Abstract
Population dynamics set the framework for human genetic and cultural evolution. For foragers, demographic and environmental changes correlate strongly, although the causal relations between ...different environmental variables and human responses through time and space likely varied. Building on the notion of limiting factors, namely that at any one time, the scarcest resource caps population size, we present a statistical approach to identify the dominant climatic constraints for hunter-gatherer population densities and then hindcast their changing dynamics in Europe for the period between 21,000 to 8000 years ago. Limiting factors shifted from temperature-related variables (effective temperature) during the Pleistocene to a regional mosaic of limiting factors in the Holocene dominated by temperature seasonality and annual precipitation. This spatiotemporal variation suggests that hunter-gatherers needed to overcome very different adaptive challenges in different parts of Europe and that these challenges varied over time. The signatures of these changing adaptations may be visible archaeologically. In addition, the spatial disaggregation of limiting factors from the Pleistocene to the Holocene coincided with and may partly explain the diversification of the cultural geography at this time.
We estimated the latitudinal velocity (km/decade) of northern and southern boundaries of core distributions for 30 woody taxa over the last 16 000 years (biotic velocities) using networks of fossil ...pollen records, and compared these with climate velocities estimated from CCSM3 simulations. Biotic velocities were faster during periods of rapid temperature change (i.e. 16 to 7 ka) than times of relative stability (i.e. 7 to 1 ka), with a consistent northward movement of northern and southern boundaries. For most taxa, biotic velocities were faster for northern than for southern boundaries between 12 and 7 ka, resulting in expanding distributions. For individual time periods, biotic velocities were as fast or faster than climate velocities calculated using multivariate approaches. These results indicate that climate change paced the rate of distribution shifts in both northern and southern populations while suggesting that northern populations were more sensitive. A similar sensitivity and pacing is expected under 21st century climate change.
Human activities have shaped large-scale distributions of many species, driving both range contractions and expansions. Species differ naturally in range size, with small-range species concentrated ...in particular geographic areas and potentially deviating ecologically from widespread species. Hence, species’ responses to human activities may be influenced by their geographic range sizes, but if and how this happens are poorly understood. Here, we use a comprehensive distribution database and species distribution modeling to examine if and how human activities have affected the extent to which 9,701 vascular plants fill their climatic potential ranges in China. We find that narrow-ranged species have lower range filling and widespread species have higher range filling in the human-dominated southeastern part of China, compared with their counterparts distributed in the less human-influenced northwestern part. Variations in range filling across species and space are strongly associated with indicators of human activities (human population density, human footprint, and proportion of cropland) even after controlling for alternative drivers. Importantly, narrow-ranged and widespread species show negative and positive range-filling relationships to these human indicators, respectively. Our results illustrate that floras risk biotic homogenization as a consequence of anthropogenic activities, with narrow-ranged species becoming replaced by widespread species. Because narrow-ranged species are more numerous than widespread species in nature, negative impacts of human activities will be prevalent. Our findings highlight the importance of establishing more protected areas and zones of reduced human activities to safeguard the rich flora of China.
1. A prevalent question in the study of plant invasions has been whether or not invasions can be explained on the basis of traits. Despite many attempts, a synthetic view of multi‐trait differences ...between alien and native species is not yet available. 2. We compiled a database of three ecologically important traits (specific leaf area, typical maximum canopy height, individual seed mass) for 4473 species sampled over 95 communities (3784 species measured in their native range, 689 species in their introduced range, 207 in both ranges). 3. Considering each trait separately, co‐occurring native and alien species significantly differed in their traits. These differences, although modest, were expressed in a combined 15% higher specific leaf area, 16% lower canopy height and 26% smaller seeds. 4. Using three novel multi‐trait metrics of functional diversity, aliens showed significantly smaller trait ranges, larger divergences and a consistent differentiation from the median trait combination of co‐occurring natives. 5. We conclude that the simultaneous evaluation of multiple traits is an important novel direction in understanding invasion success. Our results support the phenotypic divergence hypothesis that predicts functional trait differences contribute to the success of alien species.
