Browsing by Author "Waters JM"

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    Ancient mitochondrial genomes unveil the origins and evolutionary history of New Zealand's enigmatic takahē and moho
    (John Wiley and Sons, 2024-02) Verry AJF; Mas-Carrió E; Gibb GC; Dutoit L; Robertson BC; Waters JM; Rawlence NJ; Gillespie R
    Many avian species endemic to Aotearoa New Zealand were driven to extinction or reduced to relict populations following successive waves of human arrival, due to hunting, habitat destruction and the introduction of mammalian predators. Among the affected species were the large flightless South Island takahē (Porphyrio hochstetteri) and the moho (North Island takahē; P. mantelli), with the latter rendered extinct and the former reduced to a single relictual population. Little is known about the evolutionary history of these species prior to their decline and/or extinction. Here we sequenced mitochondrial genomes from takahē and moho subfossils (12 takahē and 4 moho) and retrieved comparable sequence data from takahē museum skins (n = 5) and contemporary individuals (n = 17) to examine the phylogeny and recent evolutionary history of these species. Our analyses suggest that prehistoric takahē populations lacked deep phylogeographic structure, in contrast to moho, which exhibited significant spatial genetic structure, albeit based on limited sample sizes (n = 4). Temporal genetic comparisons show that takahē have lost much of their mitochondrial genetic diversity, likely due to a sudden demographic decline soon after human arrival (~750 years ago). Time-calibrated phylogenetic analyses strongly support a sister species relationship between takahē and moho, suggesting these flightless taxa diverged around 1.5 million years ago, following a single colonisation of New Zealand by a flighted Porphyrio ancestor approximately 4 million years ago. This study highlights the utility of palaeogenetic approaches for informing the conservation and systematic understanding of endangered species whose ranges have been severely restricted by anthropogenic impacts.
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    Bis-Anagostic Structures in N,N’-Chelate Ligand Complexes of Palladium(II)
    (Wiley-VCH Verlag, 2022-04) Sajjad MA; Schwerdtfeger P; Cai Y; Waters JM; Harrison JA; Nielson AJ
    Reaction of N,N’-dibenzylidene-2,2-dimethylpropylenediamine with Pd(OAc)2 produces essentially one product which NMR spectroscopy indicates has a bis-anagostic structure. A density functional theory (DFT) calculation shows that in the square planar structure, both aromatic rings lie above the coordination plane with close approaches of two ortho-C−H bond hydrogens to both the Pd centre and the two acetato ligand coordinating oxygen atoms. N,N’-dibenzylideneethylenediamine reacts with Pd(OAc)2 similarly where a bis-anagostic structure is indicated by NMR spectroscopy and a DFT calculation shows an energy preference for an above plane positioning of the two aromatic rings. N,N,N’,N’-tetrabenzylethylenediamine reacts with Pd(OAc)2 to give a structure which X-ray crystallography shows two benzyl phenyl groups lie above and below the coordination plane respectively.
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    The population genetic structure of the urchin Centrostephanus rodgersii in New Zealand with links to Australia
    (1/09/2021) Thomas LJ; Liggins L; Banks SC; Beheregaray LB; Liddy M; McCulloch GA; Waters JM; Carter L; Byrne M; Cumming RA; Lamare MD
    The diadematid sea urchin Centrostephanus rodgersii occurs in Australia and New Zealand and has undergone recent southward range extension in Australia as a result of regional warming. Clarifying the population genetic structure of this species across its New Zealand range would allow a better understanding of recent and future mechanisms driving range changes in the species. Here, we use microsatellite DNA data to assess connectivity and genetic structure in 385 individuals from 14 locations across the Australian and New Zealand ranges of the species. We detected substantial genetic differentiation among C. rodgersii populations from Australia and New Zealand. However, the population from Port Stephens (located north of Newcastle), Australia, strongly clustered with New Zealand samples. This suggests that the New Zealand populations recently originated from this area, likely via larval transport in the Tasman Front flow that arises in this region. The weak population genetic structure and relatively low genetic diversity detected in New Zealand (global Fst = 0.0021) relative to Australia (global Fst = 0.0339) is consistent with the former population’s inferred history of recent climate-driven expansion. Population-level inbreeding is low in most populations, but were higher in New Zealand (global Fis = 0.0833) than in Australia (global Fis = 0.0202), suggesting that self-recruitment is playing an increasingly important role in the New Zealand region. Our results suggest that C. rodgersii is likely to spread southwards as ocean temperatures increase; therefore, it is crucial that researchers develop a clearer understanding of how New Zealand ecosystems will be reshaped by this species (and others) under climate change.