Threshold management in a coupled economic–ecological system

Economic analysis of optimal ecosystem management in the presence of a threshold has typically ignored the potential for induced behavioral responses. This paper contributes to the literature on non-convex ecosystem management by considering the implications of a particular behavioral response in a regional economy – that of amenity-led growth – to changes in ecosystem services generated by a lake ecosystem subject to a eutrophication threshold. The essential policy challenge is to achieve optimal levels of lake nutrients and urbanization given that improvements to water quality will induce additional migration and urbanization in the region with attendant ecological impacts. We show that policies that ignore the recursive relationship between urbanization and water quality unintentionally exacerbate boom-bust cycles of regional growth and decline and risk pushing the system towards long-run economic decline. In contrast, the optimal policy accounts for the behavioral feedbacks to improved ecosystem services, and balances regional growth and ecological degradation.     

Biogeochemical transfer and dynamics of iodine in a soil–plant system

Radioactive iodide (¹²⁵I) is used as a tracer to investigate the fate and transport of iodine in soil under various leaching conditions as well as the dynamic transfer in a soil–plant (Chinese cabbage) system. Results show that both soils (the paddy soil and the sandy soil) exhibit strong retention capability, with the paddy soil being slightly stronger. Most iodine is retained by soils, especially in the top 10 cm, and the highest concentration occurs at the top most section of the soil columns. Leaching with 1–2 pore volume water does not change this pattern of vertical distributions. Early breakthrough and long tailing are two features observed in the leaching experiments. Because of the relatively low peak concentration, the early breakthrough is really not an environmental concern of contamination to groundwater. The long tailing implies that the retained iodine is undergoing slow but steady release and the soils can provide a low but stable level of mobile iodine after a short period. The enrichment factors of ¹²⁵I in different plant tissues are ranked as: root > stem > petiole > leaf, and the ¹²⁵I distribution in the young leaves is obviously higher than that in the old ones. The concentrations of ¹²⁵I in soil and Chinese cabbage can be simulated with a dual-chamber model very well. The biogeochemical behaviors of iodine in the soil-cabbage system show that cultivating iodized cabbage is an environmentally friendly and effective technique to eliminate iodine deficiency disorders (IDD). Planting vegetables such as cabbage on the ¹²⁹I-contaminated soil could be a good remediation technique worthy of consideration.     

The spider and fly revisited: ploy–counterploy behavior in a unique predator–prey system

Earlier studies have shown that the sarcophagid fly Arachnidomyia lindae is the principal egg-sac predator of the colonial orb-weaving spider Metepeira incrassata, and that risk of egg-sac loss increases with group size. Observations of specialized behaviors for attack (flies) and defense (spiders) suggest that this predator-prey relationship may incorporate elements of ploy and counterploy behavior. Here we explore this relationship in detail and test hypotheses regarding efficacy of attack and defense behaviors. Egg-sac guarding by the spider includes defensive behaviors specific to this fly predator, which were observed during experimental "attacks" with tethered A. lindae, but not with similar presentations of non-predatory Musca domestica. Experimental studies also show that Metepeira incrassata recognizes this predatory fly by airborne cues (i.e., the signature frequency of wing-beats), and can distinguish between this predator and other flies (potential prey) on the basis of wing-beat frequency differences. Removal of female spiders results in a significantly higher probability of unguarded egg-sacs being parasitized, demonstrating the adaptive value of spider defensive behaviors. We also present evidence that A. lindae utilizes a behavioral ploy for circumventing spider guarding behavior (aggressive mimicry - producing vibrations of captured prey in the web), and that Metepeira incrassata, in turn, exhibits a counter-ploy behavior (signal thread cutting) to eliminate this potentially distracting vibratory information. While previous studies have shown that this colonial web-building spider uses a number of general attack-abatement mechanisms against a diversity of predators and parasitoids, results of this study suggest that selection pressures from a highly specialized predator may also result in evolution of predator-specific prey responses.     

