Cover illustration Climate change is altering phenology in many species. In this issue, Sevenello and colleagues analyzed how the flowering period of spring ephemerals and the activity period of the solitary bee community is affected by interannual climatic variation in an eastern North American hardwood forest. They found that the flowering phenology of Anemone spp. was very sensitive to temperature, but that of Trillium grandiflorum was more responsive to photoperiod. Bee phenology was only weakly correlated with temperature. Nevertheless, temporal overlap between these plants and bees was not affected by climatic variability. These results show that interacting plant and bee taxa may respond to different environmental variables but still maintain their temporal overlap under the conditions recorded so far. Photo credit: Jessica Forrest.
Cover illustration Marine environments are far from silent and coral reefs in particular house a large variety of vocal fishes. How can the different species communicate efficiently and avoid cacophony? Fishes may optimize their communication by selecting specific time and spectral windows to insert their signals within the acoustic space, as predicted by the Acoustic Niche Hypothesis. Bertucci et al.’s paper in this issue demonstrates that acoustic partitioning on reefs in French Polynesia are consistent with niche partitioning and turn cacophony into a "choral” reef. Photo credit: Dascyllus flavicaudus by Gilles Siu.
Cover illustration While stomach contents are a traditional approach for characterizing a predator’s dietary niche, analysis of stable isotopes (isotopic niche) have become a common method to avoid lethal sampling and obtain robust data on assimilated resources. Comparison of these methods for four large shark species provided contrasting niche descriptions, highlighting technique specific considerations and the value of both methods. A White Shark (Carcharodon carcharias) feeding on the carcass of a Humpback Whale killed by an impact with a boat in coastal waters of the northeastern U. S. is our cover photo. Photo credit: O. Shipley, T. Henshilwood, Fisheries Research Foundation.
Cover illustration Leaf-cutter ant nests change the soil CO2 dynamics in Neotropical rainforests. We designed flow-through chambers to continuously measure the convective CO2 fluxes emanating from nest openings for several days using low-cost components. The results showed CO2 emissions about ten thousand times greater than nearby soils (in average and per unit area), and those emissions followed a clear diel pattern driven by free convection with sporadic wind-forced convection. The central image shows early prototype testing at La Selva Biological Station, Costa Rica; the left, bottom image shows a worker of Attacephalotes carrying a leaf cutting to the nest with smaller workers hitchhiking, likely to protect the bearer from parasitic wasps and to prepare the leaf fragment before entering the nest. Photo credit: Angel Santiago Fernandez-Bou (flow-chambers prototype) and Carlos de La Rosa (Attacephalotes workers).
Cover illustration The arctic fox population in Iceland has increased steadily over a period of 30 years, beginning in the end of the 1970s. Based on stable isotope analyses, our results suggest that the foxes benefitted from increasing prey populations without major changes in their dietary habits. Sea birds were the main resource supporting this prolonged growth, but geese, which have become considerably more numerous in Iceland in the same period, have played only a minor role. Photo credit: Phil Garcia.
Biodiversity has been hypothesized to decrease prevalence of disease in a wide variety of host-pathogen systems. However, the generality of this hypothesis remains debated, particularly for some rodent-borne pathogens such as hantavirus. Long-term studies of small rodent communities are crucial to the understanding of the eﬀect of biodiversity on hantavirus transmission and prevalence.
Photo credit: María Victoria Vadell.
Biodiversity in the groundwater springs of Ash Meadows, Nevada, is predicted to change with increasing water temperatures from climate change and aquifer pumping. DNA surveying provides an eﬀ ective tool to monitor ecological communities in these systems, enabling rapid and simultaneous assessment of thousands of species.
Photo credit: Elizabeth L. Paulson.
Although experimental work has demonstrated males alter ejaculate production in response to their social environment, little is known whether this may occur within wild populations. Using an island population of Anolis sagrei, Kustra et al. fi nd that several sperm traits vary with fi ne-scale variation in density of an island population. These fi ndings extend the implications of sperm competition theory to within-population variation in the social environment. The cover photo is of a male Anolis sagrei from the population used in this study.
Photo credit: Ariel F. Kahrl.
New research shows how food availability, predators, and people all influence giraﬀe social behavior, and highlights special requirements needed by mother giraﬀes to keep their babies safe. Groups of adult giraﬀes are food-focused and not influenced by predation risk, while baby giraﬀes hide in bushes from lions and seek out areas near pastoralist people where lions are rarer—but avoid higher-impact human areas. This information can help land managers to protect the places most important for giraﬀes.
Photo credit: Derek Lee.
The study by Yoon et al. in this issue highlights the value of investigating immune systems in wild animals. The insect immune response was investigated using the Melissa blue butterfly (Lycaeides melissa) and found to be aﬀ ected by a complex suite of factors including phytochemical diversity, host plant-associated microbes, and foliar protein. Shown in the photo is a nectaring male Melissa blue butterfly.
Photo credit: M. Forister.
Survival and movement are central to the ecology of organisms and can vary among demographic groups within species. Through the use of spatial capture-recapture data, Honeycutt et al. reveal evidence of age-specifi c survival and age- and sex-specifi c movement in tailed frogs, a group comprised of two ancient species that inhabit cold streams of northwestern North America. The cover photograph shows a female coastal tailed frog cryptically blending with her surroundings in a mountain stream of California, USA.
Photo credit: Justin M. Garwood.
Globally, turtles are among the most imperiled of vertebrate animals. Slow growth, late maturity, and longevity makes turtles particularly susceptible to population decline with habitat loss or modifi cation. In general, ecologists and conservationists know very little about the natural nest sites of freshwater turtles. Undergraduate student Elizabeth Ann Francis lead research examining the nesting habitat and habits of Snapping Turtles (Chelydra serpentina) in natural and manmade sites as part of a long-term study in Algonquin Provincial Park, Canada. Francis and colleagues show in a highlighted student research paper in this issue of Oecologia that natural and manmade nest sites share many physical characteristics, which explains, in-part, why turtles are attracted to nesting in human-modifi ed landscapes. Despite their physical similarities, manmade nesting sites were signifi cantly warmer than natural nest sites. Such elevated temperatures in human-modifi ed nesting habitat have the potential to alter embryonic development and skew sex ratios of developing oﬀ spring (through temperature-dependent sex determination). The researchers report that their fi ndings explain one of the most pervasive threats to turtle populations: road mortality and roads as an ecological trap.
