Predation on invasive cane toads (Rhinella marina) by native Australian rodents

Journal of Pest Science - The success of an invasive species can be reduced by biotic resistance from the native fauna. For example, an invader that is eaten by native predators is less likely to...     

A single amino acid mutation contributes to adaptive beach mouse color pattern

Natural populations of beach mice exhibit a characteristic color pattern, relative to their mainland conspecifics, driven by natural selection for crypsis. We identified a derived, charge-changing amino acid mutation in the melanocortin-1 receptor (Mc1r) in beach mice, which decreases receptor function. In genetic crosses, allelic variation at Mc1r explains 9.8% to 36.4% of the variation in seven pigmentation traits determining color pattern. The derived Mc1r allele is present in Florida's Gulf Coast beach mice but not in Atlantic coast mice with similar light coloration, suggesting that different molecular mechanisms are responsible for convergent phenotypic evolution. Here, we link a single mutation in the coding region of a pigmentation gene to adaptive quantitative variation in the wild.     

Nannizziopsis guarroi infection in 2 Inland Bearded Dragons (Pogona vitticeps): clinical,cytologic, histologic,and ultrastructural aspects

Chrysosporium‐related infections have been increasingly reported in reptiles over the last 2 decades. In this report, we describe clinical, cytologic, histopathologic, and ultrastructural aspects of Chrysosporium‐related infection in 2 Inland Bearded Dragons (Pogona vitticeps). Case 1 was presented for an enlarging raised lesion over the left eye and multiple additional masses over the dorsum. Case 2 was submitted to necropsy by the referring veterinarian for suspected yellow fungus disease. Impression smears of the nodules in case 1 revealed granulomatous to pyogranulomatous inflammation and many septate, variably long, 4–10 μm wide, often undulated hyphae, and very rare conidia. Postmortem impression smears of the superficial lesions of case 2 contained large numbers of solitary conidia and arthroconidia and low numbers of hyphae with similar morphology to case 1. Histopathology of the 2 cases revealed severe, multifocal, chronic, ulcerative, nodular pyogranulomatous dermatitis, with myriad intralesional septate hyphae, and arthroconidia. Fungal culture and molecular sequencing in both cases indicated infection with Nannizziopsis guarroi.     

Evaluation of models used to assess the fate of chemicals in aquatic systems

Five reference chemicals, 2,5,4′-trichlorobiphenyl (3-CB), chloroform, parathionmethyl (MEP), pentachlorophenol (PCP) and 3,4-dichloroaniline (DCA), were applied to experimental outdoor ponds by sub-surface injection. Samples of water, sediment and vegetation were removed and analysed for residues at various intervals after treatment. The fate of these chemicals in the ponds was predicted through the use of process analyses and mathematical models. The predicted rates of loss were compared with experimental observations. Data obtained for 3-CB were fitted to a three-compartment model and this was used to calculate the rates of transport between water and sediment, and between water and vegetation. These processes are primarily dependent on turbulent mixing. In experiments with MEP it was shown that biodegradation was primarily associated with bacterial populations in the sediment rather than with those suspended in the water. The rate of biodegradation in sediment was relatively fast and there was no detectable lag phase. The sediment could therefore be considered a sink for MEP and the overall rate of loss of the latter was dependent on its rate of transport to the sediment. In an experiment with chloroform there was reasonably good agreement between predicted and observed rates of evaporation. However, observed rates were always greater than predicted rates, suggesting a systematic bias that may warrant further investigation. In experiments with PCP and DCA there was good agreement between predicted and observed rates of phototransformation.     

Mass mortality of native anuran tadpoles in tropical Australia due to the invasive cane toad (Bufo marinus)

Specific pathways of the ecological impact of invasive species remain poorly known. Although the spread of toxic cane toads (Bufo marinus) through tropical Australia is widely believed to have caused extensive mortality of native reptiles and mammals, effects of toad ingestion on native anurans have been virtually ignored. Our studies on the Adelaide River floodplain show that the most numerous vertebrate victims of toad invasion are native tadpoles that die when they attempt to consume toad eggs. We documented 11 episodes of mass mortality, totalling >1300 tadpoles of 10 species, in five waterbodies within a single wet-season shortly after the toads invaded. A causal link between toad breeding and tadpole mortality is supported by observations that: (1) in at least 9 of the 11 waterbodies involved, toads bred immediately prior to mortality events; (2) water quality was indistinguishable from that of control ponds, and tadpoles placed in that water remained healthy; (3) dead tadpoles showed no sign of disease; and (4) laboratory trials showed rapid, 100% mortality in native tadpoles exposed to freshly-laid toad eggs. Despite these high mortality rates, toad invasion does not appear to threaten the viability of anuran populations because frogs often breed in ponds not used by toads, and because density-dependent growth and survival within tadpole communities mean that additional mortality may not reduce the total effective recruitment of metamorph frogs from a waterbody.