Turning the game around: toxicity in a nudibranch-sponge predator–prey association

Escalation theory proposes enemy-related selection as the most relevant factor of natural selection among individual organisms. When hazardous to predators, prey might be considered enemies that influence predator evolution. Opisthobranch molluscs that prey on chemically defended prey are an interesting study case on this subject. Predation on chemically defended species paved the way for opisthobranchs to enter in an arms race, developing means to detoxify and/or excrete harmful compounds, which led to the sequestration of those compounds and their self-defensive use, an escalation of defenses. Here we aim to understand whether the opisthobranch predator is better protected than its chemically defended prey, using as predator–prey model, a nudibranch (Hypselodoris cantabrica) and the sponge it preys upon (Dysidea fragilis), and from which it obtains deterrent chemical compounds. Specimens of both species were collected on the Portuguese coast, and their crude extracts were analyzed and used in palatability tests. Nudibranchs revealed a higher natural concentration of crude extract, probably due to a progressive accumulation of the compounds. Both predator and prey extracts revealed similar mixtures of deterrent metabolites (furanosesquiterpenes). Palatability tests revealed a more effective deterrence in the nudibranch extracts because significant rejection rates were observed at lower concentrations than those necessary for the sponge extracts to have the same effect. We concluded that the predator is chemically better protected than its prey, which suggests that its acquisition of chemical defenses reveals a defensive escalation.     

The benefit of obligate versus facultative strategies in a shrimp–goby mutualism

Obligate mutualists are predicted to benefit more from mutualism than facultative mutualists and harbor traits that help derive this extra benefit. I tested these predictions with a shrimp–goby mutualism. Individual shrimp (Alpheus floridanus) construct burrows that are shared with individual gobiid fishes that warn shrimp when emergence from burrows is unsafe. The benefit to gobies is refuge from predation. I compared predator avoidance performance of obligate (Nes longus) and facultative (Ctenogobius saepepallens) shrimp-associated gobies with access to a shell, a shrimp burrow, or no shelter. The two gobies performed similarly with shells and no shelter, but N. longus outperformed C. saepepallens with shrimp burrows. Thus, N. longus benefits more from mutualism than C. saepepallens. Also, N. longus has four behavioral traits that likely allow it to benefit from mutualism more than does C. saepepallens: (1) diving into the nearest shrimp burrow when confronted with predators, (2) long flight initiation distance, (3) long time-until-re-emergence after taking refuge, and (4) remaining close to shelter. The latter three likely come with a cost to foraging or mate acquisition as they limit searching range outside the burrow and detract from time spent outside burrows. Thus, N. longus likely harbors traits that allow it to deal with these costs. I discuss a framework for determining whether traits crucial to obligate association with shrimp (both for reaping benefits and dealing with costs) are pre-adaptations or are created through coevolution with shrimp.     

Sensitivity of a coupled physical–biological model to turbulence: high-frequency simulations in a northern Adriatic station

This paper investigates the impacts of different turbulence models on the biological state at an ocean station in the northern Adriatic sea, named S3, comparing them with other uncertainties inherent to coupled physical–biological simulations. The numerical tool is a 1-D model resulting from the coupling of two advanced numerical models. The hydrodynamic part is modelled using the General Ocean Turbulence Model (www.gotm.net), in a version adopting state-of-the-art second-moment Turbulence Closure Models (TCMs). Marine biogeochemistry is parameterized with the Biogeochemical Flux Model (http://www.bo.ingv.it/bfm), which is a direct descendant of ERSEM (European Regional Sea Ecosystem Model). Results, obtained by forcing the model with hourly wind and solar radiation data and assimilating salinity casts, are compared against monthly observations made at the station during 2000–2001. Provided that modern second-moment TCMs are employed, the comparisons indicate that both the physical and the biological dynamics are relatively insensitive to the choice of the particular scheme adopted, suggesting that TCMs have finally ‘converged’ in recent years. As a further example, the choice of the nutrient boundary conditions has an impact on the system evolution that is more significant than the choice of the specific TCM, therefore representing a possible limitation of the 1-D model applied to stations located in a Region of Freshwater Influence. The 1-D model simulates the onset and intensity of the spring–summer bloom quite well, although the duration of the bloom is not as prolonged as in the data. Since local dynamics appears unable to sustain the bloom conditions well into summer, phytoplankton at the station was most likely influenced by river input or advection processes, an aspect that was not found when the S3 behaviour was adequately modelled using climatological forcings. When the focus is in predicting high-frequency dynamics, it is more likely that lateral advection cannot be neglected. While the physical state can be satisfactorily estimated at these short time scales, the accurate estimation of the biological state in coastal regions still appears as rather elusive.     

