A new leaf species of Proteaceae and other Gondwanan elements from the early Paleogene Lota–Coronel flora of south–central Chile

Leaf fossils collected in 1908 from the Arauco–Concepción Coal Measures of Chile (the Lota–Coronel flora) during a Swedish expedition to southern South America are formally assigned to the important Gondwanan family Proteaceae as Proteaceaefolia araucoensis R.J.Carp. & McLoughlin gen. nov., sp. nov. This is the oldest South American record of macrofossils that can be assigned to Proteaceae with confidence due to the likelihood of the age dating to the latest Paleocene. The fossils lack cuticle but the large, lobed and minutely toothed form is consistent only with extant species of the subfamily Grevilleoideae (notably, Orites excelsus R.Br.) that are confined to eastern Australian rainforests. A new assessment of the Swedish Lota–Coronel collection and review of previous palynological and macrofossil studies, also provide evidence of the strong biogeographic connection that existed between southern South America and Australasia during the early Paleogene, and contradict a traditional view that several Chilean floras of this age consist wholly or largely of Neotropical taxa. Notable austral taxa include Casuarinaceae (as abundant pollen), diverse Podocarpaceae (as both foliage and pollen) and likely Cunoniaceae (leaves). No taxa with clearly Neotropical nearest living relatives have been found to date, but previous conclusions for a warm and very wet early Paleogene climate are supported

Nanoparticles of iridium and other platinum group elements identified in Chicxulub asteroid impact spherules – Implications for impact winter and profound climate change

The Chicxulub asteroid that ended the Cretaceous Era ∼66.05 million years ago caused a prolonged time of global darkness – the impact winter – leading to mass extinctions. Elements from the asteroid, including the platinum group elements (PGEs) osmium, iridium and platinum are known from the globally distributed boundary clay but their carrier elements have so far been unknown. We identify, for the first time in detail, the presence of these PGEs within Chicxulub impact spherules and importantly, we identify their carrier elements. We show through synchrotron Nano-XRF how these PGEs occur in nanostructures as un-ordered cube- and/or needle-like crystals co-localizing with both siderophile and chalcophile elements including Co, Ni, Cu, Zn, and Pb, derived from the asteroid. These crystals are set within a matrix of iron-rich calcium and silica glass revealing the mix of vaporized target rock and the asteroid. The results provide insights into the combination of elements present in the spherules, indicating formation of new minerals. We argue that the nano-shards of unreactive elements such as platinum, iridium and copper acted as nuclei for aerosol formation and potentially contributed to a prolonged impact winter with darkness and cooling leading to a profound and long-term climate change.This work was supported by Swedish Research Council, Sweden, grants VR 2019-4061 (V·V.); and Knut and Alice Wallenberg Foundation, Sweden, grant KAW 2020.0145  (V·V.), and Wenner-Gren Foundation SSh2023-0016, Sweden (V·V.). We thank beamline scientists and staff at MAX IV synchrotron facility. We acknowledge MAX IV Laboratory for time on Beamline NanoMAX under Proposal 20190340 and Beamline Balder, Sweden, under Proposal 20210384. Research conducted at MAX IV, a Swedish national user facility, is supported by the Swedish Research council, Sweden under contract 2018-07152, the Swedish Governmental Agency for Innovation Systems under contract 2018-04969, and Formas, Sweden, under contract 2019-02496. XRM data acquisition was supported by a grant to the Stockholm University Brain Imaging Centre, Sweden (SU FV-5.1.2-1035-15).</p

Integrated population model reveals human- and environment-driven changes in Baltic ringed seal Pusa hispida botnica demography and behavior

Integrated population models (IPMs) are a promising approach to test ecological theories and assess wildlife populations in dynamic and uncertain conditions. By combining multiple data sources into a unified model, they enable the parametrization of versatile, mechanistic models that can predict population dynamics in novel circumstances. Here, we present a Bayesian IPM for the ringed seal Pusa hispida botnica population inhabiting the Bothnian Bay in the Baltic Sea. Despite the availability of long-term monitoring data, traditional assessment methods have faltered due to dynamic environmental conditions, varying reproductive rates, and recently re-introduced hunting, thus limiting the quality of information available to managers. We fit our model to census and various demographic, reproductive, and harvest data from 1988 to 2023 to provide a comprehensive assessment of past population trends, and predict population response to alternative hunting scenarios. We estimated that 20000–36000 ringed seals inhabited the Bothnian Bay in 2024, increasing at a rate of 3–6% yr–1. Reproductive rates have increased since 1988, leading to a substantial increase in the growth rate up until 2015. However, the re-introduction of hunting has since reduced the growth rate, and even minor quota increases are likely to reduce it further. Our results also support the hypothesis that a greater proportion of the population hauls out under lower ice cover circumstances, leading to higher aerial survey results in such years. In general, our study demonstrates the value of IPMs for monitoring wildlife populations under changing environments and for supporting science-based management decisions