This photo shows Snapping Turtle “H06”, a member of the study since 1989, as she completes nesting on a gravel road.
Photo credit: Patrick D. Moldowan.
Arthropod body size can vary with environmental conditions, as well as between males and females within a species, i.e. sexual size dimorphism (SSD). From zooplankton to butterflies, Horne et al. investigate patterns in SSD across a broad range of arthropod species and environmental gradients. Their meta-analysis shows that size at maturity is more variable in males than females across latitude, suggesting that over evolutionary time, directional selection has acted more strongly on male than female size. By contrast, size clines across altitudinal and seasonal temperature gradients appear not to differ systematically between the sexes. These findings provide afi eld-based comparison to earlier laboratory studies, and should interest a diverse range of ecologists, physiologists and evolutionary biologists. Pictured: Hylemya vagans (♂).
Photo credit: Curtis R. Horne.
One of the most notorious invaders of marine ecosystems is the Pacifi c oyster (Magallana gigas). Originally introduced from Asia for aquaculture, this species has rapidly established in wild populations worldwide (cover photo: anoyster reef at the Wadden Sea coast of the Dutch island of Texel). Goedknegt et al. investigated the relative importance of invasive oysters in determining native and introduced parasite infection levels in native mussels in the Wadden Sea. While invasive oysters were determinants for the presence and infection of native mussels with some parasite species, host size and density of alternative host species also determined levels of infection. These results show that the eff ects of invaders on parasitism in native species are detectable in the fi eld, but that other biological and environmental factors additionally infl uence infection levels in native host communities.
Photo credit: Maria Anouk Goedknegt.
Avian cholera recurrently causes massive mortality of yellow-nosed albatross nestlings on Amsterdam Island (IndianOcean). By combining individual immunological and demographic data, Gamble et al. demonstrated that a signifi cant proportion of adult yellow-nosed albatrosses are exposed to avian cholera. However, in contrast to nestlings, adults are able to mount a specifi c immune response and survive exposure. In addition, vaccination of breeding females induced the production of antibodies that could be transmitted to their off spring, opening possibilities for conservation strategies in these systems.
Photo credit: Thierry Boulinier.
Pumas are ecosystem engineers that provision crucial habitat for numerous beetle species. Pumas in the Greater Yellowstone Ecosystem, USA, create large, intact carcasses that become critical habitat for carrion-dependent beetles to forage, hide from predators, reproduce, mate and disperse. Pumas also provide carcasses to beetles reliably and regularly during a time of year when beetles need them the most, highlighting the important role of pumas in engineering their environment to support biodiversity.
Photograph by Mark Elbroch.
Sarcodes sanguinea has no chlorophyll and is an obligate mycoheterotrophic plant. Cormier et al. show in this issue that hydrogen isotopes in plant-derived lipids or cellulose can inform on the carbon metabolism (i.e. the carbon autonomy) of heterotrophic plants and their autotrophic hosts. Shown in thepicture is a plant of Sarcodes sanguinea (Ericaceae) in the Sierra Nevada mountains of California, USA.
Photo credit: Ansgar Kahmen.
For desert plants, extreme high temperatures are more acute for leaves experiencing the highest radiation and lowest cooling winds. In the Australian desert shrub, Acacia papyrocarpa, the greatest stressful microclimatic conditions occur at lower and north-facing positions in the canopy and leaves at these positions have signifi cantly higher thermal tolerance. This species may optimise resources to protect against heat-induced damage across the whole plant.
Photo credit: Andy Leigh.
When parasites are important sources of mortality, males can advertise their health to prospective mates directly through sexual displays whose expression is modulated by infection, or indirectly, through sexual displays whose expression changes with age. In a longitudinal study of male common yellowthroats, Freeman-Gallant and Taff show that infection with blood parasites is associated with slower growth of the black mask but not the yellow bib. Indeed, different populations of males are identified by the largest ornaments – older males in the case of bib, and a combination of older males and young, uninfected males in the case of mask. Female prefer large bibs in their population, and the authors suggest that if infection is opportunistic, females may benefit by preferring older males who are more likely to have withstood prior episodes of infection than young, uninfected males may not possess good genes for parasite resistance but simply good luck.
Photo credit: Conor C. Taff .
Among living tree species, Acacia raddiana and Acacia tortilis (the genus name changed to Vachellia) inhabit some of the hottest and driest places on Earth. These Acacia trees are major components of savannas and open woodlands in many arid regions of Africa and the Middle East, yet little is known about their growth dynamics in situ. Studying these trees in the Arava valley in Israel, Winters et al. in this issue show that their cambial growth occurs during most of the dry season. Active growth at maximum daily temperatures as high as 45 °C relies on concurrent leaf gas exchange,which is in turn permitted by access to deep soil water, in spite of extreme heat and drought.
Photo credit: Neil Shtiglitz.
Flower abundance is known to influence plant reproduction through its effects on pollination quantity and quality. However, eff ects of flower abundance on these pollination components can act at different spatial scales. In particular, fl ower availability at the landscape and neighborhood scales can be important in governing plant reproductive output by differentially aff ecting quantitative and qualitive components of the pollination process. Scotch broom is a vigorous invader in many regions worldwide. This pollinator-dependent legume can form large monospecific stands in the Patagonian region of southern Argentina. Taking advantage of its synchronous mass-blooming and bright – yellow flowering display, Cavallero et al. used aerial photographs to estimate flower availability at differentspatial scales in order to study its infl uence on scotch broom’s pollination and reproduction. Increasing fl ower availability at the landscape scale reduced pollination quantity, whereas at the neighborhood-scale it increased pollination quality. Moreover, pollination quality had a higher positive effect on seed output than pollination quantity. Thus, fl ower availability can strongly affect seed output, due to contrasting and scale-dependent effects on pollination quantity and quality. This result has implications to understand the dynamics of invasive plants as well as in yield maximization of pollinator dependent crops.
Photo credit: Laura Cavallero.
Whose dung do dung beetles eat? Dung beetles (Scarabaeinae, > 6000 species) are important in burying and consuming dung. Dung use by dung beetles has hitherto relied on observations of dung ball formation, these used for larval feeding. However, adult diets are suspected to differ. Kerley and colleagues used DNA metabarcoding of feces of adult fl ightless dung beetles (Circellium bacchus), a supposed specialist on megaherbivore dung, to identify the source of dung on which the adults had fed. Rodent feces were most commonly fed on, and preferences among large herbivores are for cover-loving species, while dung of megaherbivores was avoided. The approach also allowed the detection of cryptic mammal species in the area. The differences in brood ball and adult feeding dung sources refl ect life history specific feeding abilities. Feeding on rodent feces is a hitherto unsuspected, but ecologically important, role for these dung beetles.