Same-sex pair-bonds are equivalent to male–female bonds in a life-long socially monogamous songbird

Same-sex sexual behaviors are well documented in both captive and wild animals. In monogamous species, these behaviors are often exclusive, each individual having only one same-sex partner. A bias in sex ratio has been proposed as a social context yielding same-sex pair-bonding, but this hypothesis has rarely been tested. Focusing on a life-long pair-bonding songbird, the zebra finch Taeniopygia guttata, we tested whether same-sex pairing results from a shortage of individuals of the opposite sex. By experimentally skewing the sex ratio towards members of one sex, we observed a greater proportion of same-sex pair-bonds of that sex. Moreover, we assessed whether the quality and stability of social interactions were equivalent in same-sex and male–female pairs. Male–male and female–female same-sex bonds display the same behavioral characteristics as male–female ones: they are intense, highly selective, and stable affinitive relationships involving the same behavioral displays already described in wild birds. Moreover, same-sex male bonds were sufficiently strong not to split up when individuals were given the opportunity to reproduce with females. Because the pair-bond in socially monogamous species represents a partnership that may give advantages for survival (e.g., resources defense, fighting against predators, etc.), we propose that same-sex pairing in the zebra finch may result from the pressure to find a social partner.     

Testing a stochastic version of the Beddington–DeAngelis functional response in foraging shore crabs

Current behaviour-based interference models assume that the predator population is infinitely large and that interference is weak. While the realism of the first assumption is questionable, the second assumption conflicts with the purpose of interference models. Here, we tested a recently developed stochastic version of the Beddington–DeAngelis functional response—which applies to a finite predator population without assuming weak interference—against experimental data of shore crabs (Carcinus maenas) foraging on mussels (Mytilus edulis). We present an approximate maximum likelihood procedure for parameter estimation when only one focal individual is observed, and introduce ‘correction factors’ that capture the average behaviour of the competing but unobserved individuals. We used the method to estimate shore crab handling time, interaction time, and searching rates for prey and competitor. Especially the searching rates were sensitive to variation in prey and competitor density. Incorporating constant parameter values in the model and comparing observed and predicted feeding rates revealed that the predictive power of the model is high. Our stochastic version of the Beddington–DeAngelis model better reflects reality than current interference models and is also amenable for modelling effects of interference on predator distributions.     

Chelipeds are the real weapon: cheliped size is a more effective determinant than body size in male–male competition for mates in a hermit crab

To understand the evolution of weapons, we must understand both their functions and relative importance compared to body size in determining fighting success. Many decapod crustaceans develop disproportionately large chelipeds for their body size and use them as a weapon in agonistic interaction. There are, however, examples where weapons are merely signals of resource holding potential (RHP) and the RHP is actually determined by body size. We investigated the function and relative efficacy of body size and major cheliped size in male–male contests for females in the hermit crab Diogenes nitidimanus. Contests over females took two forms: (1) males preemptively guarded females and opponents did not fight with the guarding male. Cheliped size contributed significantly to the settlement of these contests and probably functioned as a visual signal for the opponents. (2) Guarding males engaged in physical combat with an opponent. In these cases, both body and cheliped sizes affected contest outcomes. The effect size for cheliped size was as strong, or stronger, than that for body size. These results suggest that large chelipeds have evolved as a true weapon and are effective in escalated fights for resources. Therefore they are also efficient visual signals for settling contests with only display. Our results are a rare example that clearly demonstrate that weapons are a more important determinant of fights than body size when both body and weapon size affect resource acquisition.     

