pinecone/core-2020-05-10-deduplication huggingface dataset:
Adaptive latitudinal variation in Common Blackbird Turdus merula nest characteristics

Nest construction is taxonomically widespread, yet our understanding of adaptive\ud
intraspecific variation in nest design remains poor. Nest characteristics are\ud
expected to vary adaptively in response to predictable variation in spring temperatures\ud
over large spatial scales, yet such variation in nest design remains largely\ud
overlooked, particularly amongst open-cup-nesting birds. Here, we systematically\ud
examined the effects of latitudinal variation in spring temperatures and precipitation\ud
on the morphology, volume, composition, and insulatory properties of\ud
open-cup-nesting Common Blackbirds’ Turdus merula nests to test the hypothesis\ud
that birds living in cooler environments at more northerly latitudes would build\ud
better insulated nests than conspecifics living in warmer environments at more\ud
southerly latitudes. As spring temperatures increased with decreasing latitude, the\ud
external diameter of nests decreased. However, as nest wall thickness also\ud
decreased, there was no variation in the diameter of the internal nest cups. Only\ud
the mass of dry grasses within nests decreased with warmer temperatures at lower\ud
latitudes. The insulatory properties of nests declined with warmer temperatures at\ud
lower latitudes and nests containing greater amounts of dry grasses had higher insulatory\ud
properties. The insulatory properties of nests decreased with warmer temperatures\ud
at lower latitudes, via changes in morphology (wall thickness) and\ud
composition (dry grasses). Meanwhile, spring precipitation did not vary with latitude,\ud
and none of the nest characteristics varied with spring precipitation. This suggests\ud
that Common Blackbirds nesting at higher latitudes were building nests with\ud
thicker walls in order to counteract the cooler temperatures. We have provided evidence\ud
that the nest construction behavior of open-cup-nesting birds systematically\ud
varies in response to large-scale spatial variation in spring temperatures
Differing impact of a major biogeographic barrier on genetic structure in two large kangaroos from the monsoon tropics of Northern Australia

Tropical savannas cover 20-30% of the world\u27s land surface and exhibit high levels of regional endemism, but the evolutionary histories of their biota remain poorly studied. The most extensive and unmodified tropical savannas occur in Northern Australia, and recent studies suggest this region supports high levels of previously undetected genetic diversity. To examine the importance of barriers to gene flow and the environmental history of Northern Australia in influencing patterns of diversity, we investigated the phylogeography of two closely related, large, vagile macropodid marsupials, the antilopine wallaroo (Macropus antilopinus; n&emsp;=&emsp;78), and the common wallaroo (Macropus robustus; n&emsp;=&emsp;21). Both species are widespread across the tropical savannas of Australia except across the Carpentarian Barrier (CB) where there is a break in the distribution of M.&emsp;antilopinus. We determined sequence variation in the hypervariable Domain I of the mitochondrial DNA control region and genotyped individuals at 12 polymorphic microsatellite loci to assess the historical and contemporary influence of the CB on these species. Surprisingly, we detected only limited differentiation between the disjunct Northern Territory and QueenslandM.&emsp;antilopinus populations. In contrast, the continuously distributedM.&emsp;robustus was highly divergent across the CB. Although unexpected, these contrasting responses appear related to minor differences in species biology. Our results suggest that vicariance may not explain well the phylogeographic patterns in Australia\u27s dynamic monsoonal environments. This is because Quaternary environmental changes in this region have been complex, and diverse individual species\u27 biologies have resulted in less predictable and idiosyncratic responses
Possible effects of global environmental changes on Antarctic benthos: a synthesis across five major taxa

Because of the unique conditions that exist around the Antarctic continent, Southern Ocean (SO) ecosystems are very susceptible to the growing impact of global climate change and other anthropogenic influences. Consequently, there is an urgent need to understand how SO marine life will cope with expected future changes in the environment. Studies of Antarctic organisms have shown that individual species and higher taxa display different degrees of sensitivity to environmental shifts, making it difficult to predict overall community or ecosystem responses. This emphasizes the need for an improved understanding of the Antarctic benthic ecosystem response to global climate change using a multitaxon approach with consideration of different levels of biological organization. Here, we provide a synthesis of the ability of five important Antarctic benthic taxa (Foraminifera, Nematoda, Amphipoda, Isopoda, and Echinoidea) to cope with changes in the environment (temperature, pH, ice cover, ice scouring, food quantity, and quality) that are linked to climatic changes. Responses from individual to the taxon-specific community level to these drivers will vary with taxon but will include local species extinctions, invasions of warmer-water species, shifts in diversity, dominance, and trophic group composition, all with likely consequences for ecosystem functioning. Limitations in our current knowledge and understanding of climate change effects on the different levels are discussed
Filling the gap in functional trait databases: Use of ecological hypotheses to replace missing data

