Tracking the altitudinal adaptation of Andean maize using archaeogenomics

了解作物如何适应水资源减少、温度降低和生长季节缩短的条件，对于我们考虑新的农业环境以满足我们的粮食安全需求至关重要。这种适应在过去已经发生，特别是对高海拔的适应。玉米从海平面低地到海拔超过4000米的安第斯山脉的高度的适应性是任何作物中最极端的海拔适应性之一，并且在过去2600年中随着一系列复杂的安第斯文化扩展到山脉的一系列玉米考古样本中记录下来。关于这些文化是如何相互作用的，以及玉米是如何在相对较短的时间内实现这种极端适应的，仍然有很多东西不清楚。近年来，我们发现玉米不是一次而是多次从其大刍草祖先的原产地扩展出去，每一波都携带着不同的遗传多样性成分，可能具有不同的适应潜力。特别是，后来的玉米扩张浪潮携带了来自第二个野生祖先物种的遗传多样性，这种物种适应了中美洲的高地。我们不知道在多大程度上这后一波负责玉米的进展，以高海拔地区或是否高海拔适应已经通过新的适应当地实现。我们也不知道这种玉米是如何在不同的文化领域进行交换的。为了梳理这些因素，理想的做法是检查当时玉米的基因组，以确定它们的适应性和祖先的性质以及它们何时发生变化。考古基因组学技术的现状是，从考古材料中恢复基因组已经成为主流，并且可以大规模进行。我们拥有277个考古玉米样本的独特收藏，涵盖了玉米从海平面以上到4000米以上的扩展-比今天已知的任何玉米都要高。在这个项目中，我们将从安第斯地区的10个文化中恢复至少150个古基因组，以跟踪玉米对高海拔的适应。通过这种方式，我们将能够回答上面关于玉米如何适应的问题，它是否以及如何在文化之间进行交换，以及过去的玉米是否具有意味着它可以长得比今天的玉米更高的特性。这些发现对于理解安第斯考古学、玉米生物学和进化研究以及未来玉米育种的潜在产出都很重要。

Understanding how crops can adapt to conditions of lower water availability, lower temperatures and shorter growing seasons is of importance as we consider new environments for agriculture to meet our food security needs. Such adaptations have occurred in the past, in particular adaptations to high altitude. The adaptation of maize from the sea level lowlands to the heights of the Andes at over 4000 metres above sea level represents one of the most extreme altitudinal adaptations of any crop and is recorded in a series of archaeological samples of maize over time spanning the last 2600 years as a complex series of Andean cultures expanded into the mountain chain. Much is still not understood about how these cultures may have interacted, and how maize achieved such an extreme adaptation in a relatively short period of time. In recent years we have discovered that maize expanded out of its area of origin from its teosinte progenitor not once but on multiple occasions, each wave carrying different compositions of genetic diversity that may have had different adaptive potential. In particular, later waves of maize expansion carried genetic diversity from a second wild progenitor species of teosinte that was adapted to the highlands of Mesoamerica. We do not know to what extent this later wave was responsible for maize's progression to high altitude or whether high altitude adaptations had already been achieved through novel adaptations locally. Nor do we know how such maize might have been exchanged throughout the different cultural spheres. To tease apart these factors it would be ideal to examine the genomes of the maize of that time to identify the nature of their adaptations and their ancestry and when they changed.The state of archaeogenomics technology is such now that recovery of genomes from archaeological materials has become mainstream and can be carried out at scale. We have a unique collection of 277 archaeological maize samples that cover the expansion of maize from just above sea level to over 4000 metres - higher than any maize is known to grow today. In this project we will recover at least 150 archaeogenomes from across 10 cultures in the Andean area to track the adaptation of maize to high altitude. In this way we will be able to answer the questions above about how maize adapted, if and how it was exchanged between cultures, and whether the maize of the past had properties that meant that it could grow higher than maize today. Together these findings will be important for understanding Andean archaeology, maize biology and evolutionary studies in general with potential outputs for maize breeding in the future.