末次冰消期以来黄土高原陆生软体动物生物多样性变化对气候转暖过程的响应

How biodiversity response, increases or losses to climate warming, is one of the most controversial scientific issues in the global change research. To date, assessments of climate-change impacts on biodiversity have solely been based on empirical niche models or observation data in recent decades. Understanding how biodiversity changes responded to past environmental change is a fundamental and important approach for accurate prediction of biodiversity variations in current and future warming. The mollusks are the second largest category in animal kingdom that is a key food chain connection of plants and animals. Land snails are particularly sensitive to changing climate such as temperature and precipitation etc. But until now, little is known of their response to rising temperature and the relationship between its diversity and climate change. This project intends to investigate the diversity, abundance and distribution of land snails in temporal and spatial in the Chinese Loess Plateau, based on the existing database of extant land-snail and other biological-environmental proxies. The objectives are to 1) obtain eight or nine high-resolution land-snail sequences of the last 20 ka, which are designed to span different areas in latitudes and latitudes across the Loess Plateau; 2) study the temporal and spatial variation of land-snail diversity, adaptation and shift during different warming processes since the last deglaciation, 3) examine community changes of land mollusks during the last 'natural' global warming period at the Pleistocene-Holocene transition and indicate how land-snail species losses and gains, combined with changes in abundance, evenness and richness of snail communities; 4) provide scientific evidence for a better understanding of how climate - particularly rising temperature - affects biodiversity changes of different biological groups in the natural warming process, and make an implementation of adaptation strategies.

气候升温过程中生物多样性是增加还是减少？是目前全球变化研究中最具有争议的科学问题之一。已有生物多样性与气候关系的知识，多依据最近几十年来年际或十年际生物观察记录，重建特征地质历史时期气候转暖过程中生物种群演化、生物多样性变化过程等，是正确判断目前全球变暖背景下生物多样性变化性质和未来是否发生大规模生物绝灭的重要途径。软体动物是动物界的第二大门类，是连接动物和植物界的关键食物链，迄今缺少其多样性与气候关系的系统研究。本项目计划利用和完善我国已有现生软体动物蜗牛-生态环境数据库，通过对黄土高原东南－西北向不同环境－温度梯度区现生和化石蜗牛分析，提取约2万年来高分辨率蜗牛化石等生物-环境指标, 重点研究末次冰消期以来气候转暖的不同幅度、速率过程中，蜗牛生物多样性在时间和空间上的变化，适应、迁移的过程和规律。本项目希望为正确认识气候自然转暖过程中生物多样性变化规律和实施正确的适应策略提供科学证据。

对于人类赖以生存的地球生物圈的发展、演化来说，全球增温在多大的幅度范围内变化，生物多样性、生态系统才是安全的？这是当前全球变化研究中最关注的热点科学问题之一。地质历史时期，特别是气候增温过程中，典型地区代表性生物类群物种多样性时空变化特征，对正确认识气候变暖对生物多样性的影响具有重要的启示意义。本项目通过对黄土高原及周边地区359个表土蜗牛组合的系统分析，获得黄土高原现生蜗牛多样性的空间分布特征，表现为蜗牛多样性由东南向西北逐渐减少，研究显示蜗牛多样性的这种分布特征主要受控于蜗牛生长季长度和生长期内季节性水热格局的影响。. 在较高精度的年代序列基础上，分析7个代表性的黄土剖面，计630余个蜗牛化石组合，建立黄土高原末次盛冰期以来蜗牛化石组合及多样性变化序列，重点探讨末次冰消期以来气候转暖对蜗牛生物多样性时空分布的影响；通过对14个剖面的蜗牛记录的集成分析，重建3个特征时期（18ka、9ka、6ka）蜗牛多样性分布的空间格局和演变规律。. 在对7个剖面~25 ka以来百年级分辨率的蜗牛化石多样性变化序列的研究基础上，对蜗牛群落多样性指数和群落组成结构进行综合分析，得到末次盛冰期以来蜗牛多样性在时间序列和空间格局上的变化过程和特征，时间序列上，末次盛冰期（约18 ka左右）蜗牛物种单调，复合分异度低，末次冰消期（约15 ka前后）属种组成和多样性显著增加，全新世达到最高值；空间格局上，末次盛冰期以来黄土高原东南部地区的蜗牛种数和分异度始终高于西北部地区，西北部地区蜗牛多样性的变化幅度较东南部地区显著增大，研究表明在自然环境背景下，气候变暖更有利于西北生态脆弱区蜗牛生物多样性的增加。. 对末次冰消期以来黄土高原蜗牛多样性序列的进一步分析，揭示出不同生态类型的蜗牛种类多样性对气候变化具有完全不同的响应模式，表现为喜冷干类型在冰消期-全新世增温过程中多样性和丰度呈显著降低的趋势，而喜温湿类型与增温过程呈同步的变化特点，多样性和丰度明显增加，这为准确评价未来气候变化对生物多样性的综合影响具有明确的借鉴意义。