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Context The cane toad (Rhinella marina) is one of the most globally significant and well-studied invasive alien species, and the detrimental impacts of its invasions warrant the design and application of decision support tools. While many models have been developed for guiding policies addressing cane toad invasions, none reliably predict the species’ population dynamics at scales relevant to on-the-ground management. Objectives We describe virToad—an individual-based life-history simulator of the cane toad. We then illustrate virToad’s ability to forecast the cane toad’s spatiotemporal population dynamics at local- to landscape-scales, and its potential for improving management responses to cane toad invasions. Methods We designed virToad to make population dynamics an emergent consequence of the cane toad’s fitness-maximising behavioural responses to mechanistic constraints (e.g., water availability, kin selection), and to management actions. We used virToad to simulate cane toad population dynamics in the absence of management, and under alternative management strategies implemented across a spectrum of effort: hand-capturing and trapping of juveniles and adults, fencing waterbodies, and trapping and chemically suppressing tadpoles. Results virToad produced plausible predictions of cane toad population densities, detection probabilities, distributions, and spatial segregation. Simulation experiments indicated that the efficacy of competing management actions varied significantly, and that only moderate to high effort hand-capturing and trapping of juveniles and adults had the potential to suppress invasions. Conclusion virToad is an open-source, rigorous, and extensible decision support platform that will enable researchers and practitioners to defensibly forecast local- to landscape-scale cane toad spatiotemporal population dynamics and management outcomes.

Niche shifts and environmental non-equilibrium in invading alien species undermine niche-based predictions of alien species’ potential distributions and, consequently, their usefulness for invasion risk assessments. Here, we compared the realized climatic niches of four alien amphibian species (Hylarana erythraea, Rhinella marina, Hoplobatrachus rugulosus, and Kaloula pulchra) in their native and Philippine-invaded ranges to investigate niche changes that have unfolded during their invasion and, with this, assessed the extent of niche conservatism and environmental equilibrium. We investigated how niche changes affected reciprocal transferability of ecological niche models (ENMs) calibrated using data from the species’ native and Philippine-invaded ranges, and both ranges combined. We found varying levels of niche change across the species’ realized climatic niches in the Philippines: climatic niche shift for H. rugulosus; niche conservatism for R. marina and K. pulchra; environmental non-equilibrium in the Philippine-invaded range for all species; and environmental non-equilibrium in the native range or adaptive changes post-introduction for all species except H. erythraea. Niche changes undermined the reciprocal transferability of ENMs calibrated using native and Philippine-invaded range data. Our paper highlights the difficulty of predicting potential distributions given niche shifts and environmental non-equilibrium; we suggest calibrating ENMs with data from species’ combined native and invaded ranges, and to regularly reassess niche changes and recalibrate ENMs as species’ invasions progress.

Containing the spread of established invasive species is critical for minimizing their ecological impact. Effective containment requires sensitive sampling methods capable of detecting new introductions when invaders are at low density. Here we explore whether environmental DNA (eDNA) sampling could be used as a surveillance tool to detect new incursions of aquatic invasive species on offshore islands. We develop an eDNA molecular assay for invasive cane toads (Rhinella marina) in Australia, validate our assay on the mainland, and apply it to an offshore island (Moreton Island) that is a target of ongoing cane toad surveillance. Our eDNA assay correctly identified four mainland sites at which cane toads were observed, as well as a fifth site within 1 km of known populations. Five additional sites outside the cane toad’s current distribution tested negative for cane toad eDNA. Site occupancy detection models indicated that two water samples and three qPCR replicates were sufficient to achieve a cumulate detection probability > 0.95. Applying our eDNA assay to samples from 19 sites on an offshore island over a 2-year period revealed the absence of cane toad eDNA, in line with our current understanding of cane toad distribution. Our results suggest that eDNA sampling could be strategically applied to meet the Australian Commonwealth’s objective of maintaining cane toad-free offshore islands.

We document the successful establishment of a European newt (Lissotriton vulgaris) in south-eastern Australia, the first recorded case of a caudate species establishing beyond its native geographic range in the southern hemisphere. Field surveys in south-eastern Australia detected L. vulgaris at six sites, including four sites where the species had been detected 15 months earlier. Larvae were detected at three sites. Individuals had identical NADH dehydrogenase subunit 2 and cytb mtDNA gene sequences, and comparisons with genetic data from the species’ native range suggest that these individuals belong to the nominal subspecies L. v. vulgaris. Climatic conditions across much of southern Australia are similar to those experienced within the species’ native range, suggesting scope for substantial range expansion. Lissotriton vulgaris had been available in the Australian pet trade for decades before it was declared a ‘controlled pest animal’ in 1997, and thus the invasion documented here likely originated via the release or escape of captive animals. Lissotriton vulgaris is the sole member of an entire taxonomic order to have established in Australia, and given the potential toxicity of this species, further work is needed to delimit its current range and identify potential biodiversity impacts.

