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Isotopic, tagging and diet studies of modern-day teleosts lack the ability to contextualise life-histories and trophic dynamics with a historical perspective, when exploitation rates were lower and climatic conditions differed. Isotopic analysis of vertebrae, the most plentiful hard-part in archaeological and museum collections, can potentially fill this data-gap. Chemical signatures of habitat and diet use during growth are retained by vertebrae during bone formation. However, to fulfil their potential to reveal life-history and trophic dynamics, we need a better understanding of the time-frame recorded by vertebrae, currently lacking due to a poor understanding of fish bone remodelling. To address this issue, we serially-sectioned four vertebral centra of the highly migratory Atlantic bluefin tuna (Thunnus thynnus; BFT) captured off Sardinia (Italy) and analysed their isotopic composition. We show how carbon (δ13C), nitrogen (δ15N) and sulfur (δ34S) isotope values can vary significantly across BFT vertebrae growth-axes, revealing patterning in dietary life-histories. Further, we find similar patterns are revealed through incremental isotopic analysis of inner and outer vertebrae centra samples from thirteen archaeological BFT vertebrae dating between the 9th-13th century CE. Our results indicate that multi-year foraging signatures are retained in vertebrae and allow for the study of life-histories in both modern and paleo-environments. These novel methods can be extended across teleost taxa owing to their potential to inform management and conservation on how teleost trophic dynamics change over time and what their long-term environmental, ecological, and anthropological drivers are.

International audience; In recent decades, the development of archaeobotany in the western Mediterranean has made it possible to document the main plant resources exploited, the agricultural practices implemented, as well as major phenomena of circulation and integration of new plant resources within historical societies. During the Middle Ages, Iberia is for a great part under Muslim rule, and is the theater of what has been widely considered in the literature as a “green revolution”. This period also sees the expansion of the northern Christian kingdoms into the Peninsula, often found under the debated name of “Reconquista”, that ended in 1492 with the fall of Granada. These changes disrupted economic systems, demographic and environmental pressures which changed radically, entering a new scale. But what effect did they have on agriculture? Regarding the reel expansion of medieval Arab-Berber agriculture in Iberia and the so-called “green revolution”, we hypothesize that it was in fact limited to A) the landed estates that depended on the urban aristocracy, and B) to the large areas of specialized production well known from the written sources. But how was agriculture practiced in the rural areas far from these productive regions: did they evolve as in Andalusia? Perpetuate ancient practices (Iberian, Roman)? Or undergo developments similar to those observed in neighboring Christian regions (Mediterranean France)? Regarding the areas that come under Christian rule, the weight of the Andalusian agricultural legacy is yet to be determined, although we hypothesize continuity in the staple productions and practices. To document these questions, the main objectives of this paper are: 1) to reconstruct ancient agrosystems and agrobiodiversities using archaeobotanical data; 2) to assess how societies, depending on local environmental parameters, have developed their agrarian strategies, following the evolution of the cultural and socio-economic context; 3) to determine what role socio-economic dynamics have played in the large-scale diffusion of certain agricultural productions. The paper will present results of new studies carried out in a range of frontier medieval sites in Spain (Aragon, Catalonia, Extremadura, Guadalajara, Malaga, Ibiza), a large part of which is drawn from the research project "Landscapes of (Re)Conquest: Dynamics of Multicultural Frontiers in Medieval South Western Europe", funded by AHRC. The results, based on studies of seeds remains issued from samples dated from the 10th to the 15th c., make it possible to draw up a list of the main agro-horticultural productions and their evolution in the face of changing socio-economic dynamics.

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Funder: University of Leicester; Id: http://dx.doi.org/10.13039/501100000738, Funder: University of Tennessee; Id: http://dx.doi.org/10.13039/100007135, RATIONALE: Dental calculus (mineralised dental plaque) is composed primarily of hydroxyapatite. We hypothesise that the carbonate component of dental calculus will reflect the isotopic composition of ingested simple carbohydrates. Therefore, dental calculus carbonates may be an indicator for sugar consumption, and an alternative to bone carbonate in isotopic palaeodiet studies. METHODS: We utilised Fourier transform infrared attenuated total reflectance analysis to characterise the composition and crystallisation of bone and dental calculus before isotope analysis of carbonate. Using a Sercon 20-22 mass spectrometer coupled with a Sercon GSL sample preparation system and an IsoPrime 100 dual inlet mass spectrometer plus Multiprep device to measure carbon, we tested the potential of dental calculus carbonate to identify C4 resources in diet through analysis of δ13 C values in paired bone, calculus and teeth mineral samples. RESULTS: The modern population shows higher δ13 C values in all three tissue carbonates compared to both archaeological populations. Clear differences in dental calculus δ13 C values are observed between the modern and archaeological individuals suggesting potential for utilising dental calculus in isotope palaeodiet studies. The offset between dental calculus and either bone or enamel carbonate δ13 C values is large and consistent in direction, with no consistent offset between the δ13 C values for the three tissues per individual. CONCLUSIONS: Our results support dental calculus carbonate as a new biomaterial to identify C4 sugar through isotope analysis. Greater carbon fractionation in the mouth is likely due to the complex formation of dental calculus as a mineralized biofilm, which results in consistently high δ13 C values compared to bone and enamel.