Functional trait databases are powerful tools in ecology, though most of them contain large amounts of missing values. The goal of this study was to test the effect of imputation methods on the evaluation of trait values at species level and on the subsequent calculation of functional diversity indices at community level using functional trait databases. Two simple imputation methods (average and median), two methods based on ecological hypotheses, and one multiple imputation method were tested using a large plant trait database, together with the influence of the percentage of missing data and differences between functional traits. At community level, the complete-case approach and three functional diversity indices calculated from grassland plant communities were included. At the species level, one of the methods based on ecological hypothesis was for all traits more accurate than imputation with average or median values, but the multiple imputation method was superior for most of the traits. The method based on functional proximity between species was the best method for traits with an unbalanced distribution, while the method based on the existence of relationships between traits was the best for traits with a balanced distribution. The ranking of the grassland communities for their functional diversity indices was not robust with the complete-case approach, even for low percentages of missing data. With the imputation methods based on ecological hypotheses, functional diversity indices could be computed with a maximum of 30% of missing data, without affecting the ranking between grassland communities. The multiple imputation method performed well, but not better than single imputation based on ecological hypothesis and adapted to the distribution of the trait values for the functional identity and range of the communities. Ecological studies using functional trait databases have to deal with missing data using imputation methods corresponding to their specific needs and making the most out of the information available in the databases. Within this framework, this study indicates the possibilities and limits of single imputation methods based on ecological hypothesis and concludes that they could be useful when studying the ranking of communities for their functional diversity indices. (Résumé d'auteur
Dynamics of non-structural carbohydrates in terrestrial plants : a global synthesis

Plants store large amounts of non-structural carbohydrates (NSC). While multiple functions of NSC have long been recognized, the interpretation of NSC seasonal dynamics is often based on the idea that stored NSC is a reservoir of carbon that fluctuates depending on the balance between supply via photosynthesis and demand for growth and respiration (the source–sink dynamics concept). Consequently, relatively high NSC concentrations in some plants have been interpreted to reflect excess supply relative to demand. An alternative view, however, is that NSC accumulation reflects the relatively high NSC levels required for plant survival; an important issue that remains highly controversial. Here, we assembled a new global database to examine broad patterns of seasonal NSC variation across organs (leaves, stems, and belowground), plant functional types (coniferous, drought-deciduous angiosperms, winter deciduous angiosperms, evergreen angiosperms, and herbaceous) and biomes (boreal, temperate, Mediterranean, and tropical). We compiled data from 121 studies, including seasonal measurements for 177 species under natural conditions. Our results showed that, on average, NSC account for ~10% of dry plant biomass and are highest in leaves and lowest in stems, whereas belowground organs show intermediate concentrations. Total NSC, starch, and soluble sugars (SS) varied seasonally, with a strong depletion of starch during the growing season and a general increase during winter months, particularly in boreal and temperate biomes. Across functional types, NSC concentrations were highest and most variable in herbaceous species and in conifer needles. Conifers showed the lowest stem and belowground NSC concentrations. Minimum NSC values were relatively high (46% of seasonal maximums on average for total NSC) and, in contrast to average values, were similar among biomes and functional types. Overall, although starch depletion was relatively common, seasonal depletion of total NSC or SS was rare. These results are consistent with a dual view of NSC function: whereas starch acts mostly as a reservoir for future use, soluble sugars perform immediate functions (e.g., osmoregulation) and are kept above some critical threshold. If confirmed, this dual function of NSC will have important implications for the way we understand and model plant carbon allocation and survival under stress
The interactive effects of press/pulse intensity and duration on regime shifts at multiple scales