Geographic information systems (GIS) allow researchers to make cost-effective, spatially explicit predictions of species’ distributions across broad geographic areas. However, there has been little research on whether using fine-scale habitat data collected in the field could produce more robust models of species’ distributions. Here we used radio-telemetry data collected on a declining species, the North American wood turtle (Glyptemys insculpta), to test whether fine-scale habitat variables were better predictors of occurrence than land-cover and topography variables measured in a GIS. Patterns of male and female occurrence were similar in the spring; however, females used a much wider array of land-cover types and topographic positions in the summer and early fall, making it difficult for GIS-based models to accurately predict female occurrence at this time of year. Males on the other hand consistently selected flat, low-elevation, riparian areas throughout the year, and this consistency in turn led to the development of a strong GIS-based model. These results demonstrate the importance of taking a more sex-specific and temporally dynamic view of the environmental niche.

A new series of bis-triazenes, the 1-aryl-2-[3-(3-[2-aryl-1-diazenyl]-1,3-diazepan-1-ylmethyl)-1,3-diazepan-1-yl]-1-diazenes has been synthesized from the reaction of diazonium salts with a mixture of 1,4-diaminobutane and formaldehyde. The structures of 1-(p-bromophenyl)-2-[3-{3-[2-(p-bromophenyl)-1-diazenyl]-1,3-diazepan-1-ylmethyl}-1,3-diazepan-1-yl]-1-diazene(1), 1-(p-cyanophenyl)-2-[3-{3-[2-(p-cyanophenyl)-1-diazenyl]-1,3-di azepan-1-ylmethyl}-1,3-diazepan-1-yl]-1-diazene(2), and 1-(p-methoxyphenyl)-2-[3-{3-[2-(p-methoxy-phenyl)-1-diazenyl]-1,3-diazepan-1-ylmethyl}-1,3-diazepan-1-yl]-1 diazene(3) have been unequivocally determined by X-ray crystallography. The new bis-triazenes are important since the structure contains the novel saturated heterocycle, 1,3-diazepane. The general conclusion of this study is that alkanediamines with 3 or 4 carbon atoms in the spacer link between the nitrogen atoms give rise to the linear bicyclic molecules of type 5, in contrast to the case of ethylenediamine (spacer link 2 carbon atoms), which affords molecules of type 6, which exemplify the general cage structure of type 4. The crystal structures of 1, 2 and 3 are compared with the previously reported structure of the hexahydropyrimidine analogue 8a(X=CN); compounds 2 and 8a(X=CN) are homologous with respect to the alkane spacer moiety. The structures of 2 and 8a(X=CN) are very different in one respect; in 2 the aryldiazenyl-1,3-diazepanyl groups are in the s-trans orientation around the central methylene group whereas in 8a(X=CN) the arrangement of the aryldiazenyl-hexahydropyrimidinyl groups is the s-cis orientation. Crystal data: 1 C23H30N8Br2, triclinic, space group P-1, a=8.3979(2), b=10.7828(3), c=14.4692(5) A, α=83.670(1), β=78.662(1), γ=78.758(1)°, V=1256.48(6) A3, for Z=2. 2 C25H30N10, monoclinic, space group P2 1 /n, a=13.4046(6), b=9.4482(4), c=10.6913(4)A, β=103.239(2)°, V=2490.5(2) A3, for Z=4. 3 C25H36N8O2, triclinic, space group P-1, a=8.5223(3), b=10.6913(4), c=14.4034(7)A, α=85.657(2), β=78.731(2), γ=80.153(1)°, V=1266.88(9) A3, for Z=2.

1-[(E)-2-(4-bromophenyl)-1-diazenyl]-3-({3-[(E)-2-(4-bromophenyl)-1-diazenyl]-6-ethylhexahydro-1-pyrimidinyl}methyl)-4-ethylhexahydropyrimidine (1) has been synthesized by reaction of a mixture of formaldehyde and 1,3-pentanediamine{DYTEK®EPdiamine} with p-bromobenzenediazonium chloride. This compound crystallizes in two polymorphic forms 1-α and 1-β whose crystal structures have been determined by single crystal X-ray diffraction analysis. Both polymorphs 1-α and 1-β display crystallographic disorder within the hexahydropyrimidine rings. The molecule of 1 is built up of two equivalent 3-(aryldiazenyl)-6-ethylhexahydro-1-pyrimidinyl groups in the s-trans orientation around the central methylene group (C13). In both structures the triazene moieties adopt the anti configuration around the N=N bonds, displaying significant π-conjugation. The crystal packings are determined only by van der Waals interactions. The crystal structures of 1-α and 1-β are compared with the previously reported structure of the 5,5-dimethylhexahydropyrimidine analogue 3. Compounds 1 and 3 are isomeric with respect to the hexahydropyrimidine moiety. The structures of 1 and 3 are very different in one respect; in 1 the aryldiazenyl-hexahydropyrimidinyl groups are in the s-trans orientation around the central methylene group, whereas in 3 the arrangement of the aryldiazenylhexahydropyrimidinyl groups is the s-cis orientation. Crystal data: 1-α C25H34N8Br2, monoclinic, space group P2(1)/c, a = 9.2150(3), b = 19.4059(6), c = 15.4324(5) A, β = 98.738(1)∘, V = 2727.7(2) A3, for Z = 4; 1-β C25H34N8Br2, triclinic, space group P-1, a = 9.6009(3), b = 10.7509(4), c = 14.2169(5) A, α = 99.830(2), β = 105.973(3), γ = 95.578(1)∘, V = 1373.9(1) A3, for Z = 2.