Photo credit: Graham Kerley.
Special Issue on “Honoring the Career of Professor James R. Ehleringer”. In this special issue seventeen papers are presented to reflect and honor the career of Professor James Ehleringer, who in addition to his many scientific accomplishments and discoveries, served as Editor-in-Chief for Oecologia for thirteen years. Shown in the cover photo is part of a population of Encelia farinosa taken near Oatman, Arizona in the Sonoran Desert. Professor Ehleringer, along with colleagues and students, has studied the population dynamics and ecophysiology of this unique desert shrub for nearly 40 years in deserts of the southwestern United States. The first paper of this issue describes the coupling of population dynamics in E. farinosa and two other species to prominent climate cycles in Pacific Ocean sea surface temperature, and the potential for desert topography to modify those dynamics.
Photo credit: James Ehleringer.
As other resident herbivores in the high Arctic, Arctic hare (shown in the picture) forage on the few plants that can be accessed through the snow-pack. However, despite the limitedavailability of plant forage, molecular and stable isotope analyses described by Schmidt et al. revealed limited dietary overlap amongst Arctic hare, muskox and rock ptarmigan. Hence, despite consuming the same plant species in the same snow-free patches, these three herbivore species consume diff erent parts of the plants and/or consume the plant species in diff erent proportions.
Photo credit: Niels Martin Schmidt.
Inga (Fabaceae), a speciose neotropical genus of trees, is attacked by a diversity of herbivores including this Automeris (Saturniidae) feeding on the underside of a young leaf. Years of research by Coley, Kursar and colleagues have provided key insights into how interspecifi c variation in anti-herbivore defenses may have evolved, how defenses shape host choice by herbivores and how they might regulate community composition and infl uence species radiations. In the review by Coley et al. they show that diverse defensive traits exhibit evolutionary lability, that interspecifi c diversity in secondary metabolites arose from novel combinations of common compounds, that divergence in defenses appears to be driven by herbivores, and that neighboring plants escape each other’s pests if their defenses diff er enough. Moreover, while related herbivores feed on hosts with similar defenses, there is a lack of congruence between herbivore and host phylogeny, suggesting evolutionary tracking, rather than coevolution.
Photo credit: Thomas A. Kursar.
Pileated woodpeckers are a successful suburban species that occupy large home ranges and defend territories by vocal and mechanical (drumming) means. In studying woodpecker use of suburbs around Seattle, WA, USA, Tomasevic and Marzluff unravel the relationship between home range and territory.Combining radiotelemetry, space use, and behavioral observations,the authors demonstrate that approximately a third of the home range is highly defended, that is defensive behaviors occurred more frequently there than did non defensive behaviors. Resources underlying such highly defended areas may be important to the persistence of organisms and, in the case of pileated woodpeckers, typically included locations of critical features, such as the nest and roost site.
Photo credit: John M. Marzluff
Do butterflies share their host plants or not? The question of whether endemic butterfly species distributed throughout Japan compete for the same host plants, or manage to create exclusive distributions so they do not overlap, is the topic of the paper by Nakadai et al. in this issue. The study demonstrates that indeed the butterflies are more likely to share their host plants, thus giving support to the idea that there is resource niche fi ltering in the overlapping distribution of these insects. The photo shows Luehdorfi a japonica (Papilionidae), one of the endemic butterfly species in Japan.
Photo credit: Koya Hashimoto.
In the Brazilian cerrado savanna, ant-treehopper associations frequently occur on inflorescences, but their effect on plant reproduction remains uncertain. Experimental manipulations by Ibarra-Isassi and Oliveira demonstrate that presence of treehoppers increases ant abundance on flowers and disrupts pollination, decreasing the frequency and duration of floral visits and ultimately reducing fruit and seed set. Treehopper herbivory has no direct effect on fruit or seed production. Experiments using dried ants pinned to inflorescences reveal that ant identity mediates flower visitation, with aggressive ants (Ectatomma brunneum) causing increased avoidance by floral visitors. These results highlight the importance of studying other interactions near flowers, in addition to just observing pollinators, for a proper understanding of plant reproduction. The main image shows an oil-collecting bee (Centrisvaria) approaching an inflorescence of Byrsonima intermedia occupied by ants attending honeydew-producing treehoppers (upper left). Oil glands at the calyx are shown on the image in the lower right corner.
Photo credit: J. Ibarra-Isassi and H. Soares Jr.
Monocultures and farmland biodiversity. From experiments in outside enclosures Tissier et al. report that sowing only one crop reduces invertebrate and plant species richness by up to 38% compared to sowing a mix of crops. It also strongly reduces the reproductive success of the critically endangered European hamster, by up to 82%, suggesting nutritional defi ciencies impairing reproduction.
Photo credit: Nicolas Busser, CNRS/IPHC.
Understanding the effects of habitat fragmentation on species diversity independent of the eff ects of habitat loss is challenging. In this issue, MacDonald et al. use butterfly assemblages on lake islands to decouple habitat fragmentation from habitat loss and test the habitat amount hypothesis, which negates direct effects of habitat fragmentation on species diversity. By differentiating between potentially reproducing and transient butterfly species on individual islands based on larval food plant occurrences, the study shows that inter-fragment movements of highly mobile species may inflate the observed diversity of small habitat fragments, obscuring important fragmentation eff ects on resident species diversity. Shown is an Atlantis fritillary (Speyeria atlantis), a highly mobile butterfly species that frequents the study area.
Photo credit: Zachary G. MacDonald.
An animal’s personality has been shown to influence its ability to learn. Individuals that explore their environment more actively under both benign and threatening conditions are thought to learn new tasks at a faster rate, yet at the cost of accuracy. Those animals tending to be more neophobic and inactive learn slower but make fewer mistakes and are more flexible in their learning style. In this issue, Chung et al. show that an individual’s personality does not always dictate cognitive ability highlighting the need to test these predictions across taxa. This image shows a delicate skink boldly assessing the level of threat imposed by the photographer.
Photo credit: Shannon Walsh.
