Periodic Reporting for period 1 - FABA-SHAPE (Unveiling the Origins of the Faba Bean by means of Shape and Stable Carbon Isotope Analyses of Archaeological Remains)
Période du rapport: 2019-02-01 au 2021-01-31
Among the staple crops, the faba bean played a major role. Faba has one of the longest established traditions of cultivation; furthermore, it remains a critical resource in many countries and plays an essential role in crop rotation.
The thousands of faba beans that are preserved in archaeological contexts from prehistory to the pre-modern era attest to faba’s importance to early sedentary communities in Europe and the Mediterranean. As a protein-rich food, it served as a valuable meat substitute for early farmers as they transitioned from hunting large game to agrarian sustenance. Despite its importance, little is known about the faba bean’s origins. All living varieties are fully domesticated and no extant wild representatives of this species or any closely related species have been found. In the absence of a wild living progenitor, it is difficult to estimate the range of genetic mutations brought about by domestication and adaptation to new environments in the modern landraces.
One way to solve the enigma of the faba bean’s origins is to look at the archaeological remains found in the prehistoric villages where hunter-gatherers and early farmers settled and to search for clues about the legume’s original geographical distribution, the ecological requirements of its pre-domesticated forms and the changes induced by geographical isolation and human selection. Tracing the spread of the faba bean from its original centres of domestication is crucial to understanding the impact of adaptation to new ecological settings on morphometric and, indirectly, genetic traits. In this regard, archaeobotany provides the most direct record of some of the key evolutionary changes that plants underwent as part of the domestication process.
The project FABA-SHAPE has 5 major Objectives for the project: 1) date the exploitation and development of the faba bean, from the initial collection of the wild type to the early selection of profitable characters (domestication); 2) define the ecological requirements of wild and domesticated types of faba bean; 3) study the agrobiology of early domesticated faba bean; 4) reconstruct the early history and the diffusion of faba bean in the Mediterranean and Europe;5) identify changes induced by the selection of new phenotypes more adapted for new type of environments.
Within the context of this project, we will combine the most innovative methods available to archaeobotanists: Climate Modelling, Geometric Morphometry, Stable Carbon Isotope Analysis (also known as Δ13C analysis) and Radiocarbon Dating to investigate the origin of faba bean domestication. The combined use of these methods will allow us to identify the types of faba used by early farmers, to assess the ecological requirements of the primitive forms of faba beans, and to study the routes of dispersal outside the area of its early domestication.
The thousands of faba beans that are preserved in archaeological contexts from prehistory to the pre-modern era attest to faba’s importance to early sedentary communities in Europe and the Mediterranean. As a protein-rich food, it served as a valuable meat substitute for early farmers as they transitioned from hunting large game to agrarian sustenance. Despite its importance, little is known about the faba bean’s origins. All living varieties are fully domesticated and no extant wild representatives of this species or any closely related species have been found. In the absence of a wild living progenitor, it is difficult to estimate the range of genetic mutations brought about by domestication and adaptation to new environments in the modern landraces.
One way to solve the enigma of the faba bean’s origins is to look at the archaeological remains found in the prehistoric villages where hunter-gatherers and early farmers settled and to search for clues about the legume’s original geographical distribution, the ecological requirements of its pre-domesticated forms and the changes induced by geographical isolation and human selection. Tracing the spread of the faba bean from its original centres of domestication is crucial to understanding the impact of adaptation to new ecological settings on morphometric and, indirectly, genetic traits. In this regard, archaeobotany provides the most direct record of some of the key evolutionary changes that plants underwent as part of the domestication process.
The project FABA-SHAPE has 5 major Objectives for the project: 1) date the exploitation and development of the faba bean, from the initial collection of the wild type to the early selection of profitable characters (domestication); 2) define the ecological requirements of wild and domesticated types of faba bean; 3) study the agrobiology of early domesticated faba bean; 4) reconstruct the early history and the diffusion of faba bean in the Mediterranean and Europe;5) identify changes induced by the selection of new phenotypes more adapted for new type of environments.
Within the context of this project, we will combine the most innovative methods available to archaeobotanists: Climate Modelling, Geometric Morphometry, Stable Carbon Isotope Analysis (also known as Δ13C analysis) and Radiocarbon Dating to investigate the origin of faba bean domestication. The combined use of these methods will allow us to identify the types of faba used by early farmers, to assess the ecological requirements of the primitive forms of faba beans, and to study the routes of dispersal outside the area of its early domestication.
To achieve these goals, the archaeobotanical literature, available for prehistoric sites in SW Asia, Mediterranean basin and Europe, was surveyed. Among the sites that yielded remains of faba bean, only those which had radiocarbon dates were considered for the present study.
Past climate conditions at each archeological site were retrieved from one of the BRIDGE HadCM3 family of climate models whic allowed to reconstructed the climate conditions for each site and compare those with the ecological requirements of the plant to identify when and where a new phenotype, characterized by a different biological cycle, was selected. Two cycles were considered: the first, between autumn and spring, corresponds to the cycle of the Mediterranean type of faba bean, while the second, between spring and and summer is typical of the spring type.
