The influence of Holocene sea-ice variability on Arctic biota: using the past to predict the future

海冰为北极许多物种提供了重要的季节性或常年栖息地和扩散走廊，也是其他物种的主要地理屏障；因此，海冰影响着海洋和陆地生物群的分布、基因流动和物种相互作用。由于气候变化，预计本世纪北冰洋将实现季节性无冰。这一变化的生态和进化后果仍然知之甚少，尽管高度依赖海冰完成生命历史的物种可能特别脆弱。由于我们对物种如何对海冰的长期时空变化作出反应的了解有限，我们量化海冰损失影响的能力受到了阻碍。这是由于缺乏许多物种的历史和现代观测数据，以及关于自上一次冰盛期以来海冰自然变异性的稀少数据，尽管正在出现高分辨率的海冰重建。另一个挑战是改进将海冰作为物种动态的主要驱动力的归属，因为由于缺乏适当的海冰和/或生物数据，许多关联仍然是推测的，在许多情况下甚至根本不使用海冰数据。该项目旨在通过提高我们对海冰与北极物种之间长期相互作用的理解，促进对当前海冰消失影响的预测，特别是：海冰的变异性如何影响全新世(11700年至今)的北极生物群。研究的三个主要领域是：i.选定的与冰有关的物种在全新世期间的时空历史是什么？全新世海冰与北极物种动态之间的关系是什么？海冰如何继续影响北极地区的植物扩散，现代植物扩散路径与重建的扩散路径相比如何？对哪些物种最依赖海冰，哪些物种因此最有可能面临海冰消失的风险进行分析前的系统审查，将有助于选择重点物种并帮助产生假说。该项目将使用新出现的基于浮木的全新世北极海冰的高分辨率重建(Hole&Macias-Fauria，2017)，这将提供有关海冰动态自然变异性的详细信息。对于问题(I)，将汇编来自化石的古代DNA和现代分子数据，以使用以下方法重建和模拟物种动态：种群遗传分析(人口变化、种群连通性和遗传多样性)和物种分布模型(射程变化和扩散事件)。对于(3)，该项目将结合重建海冰和物种动态，从协变性的时空模式中评估因果关系。该分析还将考虑物种动态变化的其他可能来源，例如：气候、地理和生物相互作用的其他方面。此外，由于北极的可及性越来越高，北极的人类压力越来越大，物种动态也可能受到影响。问题(4)将需要对斯瓦尔巴群岛海岸海冰沉积的植物材料进行实地分析。这将涉及到对繁殖体的收集、鉴定和活性测试，鉴定可能的来源区域，以及分析现代扩散路径是否与研究植物的时空历史相一致。有可能与斯瓦尔巴特岛省长环境部合作开发一个公民科学项目。该项目的结果将揭示海冰在历史上对北极生物群的影响程度，并对当前海冰消失的潜在生态和进化反应提供洞察；从而能够更准确地预测气候变化对北极的影响。

Sea ice provides an important seasonal or perennial habitat and dispersal corridor for many Arctic species and acts as a major geographic barrier for others; it therefore influences the distributions, gene flow, and species interactions of marine and terrestrial biota. The Arctic Ocean is predicted to become seasonally ice-free this century as a result of climate change. The ecological and evolutionary consequences of this change remain poorly understood, although species with a high reliance on sea ice to complete their life histories are likely to be particularly vulnerable. Our ability to quantify the impacts of sea ice loss is hampered by our limited understanding of how species respond to long-term spatial and temporal variation in sea ice. This is due to a shortage of historic and modern observational data for many species, as well as sparse data on the natural variability of sea ice since the Last Glacial Maximum, although high-resolution sea ice reconstructions are emerging. Another challenge is to improve attribution of sea ice as the primary driver of species dynamics, as many associations remain speculative due to lack of appropriate sea ice and/or biotic data, in many cases not even using sea ice data at all.This project aims to advance predictions of impacts of current sea ice loss by improving our understanding of the long-term interactions between sea ice and Arctic species, specifically: how sea ice variability influenced Arctic biota during the Holocene (11,700 years - present). The three main areas of study are:i. What is the spatiotemporal history of selected ice-associated species during the Holocene?ii. What is the relationship between sea ice and Arctic species dynamics in the Holocene?iii. How does sea ice continue to influence plant dispersal in the Arctic, and how do modern plant dispersal pathways compare with reconstructed dispersal pathways?A pre-analysis systematic review of which species are most dependent on sea ice, and which are therefore most likely to be at risk from sea ice loss, will help inform selection of focal species and help generate hypotheses. The project will use emerging high-resolution driftwood-based reconstructions of Holocene Arctic sea ice (Hole & Macias-Fauria, 2017) which will give detailed information on the natural variability of sea ice dynamics. For question (i), ancient DNA from fossils and modern molecular data will be compiled to reconstruct and model species dynamics using: population genetic analysis (demographic change, population connectivity, and genetic diversity) and species distribution modelling (range shifts and dispersal events). For (iii) the project will combine reconstructions of sea ice and species dynamics to assess causality from the spatiotemporal patterns of covariability. The analysis will also account for other possible sources of variation in species dynamics, for example: other aspects of climate, geography, and biotic interactions. In addition, species dynamics may also be impacted by increasing human-driven pressures in the Arctic, as a result of its increasing accessibility. Question (iv) will entail fieldwork analysing plant material that is deposited by coastal sea ice on Svalbard beaches. This will involve collection, identification, and viability-testing of propagules, identification of possible source regions, and an analysis of whether modern dispersal pathways agree with the spatiotemporal histories of the study plants. There is potential to develop a citizen-science project in collaboration with the Environment Department of the Svalbard Governor.The results from this project will reveal the extent to which sea-ice has historically influenced Arctic biota, and give insights into potential ecological and evolutionary responses to current sea ice loss; thereby enabling more accurate predictions of the impacts of climate change in the Arctic.