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1. The hidden legacy of megafaunal extinction: Loss of functional diversity and resilience over the Late Quaternary at Hall’s Cave

   https://doi.org/10.1111/geb.13428  

   Hedberg, Carson P. ; Lyons, S. Kathleen ; Smith, Felisa A. ; Schrodt, ed., Franziska ( November 2021 , Global Ecology and Biogeography)

   Functional traits mediate the interactions of species among themselves and with their environment, providing a link between diversity and ecosystem function. Crucially, the loss of biodiversity can jeopardize the functionality of ecosystems. Much focus is on predicting the impacts of current and future species loss; however, modern ecosystems have undergone biodiversity decline throughout the Late Quaternary, starting with the Pleistocene megafaunal extinctions. Thus, the fossil record offers the opportunity to investigate the long‐term legacy of biodiversity erosion and how this is affecting modern ecosystems in a cumulative manner. We aimed to investigate changes in functional diversity and redundancy of a local mammal community at Hall’s Cave, a site with a continuous record from 21,000 years ago to the present. Additionally, we included several common introduced species in the modern community to test whether they restore some lost ecological function.

   Central Texas.

   Late Pleistocene to Present.

   Mammals.

   We used eight functional traits (mass, diet, arboreality, cursoriality, soil disturbance, group size, activity period and migration habit), which, collectively, describe the ecological role of a species and its influence on ecosystem processes, to construct a multidimensional functional space. The functional richness, range and distribution of the Hall’s Cave community and the degree of functional redundancy were characterized statistically over time.

   We found that declines in functional diversity were greater than expected given the decrease in species richness, implying that lost taxa contributed higher than average distinct ecological function. Functional distances between the remaining species increased through time, leading to reduced functional redundancy in younger communities. However, recently introduced taxa increased functional diversity to levels similar to those in the Holocene and partly restored the functional space occupied by Late Pleistocene fauna.

   Our local‐scale analysis demonstrates how prolonged biodiversity erosion not only leads to functionally depauperate communities, but, crucially, lowers ecological resilience to future disturbance.

    

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2. Late Pleistocene shrub expansion preceded megafauna turnover and extinctions in eastern Beringia

   https://doi.org/10.1073/pnas.2107977118  

   Monteath, Alistair J. ; Gaglioti, Benjamin V. ; Edwards, Mary E. ; Froese, Duane ( December 2021 , Proceedings of the National Academy of Sciences)

   The collapse of the steppe-tundra biome (mammoth steppe) at the end of the Pleistocene is used as an important example of top-down ecosystem cascades, where human hunting of keystone species led to profound changes in vegetation across high latitudes in the Northern Hemisphere. Alternatively, it is argued that this biome transformation occurred through a bottom-up process, where climate-driven expansion of shrub tundra ( Betula , Salix spp.) replaced the steppe-tundra vegetation that grazing megafauna taxa relied on. In eastern Beringia, these differing hypotheses remain largely untested, in part because the precise timing and spatial pattern of Late Pleistocene shrub expansion remains poorly resolved. This uncertainty is caused by chronological ambiguity in many lake sediment records, which typically rely on radiocarbon ( 14 C) dates from bulk sediment or aquatic macrofossils—materials that are known to overestimate the age of sediment layers. Here, we reexamine Late Pleistocene pollen records for which 14 C dating of terrestrial macrofossils is available and augment these data with 14 C dates from arctic ground-squirrel middens and plant macrofossils. Comparing these paleovegetation data with a database of published 14 C dates from megafauna remains, we find the postglacial expansion of shrub tundra preceded the regional extinctions of horse ( Equus spp.) and mammoth ( Mammuthus primigenius ) and began during a period when the frequency of 14 C dates indicates large grazers were abundant. These results are not consistent with a model of top-down ecosystem cascades and support the hypothesis that climate-driven habitat loss preceded and contributed to turnover in mammal communities. 

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3. ISOTOPIC EVIDENCE OF SEASONALITY AND MIGRATION DURING THE LAST GLACIAL PERIOD OF KENYA

   O'Brien, K. ; Podkovyroff, K. ; Fernandez, D. P. ; Tryon, C. A. ; Cerling, T. E. ; Ashioya, L. ; Faith, J. T. ( October 2023 , Society of Vertebrate Paleontology)