Climate change is expected to cause widespread changes in tree communities in the vast Amazonian forests of South America. In this issue, Stropp et al. use historical herbarium specimens of six Amazonian tree species to assess whether changes in leaf morphology over the past 60 years coincide with meteorological trends. In some species, leaves showed a significant trend for smaller size after the mid-1970s as the Amazonian climate became drier. This correlation between climate and leaf size suggests that some Amazonian trees have the capacity to respond to reduced precipitation with morphological changes that may be adaptive for survival. The picture was taken in the Amazonian rainforestin Colombia.Photo credit: Grégoire Dubois.
Fruit-frugivore interactions are of major importance in a variety of ecosystems. In this issue, Guerra et al. built an ecological network linking individuals of Miconia irwinii to their avian seed dispersers. The study exemplifi es how individual-based networks linking plants to frugivores that diff er in their seed dispersal eff ectiveness can advance our understanding of intraspecifi c variation in the outcomes of fruit–frugivore interactions.The picture shows the “Campo Rupestre” vegetation at the study site in the Serra do Cipó region (Brazil).
Photo credit: Tadeu J. Guerra
Small, shallow lakes may have crystal clear water and dense growth of submerged macrophytes, notably charophytes as shown on this underwater photograph from a South Scandinavian lake. In this issue, Kragh et al., report extensive increases of oxygen, temperature, and pH values, and dramatic depletion of dissolved inorganic carbon and CO2 from the morning to the afternoon, which generated afternoon depression of primary production on virtually every day. Charophyte species appear to be particularly tolerant to anoxia and high sulfi de concentrations in the bottom waters during daytime stratifi cation in small lakes.
Photo credit: Theis Kragh.
Small carnivores are arguably under the greatest competitive pressure among all carnivores. In this issue, de Satgé et al. utilise camera-trap data to show that a guild of five African small carnivores – African wildcat Felis silvestris lybica (shown in the picture), grey mongoose Galerella pulverulenta, small-spotted genet Genetta genetta, striped polecat Ictonyx striatus, and yellow mongoose Cynictis penicillata– partition their activity along spatial, temporal and dietary axes, likely as a means to reduce their competitive interactions.
Photo credit: The Cape Leopard Trust.
Juvenile resources can crucially shape adult life-histories, often via alteration in body mass. In this issue, Rosa and Saastamoinen show that larval food stress induces diff erential responses between the sexes in the Glanville fritillary butterfly (Melitaea cinxia). In females larval food stress reduces body mass and subsequently impacts reproductive output, whereas in males body mass remains unaffected. In males territorial behavior is nevertheless affected by food stress, potentially reducing their reproductive output.
Photo credit: Elena Rosa.
The abundance of plants with crassulacean acid metabolism (CAM) is increasing worldwide. In this issue, Yu et al. show that under drought and saline conditions a facultative CAM species (Mesembryanthemum crystallinum) had a competitive advantage over grasses (Bromus mollis). In wet environments, M. crystallinum adapted to the moderate competition with Bromus mollis by switching from C3 photosynthesis to CAM photosynthesis. These results demonstrate the ability of facultative CAM plants to capitalize on their photosynthetic plasticity to cope with biological stress from competition with grasses. CAM plants, like Carnegiea gigantea shown in this picture, feature water storage, photosynthetic plasticity and a high water usage effi ciency, which can off er a competitive advantage under certain ecological conditions.
Photo credit: Kailiang Yu.
Stream features such as tree trunks and undercut banks provide habitat and protection for many species in freshwater streams but what do they do for returning adult salmon? In this issue, Andersson and Reynolds examine whether these features can provide refuge for spawning salmon from size-biased predation imposed by hunting bears. Streams with large amounts of wood and undercut banks limited size-selective predation pressure from bears, and streams with these features had larger salmon. Thus, habitat features can indirectly influence the body size of salmon by influencing size-selective predation pressure that salmon populations otherwise encounter. The photo shows an example of a tangled stream section in Hooknose Creek, on the central coast of British Columbia, Canada.
Photo credit: Aaron Gaffney.
Habitat diversity within agricultural landscapes can have direct and indirect eff ects on the reproductive success of birds. In this issue, Michel et al. show that the habitat configuration influences parental home-range dimensions and reproduction of little owls (Athene noctua). Experimental food supplementation improved nestling survival and condition. Paternal home-range size was positively correlated with nestling survival and negatively with condition at fl edging. This study shows how habitat characteristics influence individual behaviour, thereby determining spatial variation in reproductive performance. The photo shows a radio-tagged male little owl with the antenna sticking out of the plumage above the bird’s tail.
Photo credit: Silvio Bartholdi
As charismatic megafauna, nesting and foraging sea turtles are increasingly the focus of ecotourism activities. In this issue of Oecologia, Griffi n et al. quantify the behavioral responses of immature green turtles (Chelonia mydas) to disturbance by snorkelers and document a variation in personality types across individual turtles. This photo, taken at the study site Culebra Island, Puerto Rico, shows a turtle fl eeing after a snorkeler encounter.
Photo credit: Jacob W. Brownscombe
Classic hypotheses regarding the regulation of avian clutch size do not account for variation in nutrients among females at the end of egg laying, strong right truncations in clutch size distributions, or the fact that many species with precocial young are determinate layers. One solution is that there is a maximum clutch size, above which the number of fl edged young declines. In this issue, Sedinger et al. show through experimental manipulations that the most productive brood size in Black Brent (Branta bernicla nigricans) is larger than that typically produced. Therefore, reduced gosling survival in large broods is not by itself the sole mechanism limiting maximum clutch size in brent. The image shows a female brent and her gosling on the Tutakoke River Colony in western Alaska.
Photo credit: David Stimac
Using stable isotope composition in plant materials as indicators of palaeoclimate relies on a mechanistic understanding of the drivers of isotopic enrichments in leaf water and associated organic compounds. Munksgaard et al. assessed the isotopic compositions in eucalypt leaf and stem water and leaf cellulose across Australian aridity gradients, demonstrating that 18O enrichment in leaf water is determined by the leaf to air water vapour pressure diff erence, which is also a strong predictor of leaf cellulose O-isotope composition.
Photo credit: Ansgar Kahmen; Corymbia aparrerinja near Alice Springs.
