Climate and Water Conflicts Coevolution from Tropical Development and Hydro‐Climatic Perspectives: A Case Study of Costa Rica

Costa Rica is a nation with a vast wealth of water resources; however, recently the country has faced water conflicts (WC) due to social, economic, legal, and political impediments in response to limited water availability during El Niño events and inefficient use of its water resources. This study presents a spatial distribution and temporal analysis of WC in Costa Rica from 2005 to 2015. In total, 719 WC were analyzed of which 54% were among private individuals and government. The largest urban areas and the Grande de Tárcoles Basin were identified as the main “hot spot” for the conflicts. WC were mainly caused by spills of wastewater, water pollution, water shortage, infrastructure damage, and flooding, and can be predicted using a multiple linear model including the population size and the number of hydro‐meteorological events (HME) (R² = 0.77). The identified HME also coevolved significantly with the changes in precipitation regimes (r = 0.67, p = 0.021). Our results suggest that there is a need to recognize that water infrastructure longevity across the country concatenates and amplifies WC, mainly in the most populated area located in the Central Valley. Implications of our findings include the need for truly integrated water resources management plans that include, for example, WC as indicators of hydro‐climatic changing conditions and water supply and sanitation infrastructure status.     

Does the nutrition profile of vitamins, fatty acids and microelements counteract the negative impact from organohalogen pollutants on bone mineral density in Greenland sledge dogs (Canis familiaris)?

There is a great need for understanding the impact from dietary OHCs (organohalogen compounds) on bone mineral composition - and thereby osteoporosis - in especially arctic wildlife such as polar bears (Ursus maritimus) as well as humans. For that purpose, we measured BMD (bone mineral density) by DXA scanning (g/cm(-2)) in 15 age and weight normalized sledge dog (Canis familiaris) bitches and their 26 pups divided into a control group (n=26) given 50-200 g/day clean pork (Suis scrofa) fat and a treated group (n=15) given 50-200 g/day OHC polluted minke whale (Balaenoptera acutorostrata) blubber as main lipid sources. The results showed that BMD increased significantly with age (linear regression: p<0.0001, r(2)=0.83, n=41) while no sex difference was found in the F-generation (two-way ANOVA: all p>0.3). No differences in BMD(femur) or BMD(vertebrae) between exposed and control individuals in the bitch generation were found (linear mixed effect model: both p>0.38). Likewise, no difference between exposed and control subadults and juveniles in the F-generation was found (two-way ANOVA: all p>0.33). Correlation analyses between BMD(femur), BMD(vertebrae) and groups of OHCs, respectively, did not show any statistically significant relationships nor a clear or decreasing trend (Pearson's: p: 0.07-0.78; r: -0.2-0.59; n: 10-18). As the groups were similar regarding genetics, age and sex are the only factors that can explain this observation. Either the pollutants did not have an impact on BMD using the present time frame and OHC concentrations (threshold levels not reached), or the difference in food composition (mainly vitamins and n3 fatty acids) conceal the potential OHC impact on BMD. Such information is important when evaluating the positive and negative health consequences from eating polluted marine species.     

Individual roosting strategies in a flock-living bird: movement and social cohesion of hooded crows (Corvus corone cornix) from pre-roost gatherings to roost sites

The function of the conspicuous pre-roost gathering in communally roosting birds is poorly known. We studied movement and social cohesion of radio-tagged hooded crows (Corvus corone cornix) from their daytime location via pre-roost to roost in autumn and winter. With increasing snowfall the previous 24 h, the crows attended pre-roosts farther from the territory, and moved longer from pre-roost to roost. The crows became more likely to roost communally as distance to their territory increased. Attending a pre-roost on average almost doubled the travel distance to a communal roost. Crows were much more likely to join the same roost when they had attended the same pre-roost than otherwise. Breeding mates were more likely to keep together from pre-roost to roost than were other assigned pairs of a territorial male and female. For assigned pairs of non-mates, cohesion from pre-roost to roost decreased with increasing distance to roost, and was higher when both crows roosted communally compared to when at least one of them roosted in its territory. When both roosted communally, cohesion decreased with increasing snowfall and increasing number of crows attending the pre-roost, increased with increasing snow depth, and became higher among two females, compared to other combinations of two crows, with increasing number of crows attending the pre-roost. These patterns may be interpreted as supporting several of the current hypotheses on the function of pre-roost gathering. Electronic Publication     