The influence of symbiont type on photosynthetic carbon flux in a model cnidarian–dinoflagellate symbiosis

We measured the relationship between symbiont diversity, nutritional potential, and symbiotic success in the cnidarian–dinoflagellate symbiosis, by infecting aposymbiotic (i.e. symbiont-free) specimens of the model sea anemone Aiptasia sp. with a range of Symbiodinium types. Four cultured heterologous Symbiodinium types (i.e. originally isolated from other host species) were used, plus both cultured and freshly isolated homologous zooxanthellae (i.e. from Aiptasia sp.). Rates of photosynthesis, respiration, and symbiont growth were measured during symbiosis establishment and used to estimate the contribution of the zooxanthellae to the animal’s respiratory carbon demands (CZAR). Anemones containing Symbiodinium B1 (both homologous and heterologous) tended to attain higher CZAR values and hence benefit most from their symbiotic partners. This was despite Symbiodinium B1 not achieving the highest cell densities, though it did grow more quickly during the earliest stages of the infection process. Rather, the heterologous Symbiodinium types A1.4, E2, and F5.1 attained the highest densities, with populations of E2 and F5.1 also exhibiting the highest photosynthetic rates. This apparent success was countered, however, by very high rates of symbiosis respiration that ultimately resulted in lower CZAR values. This study highlights the impact of symbiont type on the functionality and autotrophic potential of the symbiosis. Most interestingly, it suggests that certain heterologous symbionts may behave opportunistically, proliferating rapidly but in a manner that is energetically costly to the host. Such negative host–symbiont interactions may contribute to the host–symbiont specificity seen in cnidarian–dinoflagellate symbioses and potentially limit the potential for partner switching as an adaptive mechanism.     

Effects of small-scale habitat fragmentation on predator–prey interactions in a temperate sea grass system

During the last decades, fragmentation has become an important issue in ecological research. Habitat fragmentation operates on spatial scales ranging over several magnitudes from patches to landscapes. We focus on small-scale fragmentation effects relevant to animal foraging decision making that could ultimately generate distribution patterns. In a controlled experimental environment, we tested small-scale fragmentation effects in artificial sea grass on the feeding behaviour of juvenile cod (Gadus morhua). Moreover, we examined the influence of fragmentation on the distribution of one of the juvenile cod’s main prey resources, the grass shrimp (Palaemon elegans), in association with three levels of risk provided by cod (no cod, cod chemical cues and actively foraging cod). Time spent by cod within sea grass was lower in fragmented landscapes, but total shrimp consumption was not affected. Shrimp utilised vegetation to a greater extent in fragmented treatments in combination with active predation. We suggest that shrimp choose between sand and vegetation habitats to minimize risk of predation according to cod habitat-specific foraging capacities, while cod aim to maximize prey-dependent foraging rates, generating a habitat-choice game between predator and prey. Moreover, aggregating behaviour in grass shrimp was only found in treatments with active predation. Hence, we argue that both aggregation and vegetation use are anti-predator defence strategies applied by shrimp. We therefore stress the importance of considering small-scale behavioural mechanisms when evaluating consequences from habitat fragmentation on trophic processes in coastal environments.     