Climate change enhances the effects of eutrophication and forces Lake Victoria cichlids to respond morphologically. In this issue, van Rijssel et al. report that during a period of severe eutrophication, reduced wind speeds coincided with low oxygen levels and an increased gill surface area of three cichlid species. The photo shows the research transect in the Mwanza Gulf of Lake Victoria which has been monitored by the Haplochromis Ecology Survey Team (HEST) since the 1970s.
Photo credit: Crista van Geest.
It is commonly assumed that whole-tree carbon gain is optimized when leaf photosynthetic capacity varies in proportion to vertical light gradients, yet observed photosyntheticprofi les do not follow this prediction. In this issue, Ambrose et al. show that this apparent discrepancy can be explained by increasing hydraulic constraints with height in giant sequoia trees in the Sierra Nevada Mountains of California. The study found that within-crown adjustments partially compensate for increasing hydraulic constraints, leading to the largest ever reported daily whole-tree water use rates, consistent with immense growth rates observed in these massive trees (pictured).
Photo credit: A.R. Ambrose.
The ability of plants to alter the life span and biochemical properties of their leaves in response to resource availability has been well documented and is the basis for theoretical predictions concerning the optimization of photosynthesis and carbon gain. Predictions of this theory have not been tested for non-vascular autotrophs such as macroalgae. In this issue of Oecologia, Rodriguez et al. show that the life span, size, thickness, pigment concentrations and photosynthetic performance of vegetative blades of the habitat forming marine alga Macrocystis pyrifera varied across a strong light gradient in a manner that was generally consistent with the prevailing theory of leaf life span in plants. Shown in the image is the apical meristem of the giant kelp M. pyrifera.
Photo credit: Ron H. McPeak.
Sea otter (Enhydra lutris) predation on herbivorous urchins in kelp forests is one of the classic examples of a top predator benefi tting a vegetated ecosystem through a trophic cascade. But what is the sea otter’s role in estuarine ecosystems? It has been documented that bloom-forming algae when stimulated by anthropogenic nutrient loading can drive the loss of important seagrass habitats. In this issue, Hughes et al. show how sea otters, through the consumption of crabs, can create a trophic cascade that influences the interaction between seagrass (Zostera marina) and bloom-forming green algae (Ulva spp.), which ultimately drives the resilience of seagrass.
Photo credit: Robert Scoles.
Plant species from the high Andes are able to survive very low temperatures, particularly under drought conditions, but this freezing tolerance could be affected by climate change. In this issue, Sierra-Almeida et al. show that warmer and moister growing seasons could threaten plant survival and persistence of alpine species in dry mountains. The image shows a close up of a Phacelia secunda (Boraginaceae) plant during a freezing temperature event in the central Chilean Andes.
Photo credit: Lohengrin A. Cavieres.
Invasive species can present new challenges to the ecological communities they invade. Can native species adapt to overcome these challenges? In this issue, Herr et al. show that native Eastern Fence Lizards cope with dangerously venomous invasive fire ants by consuming them. Both within the lifetime of individual lizards and across multiple generations, previous exposure to fire ants results in lizards that consume them at a greater rate than their fire ant naïve counterparts. This photo shows an Eastern Fence Lizard in the process of consuming its invasive prey.
Photo credit: Tracy Langkilde and Travis Robbins
Montane forests of southern Patagonia are one of the few natural landscapes of the world dominated by a single species, in this case Nothofagus pumilio (lenga). Lenga can flourish in a broad range of temperature and precipitation regimes and is often the dominant species along mountain slopes in the region. In this issue of Oecologia, Mathiasen and Premoli report on the evolutionary potential for adaptation of lenga at contrasting elevations of an altitudinal gradient. Using a reciprocal transplant experiment, the authors show that low-elevation plants outperform high-elevation plants even at high elevation, suggesting that under global warming scenarios the former may drive the high-elevation variants to local extinction. These results suggest that the upslope migration process may be led by low elevation trees, and not the upper treeline forests as previously thought. The photo shows both high- and low-elevation lenga trees growing near treeline at the Challhuaco Valley, Rio Negro, Argentina
Photo credit: Paula Mathiasen
Winter conditions are believed to play an important role in the population dynamics of northern temperate stream fi sh, challenging the ability of fi sh to physiologically and behaviourally adapt. In this issue, Watz et al. show that brown trout (Salmo trutta) that spent the winter under ice cover grew more and used a broader range of habitats than trout in uncovered stream sections. These results indicate that the presence of surface ice may function as overhead cover against terrestrial piscivores and improve the energetic status of stream fi sh during winter.
Photo credit: Johan Watz
Functional traits have been used to group ecologically similar species, but their potential goes far beyond: the Special Section of nine articles in this issue illustrates how functional traits are linked to species coexistence and to key ecological services and processes. Thus, trait-based ecology is becoming a powerful conceptual and operative tool. The photo shows a highly diverse shrub-perennial plant community developed on calcic gypsisols in central Spain where the functional structure of the community was controlled at fine scales by both biotic filtering and resource partitioning. The site was used by Chacon-Labella et al. for their study.
Photo credit: Julia Chacon-Labella
Coral reefs are some of the most productive and biodiverse ecosystems in the world, yet we still know little about the food web architecture maintaining these vital ecosystems. In this issue, McMahon et al. used a compound-specific stable isotope fingerprinting approach to quantify carbon fl ow from key baseline end members to coral reef fi shes in the Red Sea. The study suggests that the tremendous diversity in food web architecture on coral reefs likely plays a critical role in maintaining coral reef productivity and biodiversity.
Photo credit: Tane Sinclair-Taylor.
Climate change may be driving lizard population declines in tropical rainforests. In this issue, Brusch IV et al. uset hermal physiology metrics to make predictions about what lizard species may be at greatest risk. They show that habitat specialists may be most impacted by future warming. This photo shows a Jesus-Christ Lizard (Basiliscus plumifrons), a species from lowland tropical forests.
Photo credit: Ellen B. Sperr.
Peatlands dominated by peat mosses are important sinks of atmospheric carbon, but their role is potentially at stake as climate change promotes the encroachment of vascular plants. In this issue, Gavazov et al. demonstrate the competitive strategies for nutrient acquisition of dominant vascular plant species.Along an altitudinal gradient (in the photo the highest altitude peatland at 1885 m a.s.l.), foliar isotopic signatures of vascular plants reveal the intimate association of shrubs with their mycorrhizae and the intensified transfer of nitrogen via this symbiosis under warmer and drier climate.