   Paleoenvironmental reconstructions of the Last Glacial Period of eastern Africa paint a picture of a landscape dominated by grasslands and herds of diverse grazing herbivores unlike anywhere in modern Africa. However, the scale of such reconstructions is often at the site level and greatly time-averaged. To elucidate the impact of glacial conditions on tropical grassland animal behavior, a more direct proxy is needed. Using stable strontium, carbon, and oxygen isotopes, we reconstruct paleoenvironmental conditions and behavior of 18 bovid and equid species from four sites dating to the Last Glacial Period in Kenya (Karungu, Rusinga, Kibogo, and Lukenya Hill). In doing so, we address i) migration patterns, ii) seasonality of precipitation and diet, and iii) the role that seasonal responses played in niche separation of closely related species. We find that migration played a similar role in Last Glacial Period grasslands to what it does today but with a notably different set of species; that animals had relatively stable, grass-dominated diets year-round, peaking in C4 grass abundance during the Last Glacial Maximum; that precipitation and seasonality fell within the range of modern eastern African ecosystems; and that a diverse guild of ungulate grazers was able to coexist due to niche separation detectable as isotopic differences. These results combine to extend the theory that eastern African grasslands were greatly expanded and resource-rich year-round during the Last Glacial Period, creating highly favorable conditions for grazing ungulates. Additionally, they demonstrate the geologic recency of the modern guild of migratory species in eastern Africa, which replaced a set of now-extinct migratory species once common in grasslands during the Last Glacial Period, most notably the enigmatic bovid Rusingoryx. Our results illustrate the ecosystem dynamics of Late Pleistocene Kenya on a scale not attainable with most other paleoenvironmental proxies: the scale of individual animals’ lifetimes. This is nearly as close as possible to an actualistic ecological survey of ungulate behavior during the Last Glacial Period in a setting not analogous to any ecosystem on Earth today. 

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4. Paleobiology of a large mammal community from the late Pleistocene of Sonora, Mexico

   https://doi.org/10.1017/qua.2020.125  

   Short, Rachel A. ; Emmert, Laura G. ; Famoso, Nicholas A. ; Martin, Jeff M. ; Mead, Jim I. ; Swift, Sandy L. ; Baez, Arturo ( January 2021 , Quaternary Research)

   null (Ed.)

   A paleontological deposit near San Clemente de Térapa represents one of the very few Rancholabrean North American Land Mammal Age sites within Sonora, Mexico. During that time, grasslands were common, and the climate included cooler and drier summers and wetter winters than currently experienced in northern Mexico. Here, we demonstrate restructuring in the mammalian community associated with environmental change over the past 40,000 years at Térapa. The fossil community has a similar number of carnivores and herbivores whereas the modern community consists mostly of carnivores. There was also a 97% decrease in mean body size (from 289 kg to 9 kg) because of the loss of megafauna. We further provide an updated review of ungulates and carnivores, recognizing two distinct morphotypes of Equus, including E. scotti and a slighter species; as well as Platygonus compressus; Camelops hesternus; Canis dirus; and Lynx rufus; and the first regional records of Palaeolama mirifica, Procyon lotor, and Smilodon cf. S. fatalis. The Térapa mammals presented here provide a more comprehensive understanding of the faunal community restructuring that occurred in northern Mexico from the late Pleistocene to present day, indicating further potential biodiversity loss with continued warming and drying of the region. 

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5. The stories people tell, and how they can contribute to our understanding of megafaunal decline and extinction in Madagascar

   Nomenjanahary, E.S. ; Freed, B.Z. ; Dollar, L.J. ; Randrianasy, J. ; Godfrey, L.R. ( December 2021 , Malagasy nature)

   Most researchers believe that Madagascar’s megafauna went extinct between 2000 and 1000 years ago. Across Madagascar, fossil specimens of the island’s endemic (and now extinct) pygmy hippopotamuses, elephant birds, giant lemurs, horned crocodiles, and other vertebrates larger in body size than 10 kg commonly date to the first millennium of the Common Era (CE) or earlier; few records date to the second millennium CE. Whereas megafaunal populations appear to have crashed almost simultaneously near the end of the first millennium CE, small populations can survive in remote pockets for centuries after precipitous species decline, perhaps longer. Examining the differences in the population dynamics of declining species and other factors can help to better identify the ultimate timing of extinction. Ever since Etienne de Flacourt traveled to Madagascar in the late 1600s, Malagasy stories of large-bodied wild animals have been recorded. Many include fantastic, clearly mythical creatures, but some provide anatomical or behavioral details which are consistent with legends or even direct observations of real, albeit potentially already extinct, species (including elephant birds, hippopotamuses, and some giant lemurs). In December 1989, at 06:00 hours, one of us (BZF) witnessed a large euplerid carnivoran locally known as fosabe (big fosa) or fosa jobijoby (blackish fosa) who had entered his field tent at Montagne d’Ambre. The animal was “twice the size and much darker than the common fossa” (Freed, 1996, p. 34). The individual was black and weighed approximately 20-25 kg. Freed wrote that the animal was well known to the local people and that “many local people also reported seeing it”. The animal fits paleontologists’ expectations for Cryptoprocta spelea, a large carnivoran known from the fossil record, believed to have been extinct for at least 1000 years. In June 2020, we recorded modern accounts of the big fosa. One of us (ESN) visited villages in four different sectors (Northwest, Northeast, East, and West) of Montagne d’Ambre National Park and the Forêt d’Ambre Special Reserve to examine potential regional differences and/or similarities in the stories of this animal, and whether such accounts include mythical elements, relevant anatomical information, and/or credible recent sightings. We also recorded stories of an Endangered extant animal, the aye-aye of the genus Daubentonia (also known locally as the kakahely). Ultimately, we believe this folklore provides clues that may help elucidate the geography of decline and possible late survival of an “extinct” megafaunal animal on Madagascar. 

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