Trends in precipitation chemistry in Alaska, 1980–1998

Nineteen years (1980–1998) of precipitation chemistry data from a site in Alaska are examined for trends using a least squares general linear model. The annual concentrations of SO^2– ₄ show a significant decreasing trend at 0.001 level and the annual change in concentration is —0.012mg 1^–1 yr^–1. The annual concentrations of NO ^– ₃ show an increasing tendency non‐significant. The annual base cation concentrations show a clear significant decreasing trend at 0.001 level and the decrease is —0.009mg 1^–1 yr^–1. Ca²⁺ concentrations exhibit a significant decreasing trend at 0.001 level and the annual change of concentration is —0.003 mg 1^–1 yr^–1. Mg²⁺ and Na⁺ concentrations show a significant decreasing trend at 0.01 level and the annual change is —0.001 mg1^–1 yr^–1 for Mg²⁺ and —0.004 mg1^–1 yr^–1 for Na⁺. K⁺ concentrations are characterised by a decreasing trend, significant at 0.05 level. K⁺ concentrations have decreased —0.002mg1^–1 yr^–1. The strongest rates of concentration decline for base cations, Ca²⁺, Mg²⁺, K⁺ and Na⁺ occurred in fall and winter season. The annual values of pH show a decreasing trend non‐significant. The values of pH oscillate between 5.1 and 5.6 during the period considered.     

Kelvin–Helmholtz Instability as a Boundary-Value Problem

The Kelvin–Helmholtz (KH) instability is traditionally viewed as an initial-value problem, wherein wave perturbations of a two-layer shear flow grow over time into billows and eventually generate vertical mixing. Yet, the instability can also be viewed as a boundary-value problem. In such a framework, there exists an upstream condition where a lighter fluid flows over a denser fluid, wave perturbations grow downstream to eventually overturn some distance away from the point of origin. As the reverse of the traditional problem, this flow is periodic in time and exhibits instability in space. A natural application is the mixing of a warmer river emptying into a colder lake or reservoir, or the salt-wedge estuary. This study of the KH instability from the perspective of a boundary-value problem is divided into two parts. Firstly, the instability theory is conducted with a real frequency and complex horizontal wavenumber, and the main result is that the critical wavelength at the instability threshold is longer in the boundary-value than in the initial-value situation. Secondly, mass, momentum and energy budgets are performed between the upstream, unmixed state on one side, and the downstream, mixed state on the other, to determine under which condition mixing is energetically possible. Cases with a rigid lid and free surface are treated separately. And, although the algebra is somewhat complicated, both end results are identical to the criterion for complete mixing in the initial-value problem.     

Fast dispersive liquid–liquid microextraction of pesticides in water based on a thermo-switchable deep eutectic solvent

Environmental Chemistry Letters - Accurate measurements of pesticide levels in the environment are necessary to set policies, yet actual analytical methods are limited by the use of toxic solvents...     

Quantifying plant pigments and live diatoms in aphotic sediments of Scandinavian coastal waters confirms a major route in the pelagic–benthic coupling

The fate of pelagic diatoms in marine coastal aphotic sediments was investigated from sediment profiles in western Scandinavian waters. We used three independent methods to estimate pigment pools in the sediment: (1) fluorometry, (2) high-performance liquid chromatography and (3) pigments estimated from germinable diatom cells, using the dilution extinction method. A strong positive relationship with an intercept close to zero was observed between fucoxanthin, a marker of diatoms, and chlorophyll a. The fucoxanthin/chl a ratio was on average 1.05, which was similar to monocultures of dominating diatom taxa, indicating that sedimentary chl a was to a large extent of diatom origin. Chl a and fucoxanthin correlated significantly and positively with, and where within the same order of magnitude as, corresponding substances predicted from live diatom cell numbers obtained with the dilution extinction method. This indicates that a major part of surficial sediment chl a was bound in live cells of pelagic diatoms. There was a consistent change in viable cells with sediment depth and with timing of dominating taxa, with the non-spore-forming Skeletonema costatum dominating in the surface sediment in March and May, while the spore forming Chaetoceros spp. dominated deep in the sediment and during periods outside of the spring bloom (February and August). This indicates that chl a is bound in several different cell pools with different degradation rates, depending on diatom taxonomy. Thus, diatoms originating predominantly from the spring bloom may provide an important direct link in the pelagic–benthic coupling in this area.     

