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Keith A Christian, Christopher R Tracy, C Richard Tracy
In an attempt to improve estimates of evaporative water loss (EWL) as a component of species distribution models, Riddell et al. (2017) compared the traditional method for empirically measuring skin resistance (ri ) to that determined by a mathematical model based in physics. They argued that the resulting differences between these two approaches had implications for estimates of species range. This article is protected by copyright. All rights reserved.
August 8, 2017: Ecology
Jacob Weiner, Yan-Lei Du, Cong Zhang, Xiao-Liang Qin, Feng-Min Li
Although the importance of group selection in nature is highly controversial, several researchers have argued that plant breeding for agriculture should be based on group selection, because the goal in agriculture is to optimize population production, not individual fitness. A core hypothesis behind this claim is that crop genotypes with the highest individual fitness in a mixture of genotypes will not produce the highest population yield, because fitness is often increased by "selfish" behaviors, which reduce population performance...
August 7, 2017: Ecology
Will Chatfield-Taylor, Jeffrey A Cole
Mass multi-species cicada emergences (broods) occur in California with variable periodicity. Here we present the first rule set that predicts the emergence of protoperiodical cicada communities. We tested two hypotheses with a dataset consisting of direct observations and georeferenced museum specimen records: first, that cicada broods are triggered to emerge by periodic ENSO events and second, that brood emergences occur after precipitation accumulates above a threshold value. The period of ENSO events does not explain the observed pattern of cicada brood emergence...
August 5, 2017: Ecology
John L Devaney, Michael Lehmann, Ilka C Feller, John D Parker
Recent climate warming has led to asynchronous species migrations, with major consequences for ecosystems worldwide. In woody communities, localized microclimates have the potential to create feedback mechanisms that can alter the rate of species range shifts attributed to macroclimate drivers alone. Mangrove encroachment into saltmarsh in many areas is driven by a reduction in freeze events, and this encroachment can further modify local climate, but the subsequent impacts on mangrove seedling dynamics are unknown...
August 5, 2017: Ecology
Jared D Wolfe, C John Ralph, Andrew Wiegardt
Changes in climate can indirectly regulate populations at higher trophic levels by influencing the availability of food resources in the lower reaches of the food web. As such, species that rely on fruit and nectar food resources may be particularly sensitive to these bottom-up perturbations due to the strength of their trophic linkages with climatically-influenced plants. To measure the influence of climatically-mediated, bottom-up processes, we used climate, bird capture, bird count, and plant phenology data from the Big Island of Hawaii to construct a series of structural equation and abundance models...
August 5, 2017: Ecology
Yuzu Sakata, Timothy P Craig, Joanne K Itami, Michimasa Yamasaki, Takayuki Ohgushi
Geographic variation in the traits of a species is shaped by variation in abiotic conditions, biotic interactions, and evolutionary history of its interactions with other species. We studied the geographic variation in the density of the lace bug, Corythucha marmorata, and the resistance of tall goldenrod Solidago altissima to the lace bug herbivory in their native range in the USA and invaded range in Japan. We conducted field surveys and reciprocal transplant experiments to examine what abiotic and biotic factors influence variation in lace bug density, and what ecological and evolutionary factors predict the resistance of the host plant between and within the native and invaded ranges...
August 3, 2017: Ecology
Claudio Gratton, David Hoekman, Jamin Dreyer, Randall D Jackson
Allochthonous resource movement across ecosystem boundaries creates episodic linkages between ecosystems. The sensitivity of the community to external resources of varying duration can alter the baseline upon which future pulses of allochthony can act. We explored the terrestrial ecosystem response to pulsed inputs of lake-derived resources with a manipulative experiment in a subarctic heathland where we assessed plant community and nutrient availability responses to additions of midge carcasses (Diptera: Chironomidae)...