The evidence collected in the study show that the wild progenitor originated from SW Asia (14 kyrs) where it adapted to the autumn-spring period. The early domesticated forms retained the same biological cycle, which is characteristic of the Mediterranean type of faba bean. The Δ13C analysis shows that these early domesticated forms received ca. 400 mm of water during their biological cycles. From SW Asia the crop was brough in other areas of the Mediterranean with the first waves of Neolithic seafarers (8,500-7,000 years ago). The cultivation of the faba bean was limited by environmental constrains between the 32°N and 41°N parallel until a new type of faba bean, characterized by a spring/summer cycle, was selected about 4,000 years ago. The selection of the spring type made the cultivation of the faba bean possible at latitudes above 45°C where harsh winters and cool spring had been unsuitable for the original Mediterranean type.
The results were disseminated in several conferences and a mid-term workshop was held in occasion of the 18th IWGP conference at the UniSalento, Italy, in 2019. The final results of the project were presented as a talk at the Symposium on Neolithic Plant Management Strategies in southwest Asia held School of Archaeology, Oxford University, UK.
Past climate conditions at each archeological site were retrieved from one of the BRIDGE HadCM3 family of climate models whic allowed to reconstructed the climate conditions for each site and compare those with the ecological requirements of the plant to identify when and where a new phenotype, characterized by a different biological cycle, was selected. Two cycles were considered: the first, between autumn and spring, corresponds to the cycle of the Mediterranean type of faba bean, while the second, between spring and and summer is typical of the spring type.
The evidence collected in the study show that the wild progenitor originated from SW Asia (14 kyrs) where it adapted to the autumn-spring period. The early domesticated forms retained the same biological cycle, which is characteristic of the Mediterranean type of faba bean. The Δ13C analysis shows that these early domesticated forms received ca. 400 mm of water during their biological cycles. From SW Asia the crop was brough in other areas of the Mediterranean with the first waves of Neolithic seafarers (8,500-7,000 years ago). The cultivation of the faba bean was limited by environmental constrains between the 32°N and 41°N parallel until a new type of faba bean, characterized by a spring/summer cycle, was selected about 4,000 years ago. The selection of the spring type made the cultivation of the faba bean possible at latitudes above 45°C where harsh winters and cool spring had been unsuitable for the original Mediterranean type.
The results were disseminated in several conferences and a mid-term workshop was held in occasion of the 18th IWGP conference at the UniSalento, Italy, in 2019. The final results of the project were presented as a talk at the Symposium on Neolithic Plant Management Strategies in southwest Asia held School of Archaeology, Oxford University, UK.
Studies of the molecular markers of modern faba bean cultivars and landraces allow to characterize the intraspecific variability of the species and point out at geographic hotspots in Europe, Asia and Africa, that might have acted as centers for genetic diversification. Before these recent molecular studies highlighted the complex history of faba bean, agronomists had debated about the possible origin of the pulse for decades, but there was no conclusive evidence to support any of these hypotheses. The archaeological evidence provides clues about the origin and the early history of the crop, but it remains unclear how the domestication started, when the faba bean was brought into new environments and how this has changed the phenology of the plant.
With the project FABA-SHAPE we search for clues to the legume’s original geographical distribution, the ecological requirements of its early-domesticated forms and the changes induced by the selection of new phenotypes more adapted for new type of environments.
The creation of new faba bean phenotypes, through the selection of genotypes with different flowering time, was a crucial step to expand the cultivation at different latitudes where photoperiod and temperatures were substantially different from the area of origin of the faba bean. Recent studies have identified the candidate genes responsible for the alteration of the flowering time, but it is unclear when and where the selection of such fundamental trait took place.
Our study addresses the issue of the phenological diversification of the faba bean and use archaeological findings as a mean to characterize the ecological requirements of the wild progenitor and the original domesticated types and to date the appearance of new phenotypes into different ecological regions. Reliable dating is essential to time the expansion of the crop across the Mediterranean and Europe, while paleoclimate modelling provides crucial information about the best sowing conditions in different eco-regions. By estimating the best time for sowing (and harvesting), it is possible to assess where and when new phenological types were selected and ultimately to reconstruct the early history of this elusive crop.
The results of this project will serve as a basis for agronomists and plant breeders seeking to search the genome of primitive landraces for useful mutations that can improve the resistance of the faba bean to drought and pests.
With the project FABA-SHAPE we search for clues to the legume’s original geographical distribution, the ecological requirements of its early-domesticated forms and the changes induced by the selection of new phenotypes more adapted for new type of environments.
The creation of new faba bean phenotypes, through the selection of genotypes with different flowering time, was a crucial step to expand the cultivation at different latitudes where photoperiod and temperatures were substantially different from the area of origin of the faba bean. Recent studies have identified the candidate genes responsible for the alteration of the flowering time, but it is unclear when and where the selection of such fundamental trait took place.
Our study addresses the issue of the phenological diversification of the faba bean and use archaeological findings as a mean to characterize the ecological requirements of the wild progenitor and the original domesticated types and to date the appearance of new phenotypes into different ecological regions. Reliable dating is essential to time the expansion of the crop across the Mediterranean and Europe, while paleoclimate modelling provides crucial information about the best sowing conditions in different eco-regions. By estimating the best time for sowing (and harvesting), it is possible to assess where and when new phenological types were selected and ultimately to reconstruct the early history of this elusive crop.
The results of this project will serve as a basis for agronomists and plant breeders seeking to search the genome of primitive landraces for useful mutations that can improve the resistance of the faba bean to drought and pests.