ALBERT

Description: Abstract An animal's trajectory is a fundamental object of interest in movement ecology, as it directly informs a range of topics from resource selection, to energy expenditure and behavioral states. However, optimally inferring the mostly unobserved movement path and its dynamics from a limited sample of telemetry observations is a key unsolved problem. The field of geostatistics has focused significant attention on a mathematically analogous problem that has a statistically optimal solution coined after its inventor Krige. Kriging revolutionized geostatistics and is now the gold standard for interpolating between a limited number of autocorrelated spatial point observations. Here we translate Kriging for use with animal movement data. Our Kriging formalism encompasses previous methods to estimate animal's trajectories|the Brownian bridge and continuous‐time correlated random walk library|as special cases, informs users as to when these previous methods are appropriate and provides a more general method when they are not. We demonstrate the capabilities of Kriging on a case study with Mongolian gazelles where, compared to the Brownian bridge, Kriging with a more optimal model was 10% more precise in interpolating locations and 500% more precise in estimating occurrence areas. This article is protected by copyright. All rights reserved.

Description: Abstract Central to understanding global C cycle dynamics is the functional relationship between precipitation and net primary production (NPP). At large spatial (regional) scales, the responsiveness of aboveground NPP (ANPP) to inter‐annual variation in annual precipitation (AP; ANPPsensitivity) is inversely related to site‐level ANPP, coinciding with turnover of plant communities along precipitation gradients. Within ecosystems experiencing chronic alterations in water availability, plant community change will also occur with unknown consequences for ANPPsensitivity. To examine the role plant community shifts may play in determining alterations in site‐level ANPPsensitivity, we experimentally increased precipitation by ~35% for two decades in a native Central US grassland. Consistent with regional models, ANPPsensitivity decreased initially as water availability and ANPP increased. However, ANPPsensitivity shifted back to ambient levels when mesic species increased in abundance in the plant community. Similarly, in grassland sites with distinct mesic and xeric plant communities and corresponding 50% differences in ANPP, ANPPsensitivity did not differ over almost three decades. We conclude that responses in ANPPsensitivity to chronic alterations in water availability within an ecosystem may not conform to regional AP‐ANPP patterns, despite expected changes in ANPP and plant communities. The result is unanticipated functional resistance to climate change at the site scale. This article is protected by copyright. All rights reserved.

Description: Abstract Avoidance and tolerance of herbivory are important components of plant interactions with herbivores. Their relationship to each other and to plant defense is important in understanding how plants maximize fitness in the face of herbivore pressure. Various tarweed species have populations comprised of both early‐season and late‐season flowering individuals. Late‐season flowering individuals employ a recently described indirect defense against herbivores in which the accumulation of dead insects on their sticky surfaces attracts predatory insects that eat herbivores. In two tarweed species (Hemizonia congesta and Madia elegans), we observed that key herbivores rarely interact with early‐season individuals in the field, and early‐season individuals did not invest in dense glandular trichomes that cause indirect defense. We conducted field and greenhouse bud‐removal experiments to assess tolerance of M. elegans to herbivore damage. We found that late‐season individuals were more tolerant of simulated herbivory than early‐season individuals in both the field and the greenhouse. Late‐season individuals that were forced into an earlier phenology with a 24‐hr light cue lost their tolerance to simulated herbivory. One possible mechanism linking phenological avoidance of herbivores with decreased tolerance is that early‐season individuals invested less in belowground biomass than late‐season individuals, which may accumulate belowground resources for re‐growth at the expense of early flowering. This article is protected by copyright. All rights reserved.

Description: Abstract The ‘landscape of fear’ model, recently advanced in research on the non‐lethal effects of carnivores on ungulates, predicts that prey will exhibit detectable antipredator behavior not only during risky times (i.e., predators in close proximity) but also in risky places (i.e., habitat where predators kill prey or tend to occur). Aggregation is an important antipredator response in numerous ungulate species, making it a useful metric to evaluate the strength and scope of the landscape of fear in a multi‐carnivore, multi‐ungulate system. We conducted ungulate surveys over a two‐year period in South Africa to test the influence of three broad‐scale sources of variation in the landscape on spatial patterns in aggregation: 1) habitat structure, 2) where carnivores tended to occur (i.e., population‐level utilization distributions) and 3) where carnivores tended to kill ungulate prey (i.e., probabilistic kill site maps). We analyzed spatial variation in aggregation for six ungulate species exposed to predation from recently reintroduced lion (Panthera leo) and spotted hyena (Crocuta crocuta). Although we did detect larger aggregations of ungulates in ‘risky places’, these effects existed primarily for smaller‐bodied (〈150kg) ungulates and were relatively moderate (change of ≤4 individuals across all habitats). In comparison, ungulate aggregations tended to increase at a slightly lower rate in habitat that was more open. Lion, an ambush (stalking) carnivore, had stronger influence on ungulate aggregation than hyena, an active (coursing) carnivore. In addition, places where lions tended to kill prey more strongly affected ungulate aggregation than places where lions tended to occur, but an opposing pattern existed for hyena. Our study reveals heterogeneity in the landscape of fear and suggests broad‐scale risk effects following carnivore reintroduction only moderately influence ungulate aggregation size and vary considerably by predator hunting mode, type of predation risk, and prey species. This article is protected by copyright. All rights reserved.

