Niche dynamics of Palaeolithic modern humans during the settlement of the Palaearctic

Aim During the Late Pleistocene (c. 126–10 ka), modern humans (Homo sapiens) expanded their geographical range across Eurasia and eventually colonized the Americas. Although the routes by which they migrated have been intensively analysed, the dynamics of their realized climatic niche are still largely unknown. We assess temporal changes in the climatic niche of modern humans, the geographical distribution of their climatic niche and whether niche dynamics correlate with the magnitude of climate change and cultural advances, between 46 and 11 ka. Location Palaearctic. Methods Using the radiocarbon dated archaeological record and spatial palaeoclimatic simulations, we quantify different parameters of the realized climatic niche of modern humans (niche overlap, niche breadth and climatic marginality) between consecutive 1000–2000 year intervals. Moreover, using climate envelope models, we map the potential distributions of modern humans for each time interval and identify the regions that remained more climatically suitable and stable for modern humans through time. Results Between 46 and 22 ka the climatic niche of modern humans expanded, including periods of intense growth in niche breadth at 40 and 30 ka. Changes in seasonal water availability and technological innovations partly correlate with dynamics in niche parameters. We document a persistent climatically suitable mid-latitude belt in south Siberia linking western Europe to the Far East that may have facilitated human migration, and a potential climatic refugium in Beringia. Main conclusions The climatic niche of modern humans changed across the Late Pleistocene, as the result of both climatic and cultural changes. These populations of hunter-gatherers occupied novel climatic conditions but also remained in previously occupied areas under changing climates during the settlement of the Palaearctic. Our approach can provide clues as to where early modern humans may have overlapped in geographical and environmental space with Neanderthals or Denisovans, as evidenced by their contribution to the genetic heritage of some current population

Late Quaternary horses in Eurasia in the face of climate and vegetation change.

Wild horses thrived across Eurasia until the Last Glacial Maximum to collapse after the beginning of the Holocene. The interplay of climate change, species adaptability to different environments, and human domestication in horse history is still lacking coherent continental-scale analysis integrating different lines of evidence. We assembled temporal and geographical information on 3070 horse occurrences across Eurasia, frequency data for 1120 archeological layers in Europe, and matched them to paleoclimatic and paleoenvironmental simulations for the Late Quaternary. Climate controlled the distribution of horses, and they inhabited regions in Europe and Asia with different climates and ecosystem productivity, suggesting plasticity to populate different environments. Their decline in Europe during the Holocene appears associated with an increasing loss and fragmentation of open habitats. Europe was the most likely source for the spread of horses toward more temperate regions, and we propose both Iberia and central Asia as potential centers of domestication.M.L. was supported by a Marie-Curie Individual Fellowship (MSCA-IF-657852). This work was supported by the Danish National Research Foundation (grant no. DNRF94); Initiative d’Excellence Chaires d’attractivité, Université de Toulouse (OURASI); and the Villum Fonden miGENEPI research project. This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement no. 681605). K.G. and D.N.-B. thank Sapere Aude EliteForsk, DFF (Det Frie Forskningsråd), and the Danish National Research Foundation (DNRF96). A.M., M.K., and R.M.B. were supported by the European Research Council Consolidator grant 647787-LocalAdaptation

The population history of northeastern Siberia since the Pleistocene.

Northeastern Siberia has been inhabited by humans for more than 40,000 years but its deep population history remains poorly understood. Here we investigate the late Pleistocene population history of northeastern Siberia through analyses of 34 newly recovered ancient genomes that date to between 31,000 and 600 years ago. We document complex population dynamics during this period, including at least three major migration events: an initial peopling by a previously unknown Palaeolithic population of 'Ancient North Siberians' who are distantly related to early West Eurasian hunter-gatherers; the arrival of East Asian-related peoples, which gave rise to 'Ancient Palaeo-Siberians' who are closely related to contemporary communities from far-northeastern Siberia (such as the Koryaks), as well as Native Americans; and a Holocene migration of other East Asian-related peoples, who we name 'Neo-Siberians', and from whom many contemporary Siberians are descended. Each of these population expansions largely replaced the earlier inhabitants, and ultimately generated the mosaic genetic make-up of contemporary peoples who inhabit a vast area across northern Eurasia and the Americas

Differences in Forage-Acquisition and Fungal Enzyme Activity Contribute to Niche Segregation in Panamanian Leaf-Cutting Ants

