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Biotic responses to environmental change: dwarf mammals of Mediterranean islands as evolutionary experiments in the Quaternary

对环境变化的生物反应：地中海岛屿的侏儒哺乳动物作为第四纪的进化实验

基本信息

批准号：
NE/F017839/2
负责人：
Adrian Lister
金额：
$ 10.41万
依托单位：
Natural History Museum
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2011
资助国家：
英国
起止时间：
2011 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FF017839%2F2
关键词：
Biotic responses environmental change dwarf

项目摘要

Climate change over the last million years has seen rapid fluctuations between ice ages and warmer 'interglacials'. At the height of an ice age the sea level could be up to 120 metres lower than it is today; then, when the climate warmed, the sea would rise once more. Understanding the impact of these changes has direct relevance to understanding the possible ramifications of the current global warming trend. The impact of such changes was felt most strongly on islands. Many island features are linked with sea level - they become larger and closer to the mainland (maybe forming a landbridge) as sea level drops; the opposite happens when levels rise. We know from modern islands that the smaller they are, the fewer species they can support. Island species are also often unique to that island, and they are vulnerable to extinction. Consequently, island species form a 'front-line' of response to climate change. We will investigate the effects of climate change over the last million years on island elephants and deer in the Mediterranean. Their commonest evolutionary response was to become dwarfed - a phenomenon that came to prominence with the discovery of a fossil dwarfed human on the island of Flores in Indonesia. In some species, dwarfing was extreme (elephants on Sicily, for example, weighed 150 kg, compared to a mainland ancestor of 10,000 kg), and we will use this as a 'marker' for evolutionary change. Until now, no one has considered the evolution of dwarf mammals in the context of climate change, because there are few reliable dates to tell us when these species evolved. To answer these questions we will first conduct detailed examination and measurement of fossils of the dwarf deer and elephants preserved in museums. We already have similar data on mainland species, and the comparison will allow us to determine how many species of dwarfs there were, and their ancestry. Comparison of measurements will then allow us to calculate the percentage reduction in body size and weight, and more detailed features of the teeth and bones will reveal whether the dwarfs had become specially adapted to the island environments. Secondly, we will use cutting-edge techniques to determine the geological age of the dwarf species. We will employ four different methods of dating that between them will allow us to determine ages within a narrow range of error. These methods use tooth remains of the mammals, and shells and sediments from the deposits in which they were found, and also require measurements to be taken at the sites. To this end we will visit a number of key localities on Sicily, Malta, Crete and Cyprus where remains of dwarf elephants have been found, and conduct small excavations to produce fresh material for dating and for comparison with previously-excavated fossils. Thirdly, we will use existing knowledge about climate and sea-level changes over the past million years to plot maps of the changing size and shape of the islands and, in the case of Sicily and Malta, their possible connections to each other and to the mainland. Putting together these three strands, we will be able to determine how global changes impacted the evolution of the mammals. Did major climatic events trigger bursts of evolution on many islands? What was the speed of evolutionary change? Did the dwarf species endure for a long time, or did they soon become extinct, perhaps due to further climate change? Did the same thing happen repeatedly in a cyclic fashion? Was the degree of dwarfing influenced by island size, time of separation, or other factors such as available vegetation? The results of this project will provide a microcosm of the impact of global change on mammal evolution. It will also help explain a long-debated phenomenon - that of island dwarfing. It will, finally, refine methods and produce data of broader application, especially in the proposed dating of important geological sites around the Mediterranean.

过去一百万年的气候变化见证了冰河时代和温暖的“间冰期”之间的快速波动。在冰河时期的高峰期，海平面可能比现在低 120 米；然后，当气候变暖时，海平面会再次上升。了解这些变化的影响与了解当前全球变暖趋势可能产生的后果有直接关系。这些变化对岛屿的影响最为强烈。许多岛屿特征与海平面有关——随着海平面下降，它们变得更大、更靠近大陆（可能形成陆桥）；当水平升高时，情况恰恰相反。我们从现代岛屿中知道，岛屿越小，能够支持的物种就越少。岛屿物种通常也是该岛屿独有的，并且很容易灭绝。因此，岛屿物种构成了应对气候变化的“前线”。我们将调查过去一百万年气候变化对地中海岛屿象和鹿的影响。他们最常见的进化反应是变得侏儒——随着在印度尼西亚弗洛勒斯岛发现侏儒人类化石，这种现象变得突出。在某些物种中，矮化现象非常严重（例如，西西里岛的大象重 150 公斤，而大陆祖先的体重为 10,000 公斤），我们将以此作为进化变化的“标记”。到目前为止，没有人考虑过气候变化背景下侏儒哺乳动物的进化，因为几乎没有可靠的日期告诉我们这些物种的进化时间。为了回答这些问题，我们首先对博物馆保存的矮鹿和大象化石进行详细的检查和测量。我们已经有了关于大陆物种的类似数据，通过比较，我们可以确定有多少种矮人，以及它们的祖先。然后，测量结果的比较将使我们能够计算出身体尺寸和重量的减少百分比，而牙齿和骨骼的更详细特征将揭示矮人是否已经特别适应了岛屿环境。其次，我们将利用尖端技术确定矮物种的地质年龄。我们将采用四种不同的约会方法，它们将使我们能够在较小的误差范围内确定年龄。这些方法使用哺乳动物的牙齿残骸以及发现它们的沉积物中的贝壳和沉积物，并且还需要在现场进行测量。为此，我们将访问西西里岛、马耳他、克里特岛和塞浦路斯的一些发现了矮象遗骸的重要地点，并进行小型挖掘，以获取新的材料，用于年代测定并与之前挖掘的化石进行比较。第三，我们将利用过去数百万年有关气候和海平面变化的现有知识，绘制岛屿大小和形状变化的地图，以及西西里岛和马耳他岛之间以及它们与大陆之间可能存在的联系。将这三条线索放在一起，我们将能够确定全球变化如何影响哺乳动物的进化。重大气候事件是否引发了许多岛屿的进化爆发？进化变化的速度是多少？这些矮人物种是否存在了很长一段时间，或者它们是否很快就灭绝了，也许是由于进一步的气候变化？同样的事情是否以循环方式重复发生？矮化程度是否受到岛屿大小、分离时间或其他因素（例如可用植被）的影响？该项目的结果将提供全球变化对哺乳动物进化影响的缩影。它还将有助于解释一个长期争论的现象——岛屿矮化。最后，它将完善方法并产生更广泛应用的数据，特别是在地中海周围重要地质遗址的拟议测年方面。