Photo credit: Konstantin Gavazov
Galapagos sea lions (Zalophus wollebaeki) are endemic to the geographically small extend of the Galapagos Islands, yet recent work has shown genetic and morphological differences between sea lions from the western and the central archipelago. In this issue, Jeglinski et al. show that these differences align with differences in foraging habitat, diving behaviour and dietary composition, and already exist between juvenile sea lions from both regions that just started to forage independently. These results highlight a case of incipient ecological speciation in a highly mobile marine top predator and suggest a role of early learning in driving the ecological and ultimately genetic differences in the population.
How do plant water use strategies contribute to ecosystem scale drought eff ects? In this issue, Roman et al. develop a framework for classifying water use strategies and evaluate the impact of a severe drought on carbon cycling in the Morgan-Monroe State Forest in south-central Indiana (pictured). The study is based on a long term (1999–2013) eddy covariance record of carbon fluxes, and a 3 year (2011–2013) record of weekly leaf-level gas exchange and water potential measurements. Their results show that drought tolerant species, such as oaks (Quercus spp.), play a critical role in mitigating the impacts of drought on the forest carbon sink, which is of particular concern given that oaks are declining in many eastern US forests.
Photo credit: D. Tyler Roman
Predation by introduced mammals has driven declines of New Zealand forest birds. In this issue, Parlato et al. show that cavity nesting was the key trait associated with more extensive range contraction, suggesting that cavity nesting species are the most vulnerable to predation. This photo shows an adult kakapo (Strigops habroptilus) with two chicks. The kakapo is a critically endangered cavity-nesting species that has been completely extirpated from the New Zealand mainland.
Photo credit: Don Merton, Department of Conservation.
How are herbivorous insects able to subsist on a diet that is often rich in toxic chemical compounds? In this issue, Hammer and Bowers argue that symbioses with gut microorganisms may help insects overcome plant chemical defenses. Many bacteria and fungi in soil, leaves, and the mammalian gut can withstand and degrade plant toxins, but the importance of such microbial activity to the ecology and evolutionary diversification of insect herbivores is just beginning to be unveiled. Shown is the caterpillar Citheronia lobesis consuming Spondias mombin leaves, which contain a variety of secondary metabolites.
Photo credit: Tobin Hammer
The North Adriatic Karst is covered by species-rich grasslands, but land abandonment has resulted intheir replacement by woodlands. In this issue, Batalha et al. Show that grasslands and woodlands are assembled by different rules, with environmental filtering being the dominant force in the former and competitive exclusion becoming more important in the latter. Understanding community assembly rules in grasslands and woodlands could contribute to improve conservation efforts.
Photo credit: Mitja Kaligarič.
White-collared Manakins (Manacus candei) are tropical birds that feed almost exclusively on fruit in Young and mature forest. In this issue, Wolfe et al. show that dry El Niño events were associated with strikingly low manakin survival in young forests, while El Niño events had little effect on survival in mature forests. These results suggest that mature forests may serve as refugia for fruit-eating birds during periods of climatic instability.
Photo credit: Chris Jiménez.
Chemotactile spider cues alter food web structure and reduce local herbivory in the field. In this issue, Bucher et al. show that changes in insect communities due to the predation risk of nursery web spiders (Pisaura mirabilis) can reduce herbivory pressure on nettle plants (Urtica dioica), which in turn reduces leaf damage. These results suggest that non-consumptive effects can be very important within predator guilds.Photo credit: Roman Bucher.
This issue includes a special section of 11 articles on Individual-level niche specialization. The papers in this volume illustrate a growing body of literature that asks: what has been overlooked by focusing on population-level mean phenotypes in ecology, and how might ecological systems and evolutionary processes be better understood by explicit recognition of phenotypic variation among individuals? These studies suggest that population-level means may be more appropriately viewed as emergent properties than principal entities of interest. Rosenblatt et al. investigate the prevalence, causes, and consequence of individual-level niche specialization in foraging behaviors across different populations of American alligators (Alligator mississippiensis), the dominant aquatic apex predator across the southeast US, using stomach contents and stable isotope data.
Photo credit: Garrett Miller.
Coordinated approaches to global change research: This issue includes a Special Section of ten articles that highlight key requirements to advance integrated ecological research to study ecosystem responses to global changes. Such requirements include long-term studies, combinations of observational and experimental research, and reference to large-scale context. The photo shows Ramat Hanadiv Park in the coastal plane of Israel, with a patchwork of habitats and land-uses representing the complexity and diversity of the Mediterranean ecological reality. This is an extensively investigated research site, and It was the site of the Batsheva workshop that led to this special section.
Photo was taken by Albatross; email@example.com
Phenology and abundance influence species interactions. For amphibians and many other taxa, these factors are primarily investigated in experimental settings, leaving the applicability to natural populations unknown. In this issue, Anderson et al. (pp. 761–773) provide evidence from natural populations that both recruitment and demographic traits of two pondbreeding salamanders are correlated with complex intra-Zand interspecific processes. Important factors include the timing of breeding, the abundance of breeding adults, and metamorph survival and body size. Shown is an adult spotted salamander (Ambystoma maculatum), one of the species under investigation.
Photo credit: William E. Peterman.
Fruit secondary compounds protect fruits fromplant enemies, but how do they influence beneficial animals like seed dispersers? Studying bat-dispersed pepper plants (Piper spp.) in Costa Rica, Baldwin and Whitehead (pp., 453–466) showed that amides, a nitrogen-based class of compounds that are typical to many tropical pepper plants, decreased the retention times of seeds in the guts of the main bat disperser, Seba’s Shorttailed Fruit Bat (Carollia perspicillata). Their results suggest that fruit secondary compounds not only defend fruits against pests, but can also mediate seed disperser physiology and patterns of dispersal in tropical forests.
Photo credit: Susan Whitehead.
Nitrogen Deposition Reassessed. This special feature includes six articles that focus on the effects of chronic atmospheric N deposition in contrasting ecosystem types ranging from acidic grasslands in Europe, boreal forests in Canada, alpine grasslands in China, to temperate forests in the Midwest and Northeastern USA. The articles deal specifically with two distinct topics: the effects of N deposition on species composition; and the responses of pools and fluxes of N. The photo shows one of the atmospheric deposition collectors at the Tirasse site about 120 km north of Saint-Félicien, Quebec, Canada.
Image courtesy of Charles Marty.