Numerical study of wave–current–vegetation interaction in coastal waters

Research on interactions among wave, current, and vegetation has received increasing attention. An explicit depth-averaged hydrodynamic model coupled with a wave spectral model (CMS-wave) was proposed in this study in order to simulate the wave and wave-induced current in coastal waters. The hydrodynamic model was based on the finite volume method while the intercell flux was computed by employing the Harten–Lax–van Leer approximate Riemann solver to investigate the dry-to-wet interface, and the drag force of vegetation was modeled as the sink terms in the momentum equations. The CMS-wave model was used to investigate the non-breaking and the breaking random waves propagation in vegetation fields. Afterwards, an empirical wave energy dissipation term with plant effect was derived to represent the resistance induced by aquatic vegetation in the wave-action balance equation. The established model was calibrated and validated with both the experimental and field data. The results showed that the wave height decreased significantly along the wave propagation direction in the presence of vegetations. The sensitivity analysis for the plant density, the wave height, and the water depth were performed by comparing the numerical results for the wave height attenuation. In addition, wave and wave-induced current through a finite patch of vegetation in the surf zone were investigated as well. The strong radiation stress gradient could be produced due to the variation of the energy dissipation by vegetation effect in the nearshore zone, which impacted the direction and amplitude of the longshore current. The calculated results showed that the coupling model had good performance in predicting wave propagation and the current over vegetated water regions.     

An investigation into the occurrence and distribution of polycyclic aromatic hydrocarbons in two soil size fractions at a former industrial site in NE England,UK using in situ PFE–GC–MS

Polycyclic aromatic hydrocarbon (PAH) concentrations were determined in 16 topsoils (0–10 cm) collected across the site of a former tar works in NE England. The soils were prepared in the laboratory to two different particle size fractions: <250 μm (fraction A) and >250 μm to <2 mm (fraction B). Sixteen priority PAHs were analysed in the soils using in situ pressurised fluid extraction (PFE) followed by gas chromatography—mass spectrometry (GC–MS). The average total PAH concentration in the soils ranged from 9.0 to 1,404 mg/kg (soil fraction A) and from 6.6 to 872 mg/kg (soil fraction B). These concentrations are high compared with other industrially contaminated soils reported in the international literature, indicating that the tar works warrants further investigation/remediation. A predominance of higher-molecular-weight compounds was determined in the samples, suggesting that the PAHs were of pyrogenic (anthropogenic) origin. Statistical comparison (t-test) of the mean total PAH concentrations in soil fractions A and B indicated that there was a significant difference (95% confidence interval) between the fractions in all but two of the soil samples. Additionally, comparisons of the distributions of individual PAHs (i.e. 16 PAHs × 16 soil samples) in soil fractions A and B demonstrated generally higher PAH concentrations in fraction A (i.e. 65.8% of all individual PAH concentrations were higher in soil fraction A). This is important because fraction A corresponds to the particle size thought to be most important in terms of human contact with soils and potential threats to human health.     

Circadian shelter occupancy patterns and predator–prey interactions of juvenile Caribbean spiny lobsters in a reef lagoon

The spiny lobster, Panulirus argus, is predominantly nocturnal, remaining inside shelters during the day and foraging outside at night, presumably to minimize predation risk. Predation risk generally decreases with increasing lobster size. Therefore, this study examined the hypothesis that size would influence this basic circadian pattern. Video cameras continuously recorded the shelter occupancy of juvenile lobsters (n = 72) having a carapace length (CL) of 30–62 mm that were tethered to shelters in a shallow reef lagoon. The lobsters’ shelter occupancy was 100% during the day, but declined linearly from shortly before sunset to a minimum of 50% shortly after midnight and then increased linearly, reaching 100% by 1 h after sunrise. The percent time the lobsters spent in the shelters followed a similar trend, but there was wide variability at night (0–100%) for individual lobsters. Lobsters left their shelters 2–30 times night⁻¹, with a majority of excursions lasting <10 min. These results suggest that juvenile P. argus minimize predation risk by remaining in their shelters as long as possible but offset the energetic cost of this behavior by foraging close to their shelters for several short periods at night. This emergence pattern contrasts with those of early benthic phase lobsters (<15 mm CL), which seldom leave their shelters, and adults (>80 mm CL), which have a dusk/early evening peak in activity and leave the shelter for extended periods of time during the night. Furthermore, a minimum shelter occupancy in the middle of the night appears especially well adapted to avoid exposure to daytime predators. Videotaped observations also included interactions between lobsters and two dominant lobster predators, the triggerfish, Balistes capriscus, and the octopus Octopus cf. vulgaris. Lobsters responded differently to these predators: remaining in the shelter when attacked by a triggerfish and fleeing the shelter when attacked by an octopus. Triggerfish were nearly twice as likely to attack a lobster that was outside of the shelter than inside. Once under attack, however, a lobster had nearly the same chance of surviving if it was inside or outside. Results suggest that the patterns of shelter use and emergence change as lobsters grow, probably reflecting the interplay between perception of predation risk and the need to forage. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Improving human micronutrient nutrition through biofortification in the soil–plant system: China as a case study

