in Africa, New Zealand, South America and parts of Southern Europe, in addition to street trees in parts of its native range of Australia. In South Africa, pronounced fluctuations in the population densities have been observed. To characterise spatiotemporal variability in T. peregrinus abundance and the factors that might influence it, we monitored adult population densities at six sites in the main eucalypt growing regions of South Africa. At each site, twenty yellow sticky traps were monitored weekly for 30 months, together with climatic data. We also characterised the influence of temperature on growth and survival experimentally and used this to model how temperature may influence population dynamics. T. peregrinus was present throughout the year at all sites, with annual site-specific peaks in abundance. Peaks occurred during autumn (February-April) for the Pretoria site, summer (November-January) for the Zululand site and spring (August-October) for the Tzaneen, Sabie and Piet Retief monitoring sites. Temperature (both experimental and field-collected), humidity and rainfall were mostly weakly, or not at all, associated with population fluctuations. It is clear that a complex interaction of these and other factors (e.g. host quality) influence population fluctuations in an annual, site specific cycle. The results obtained not only provide insights into the biology of T. peregrinus, but will also be important for future planning of monitoring and control programs using semiochemicals, chemical insecticides or biological control agents. © 2014 Springer-Verlag Berlin Heidelberg.

Host Tree Influences on Longicorn Beetle (Coleoptera: Cerambycidae) Attack in Subtropical Corymbia (Myrtales: Myrtaceae)

Phoracantha longicorn beetles are endemic to Australia, and some species have become significant pests of eucalypts worldwide, yet little is known about their host plant interactions and factors influencing tree susceptibility in Australia. Here, we investigate the host relationships of Phoracantha solida (Blackburn, 1894) on four eucalypt taxa (one pure species and three hybrid families), examining feeding site physical characteristics including phloem thickness, density, and moisture content, and host tree factors such as diameter, height, growth, taper, and survival. We also determine the cardinal and vertical (within-tree) and horizontal (between-tree) spatial distribution of borers. Fewer than 10% of P. solida attacks were recorded from the pure species (Corymbia citriodora subsp. variegate (Hook)), and this taxon also showed the highest survival, phloem thickness, relative growth rate, and bark:wood area. For the two most susceptible taxa, borer severity was negatively correlated with moisture content, and positively related to phloem density. Borers were nonrandomly and nonuniformly distributed within trees, and were statistically aggregated in 32% of plots. More attacks were situated on the northern side of the tree than the other aspects, and most larvae fed within the lower 50 cm of the bole, with attack height positively correlated with severity. Trees with borers had more dead neighbors, and more bored neighbors, than trees without borers, while within plots, borer incidence and severity were positively correlated. Because the more susceptible taxa overlapped with less susceptible taxa for several physical tree factors, the role of primary and secondary chemistries in determining host suitability needs to be investigated. Nevertheless, taxon, moisture content, phloem density, tree size, and mortality of neighboring trees appeared the most important physical characteristics influencing host suitability for P. solida at this site.