<div><p>The genera <i>Atta</i> and <i>Acromyrmex</i> are often grouped as leaf-cutting ants for pest management assessments and ecological surveys, although their mature colony sizes and foraging niches may differ substantially. Few studies have addressed such interspecific differences at the same site, which prompted us to conduct a comparative study across six sympatric leaf-cutting ant species in Central Panama. We show that foraging rates during the transition between dry and wet season differ about 60 fold between genera, but are relatively constant across species within genera. These differences appear to match overall differences in colony size, especially when <i>Atta</i> workers that return to their nests without leaves are assumed to carry liquid food. We confirm that Panamanian <i>Atta</i> specialize primarily on tree-leaves whereas <i>Acromyrmex</i> focus on collecting flowers and herbal leaves and that species within genera are similar in these overall foraging strategies. Species within genera tended to be spaced out over the three habitat categories that we distinguished (forest, forest edge, open grassland), but each of these habitats normally had only a single predominant <i>Atta</i> and <i>Acromyrmex</i> species. We measured activities of twelve fungus garden decomposition enzymes, belonging to the amylases, cellulases, hemicellulases, pectinases and proteinases, and show that average enzyme activity per unit of fungal mass in <i>Atta</i> gardens is lower than in <i>Acromyrmex</i> gardens. Expression profiles of fungal enzymes in <i>Atta</i> also appeared to be more specialized than in <i>Acromyrmex</i>, possibly reflecting variation in forage material. Our results suggest that species- and genus-level identities of leaf-cutting ants and habitat-specific foraging profiles may give predictable differences in the expression of fungal genes coding for decomposition enzymes.</p></div

Differences in forage diversity.

<p>Differences in forage diversity between leaf-cutting ant species (nested within genera), using solid lines for <i>Atta</i> and dotted lines for <i>Acromyrmex</i>, and with typical foraging habitat indicated with dark green (forest), yellow (forest edge), and orange (open sunlit areas): (A) Heatmap showing differences between species and genera in the use of forage categories, with numbers representing mean proportions ±SE of the forage types. Darker colors indicate higher mean acquisition proportions, with the top-dendrogram illustrating similarities between species/genera across means of the five forage categories (vertical axis). Ant species names are given as abbreviations (volc, octo, echi, col, sex, cep). (B) Dendrogram based on the Inverse Simpson Diversity Index of the five forage categories, indicating the degree of evenness across foraging categories (numbers below the branches are mean D-values ±SE per species and means per genus), showing that <i>Acromyrmex</i> has a broader (more even) spectrum (D = 1.86±0.08 SE) of forage material than <i>Atta</i> (D = 1.42±0.13 SE; F_1,49 = 5.435, p<0.05). Numbers above the branch nodes represent Approximately Unbiased p-values (AU, red) and Bootstrap Probability values (BP, green).</p

Differences in foraging rate between loaded and unloaded foragers.

<p>Differences in foraging rate between loaded and unloaded foragers of <i>Atta</i> and <i>Acromyrmex</i> species in Gamboa, Panama, with summary statistics on the number of trails observed per species (number of colonies in brackets), the total number of minutes of observation per species, the total number of ants counted while returning to their nests, and the foraging rates for loaded and unloaded returning workers: means (± SE) per genus and per species (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0094284#pone.0094284.s001" target="_blank">Table S1</a> for details).</p

Differences in fungus garden enzyme activity.

<p>Differences in fungus garden enzyme activity between species grouped as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0094284#pone-0094284-g001" target="_blank">Figure 1</a> with solid lines for <i>Atta</i> and dotted lines for <i>Acromyrmex</i>, and with dark green, yellow and orange indicating the same habitat categories: (A) Heatmap showing differences between species and genera in fungus garden activity of enzyme classes, expressed as mean area in cm²±SE of colored halos on AZCL plates across all assays for enzymes belonging to the amylases (1), cellulases (2), hemicellulases (4), pectinases (3) and proteinases (2). Darker colors in the heatmap indicate higher mean activities, and the top-dendrogram illustrates similarities between species across all means for the five groups of enzymes, estimated by “pvclust” with 1000000 bootstraps. (B) Dendrogram based on the inverse Simpson Diversity Index of proportional enzyme activity showing that <i>Acromyrmex</i> fungus gardens have more even secretions across enzyme categories (D = 4.55±0.05 SE) than <i>Atta</i> (D = 4.18±0.07 SE, F_1,52 = 15.006, p<0.0001). Numbers above the branch nodes represent Approximately Unbiased p-values (AU, red) and Bootstrap Probability values (BP, green).</p

The population history of northeastern Siberia since the Pleistocene.

Northeastern Siberia has been inhabited by humans for more than 40,000 years but its deep population history remains poorly understood. Here we investigate the late Pleistocene population history of northeastern Siberia through analyses of 34 newly recovered ancient genomes that date to between 31,000 and 600 years ago. We document complex population dynamics during this period, including at least three major migration events: an initial peopling by a previously unknown Palaeolithic population of 'Ancient North Siberians' who are distantly related to early West Eurasian hunter-gatherers; the arrival of East Asian-related peoples, which gave rise to 'Ancient Palaeo-Siberians' who are closely related to contemporary communities from far-northeastern Siberia (such as the Koryaks), as well as Native Americans; and a Holocene migration of other East Asian-related peoples, who we name 'Neo-Siberians', and from whom many contemporary Siberians are descended. Each of these population expansions largely replaced the earlier inhabitants, and ultimately generated the mosaic genetic make-up of contemporary peoples who inhabit a vast area across northern Eurasia and the Americas