Cover illustration Is the fate of North American ash sealed? The emerald ash borer (EAB, shown in the pictures at the adult and larval stages) continues to spread and kill ash trees through larval feeding on the inner bark. However, Whitehill et al. (pp. 1047–1059) show that application of the phytohormone methyl jasmonate (MeJA) reduces EAB attack rates while inducing accumulation of a phenolic compound, verbascoside, in the inner bark. Furthermore, when supplied at MeJA-induced levels in artificial diet, verbascoside decreased growth, development, and survival of EAB larvae. This suggests that exploitation of MeJA based defences could conceivably become part of future integrated management strategies for this pest.
Special Issue on “Ecophysiological effects of predation risk: an integration across disciplines”. The threat of predation has wide-spread consequences for prey behavior, morphology and development which must be generated by changes in prey physiology. However, the physiological mechanisms that underlie the costs and benefits of responding to predators have not been well studied. In this issue, 8 articles consider the effects of predation risk on prey digestive physiology, thermal ecology and neurobiology at the scale of individual hormonal pathways to ecosystem effects. Shown in the photo is a Colorado potato beetle being attacked by a predaceous stink bug.
Photo credit: Ellen Woods.
Impacts of secondary succession on ecosystem fluxes. In this issue of Oecologia, Scartazza et al. show that the transition from the herbaceous vegetation of abandoned agricultural land to the Mediterranean shrub vegetation is associated with increased ecosystem water use efficiency at the beginning of the dry season, which might eventually translate into increased ecosystem carbon sequestration. Shown here is a false color aerial image of the Island of Pianosa in the Northern Tyrrhenian Sea (Italy), where the study was carried out, along with a sunset view of one of the flux towers used to measure biogeochemical cycling and water use.
Photo by: Franco Miglietta.
Massive expansion of Lupinus nootkatensis in Iceland. Cold high elevation and high latitude ecosystems are known for their slow nitrogen cycle and highly adapted biota. Widespread invasions by symbiotic N2 fixing species of the genus Lupinus and Alnus are currently putting this biota at risk. In this issue, Hiltbrunner et al. summarize the evidence demonstrating that increased nitrogen input by such taxa reduces biodiversity, acidifies soils, enriches groundwater and runoff with nitrate, and augments the emissions of N2O (a potent greenhouse gas).
Photo by: Christian Körner.
Why have plants evolved the ability to detect sound and vibration? In this issue, Appel and Cocroft (pp. 1257–1266) show that feeding by caterpillars (Pieris rapae) produces distinctive vibrations that propagate rapidly through the stems and leaves of Arabidopsis plants. Exposing plants to feeding vibrations in the absence of other herbivore cues caused the plants to produce more chemical defenses when later attacked by caterpillars. Defenses were primed by feeding vibrations, but not by vibrations from wind or insect song. This study shows for the first time that plants can mount a selective and ecologically meaningful response to an acoustic cue relevant to their fitness.
Photo by: Carlos F. Pinto.
Stressed by crowding? In this issue, Viblanc et al. (pages 763–772) show how the spatial location of breeding territories can affect the stress levels of colonial seabirds. In breeding king penguins, their results reveal that spatial variation in social density, rather than weather conditions or predation risk, has strong effects on the baseline stress hormones of those animals. Both during incubation and chick-rearing, crowded penguins indeed appear to have higher stress levels than their less-crowded conspecifics.
How do nitrogen and phosphorus interact to influence primary productivity? On pages 667– 676 of this issue, Perini and Bracken demonstrate through observation and experimentation that the availability of nitrogen can limit the uptake and storage of phosphorus in an important intertidal foundation species, the seaweed Fucus vesiculosus. On the wave swept rocky shores pictured here (East Point, Nahant, MA, USA), nitrogen availability varies throughout the year. As nitrogen levels fluctuate and phosphorus levels remain constant, seaweeds take up and store phosphorus only when adequate nitrogen is available, providing evidence of an intrinsic linkage between these essential nutrients in the cellular machinery of primary producers.
Photo by: Christopher Marks.
Can plants, like animals, learn and remember? On pages 63–72, Gagliano et al. address this question and demonstrate experimentally that the sensitive plant Mimosa is capable of learning in a matter of seconds and most remarkably, remembering what has been learned for several weeks. In an animal-like fashion, this plant is able to learn through direct experience, yet it does it all without a brain. Shown in the photo Mimosa pudica plants.
Photo by Monica Gagliano.
Seasonality and life history: On pages 1197–1204 Cox and Cresswell demonstrate that across 40 savannah species, the body mass gained during breeding positively correlates with adult survival and is a reflection of seasonal variation in food availability. A species that occupies a highly seasonal foraging niche such as this red-cheeked cordonbleu (Uraeginthus bengalus) will have a superabundance of food available during breeding and so will store fewer body reserves. They are thus able to raise more chicks, but at a cost to their own survival.
Photo by Martin Stervander.
Can small grazers damage large, fast growing kelps? In this issue, Poore et al. (pages 789-801) demonstrate that low levels of consumption by grazing crustaceans can result in unexpectedly large reductions in the growth of intertidal kelps due to the selective removal of photosynthetically active tissues. Clockwise from top left: blades and pneumatocysts of Macrocystispyrifera; the grazing isopod Amphoroidea typa; grazing damage by A. typa to a blade of Lessoniaspicata; beds of L. spicata in the rocky intertidal of northern-central Chile.
Photos by Ivan Hinojosa Toledo and Alistair Poore.
Photosynthesis in the shadow of giants. Coastal California redwood trees are the tallest trees in the world. Consequently the shade cast by redwood trees is severe, producing low light conditions for understory plants. Yet, most of the plant diversity in California redwood forests consists of tiny understory herbs growing under the redwood monocanopy. On pages 351 - 363 of this issue, Santiago and Dawson explain how plant use of water and nitrogen deposited by coastal summer fog contribute to utilization of fluctuating light in the deep forest. Shown here is Oxalis oregana catching an early morning sun fleck of light in the dappled light of the redwood forest understory.
Photo by: Louis S. Santiago.
