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Aim: To determine the effects of competition and divergence time on morphological dissimilarity and geographical range overlap between dasyurid species at both regional and local scales. Our hypothesis is that speciation in this group has been largely allopatric at regional scale, but involved morphological divergence at local scale through sympatric character displacement. Location: Australia, New Guinea and surrounding islands. Taxon: Dasyurid (Dasyuridae) marsupials, 67 species. Methods: Geographical range overlap was quantified using polygons representing the outer limits of species distributions. Local‐scale range overlap was quantified as the degree of co‐occurrence of two taxa across a set of ecological survey plots representing 83 sampled communities. Phylogenies were generated using a novel DNA dataset, with divergence times estimated via total‐evidence dating incorporating fossils. Morphological divergence was determined using body mass and lower molar row length as proxy traits for reconstructing niche exploitation. Results: Sister species pairs were found to be sympatric in 52% (11/21) of cases. Range overlap tended to increase with node age, which supports the hypothesis that mammalian speciation is routinely allopatric. We detected no evidence of character displacement with increasing range overlap between sister species pairs. However, a negative relationship was observed between morphological divergence in body mass and range overlap across all sampled taxa, suggesting that selection in sympatry is convergent, while divergent selection occurs in allopatry. Local‐scale co‐occurrences revealed no trace of species aversion, indicating that competition has not impacted on the spatial distribution of dasyurids. Main conclusions: Despite moderate levels of sympatry through time, our results evince low rates of spatial co‐occurrence between dasyurid species. Although this may be indicative competitive exclusion, the lack of character displacement suggests that biotic interactions have likely not acted as a dominant driver of phenotypic evolution in this radiation. We alternatively posit that abiotic factors including aridity and geographical connectivity have more feasibly propagated character convergence, and led to both niche conservatism and speciation in this ubiquitous australidelphian clade. [ABSTRACT FROM AUTHOR]

A new compilation of historical observations and archaeomagnetic measurements of magnetic inclination for the last 1000 years from eastern Australia (the eastern Australian Inclination Record [eAIR2012]) has revealed the existence of a well-defined inclination anomaly in the region. Evidence of this magnetic feature has been preserved in sedimentary records from across eastern Australia, though this has not previously been recognised. Analyses of additional sedimentary sequences have confirmed the incidence and timing of this feature, revealing its presence between the 13th and 18th centuries ad. The inclination of the field during this episode appears to have been steeper than at any time since the start of the Holocene. Lake sediment evidence suggests that the anomaly is a composite feature, displaying a distinct peak at cal. ad 1270–1386 (±2 σ uncertainty), reappearing after cal. ad 1431–1651 (±2 σ uncertainty) and disappearing before cal. ad 1822±46 (±2 σ uncertainty). The disappearance of the anomaly is tightly bracketed in the historical record between ad 1770 and 1777. The rapid shift in inclination during the 18th century ad offers considerable potential as a means of dating a critical period of Australian environmental history, an episode that currently lies beyond the reach of established dating methods. This information also provides a valuable constraint on models of regional geomagnetic field change over centennial and millennial timescales. Our examination of the historical record has revealed that the inclination measurements made by the 18th-century French explorer La Pérouse are consistently erroneous. Since La Pérouse’s data make up 13% of the total body of pre-19th century inclination records, the inclusion of these measurements in global compendia of magnetic observations may seriously skew attempts to model the geomagnetic field. We advocate that La Pérouse’s inclination measurements should therefore be employed only with considerable caution. [ABSTRACT FROM PUBLISHER]

Rocks from the Sulphur Springs Group, a newly identified stratigraphic succession hosting volcanogenic massive sulphide (VMS) base-metal deposits in the Soanesville Belt, Pilbara Craton, northwestern Australia, have been analyzed by sensitive high-resolution ion microprobe (SHRIMP) U–Pb zircon mass-spectrometry to determine their age and tectonostratigraphic relationships. Most volcanism occurred between 3238 and 3235 Ma, distinctly different from the time interval spanned by the Wyman Formation (type section is 3315 Ma, other dates ∼3325 Ma) with which it was previously correlated. Outlying volcanic rocks with similar geochemistry at the Bernts and Obelix prospects also produce dates from 3240 to 3235 Ma and are, therefore, best interpreted as structurally-detached fragments of the Sulphur Springs Group. The Strelley Granite, an intrusion which shares geochemical characteristics with the overlying volcanic rocks, also yields similar ages, thus extending the period of temporally-linked extrusive–intrusive silicic magmatism in the evolution of the Pilbara Craton. Model Pb–Pb dating of galena from the Zn–Cu mineralization at the various VMS prospects has yielded ages consistent with the zircon U–Pb ages of the host rocks, indicating that the hydrothermal mineralizing systems were contemporaneous with and apparently initiated by igneous activity. An epicontinental tectonic setting for the Sulphur Springs Group during VMS mineralization is implied by the broad range of old zircon ages obtained from a tuff at the base of the volcanic pile. As the igneous episode coincides with the peak regional metamorphic event recorded in other east Pilbara supracrustal rocks and with voluminous intrusive activity in nearby granitoid complexes, it marks a major event in the crustal evolution of the eastern Pilbara Craton. [Copyright &y& Elsevier]