Citation: Ratajczak, Z., D'Odorico, P., Collins, S. L., Bestelmeyer, B. T., Isbell, F. I., & Nippert, J. B. (2017). The interactive effects of press/pulse intensity and duration on regime shifts at multiple scales. Ecological Monographs, 87(2), 198-218. doi:10.1002/ecm.1249Regime shifts are difficult-to-reverse transitions that occur when an ecosystem reorganizes around a new set of self-reinforcing feedbacks. Regime shifts are predicted to occur when the intensity of some exogenous driver variable, such as temperature, annual harvest rate, or nutrient addition rate, gradually approaches and crosses a threshold value, initiating a transition to an alternative state. However, many driver variables now change rapidly as presses or pulses, not gradually, requiring new conceptual frameworks for understanding and predicting regime shifts. We argue that identifying and controlling regime shifts in response to presses and pulses will require a greater focus on the duration, not just the intensity, of changes in driver variables. In ecosystems with slower dynamics, transitions to an alternative state can take years to decades and as a result, a driver press with an intensity capable of resulting in a regime shift over long time spans may fail to cause a regime shift when applied for shorter durations. We illustrate these ideas using simulations of local-scale alternative stable state models and preliminary evidence from long-term grazing and eutrophication experiments. The simulations also suggest that small changes in the duration of driver presses or pulses can determine whether an ecosystem recovers to its original state. These insights may extend to larger scales. In spatially extended simulations that included patchiness, spatial heterogeneity, and spatial connectivity, all patches recovered to their original state after shorter presses. However, once press duration exceeded a threshold, growing proportions of the landscape shifted to an alternative state as press duration increased. We observed similar patchy transitions in a catchment-scale experiment that reinstated frequent fires approximately halfway through a regime shift from grassland to shrubland, initiated by fire suppression. In both the local-and larger-scale models, the threshold duration needed to elicit regime shifts decreased as press intensity increased or when factors counteracting regime shifts weakened. These multiple lines of evidence suggest that conceptualizing regime shifts as an interactive function of the intensity and duration of driver changes will increase understanding of the varying effects of driver presses, pulses, and cycles on ecosystem dynamics
Migration in geographic and ecological space by a large herbivore

Partial migration, when only part of the population migrates seasonally while the\ud
other part remains resident on the shared range, is the most common form of migration in\ud
ungulates. Migration is often defined by spatial separation of seasonal ranges and consequently,\ud
classification of individuals as migrants or residents is usually only based on geographic criteria.\ud
However, the underlying mechanism for migration is hypothesized to be movement in response\ud
to spatiotemporal resource variability and thus, migrants are assumed to travel an “ecological\ud
distance” (ED) or shift their realized ecological niches. While ecological and geographic distances\ud
should be related, their relationship may depend on landscape heterogeneity. Here, we tested\ud
the utility of ecological niche theory to both classify migratory individuals and to understand\ud
the underlying ecological factors for migratory behavior. We developed an integrative approach\ud
combining measures in geographic and ecological niche space and used this to classify and\ud
explain migratory behavior of 71 annual roe deer (Capreolus capreolus) movement trajectories\ud
in five European study areas. First, to assess the utility of the ED concept for classifying migratory\ud
behavior, we tested whether roe deer sought the same ecological conditions year-round or\ud
moved to different ecological conditions by measuring the annual ED travelled and the seasonal\ud
niche overlap using multivariate statistics. Comparing methods to classify migrants and residents\ud
based on geographic and ecological niche space, we found that migratory roe deer switched\ud
between seasons both in geographic and in ecological dimensions. Second, we tested which\ud
seasonal ecological factors separated resident from migrant niches using discriminant analysis\ud
and which broad-scale determinants (e.g., spatiotemporal forage variation and population\ud
density) predicted migration probability using generalized linear models. Our results indicated\ud
that factors describing forage and topographic variability discriminated seasonal migrant from\ud
resident niches. Determinants for predicting migration probability included the temporal variation\ud
(seasonality) and also the spatial variability of forage patches. Last, we also found suggestive\ud
evidence for a positive relationship between population density and migration probability.\ud
By applying the ecological niche concept to the study of partial migration in ungulates, our work\ud
underlines that partial migration is a form of behavioral plasticit
Global pattern and controls of soil microbial metabolic quotient

imbalanceThe microbial metabolic quotient (MMQ), microbial respiration per unit of biomass, is a fundamental factor controlling heterotrophic respiration, the largest carbon flux in soils. The magnitude and controls of MMQ at regional scale remain uncertain. We compiled a comprehensive data set of MMQ to investigate the global patterns and controls of MMQ in top 30 cm soils. Published MMQ values, generally measured in laboratory microcosms, were adjusted on ambient soil temperature using long-term (30 yr) average site soil temperature and a Q₁₀ = 2. The area-weighted global average of MMQ_Soil is estimated as 1.8 (1.5–2.2) (95% confidence interval) μmol C·h⁻¹·mmol⁻¹ microbial biomass carbon (MBC) with substantial variations across biomes and between cropland and natural ecosystems. Variation was most closely associated with biological factors, followed by edaphic and meteorological parameters. MMQ_Soil was greatest in sandy clay and sandy clay loam and showed a pH maximum of 6.7 ± 0.1 (mean ± se). At large scale, MMQ_Soil varied with latitude and mean annual temperature (MAT), and was negatively correlated with microbial N:P ratio, supporting growth rate theory. These trends led to large differences in MMQ_Soil between natural ecosystems and cropland. When MMQ was adjusted to 11°C (MMQ_Ref), the global MAT in the top 30 cm of soils, the area-weighted global averages of MMQ_Ref was 1.5 (1.3–1.8) μmol C·mmol MBC⁻¹·h⁻¹. The values, trends, and controls of MMQ_Soil add to our understanding of soil microbial influences on soil carbon cycling and could be used to represent microbial activity in global carbon models
A structural approach for understanding multispecies coexistence