Description: Abstract Long‐distance breeding and natal dispersal play central roles in many ecological and evolutionary processes, including gene flow, population dynamics, range expansion, and individual responses to fluctuating biotic and abiotic conditions. However, the relative contribution of long‐distance dispersal to these processes depends on the ability of dispersing individuals to successfully reproduce in their new environment. Unfortunately, due to the difficulties associated with tracking dispersal in the field, relatively little is known about its reproductive consequences. Furthermore, because reproductive success is influenced by a variety of processes, disentangling the influence of each of these processes is critical to understanding the direct consequences of dispersal. In this study, we used stable hydrogen and carbon isotopes to estimate long‐distance dispersal and winter territory quality in a migratory bird, the American redstart (Setophaga ruticilla). We then applied Aster life‐history models to quantify the strength of influence of these factors on apparent reproductive success. We found no evidence that male or female reproductive success was lower for long‐distance dispersers relative to non‐dispersing individuals. In contrast, carry‐over effects from the winter season did influence male, but not female, reproductive success. Use of Aster models further revealed that for adult males, winter territory quality influenced the number of offspring produced whereas for yearling males, high‐quality winter territories were associated with higher mating and nesting success. These results suggest that although long‐distance natal and breeding dispersal carry no immediate reproductive cost for American redstarts, reproductive success in this species may ultimately be limited by the quality of winter habitat. This article is protected by copyright. All rights reserved.

Description: Abstract Plant–plant and plant–soil interactions can help maintain plant diversity and ecosystem functions. Changes in these interactions may underlie experimentally‐observed increases in biodiversity effects over time via the selection of genotypes adapted to low or high plant diversity. However, little is known about such community‐history effects and particularly the role of plant–soil interactions in this process. Soil‐legacy effects may occur if co‐evolved interactions with soil communities either positively or negatively modify plant biodiversity effects. We tested how plant selection and soil legacy influence biodiversity effects on productivity, and whether such effects increase the resistance of the communities to invasion by weeds. We used two plant selection treatments: parental plants growing in monoculture or in mixture over 8 years in a grassland biodiversity experiment in the field, which we term monoculture types and mixture types. The two soil‐legacy treatments used in this study were neutral soil inoculated with live or sterilized soil inocula collected from the same plots in the biodiversity experiment. For each of the four factorial combinations, seedlings of eight species were grown in monocultures or 4‐species mixtures in pots in an experimental garden over fifteen weeks. Soil legacy (live inoculum) strongly increased biodiversity complementarity effects for communities of mixture types, and to a significantly weaker extent for communities of monoculture types. This may be attributed to negative plant–soil feedbacks suffered by mixture types in monocultures, whereas monoculture types had positive plant–soil feedbacks, in both monocultures and mixtures. Monocultures of mixture types were most strongly invaded by weeds, presumably due to increased pathogen susceptibility, reduced biomass and altered plant–soil interactions of mixture types. These results show that biodiversity effects in experimental grassland communities can be modified by the evolution of positive vs. negative plant–soil feedbacks of plant monoculture vs. mixture types. This article is protected by copyright. All rights reserved.

Description: Abstract The central role that ectomycorrhizal (EM) symbioses play in the structure and function of boreal forests pivots around the common assumption that carbon (C) and nitrogen (N) are exchanged at rates favorable for plant growth. However, this may not always be the case. It has been hypothesized that the benefits mycorrhizal fungi convey to their host plants strongly depends upon the availability of C and N, both of which are rapidly changing as a result of intensified human land use and climate change. Using large‐scale shading and N addition treatments, we assessed the independent and interactive effects of changes in C and N supply on the transfer of N in intact EM associations with ~15 yr. old Scots pine trees. To assess the dynamics of N transfer in EM symbioses, we added trace amounts of highly enriched 15NO3‐ label to the EM‐dominated mor‐layer and followed the fate of the 15N label in tree foliage, fungal chitin on EM root tips, and EM sporocarps. Despite no change in leaf biomass, shading resulted in reduced tree C uptake, ca. 40 % lower fungal biomass on EM root tips, and greater 15N label in tree foliage compared to unshaded control plots, where more 15N label was found in fungal biomass on EM colonized root tips. Short‐term addition of N shifted the incorporation of 15N label from EM fungi to tree foliage, despite no significant changes in below‐ground tree C allocation to EM fungi. Contrary to the common assumption that C and N are exchanged at rates favorable for plant growth, our results show for the first time that under N‐limited conditions greater C allocation to EM fungi in the field results in reduced, not increased, N transfer to host trees. Moreover, given the ubiquitous nature of mycorrhizal symbioses, our results stress the need to incorporate mycorrhizal dynamics into process‐based ecosystem models to better predict forest C and N cycles in light of global climate change. This article is protected by copyright. All rights reserved.