Seasonal nestmate recognition in the ant Formica exsecta

Under favorable conditions, the mound-building ant Formica exsecta may form polydomous colonies and can establish large nest aggregations. The lack of worker aggression towards nonnestmate conspecifics is a typical behavioral feature in such social organization, allowing for a free flux of individuals among nests. However, this mutual worker toleration may vary over the seasons and on spatial scales. We studied spatio-temporal variation of worker–worker aggression within and among nests of a polydomous F. exsecta population. In addition, we determined inter- and intracolony genetic relatedness by microsatellite DNA genotyping and assessed its effect on nestmate recognition. We found significant differences in the frequency of worker exchange among nests between spring, summer, and autumn. Moreover, we found significant seasonal variation in the level of aggression among workers of different nests. Aggression levels significantly correlated with spatial distance between nests in spring, but neither in summer nor in autumn. Multiple regression analysis revealed a stronger effect of spatial distances rather than genetic relatedness on aggressive behavior. Because nestmate discrimination disappeared over the season, the higher aggression in spring is most plausibly explained by cue intermixing during hibernation.     

A criterion validity test of the contingent valuation method: comparing hypothetical and actual voting behavior for a public referendum

This study pursues external validation of contingent valuation by comparing survey results with the voting outcome of a Corvallis, Oregon, referendum to fund a riverfront improvement project through increased property taxes. Survey respondents hypothetically make a voting decision—with no financial consequences—on the upcoming referendum. The survey sample consists of respondents verified to have voted in the election. We use available precinct-level election data to compare the proportion of “yes” survey and referendum votes as well as estimate voting models and mean willingness to pay (WTP) based on the two sets of data. We find that survey responses match the actual voting outcome and WTP estimates based on the two are not statistically different. Contrary to similar studies, our statistical results do not depend on re-coding the majority of “undecided” survey responses to “no.” Furthermore, such a re-coding of responses may be inappropriate for our data set.     

Baseline Study on Essential and Trace Elements in Polished Rice from South Korea

In 2000, 63 (polished) white rice samples were collected in eight administrative areas all over South Korea and analyzed for 16 elements by inductively coupled plasma atomic emission spectrometry (ICP-AES). Potassium had the highest content, next to Mg, Ca, Si, Zn, Na, Al and Fe. Most of the samples contained worldwide average concentrations of essential and trace elements in rice grains reported by various researches. For inter-area differences in those elements in the rice, the statistical analysis showed no significant differences (p > 0.05) among the eight administrative areas, suggesting that inter-area differences were not substantial in most cases. Thus, the present data can be used as national background levels of elements in rice produced in South Korea. Using the published data on daily consumption of rice in South Korea, it was possible to estimate the daily intake of As, Cd, Cu, Pb and Zn via rice. The results showed that a regular consumption of rice produced in Korea plays an important role in accumulation of essential and trace elements in Korean, especially for farm-households consuming relatively large amounts of rice.     

Nestmate recognition for eggs in the honeybee (<Emphasis Type="Italic">Apis mellifera</Emphasis> L.)

