Evolutionary dynamics of vegetative agriculture in the Ethiopian Highlands: integrating archaeobotanical and genomic science

几乎一半的食用植物是无性繁殖的，包括世界上十大最具经济价值的物种中的四个。然而，我们对营养作物的历史知之甚少——例如，它们被种植了多久，在哪里种植——因为营养组织很少能在考古记录中保存下来。在这个项目中，我们将开发新的方法，将植物岩（存在于大多数植物细胞内的硅微化石）与宏观植物考古学方法结合起来，并整合民族历史、基因组和生物地理信息，揭示埃塞俄比亚营养农业的进化史。埃塞俄比亚可能是非洲最重要的作物多样性中心，其特点是多种营养物种的进化和驯化。我们将特别关注主要的粮食安全作物enset，或“埃塞俄比亚假香蕉”（Ensete osum），一种树状多年生香蕉的近亲。Enset是撒哈拉以南非洲人口最密集地区的主食，是2000万人的主食。它被种植在广阔的海拔范围和生态梯度上，以非常高的生物量密度存在，并且与多个民族有着深厚的文化联系。因此，enset为研究长期适应、多样化和与文化的互动提供了一个理想的模型。我们的主要目标是测试植被地貌模式（即种植作物多样性的分布）是否主要通过以下方式进化：1)环境适应——即作物多样性是通过适应环境多样性（如更凉爽和更干燥的地点）而产生的；ii)文化机制-例如管理传统和口味等品种偏好，或；(3)剥削的古老——换句话说，在种植时间最长的地方，种植种类最多。在农业方面的长期证据将来自关键的考古序列，这些序列已经在埃塞俄比亚高地的一系列地点收集，并由埃塞俄比亚、美国和德国的合作伙伴进行处理。但是，我们必须通过对植物岩的系统发育位置和生长环境的潜在可塑性进行比较研究来改进解释这些遗骸的方法。我们将利用伦敦大学学院开发的方法对从大型植物组合中恢复的烧焦食物残留物进行分析。在皇家植物园邱园，我们将利用50-200年前的植物标本馆藏品开发更多的证据线，利用约900个当代地方物种的DNA数据建立一个年代久远的系统发育树。这些数据将为探索这种作物的文化和适应历史提供新的假设。最后，民族植物学田野调查将记录西南高地不同文化区域的多样性，以及近几十年来农业和文化变化在多大程度上改变了当地景观多样性的模式。考虑这些变化将有助于我们从长期历史模式中区分引进作物和农业革命的影响。本研究通过更好地了解知识和地方物种丧失的速度以及变化的驱动因素，解决了土著农业生物多样性及其在未来应对气候变化能力中的作用的关键问题。该项目将从全球角度更好地了解蔬菜的过去发展和未来潜力。营养作物是研究最少的“孤儿作物”之一，在它们的生物学、栽培、加工和驯化方面存在重大知识空白。该项目将特别促进关于埃塞俄比亚高原多样性中心粮食安全和气候变化适应能力的辩论。

Almost half of food plants are vegetatively propagated including four of the ten most economically important species worldwide. Yet we know very little about vegetative crop history - for example, how long they have been cultivated, and where - because vegetative tissues rarely preserve in the archaeological record. In this project we will develop new methods combining phytoliths (silica microfossils that exist inside most plant cells) with macro-botanical archaeological methods, as well integrating ethnohistoric, genomic and biogeographical information to reveal the evolutionary history of vegetative agriculture in Ethiopia. Ethiopia is potentially Africa's most important center of crop diversity, characterised by both the evolution and domestication of multiple vegetative species. We will specifically focus on the major food security crop enset, or "Ethiopian false banana" (Ensete ventricosum), a tree-like perennial banana relative. Enset supports some of the densest populations in sub-Saharan Africa and is the staple for 20 million people. It is cultivated over a wide elevational range and ecological gradients, exists at very high biomass densities and has a deep cultural association with multiple ethnic groups. As such enset offers an ideal model for studying long-term adaptation, diversification and interaction with culture. Our major objective is to test whether vegetative landrace patterning (i.e. the distribution of enset crop diversity) is primarily evolved through: i) Environmental adaptation - meaning that crop diversity is generated through adaptation to environmental diversity such as cooler and drier locations; ii) Cultural mechanisms - for example management traditions and variety preferences such as taste, or;iii) The antiquity of exploitation - in other words, enset could be most diverse where it has been cultivated the longest. Long-term evidence for enset in agriculture will come from key archaeological sequences, already collected across a series of sites in the Ethiopian Highlands, and being processed by partners in Ethiopia, USA and Germany. But we must refine the methods to interpret these remains by undertaking a comparative study of phytoliths considered against phylogenetic position and potential plasticity due to growth environment. We will complement this with analysis of charred food remains recovered from macrobotanical assemblages using methods developed at UCL. At Royal Botanic Gardens Kew, we will develop additional lines of evidence using herbarium collections, 50-200 years old, to build a dated phylogenetic tree using DNA data from ~ 900 contemporary landraces. These data will provide new hypotheses to explore archaeologically in terms of the cultural and adaptational history of this crop.Finally, ethnobotanical fieldwork will document present-day diversity across different cultural regions in the southwestern highlands and the extent to which agricultural and cultural changes in recent decades have altered patterns of local landrace diversity. Accounting for these changes will help us distinguish the influence of introduced crops and the agricultural revolution from long term historical patterns. This research addresses key issues at the interface of indigenous agrobiodiversity and its role in future resilience to climate change, through better understanding rates of knowledge and landrace loss, as well as drivers of change. The project will create a better understanding of both the past development and future potential of vegeculture from a global perspective. Vegetative species are amongst the least studied 'orphan crops', with major knowledge gaps about their biology, cultivation, processing and domestication. The project will specifically contribute to debates concerning food security and climate change resilience in the Ethiopian highland centre of diversity.