Aim: The influence of soil properties on photosynthetic traits in higher plants is poorly quantified in comparison with that of climate. We address this situation by quantifying the unique and joint ...contributions to global leaf-trait variation from soils and climate. Location: Terrestrial ecosystems world-wide. Methods: Using a trait dataset comprising 1509 species from 288 sites, with climate and soil data derived from global datasets, we quantified the effects of 20 soil and 26 climate variables on light-saturated photosynthetic rate (Aarea) stomatal conductance (gs), leaf nitrogen and phosphorus (Narea and Parea) and specific leaf area (SLA) using mixed regression models and multivariate analyses. Results: Soil variables were stronger predictors of leaf traits than climatic variables, except for SLA. On average, Narea, Parea and Aarea increased and SLA decreased with increasing soil pH and with increasing site aridity. gs declined and Parea increased with soil available P (Pavail). Narea was unrelated to total soil N. Joint effects of soil and climate dominated over their unique effects on Narea and Parea, while unique effects of soils dominated for Aarea and gs. Path analysis indicated that variation in reflected the combined independent influences of Narea and gs, the former promoted by high pH and aridity and the latter by low Pavail. Main conclusions: Three environmental variables were key for explaining variation in leaf traits: soil pH and Pavail, and the climatic moisture index (the ratio of precipitation to potential evapotranspiration). Although the reliability of global soil datasets lags behind that of climate datasets, our results nonetheless provide compelling evidence that both can be jointly used in broad-scale analyses, and that effects uniquely attributable to soil properties are important determinants of leaf photosynthetic traits and rates. A significant future challenge is to better disentangle the covarying physiological, ecological and evolutionary mechanisms that underpin trait-environment relationships.
As climates shift in space, tree species ranges are predicted to shift as well. While range shifts due to climate change have been typically modeled based on abiotic factors alone, interactions among ...species in diverse communities may alter these range dynamics by inhibiting or enhancing the establishment of propagules along the leading edge, or by increasing or decreasing tolerance to novel climates at the trailing edge. Here, we investigated how the rate of expansion at leading range margins, and contraction at trailing range margins of temperate tree species in response to both past and current climate change related to an important species interaction: whether temperate tree species associate with arbuscular (AM) or ectomycorrhizal (EM) fungal symbionts. Mycorrhizal symbioses can mediate plant stress tolerance, and lack of EM fungal mutualists has been linked to establishment failures of EM tree species in new ranges. We found no difference in rates of leading edge expansion between the two guilds. However, EM tree taxa showed reduced contraction at their trailing edge compared to AM taxa in response to both past and current climate change. Since the mycorrhizal guild of the dominant trees may affect ecosystem properties, differential range dynamics between these functional groups of trees may have consequences for the functioning of future forests.
The ‘home-field advantage (HFA) hypothesis’ predicts that plant litter is decomposed faster than expected in the vicinity of the plant where it originates from (i.e. its ‘home’) relative to some ...other location (i.e. ‘away’) because of the presence of specialized decomposers. Despite growing evidence for the widespread occurrence HFA effects, what drives HFA is not understood as its strength appears highly variable and context-dependent. Our work advances current knowledge about HFA effects by testing under what conditions HFA is most important. Using published data on mass loss from 125 reciprocal litter transplants from 35 studies, we evaluated if HFA effects were modulated by macroclimate, litter quality traits, and the dissimilarity between ‘home’ and ‘away’ of both the quality of reciprocally exchanged litters and plant community type. Our results confirmed the occurrence of an overall, worldwide, HFA effect on decomposition with on average 7.5% faster decomposition at home. However, there was considerable variation in the strength and direction (sometimes opposite to expectations) of these effects. While macroclimate and average litter quality had weak or no impact on HFA effects, home-field effects became stronger (regardless of the direction) when the quality of ‘home’ and ‘away’ litters became more dissimilar (e.g. had a greater dissimilarity in N:P ratio; F1,42 = 6.39, p = 0.015). Further, home-field effects were determined by the degree of difference between the types of dominant plant species in the ‘home’ versus ‘away’ communities (F2,105 = 4.03, p = 0.021). We conclude that home-field advantage is not restricted to particular litter types or climate zones, and that the dissimilarity in plant communities and litter quality between the ‘home’ and ‘away’ locations, are the most significant drivers of home-field effects.