An insectivorous bat switches to nectar diet. Although many animals change their diets with the seasons, supplementing insectivorous diets with nectar and fruit is extraordinarily rare in bats, the second largest order of mammals. In this issue, Frick et al. (pp 55-65) use stable isotopes to demonstrate strong seasonal reliance on cactus nectar by the insectivorous pallid bat (Antrozous pallidus) in desert habitats of Baja California Sur, Mexico. Pallid bats switch from a diet indistinguishable from other sympatric insectivorous bat species in winter, when no cactus nectar is available, to a diet intermediate between insectivorous and nectarivorous bats during the spring bloom of a bat-adapted cactus. The study establishes the first known plant-pollinator mutualism between a plant and a temperate bat.
Photo credit: Merlin Tuttle
Hunting under predation risk. On pages 1227-1235 of this issue, Haapakoski et al. report results from an experimental outdoor study on weasel predation on voles in fragmented landscapes. Hunting efficiency by small mammals should decrease in fragmented habitats due to small predator's own risks of avian predation in the open matrix area. As predicted, weasels killed more voles in the non-fragmented habitat which provided cover from raptors and owls during prey search.Shown here is the small snake-like mammalian predator, the least weasel (Mustela nivalis nivalis), in its summer habitat in central Finland.
Photo by: Marko Haapakoski
What animals do during metamorphosis matters. For frogs, the awkward stage between forlimb emergence and tail resorption has long been recognized as a high-risk period, yet we know little of how risk changes with the move from water to land, or if metamorphs compensate behaviorally for their morphological handicaps. In this issue, Touchon et al. (pages 801-811) show that risk of mortality for red-eyed treefrogs in the water with predatory bugs rises sharply with forelimb emergence. Metamorphs reduce activity in response to bug cues, but this is insufficient to protect them. Long-tailed metamorphs can substantially improve their survival prospects by climbing onto land to face spiders instead. Once in air, metamorphs become even less active, as they need not move to breathe. This inactivity reduces attack rates, more than compensating for their poor escape ability. Depending on predator cues, red-eyed treefrogs emerge from ponds with short or long tails; shown is a long-tailed metamorph recently emerged from a pond in Gamboa, Panama.
Photo by: Randall Jiménez
Should we stay or should we go? On pages 409-420 of this issue of Oecologia, van Beest et al. report that predation risk by wolfes and forage abundance are important scale-dependent determinants of temporal variation in site fidelity of non-migratory female elk and that their combined effect is most apparent at short temporal scales. Shown in the photo is a group of vigilant female elk in Riding Mountain National Park (MB, Canada), a long-established elk-wolf system, where the study was carried out.
Photo by Ryan K. Brook
Regulation of indirect defenses (extrafloral nectaries, EFNs) under competition. Plants often balance resource allocation between competition and defense, but the underlying mechanisms are unclear. On pages 213/221 of this issue, Izaguirre et al. demonstrate that the activity of EFNs in passionfruit (Passiflora edulis) is induced by simulated herbivory and jasmonate treatment, and strongly suppressed by a low ratio of Red to Far-Red radiation (R:FR), which is a key signal of competition in plant canopies. Strikingly, EFN responses to herbivory and light quality were restricted to the branches that received the treatments. These results demonstrate that the R:FR ratio is an important regulator of indirect defenses, which helps the plant to concentrate defense resources on those branches that are less likely to be shaded by competitors. Clockwise from top right: P. edulis flower; EFNs located in the petioles; EFNs located in the abaxial side of the sepals; close-up of a petiolar EFN visited by Argentine ants.
Photos by: Miriam M. Izaguirre.
Benevolent mistletoes dispersers? Representatives from six of the eight lineages considered mistletoe-specialist frugivores, clockwise from top left: Tyrannulus elatus, Tyrannidae (Roger Ahlman), Euphonia violacea, Fringillidae (Dario Sanches); Phainopepla nitens, Ptilogonatidae (Elaine R Wilson); Pogoniulus bilineatus, Lybiidae (Krzysztof Blachowiak); Grantiella picta, Meliphagidae (Chris Tzaros); Dicaeum hirundinaceum, Nectariniidae (Peter Menkhorst). Rather than coevolved dispersers, Watson and Rawsthorne (DOI 10.1007/s00442-013-2693-9) suggest that these specialists may be better considered exploitative, intensifying existing infections into more concentrated, reliable, and defendable resources.
Interplant communication: Damage to the leaves of a willow can decrease herbivory experienced by its close neighbors. On pages 869-875 of this issue of Oecologia (10.1007/s00442-013-2610-2), Pearse et al. report strong evidence for the importance of interplant volatile cues in mediating herbivore interactions with willows. Shown in the photo are willow bushes following a riparian corridor in the Sierra Nevada Mountains (CA, USA).
Photo by Kaori Shiojiri.
Getting ready for a date: A male orchid bee (Euglossa viridissima) collecting perfumes for his courtship display (in this case, p-dimethoxybenzene from a treated log). On pages 417-425 of this issue of Oecologia (10.1007/s00442-013-2620-0), Pokorny et al. investigate how these insects collect fragrant substances from environmental sources and balance the perfume composition in the face of seasonal, local, and habitat-dependent variations in compound availability.
Photo by Tamara Pokorny.
Indirect biotic interactions under water: A perch (Perca fluviatilis) in a lake near Uppsala, Sweden feeding among zebra mussels attached on the underside of a foot bridge. On pages 245-256 of this issue of Oecologia (10.1007/s00442-013-2611-1), Hirsch et al. investigate how the presence of invasive zebra mussels in Swedish lakes can indirectly trigger phenotypic changes in a native fish by altering the availability of pelagic and benthic food resources.
Photo by Philipp Hirsch and Katharina Büchel.
Ecosystem ecology: Terrestrial subsidies have important impacts on biogeochemistry and nutrient cycling in river and lake ecosystems. Lake Meliquina surrounded by temperate forests in Patagonia, Argentina.
Photo by: Amy T. Austin.
Studying the ecological impacts of increased atmospheric CO2. The image shows CO2 tanks used for the alpine treeline FACE experiment in Stillberg (Switzerland) after a summertimesnow event.
Photo by: Frank Hagedorn.
Seed dispersal by frugivorous birds is the basis for regeneration of fleshy-fruited plants in numerous ecosystems. A fieldfare (Turdus pilaris) feeds upon fruits of hawthorn (Crataegus spp.)."
Photo: © by S. Rösner | pixeldiversity.com
Plant-insect interactions. A larva of the Passiflora specialist insect, Agraulis vanillae (Gulf fritillary), chewing a branch of "mburucuyá" (Passionflower, Passiflora caerulea).
Photo by: Carlos L. Ballaré.