Browsing by Subject "Extinction"

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  • Popova, Dina; Agustsdottir, Arna; Lindholm, Jesse; Mazulis, Warns; Akamine, Yumiko; Castren, Eero; Karpova, Nina N. (2014)
  • Di Minin, Enrico; 't Sas Rolfes, Michael; Selier, Jeanetta; Louis, Maxi; Bradshaw, Corey J.A. (2022)
    Persistent poaching fuelled by demand for elephant ivory and rhino horn continues to threaten these species. Despite international trade restrictions operating since the 1970s, limiting poaching has remained a substantial challenge over the last decade. The poaching economy of such storable goods is driven by a combination of persistent consumer demand and market speculation, and enabled by weak governance, lack of adequate resources for species protection, and alienation of local people who pay the costs of living alongside these species. We argue that restricting the legal supply of such wildlife products has created ideal conditions for the poaching economy - `poachernomics' - to thrive. Strategies that move toward empowering local communities with stronger property rights over wildlife and delivering more benefits to them, including via carefully regulated legal trade, are underused elements in the current fight against the onslaught of the international illegal wildlife trade.
  • Boldin, Barbara; Kisdi, Eva (2016)
    Evolutionary suicide is a riveting phenomenon in which adaptive evolution drives a viable population to extinction. Gyllenberg and Parvinen (Bull Math Biol 63(5):981-993, 2001) showed that, in a wide class of deterministic population models, a discontinuous transition to extinction is a necessary condition for evolutionary suicide. An implicit assumption of their proof is that the invasion fitness of a rare strategy is well-defined also in the extinction state of the population. Epidemic models with frequency-dependent incidence, which are often used to model the spread of sexually transmitted infections or the dynamics of infectious diseases within herds, violate this assumption. In these models, evolutionary suicide can occur through a non-catastrophic bifurcation whereby pathogen adaptation leads to a continuous decline of host (and consequently pathogen) population size to zero. Evolutionary suicide of pathogens with frequency-dependent transmission can occur in two ways, with pathogen strains evolving either higher or lower virulence.
  • Fang, Xiang; Kröger, Björn; Zhang, Yuan-Dong; Zhang, Yun-Bai; Chen, Ting-En (2019)
  • Bibi, Faysal; Pante, Michael; Souron, Antoine; Stewart, Kathlyn; Varela, Sara; Werdelin, Lars; Boisserie, Jean-Renaud; Fortelius, Mikael; Hlusko, Leslea; Njau, Jackson; de la Torre, Ignacio (2018)
    Eight years of excavation work by the Olduvai Geochronology and Archaeology Project (OGAP) has produced a rich vertebrate fauna from several sites within Bed II, Olduvai Gorge, Tanzania. Study of these as well as recently re-organized collections from Mary Leakey's 1972 HWK EE excavations here provides a synthetic view of the faunal community of Olduvai during Middle Bed II at similar to 1.7-1.4 Ma, an interval that captures the local transition from Oldowan to Acheulean technology. We expand the faunal list for this interval, name a new bovid species, clarify the evolution of several mammalian lineages, and record new local first and last appearances. Compositions of the fish and large mammal assemblages support previous indications for the dominance of open and seasonal grassland habitats at the margins of an alkaline lake. Fish diversity is low and dominated by cichlids, which indicates strongly saline conditions. The taphonomy of the fish assemblages supports reconstructions of fluctuating lake levels with mass die-offs in evaporating pools. The mammals are dominated by grazing bovids and equids. Habitats remained consistently dry and open throughout the entire Bed II sequence, with no major turnover or paleoecological changes taking place. Rather, wooded and wet habitats had already given way to drier and more open habitats by the top of Bed I, at 1.85-1.80 Ma. This ecological change is close to the age of the Oldowan-Acheulean transition in Kenya and Ethiopia, but precedes the local transition in Middle Bed II. The Middle Bed II large mammal community is much richer in species and includes a much larger number of large-bodied species (>300 kg) than the modern Serengeti. This reflects the severity of Pleistocene extinctions on African large mammals, with the loss of large species fitting a pattern typical of defaunation or 'downsizing' by human disturbance. However, trophic network (food web) analyses show that the Middle Bed II community was robust, and comparisons with the Serengeti community indicate that the fundamental structure of food webs remained intact despite Pleistocene extinctions. The presence of a generalized meateating hominin in the Middle Bed II community would have increased competition among carnivores and vulnerability among herbivores, but the high generality and interconnectedness of the Middle Bed II food web suggests this community was buffered against extinctions caused by trophic interactions. (C) 2017 Published by Elsevier Ltd.
  • Cardoso, Pedro; Amponsah-Mensah, Kofi; Barreiros, João P.; Bouhuys, Jamie; Cheung, Hubert; Davies, Alisa; Kumschick, Sabrina; Longhorn, Stuart J.; Martínez-Muñoz, Carlos A.; Morcatty, Thais Q.; Peters, Gretchen; Ripple, William J.; Rivera-Téllez, Emmanuel; Stringham, Oliver C.; Toomes, Adam; Tricorache, Patricia; Fukushima, Caroline S. (2021)
    Illegal or unsustainable wildlife trade is growing at a global level, threatening the traded species and coexisting biota, and promoting the spread of invasive species. From the loss of ecosystem services to diseases transmitted from wildlife to humans, or connections with major organized crime networks and disruption of local to global economies, its ramifications are pervading our daily lives and perniciously affecting our well-being. Here we build on the manifesto 'World Scientists' Warning to Humanity, issued by the Alliance of World Scientists. As a group of researchers deeply concerned about the consequences of illegal or unsustainable wildlife trade, we review and highlight how these can negatively impact species, ecosystems, and society. We appeal for urgent action to close key knowledge gaps and regulate wildlife trade more stringently.
  • Arppe, Laura; Karhu, Juha A.; Vartanyan, Sergey; Drucker, Dorothée G.; Etu-Sihvola, Heli; Bocherens, Hervé (2019)
    The world's last population of woolly mammoths (Mammuthus primigenius) lived on Wrangel Island persisting well into the Holocene, going extinct at ca. 4000 cal BP. According to the frequency of 'radiocarbon dated mammoth remains from the island, the extinction appears fairly abrupt. This study investigates the ecology of the Wrangel Island mammoth population by means of carbon, nitrogen and sulfur isotope analyses. We report new isotope data on 77 radiocarbon dated mammoth specimens from Wrangel Island and Siberia, and evaluate them in relation to previously published isotope data for Pleistocene mammoths from Beringia and lower latitude Eurasia, and the other insular Holocene mammoth population from St. Paul Island. Contrary to prior suggestions of gradual habitat deterioration, the nitrogen isotope values of the Wrangel Island mammoths do not support a decline in forage quality/quantity, and are in fact very similar to their north Beringian forebears right to the end. However, compared to Siberian mammoths, those from Wrangel Island show a difference in their energy economy as judged by the carbon isotope values of structural carbonate, possibly representing a lower need of adaptive strategies for survival in extreme cold. Increased mid-Holocene weathering of rock formations in the central mountains is suggested by sulfur isotope values. Scenarios related to water quality problems stemming from increased weathering, and a possibility of a catastrophic starvation event as a cause of, or contributing factor in their demise are discussed. (C) 2019 The Authors. Published by Elsevier Ltd.