August 3, 2017: Ecology
Fei Li, Yunfeng Peng, Susan M Natali, Kelong Chen, Tianfeng Han, Guibiao Yang, Jinzhi Ding, Dianye Zhang, Guanqin Wang, Jun Wang, Jianchun Yu, Futing Liu, Yuanhe Yang
Large uncertainties exist in carbon (C)-climate feedback in permafrost regions, partly due to an insufficient understanding of warming effects on nutrient availabilities and their subsequent impacts on vegetation C sequestration. Although a warming climate may promote a substantial release of soil C to the atmosphere, a warming-induced increase in soil nutrient availability may enhance plant productivity, thus offsetting C loss from microbial respiration. Here, we present evidence that the positive temperature effect on carbon dioxide (CO2 ) fluxes may be weakened by reduced plant nitrogen (N) and phosphorous (P) concentrations in a Tibetan permafrost ecosystem...
August 2, 2017: Ecology
Ronald D Bassar, Joseph Travis, Tim Coulson
A longstanding problem in ecology is whether structured life cycles impede or facilitate coexistence between species. Theory based on populations with only two discrete stages in the life-cycle indicates that for two species to coexist, at least one must shift its niche between stages and each species must be a better competitor in one of the niches. However, in many cases, niche shifts are associated with changes in an underlying continuous trait like body size and we have few predictions concerning conditions for coexistence for such a widespread form of ontogenetic development...
August 2, 2017: Ecology
Jessica L Hite, Rachel M Penczykowski, Marta S Shocket, Katherine Griebel, Alexander T Strauss, Meghan A Duffy, Carla E Cáceres, Spencer R Hall
Why do natural populations vary in the frequency of sexual reproduction? Virulent parasites may help explain why sex is favored during disease epidemics. To illustrate, we show a higher frequency of males and sexually produced offspring in natural populations of a facultative parthenogenetic host during fungal epidemics. In a multi-year survey of 32 lakes, the frequency of males (an index of sex) was higher in populations of zooplankton hosts with larger epidemics. A lake mesocosm experiment established causality: experimental epidemics produced a higher frequency of males relative to disease-free controls...
August 2, 2017: Ecology
Justin Olnes, Knut Kielland, Glenn P Juday, Daniel H Mann, Hélène Genet, Roger W Ruess
Treelines in Alaska are advancing in elevation and latitude because of climate warming, which is expanding the habitat available for boreal wildlife species, including snowshoe hares (Lepus americanus). Snowshoe hares are already present in tall shrub communities beyond treeline and are the main browser of white spruce (Picea glauca), the dominant tree species at treeline in Alaska. We investigated the processes involved in a 'snowshoe hare filter' to white spruce establishment near treeline in Denali National Park...
August 2, 2017: Ecology
Megan J Hirst, Philippa C Griffin, Jason P Sexton, Ary A Hoffmann
Relatively common species within a clade are expected to perform well across a wider range of conditions than their rarer relatives, yet experimental tests of this "niche breadth-range size" hypothesis remain surprisingly scarce. Rarity may arise due to trade-offs between specialization and performance across a wide range of environments. Here we use common garden and reciprocal transplant experiments to test the niche breadth-range size hypothesis, focusing on four common and three rare endemic alpine daisies (Brachyscome spp...
August 2, 2017: Ecology
Jake M Ferguson, Brian E Reichert, Robert J Fletcher, Henriëtte I Jager
Time series analysis is an essential method for decomposing the influences of density and exogenous factors such as weather and climate on population regulation. However, there has been little work focused on understanding how well commonly collected data can reconstruct the effects of environmental factors on population dynamics. We show that analogous to similar scale issues in spatial data analysis, coarsely sampled temporal data can fail to detect covariate effects when interactions occur on timescales that are fast relative to the survey period...
July 31, 2017: Ecology
Clark S Rushing, Jeffrey A Hostetler, T Scott Sillett, Peter P Marra, James A Rotenberg, Thomas B Ryder
Untangling the spatial and temporal processes that influence population dynamics of migratory species is challenging, because changes in abundance are shaped by variation in vital rates across heterogeneous habitats and throughout the annual cycle. We developed a full-annual-cycle, integrated population model and used demographic data collected between 2011 and 2014 in southern Indiana and Belize to estimate stage-specific vital rates of a declining migratory songbird, the Wood Thrush (Hylocichla mustelina)...