When taxa go extinct, unique evolutionary history is lost. If extinction is selective, and the intrinsic vulnerabilities of taxa show phylogenetic signal, more evolutionary history may be lost than ...expected under random extinction. Under what conditions this occurs is insufficiently known. We show that late Cenozoic climate change induced phylogenetically selective regional extinction of northern temperate trees because of phylogenetic signal in cold tolerance, leading to significantly and substantially larger than random losses of phylogenetic diversity (PD). The surviving floras in regions that experienced stronger extinction are phylogenetically more clustered, indicating that non‐random losses of PD are of increasing concern with increasing extinction severity. Using simulations, we show that a simple threshold model of survival given a physiological trait with phylogenetic signal reproduces our findings. Our results send a strong warning that we may expect future assemblages to be phylogenetically and possibly functionally depauperate if anthropogenic climate change affects taxa similarly.
Aims
Phylogenetic endemism describes the extent to which unique phylogenetic lineages are constrained to restricted geographic areas. Previous studies indicate that species endemism is related to ...both past and modern climate, but studies of phylogenetic endemism are relatively rare and mainly focused on smaller regions. Here, we provide the first assessment of the patterns of species and phylogenetic endemism in angiosperm trees across the Northern Hemisphere as well as the relative importance of modern climate and glacial–interglacial climate change as drivers of these patterns.
Location
Northern Hemisphere.
Major taxa
Angiosperm trees.
Methods
Using tree assemblages at the scale of 100 km × 100 km grid cells and simultaneous autoregressive (SAR) models, we assessed the relationships between species endemism, phylogenetic endemism and modern climate variables, Last Glacial Maximum (LGM) to present temperature velocity.
Results
Species and phylogenetic endemism were associated with both modern climate and glacial–interglacial climate change, with higher values in areas with stable historical climate and warmer and wetter modern conditions. Notably, the multivariate SAR analyses showed that the combinations of variables with highest Akaike’s information criterion (AIC) weight always included both LGM–present climate instability and modern climate, that is, modern precipitation and temperature.
Main conclusions
Our results show that high phylogenetic endemism is partially dependent on long‐term climate stability, highlighting the threat posed by future climate changes to the preservation of rare, phylogenetically distinct lineages of trees.
Tree range shifts during geohistorical global change events provide a useful real-world model for how future changes in forest biomes may proceed. In North America, during the last deglaciation, the ...distributions of tree taxa varied significantly as regards the rate and direction of their responses for reasons that remain unclear. Local-scale processes such as establishment, growth, and resilience to environmental stress ultimately influence range dynamics. Despite the fact that interactions between trees and soil biota are known to influence local-scale processes profoundly, evidence linking below-ground interactions to distribution dynamics remains scarce.
We evaluated climate velocity and plant traits related to dispersal, environmental tolerance and below-ground symbioses, as potential predictors of the geohistorical rates of expansion and contraction of the core distributions of tree genera between 16 and 7 ka BP.
The receptivity of host genera towards ectomycorrhizal fungi was strongly supported as a positive predictor of poleward rates of distribution expansion, and seed mass was supported as a negative predictor. Climate velocity gained support as a positive predictor of rates of distribution contraction, but not expansion.
Our findings indicate that understanding how tree distributions, and thus forest ecosystems, respond to climate change requires the simultaneous consideration of traits, biotic interactions and abiotic forcing.
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