Colony integrity is fundamental to social insects and is threatened by the reproduction of non-nestmates. Therefore, discrimination between eggs derived from nestmates and non-nestmates would constitute an adaptation to prevent exploitation of the entire cooperative group by unrelated individuals. The removal of nestmate and non-nestmate queen and worker-laid eggs was evaluated in honeybees using colonies of Apis mellifera capensis to test female and of A. m. scutellata to test male eggs. The data show that honeybees can distinguish between nestmate and non-nestmate eggs of both sexes. Moreover, non-nestmate female queen-laid eggs were removed significantly faster than nestmate female worker-laid eggs in A. m. capensis, indicating that nestmate recognition cues can override caste-specific ones. While the experimental manipulation accounts for 37.2% (A. m. scutellata) or 1.6% (A. m. capensis) of variance in relation to egg removal, nestmate recognition explains 33.3% for male eggs (A. m. scutellata) and 60.6% for female eggs (A. m. capensis), which is almost twice as high as the impact of caste (16.7% A. m. scutellata; 25% A. m. capensis). Our data show a stronger effect of nestmate recognition on egg removal in the honeybee, suggesting that cues other than caste-specific ones (viability/kin) can dominate egg removal behavior. In light of intraspecific social parasitism, preventing the reproduction of unrelated individuals (group selection) rather than preferring queens’ eggs (kin selection) appears to be the driving force behind the evolution of egg removal behavior in honeybees.     

Design of a water quality monitoring network in a large river system using the genetic algorithm

Despite several decades of operations and the increasing importance of water quality monitoring networks, the authorities still rely on experiential insights and subjective judgments in siting water quality monitoring stations. This study proposes an integrated technique which uses a genetic algorithm (GA) and a geographic information system (GIS) for the design of an effective water quality monitoring network in a large river system. In order to develop a design scheme, planning objectives were identified for water quality monitoring networks and corresponding fitness functions were defined using linear combinations of five selection criteria that are critical for developing a monitoring system. The criteria include the representativeness of a river system, compliance with water quality standards, supervision of water use, surveillance of pollution sources and examination of water quality changes. The fitness levels were obtained through a series of calculations of the fitness functions using GIS data. A sensitivity analysis was performed for major parameters such as the numbers of generations, population sizes and probability of crossover and mutation, in order to determine a good fitness level and convergence for optimum solutions. The proposed methodology was applied to the design of water quality monitoring networks in the Nakdong River system, in Korea. The results showed that only 35 out of 110 stations currently in operation coincide with those in the new network design, therefore indicating that the effectiveness of the current monitoring network should be carefully re-examined. From this study, it was concluded that the proposed methodology could be a useful decision support tool for the optimized design of water quality monitoring networks.     

Environmental variability and allocation trade-offs maintain species diversity in a process-based model of succulent plant communities

Ecological theory suggests that environmental variability can promote coexistence, provided that species occupy differential niches. In this study, we focus on two questions: (1) Do allocation trade-offs provide a sufficient basis for niche differentiation in succulent plant communities? (2) What is the relative importance of different forms of environmental variability on species diversity and community composition? We approach these questions with a generic, individual-based simulation model. In our model, plants compete for water in a spatially explicit environment. Species differ in their size at maturity and in the allocation of carbon to roots, leaves and storage tissue. The model was fully specified with independent literature data. Model output was compared to characteristics of a species-rich community in the semi-arid Richtersveld (South Africa). The model reproduced the coexistence of plants with different sizes at maturity, the dominance of succulent shrubs, and the level of vegetation cover. We analyzed the effects of three forms of environmental variability: (a) temporal fluctuations in precipitation (rain and fog), (b) spatial heterogeneity of water supply due to run-on and run-off processes and (c) ‘rock pockets’ that limit root competition in space. The three types of variability had differential effects on diversity: diversity exhibited a strong hump-shaped response to temporal variation. Spatial variability increased diversity, with the strongest increase occurring at intermediate levels of temporal variability. Finally, rock pockets had the weakest effect, but contributed to diversity by providing refuges for small species, particularly at low temporal variability. The model thus shows that spatio-temporal variation of resource supply can maintain diversity over long time scales even in small systems, as is the case in the Richtersveld succulent communities. Trade-offs in allocation provide the basis for necessary niche differentiation. By describing resource competition between individual plants, our model provides a mechanistic basis for the link from species traits to community composition at given environmental conditions. It thereby contributes to an understanding of the forces shaping plant communities. Such an understanding is critical to reduce the threats environmental change poses to biodiversity and ecosystem services.