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.

在过去的百万年中，气候变化在冰河时代和温暖的“冰川间”之间发生了迅速的波动。在冰河时代的高处，海平面可能比今天低120米。然后，当气候变暖时，大海将再次上升。了解这些变化的影响与理解当前全球变暖趋势的可能后果有关。这种变化对岛屿的影响最大。许多岛屿特征与海平面有关 - 随着海平面的下降，它们变得更大，更靠近大陆（可能形成兰德桥）。当水平上升时，情况恰恰相反。我们从现代岛屿中知道，它们越小，它们所能支持的物种越少。岛屿物种通常也是该岛独有的，它们容易灭绝。因此，岛屿物种形成了对气候变化的反应的“前线”。我们将调查过去一百万年来气候变化对地中海岛屿大象和鹿的影响。他们最常见的进化反应是矮人 - 这种现象在印度尼西亚弗洛雷斯岛上发现了化石矮人的人，这一现象引起了人们的关注。在某些物种中，矮人是极端的（例如，与10,000公斤的大陆祖先相比，西西里岛上的大象重150公斤），我们将其用作进化变化的“标记”。到目前为止，在气候变化的背景下，没有人考虑过矮哺乳动物的演变，因为几乎没有可靠的日期可以告诉我们这些物种何时进化。为了回答这些问题，我们将首先对矮鹿和保存在博物馆中的大象的化石进行详细检查和测量。我们已经有关于大陆物种的类似数据，并且比较将使我们能够确定有多少种矮人及其祖先。然后，测量值将使我们能够计算体大小和体重的减少百分比，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，我们将使用尖端技术来确定矮种的地质年龄。我们将采用四种不同的约会方法，它们之间将使我们能够确定误差范围内的年龄。这些方法使用哺乳动物的牙齿残留物，以及发现它们的沉积物中的贝壳和沉积物，还需要在该地点进行测量。为此，我们将参观西西里岛，马耳他，克里特岛和塞浦路斯的许多关键地区，在那里发现了矮人的遗迹，并进行小型发掘以生产新鲜的材料，以与先前挖掘的化石进行比较。第三，我们将利用有关气候和海平面变化的现有知识来绘制岛屿规模和形状变化的地图，在西西里岛和马耳他的情况下，它们可能彼此之间以及与大陆的联系。将这三个链组合在一起，我们将能够确定全球变化如何影响哺乳动物的演变。重大气候事件是否触发了许多岛屿的进化爆发？进化变化的速度是多少？矮人物种是否长期存在，还是很快就灭绝了，也许是由于气候变化的进一步变化？同样的事情是否以循环方式反复发生？矮人的程度是否受岛屿规模，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的影响的缩影。它还将有助于解释一种长期存在的现象 - 岛屿矮小的现象。最后，它将完善方法并产生更广泛的应用的数据，尤其是在地中海周围重要地质地点的拟议约会中。