Description: Abstract In addition to the effect of litter quality (LQ) on decomposition, increasing evidence is demonstrating that carbon mineralisation can be influenced by the past resource history, mainly through following two processes: (i) decomposer communities from recalcitrant litter environments may have a wider functional ability to decompose a wide range of litter species than those originating from richer environments, i.e. the functional breadth (FB) hypothesis; and/or (ii) decomposer communities may be specialized towards the litter they most frequently encounter, i.e. the home‐field advantage (HFA) hypothesis. Nevertheless, the functional dissimilarities among contrasting microbial communities, which are generated by the FB and the HFA, have rarely been simultaneously quantified in the same experiment, and their relative contributions over time have never been assessed. To test these hypotheses, we conducted a reciprocal transplant decomposition experiment under controlled conditions using litter and soil originating from four ecosystems along a land‐use gradient (forest, plantation, grassland and cropland) and one additional treatment using 13C labelled flax litter allowing us to assess the priming effect (PE) in each ecosystem. We found substantial effects of LQ on carbon mineralisation (more than two‐thirds of the explained variance), whereas the contribution of the soil type was fairly low (less than one‐tenth), suggesting that the contrasting soil microbial communities play only a minor role in regulating decomposition rates. Although the results on PE showed that we overestimated litter‐derived CO2 fluxes, litter‐microbe interactions contributed significantly to the unexplained variance observed in carbon mineralisation models. The magnitudes of FB and HFA were relatively similar, but the directions of these mechanisms were sometimes opposite depending on the litter and soil types. FB and HFA estimates calculated on parietal sugar mass loss were positively correlated with those calculated on enzymatic activity, confirming the idea that the interaction between litter quality and microbial community structure may modify the trajectory of carbon mineralisation via enzymatic synthesis. We conclude that although litter quality was the predominant factor controlling litter mineralisation, the local microbial communities and interactions with their substrates can explain a small (〈 5%) but noticeable portion of carbon fluxes. This article is protected by copyright. All rights reserved.

Description: Abstract Identifying the internal and external drivers of population dynamics is a key objective in ecology, currently accentuated by the need to forecast the effects of climate change on species distributions and abundances. The interplay between environmental and density effects is one particularly important aspect of such forecasts. We examined the simultaneous impact of climate and intra‐specific density on vital rates of the dwarf shrub Fumana procumbens over 20 years, using generalized additive mixed models. We then analyzed effects on population dynamics using integral projection models. The population projection models accurately captured observed fluctuations in population size. Our analyses suggested the population was intrinsically regulated but with annual fluctuations in response to variation in weather. Simulations showed that implicitly assuming variation in demographic rates to be driven solely by the environment can overestimate extinction risks if there is density dependence. We conclude that density regulation can dampen effects of climate change on Fumana population size, and discuss the need to quantify density dependence in predictions of population responses to environmental changes. This article is protected by copyright. All rights reserved.

Description: Abstract Because it modulates the fitness returns of possible options of energy expenditure at each ontogenetic stage, environmental stochasticity is usually considered a selective force in driving or constraining possible life histories. Divergent regimes of environmental fluctuation experienced by populations are expected to generate differences in the resource allocation schedule between survival and reproductive effort and outputs. To our knowledge, no study has previously examined how different regimes of stochastic variation in environmental conditions could result in changes in both the temporal variation and mean of demographic parameters, which could then lead to intra‐specific variation along the slow–fast continuum of life history tactics. To investigate these issue, we used capture–recapture data collected on five populations of a long‐lived amphibian (Bombina variegata) experiencing two distinct levels of stochastic environmental variation: (i) constant availability of breeding sites in space and time (‘predictable environment’), and (ii) variable spatio‐temporal availability of breeding sites (‘unpredictable environment’). We found that female breeding propensity varied more from year to year in unpredictable than in predictable environments. Although females in unpredictable environments produced on average more viable offspring per year, offspring production was more variable between years. Survival at each ontogenetic stage was slightly lower and varied significantly more from year to year in unpredictable environments. Taken together, these results confirm that increased environmental stochasticity can modify the resource allocation schedule between survival and reproductive effort and outputs and may lead to intra‐specific variation along the slow–fast continuum of life history tactics. This article is protected by copyright. All rights reserved.