Although observations of species-rich communities have long served as a primary motivation for research on the coexistence of competitors, the majority of our empirical and theoretical understanding comes from two-species systems. How much of the coexistence observed in species-rich communities results from indirect effects among competitors that only emerge in diverse systems remains poorly understood. Resolving this issue requires simple, scalable, and intuitive metrics for quantifying the conditions for coexistence in multispecies systems, and how these conditions differ from those expected based solely on pairwise interactions. To achieve these aims, we develop a structural approach for studying the set of parameter values compatible with n-species coexistence given the geometric constraints imposed by the matrix of competition coefficients. We derive novel mathematical metrics analogous to stabilizing niche differences and fitness differences that measure the range of conditions compatible with multispecies coexistence, incorporating the effects of indirect interactions emerging in diverse systems. We show how our measures can be used to quantify the extent to which the conditions for coexistence in multispecies systems differ from those that allow pairwise coexistence, and apply the method to a field system of annual plants. We conclude by presenting new challenges and empirical opportunities emerging from our structural metrics of multispecies coexistence
Traditionally managed landscapes do not prevent amphibian decline and the extinction of paedomorphosis

Eco-cultural landscapes are assumed to be favourable environments for the persistence of biodiversity, but global change may affect differently their terrestrial and aquatic components. Yet, few long-term studies have examined how multiple, global change stressors may affect wetland biodiversity in such environments. Facultative paedomorphosis is a spectacular example of intra-specific variation, in which biphasic (metamorphosing) amphibians coexist with fully aquatic conspecifics which do not metamorphose (paedomorphs). Paedomorphosis is seriously threatened by global change stressors, but it is unknown to what extent traditional management will allow its long-term persistence. Here, we tested the effects of alien species introductions while taking into account land-use and climate changes on the distribution of two polymorphic newt species (Ichthyosaura alpestris and Lissotriton graecus) in Montenegro by using a 68-year data set and Bayesian mixed models integrating complex spatial and temporal structures. We found that, despite the persistence of natural landscapes, metamorphs dramatically declined, and paedomorphs were nearly extirpated, losing 99.9% of their aquatic area of occupancy and all the major populations. Fish introduction was the main determinant of decline for both phenotypes. Climate and the presence of crayfish further contributed to the decline of metamorphs, which started later and was less dramatic than that of paedomorphs. The near extinction of paedomorphosis on a country-wide scale shows how invasive species determine broad scale impacts, which can be even stronger than other global change stressors, and underlines the need for immediate management actions to avoid the extinction of a unique developmental process, paedomorphosis.Peer reviewe
Assessing the seasonal dynamics of inundation, turbidity, and aquatic vegetation in the Australian wet–dry tropics using optical remote sensing

Floodplain wetlands in the wet-dry tropics are under increasing pressure from water resource development, and there is a need for methods to assess the biophysical dynamics of these extensive and often remote ecosystems. This study assessed the capacity of optical remote sensing methods to monitor the seasonal dynamics of inundation, turbidity, and aquatic vegetation cover for a northern Australian savanna catchment. MODIS data were used to map seasonal flood inundation patterns, and Landsat 5 TM data were used to map dry-season waterbody dynamics. A network of water-depth loggers and temperature sensors provided ground observations of surface inundation dynamics, and was used to validate the inundation mapping. Post-flood waterbody surface area declined by 89% over the dry season, with 70% of the decline occurring for Palustrine (floodplain) waterbodies. All aquatic systems became increasingly disconnected as the dry season progressed. Statistical relationships were developed between seasonal measurements of turbidity, aquatic vegetation cover, and Landsat spectral data. Catchment wide predictions showed that turbidity increased and macrophyte cover decreased for the Palustrine and Lacustrine (lake) systems, while the Riverine systems became less turbid over the dry season. These results show that, for open savanna landscapes where cloud cover does not limit waterbody detection, optical remote sensing methods can be effectively applied to assess seasonal patterns of inundation and accompanying biophysical dynamics. This provides an effective tool to evaluate the impact of river flow regime changes from water resource use or climate change in these regions.Griffith Sciences, Griffith School of EnvironmentFull Tex