Establishment of a novel approach to trace Lake Tanganyika's gastropod faunal evolution

ICDP岩心开启了探索湖泊历史的新时代，也增加了对生物进化的关注。坦噶尼喀湖（Lake Tanganyika， LT）是非洲最古老、最深的湖泊，也是众所周知的全球淡水生物多样性热点。llt面临着一系列显著的生态条件变化，包括不同程度的湖泊水位波动、子流域的分离和重新连接、流域的开放和关闭以及与主要河流系统的不同连接。就贝壳的形态空间和大小占用而言，LT的海腹足类（海洋状）腹足类代表了淡水腹足类辐射的最杰出的例子。值得注意的是，超级鸟群的起源一直备受争议，但至今仍不清楚。一种令人兴奋的物种划分新方法是蛋白质组学指纹，它利用基质辅助激光解吸/电离飞行时间质谱（MALDI-TOF MS）产生的肽和小蛋白质的特定质量谱的鉴别能力。另一种新方法——贝壳古蛋白质组学——为重建湖泊古动物群提供了一个新的代理系统。它将蛋白质组学指纹识别方法扩展到非生命材料，这里是嵌入在软体动物外壳晶体结构中的蛋白质（所谓的晶体内蛋白质）。通过建立一个基于特定地区或生态系统中所有腹足类（和双壳类）物种的最近和化石壳的蛋白质库，即使使用重新加工和大量破坏的化石材料，也可以重建古群落。这些条件在湖泊沉积物中经常出现，特别是在坦噶尼喀湖等古老湖泊的沉积物中。本研究的主要目标是通过开发一种新的综合分析方法，利用蛋白质组学指纹图谱、贝壳古蛋白质组学、DNA条形码和生物多样性模型来追踪物种多样化和（元）群落进化，从而了解LT非凡的生物多样性和特有性是如何进化的。基于与整体科学深层钻探目标相关的一般问题-通过深层时间确定地方性生物多样性的驱动因素-本研究将针对以下具体目标：(1)建立蛋白质组学指纹图谱和贝壳古蛋白质组学方法；(2)鉴定和表征最近和化石腹足类组合，以空间追踪群落梯度和更替；(3)测试LT与Kivu和Rukwa连接的河流和湖泊的更新世动物亲缘关系和湖泊学联系。由于在许多湖泊沉积物中缺乏保存完好的化石，利用来自贝壳残留物的晶体内蛋白质组学数据和来自最近分类群的库来模拟过去主要进化事件的方法将引起地质学家和古生物学家的极大兴趣。

ICDP corings have opened a new era of exploration of lake histories and have also increased their focus on biological evolution. Lake Tanganyika (LT) is Africa’s oldest and deepest lake and well known to be a global hotspot of freshwater biodiversity. LT has faced a series of marked shifts in the ecological conditions including lake-level fluctuations at different magnitudes, separation and re-joining of sub-basins, opening and closing of the basin, and varying connections to major rivers systems. The thalassoid (marine-like) gastropods of LT represent the most outstanding example of any freshwater gastropod radiation in terms of morphospace and size occupation of the shells. Remarkable, the origin of the superflock has been intensively debated but remains unclear to date.An exciting new approach for species delimitation is proteomic fingerprinting, which uses the discriminative power of specific mass profiles of peptides and small proteins generated with Matrix-Assisted Laser Desorption/Ionization Time-Of-Flight Mass Spectrometry (MALDI-TOF MS). Another novel approach – shell palaeoproteomics – holds significant potential for a new proxy system for reconstructing palaeofaunas of a lake. It extents the proteomic fingerprinting approach to non-living material, here proteins embedded in crystalline structure of mollusc shells (so-called intracrystalline proteins). By developing a protein library based on both recent and fossil shells of all gastropod (and bivalve) species of a particular region or ecosystem, palaeocommunities could be reconstructed even with reworked and largely destroyed fossil material. These conditions are often met in lake sediments and particular in those of ancient lakes such as Lake Tanganyika.The main goal of this proposal is to understand how the extraordinary biodiversity and endemicity in LT evolved by developing a new integrated analytical approach employing proteomic fingerprinting, shell palaeoproteomics, DNA barcoding and biodiversity modelling to trace species diversification and (meta-)community evolution. Based on general questions that are relevant for the overall scientific deep-drilling goal - Identifying drivers of endemic biodiversity through deep time - the following specific objectives will be targeted during this study: (1) Establishment of the proteomic fingerprinting and shell palaeoproteomics approach, (2) Identification and characterization of recent and fossil gastropod assemblages to spatially trace community gradients and turnover, and (3) Testing Pleistocene faunal affinities and limnological connections of LT to connected rivers and lakes Kivu and Rukwa.Due to the lack of well-preserved fossils in many lake sediments, the approach of using intracrystalline proteomic data from shell remnants and a library from recent taxa to model major evolutionary events in the past will be of great interest for geologists and palaeontologists.