Collaborative Research: Response of Mammalian Survivors to the Late Pleistocene Extinction Event

全球变暖和更新世末期的人类狩猎导致大多数体重超过44公斤的哺乳动物灭绝。虽然物种灭绝事件的原因一直备受争议和关注，但随之而来的群落变化对在灭绝中幸存下来的物种的影响还没有得到很好的调查。然而，关于对幸存者的影响的知识对于预测未来的生物多样性将是非常有价值的。因此，与仅仅从物种灭绝的原因来研究更新世灭绝不同，pi们热衷于调查幸存的物种是如何或实际上是否受到灭绝事件的影响。因此，PIs建议利用加州沙斯塔县丰富但尚未开发的第四纪化石资源，研究在更新世-全新世过渡事件中幸存下来的哺乳动物物种的反应。他们的主要目标是确定群落、物种和幸存者对更新世-全新世过渡的反应，并弄清楚这种反应是由于巨型动物灭绝、气候变化还是两者兼而有之。为了记录晚第四纪扰动事件的性质及其对生物群的影响，他们将采用跨学科的方法，基于对哺乳动物化石形态计量学、同位素、遗传学和群落组成的追踪变化。这将通过(i)发掘和分析新发现和已知的化石地点来促进；（ii）利用多重放射性碳测年和其他地质年代学和地层学技术获得可靠的地层控制；进行遗传分析，以发现种群细分、密度变化和局部灭绝的迹象；（iv）灭绝前和灭绝后群落在分类组成、总物种丰富度、不同大小和营养类别的物种丰富度、物种丰度和均匀度方面的比较；(v)追踪种群的表型变化；（六）结合系统年代学技术，利用古代DNA直接识别化石种群的遗传结构。所有的生物变化都将在研究区域和全球范围内记录的广泛灭绝和气候变化的框架内进行解释。

Global warming and human hunting at the end of the Pleistocene led to the extinction of most of the mammalian fauna larger than 44 kg. While the causes of the extinction event are debated and of intense interest, the effect of the ensuing community changes on species that survived the extinction has not been well investigated. Yet knowledge about effects on survivors will be immensely valuable to predictions of future biodiversity. Thus, instead of studying the Pleistocene extinction solely from the perspective of why species went extinct, PIs are keen to investigate how, or in fact, whether, surviving species were affected by the extinction event. PIs therefore propose to use the rich but untapped Quaternary fossil resources of Shasta County, California, to investigate the response of the mammal species that survived the Pleistocene-Holocene transition event. Their primary goal is to determine community, species, and population response of survivors to the Pleistocene-Holocene transition and to sort out whether the response was due to megafaunal extinction, climatic change or both. To document the nature of late Quaternary disturbance events and impacts on the biota, they will use an interdisciplinary approach, based on tracing changes in morphometrics, isotopes, genetics, and community composition of fossil mammals. This will be facilitated by (i) excavations and analyses of newly discovered and known fossil sites; (ii) obtaining secure stratigraphic control with multiple radiocarbon dates and other geochronologic and stratigraphic techniques; (iii) conducting genetic analyses aimed at detecting signs of population subdivision, density changes and local extirpation; (iv) comparison of pre- and post-extinction communities in terms of taxonomic composition, total species richness, species richness within various size and trophic categories, abundance and evenness of species; (v) tracing phenotypic changes in populations; and (vi) using ancient DNA with phylochronologic techniques to directly recognize genetic structuring of fossil populations. All of the biotic changes will be interpreted within the framework of the extensive extinction and climatic changes that are documented in their study area and globally.