Micronutrient malnutrition is a major health problem in China. According to a national nutritional survey, approximately 24% of all Chinese children suffer from a serious deficiency of iron (Fe) (anemia), while over 50% show a sub-clinical level of zinc (Zn) deficiency. More than 374 million people in China suffer from goiter disease, which is related to iodine (I) deficiency, and approximately 20% of the Chinese population are affected by selenium (Se) deficiency. Micronutrient malnutrition in humans is derived from deficiencies of these elements in soils and foods. In China, approximately 40% of the total land area is deficient in Fe and Zn. Keshan and Kaschin-Beck diseases always appear in regions where the soil content of Se in low. The soil–plant system is instrumental to human nutrition and forms the basis of the “food chain” in which there is micronutrient cycling, resulting in an ecologically sound and sustainable flow of micronutrients. Soil-plant system strategies that have been adopted to improve human micronutrient nutrition mainly include: (1) exploiting micronutrient-dense crop genotypes by studying the physiology and genetics of micronutrient flow from soils to the edible parts of crops; (2) improving micronutrient bioavailability through a better knowledge of the mechanisms of the enhancers’ production and accumulation in edible parts and its regulation through soil-plant system; (3) improving our knowledge of the relationship between the content and bioavailability of micronutrients in soils and those in edible crop products for better human nutrition; (4) developing special micronutrient fertilizers and integrated nutrient management technologies for increasing both the density of the micronutrients in the edible parts of plants and their bioavailability to humans.     

Parent–offspring resource allocation in domestic pigs

Behavioural research on domestic pigs has included parent–offspring conflict, sibling competition, and the use of signals which influence resource allocation. In this paper, we review key sow–piglet behavioural studies and discuss their relevance to resource allocation theory. Sibling competition begins in the uterus and continues after birth, as piglets compete directly for access to the sow’s teats. This competition is made more severe by a unique dentition, which newborn piglets use to lacerate the faces of siblings during teat disputes. Competition often leads to the death of some littermates, especially those of low birth weight. Piglets also compete indirectly for milk, apparently by stimulating milk production at the teats that they habitually use at the expense of milk production by other teats. The complex nursing behavior of the sow appears designed to prevent the more vigorous piglets from monopolizing the milk. Sows give vocal signals which both attract piglets to suckle and synchronize their behavior during nursing episodes. Piglets give loud vocal signals when separated from the sow; calls which vary in intensity and appear to be honest signals of need. Udder massage by piglets may also serve as an honest signal of need. Parent–offspring conflict has been demonstrated experimentally in pigs. Specifically, when given the opportunity to control contact with their piglets, sows nurse less frequently, provide less milk, and lose less weight during lactation than sows that cannot control their level of contact. Because of this interesting natural history and because they are so amenable to experimentation, domestic pigs provide a rich system for testing ideas drawn from resource allocation theory. This contribution is part of the special issue “Sibling competition and cooperation in mammals” (guest editors: Robyn Hudson and Fritz Trillmich).