July 30, 2017: Ecology
Sarah J Hart, Thomas T Veblen, Dominik Schneider, Noah P Molotch
This study used Landsat-based detection of spruce beetle (Dendroctonus rufipennis) outbreak over the years 2000-2014 across the Southern Rocky Mountain Ecoregion to examine the spatiotemporal patterns of outbreak and assess the influence of temperature, drought, forest characteristics and previous spruce beetle activity on outbreak development. During the 1999-2013 period, time series of spruce beetle activity were highly spatially correlated (r >0.5) at distances <5 km, but remained weakly correlated (r = 0...
July 28, 2017: Ecology
Paul Acker, Aurélien Besnard, Jean-Yves Monnat, Emmanuelle Cam
Habitat selection theory predicts that natural selection should favor mechanisms allowing individuals to choose habitats associated with the highest fitness prospects. However, identifying sources of information on habitat quality that individuals use to choose their breeding habitat has proved to be difficult. It has also proven difficult to identify dispersal costs that prevent individuals from joining the highest-quality sites. A synthesis that integrates dispersal costs and habitat selection mechanisms across space has remained elusive...
July 26, 2017: Ecology
F Manna, R Pradel, R Choquet, H Fréville, P-O Cheptou
In plants, the presence of a seed bank challenges the application of classical metapopulation models to above-ground presence surveys; ignoring seed bank leads to overestimated extinction and colonization rates. In this article, we explore the possibility to detect seed bank using hidden Markov models in the analysis of above-ground patch occupancy surveys of an annual plant with limited dispersal. Patch occupancy data were generated by simulation under two metapopulation sizes (N = 200 and N = 1000 patches) and different metapopulation scenarios, each scenario being a combination of the presence/absence of a one-year seed bank and the presence/absence of limited dispersal in a circular 1-dimension configuration of patches...
July 22, 2017: Ecology
Emma E Hodgson, Timothy E Essington, Benjamin S Halpern
Population endangerment typically arises from multiple, potentially interacting anthropogenic stressors. Extensive research has investigated the consequences of multiple stressors on organisms, frequently focusing on individual life stages. Less is known about population-level consequences of exposure to multiple stressors, especially when exposure varies through life. We provide the first theoretical basis for identifying species at risk of magnified effects from multiple stressors across life history. By applying a population-modeling framework, we reveal conditions under which population responses from stressors applied to distinct life stages are either magnified (synergistic) or mitigated...
July 22, 2017: Ecology
Matthew C Hutchinson, E Fernando Cagua, Daniel B Stouffer
That evolutionary history can influence the way that species interact is a basic tenet of evolutionary ecology. However, when the role of evolution in determining ecological interactions is investigated, focus typically centers on just one side of the interaction. A cophylogenetic signal-the congruence of evolutionary history across both sides of anecological interaction-extends these previous explorations and provides a more complete picture of how evolutionary patterns influence the way species interact. To date,cophylogenetic signal has most typically been studied in interactions that occur between fine taxonomic clades that show high intimacy...
July 22, 2017: Ecology
W John Calder, Bryan Shuman
Ecosystems may shift abruptly when the effects of climate change and disturbance interact, and landscapes with regularly patterned vegetation may be especially vulnerable to abrupt shifts. Here we use a fossil pollen record from a regularly patterned ribbon forest (alternating bands of forests and meadows) in Colorado to examine whether past changes in wildfire and climate produced abrupt vegetation shifts. Comparing the percentages of conifer pollen with sedimentary δ(18) O data (interpreted as an indicator of temperature or snow accumulation) indicates a first-order linear relationship between vegetation composition and climate change with no detectable lags over the past 2500 years (r = 0...
July 21, 2017: Ecology
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