Ephemeral Speciation in a New Guinean Honeyeater Complex ( Aves : Melidectes )

Speciation is a fundamental concept in evolutionary biology, and understanding the mechanisms driving speciation remains the foremost research topic within this field. Hybridisation is often involved in speciation and can influence its rates, potentially accelerating, decelerating or even reversing the process. This study investigates the evolutionary history of the New Guinean bird genus Melidectes, consisting of six species that inhabit various montane regions at different elevations. While most Melidectes species have allopatric distributions, two species overlap in the central mountain range and hybridise. However, plumage differences and elevational adaptations are assumed to maintain the species' boundaries. Utilising specimens from natural history collections and comprehensive genomic analyses, including a de novo genome assembly, we characterise allopatric speciation patterns within the genus and highlight how future speciation could potentially be driven by climate change. Contrary to previous hypotheses, our findings suggest that in the two distributionally overlapping species, phenotypic differences do not prevent gene flow. We find limited acoustic differentiation and extensive admixture across most of their distributions. Divergence and admixture levels conform poorly to the current taxonomy and follow a geographical pattern in which the most isolated populations at the ends of the distributions are most divergent and show least admixture. However, in contrast, their mitochondrial genomes do group in accordance with species identity, namely, into two deeply divergent lineages. We propose that this system demonstrates the ephemeral nature of speciation, in which two incipient species have started mixing extensively as they came into secondary contact, resulting in nearly complete fusion into a single lineage

Evidence for deliberate burial of the dead by Homo naledi

In this study, we describe new results of excavations in the Dinaledi Subsystem of the Rising Star cave system, South Africa. In two areas within the Hill Antechamber and the Dinaledi Chamber, this work uncovered concentrations of abundant Homo naledi fossils including articulated, matrix-supported skeletal regions consistent with rapid covering by sediment prior to the decomposition of soft tissue. We additionally re-examine the spatial positioning of skeletal material and associated sediments within the Puzzle Box area, from which abundant H. naledi remains representing a minimum of six individuals were recovered in 2013 and 2014. Multiple lines of evidence exclude the hypothesis that skeletal remains from these three areas come from bodies that decomposed on the floor of the chamber or within a shallow depression prior to burial by sediments. The spatial positioning of skeletal material, the topography of the subsystem, and observations on sediments within and surrounding features exclude the hypothesis that rapid burial by sediment was a result of gravity-driven slumping or spontaneous movement of sediments. We present a minimal hypothesis of hominin cultural burial and test the evidence from all three areas, finding that this hypothesis is most compatible with the pattern of evidence. These results suggest that mortuary behavior, including cultural burial, was part of the repertoire of Homo naledi.Permits to conduct research in the Rising Star Cave system are provided by the South African Heritage Resource Agency (LRB). Permission to work in the Rising Star cave is given by the LRB Foundation for Research and Exploration. We would like to thank the University of the Witwatersrand’s Primate Fossil Access Committee for allowing access to the original material for study and the University Curator and Assistant Curator of Collections for assisting with logistics in studying the material. We would like to thank the Department of Diagnostic Radiology at the Charlotte Maxeke Academic Hospital for allowing access to their clinical CT scanner. We acknowledge the European Synchrotron Research Facility for providing access to facilities including the BM18 beamline. We would like to thank Matthew Caruana for discussions related to the stone object associated with the Hill Antechamber burial. We would like to thank the Spectrum Analytical Facility and the Department of Metallurgy at the University of Johannesburg for the analytical work on the sediments. Christian Reinke is specifically thanked for carrying out the XRF measurements (TM). The authors would like to acknowledge the funders of the various expeditions that recovered the fossil material and information, including 3d scanning and the production of AVR material described in this paper including the National Geographic Society (LRB, CJ, KB), the Lyda Hill Foundation (LRB) and the National Research Foundation of South Africa (LRB). Laboratory work, field work and travel was funded by the National Geographic Society (LRB, ME, AK, CJ, KB), the Lyda Hill Foundation (LRB, ME, AK) the Centre for Excellence in PalaeoSciences at the University of the Witwatersrand (now GENUS) (AK), the Fulbright Scholar Program (JH), John Templeton Foundation (LRB, JH) and National Research Foundation of South Africa (TM), University of Johannesburg Research Council (TM), and the Spectrum Analytical Facility at University of Johannesburg (TM).</p