Potential emission savings from refrigeration and air conditioning systems by using low GWP refrigerants

Purpose

Refrigeration and air conditioning systems have high, negative environmental impacts due to refrigerant charge leaks from the system and their corresponding high global warming potential. Thus, many efforts are in progress to obtain suitable low GWP alternative refrigerants and more environmentally friendly systems for the future. The system’s life cycle climate performance (LCCP) is a widespread metric proposed for the evaluation of the system’s environmental impact.

Methods

In this paper, the potential emission reductions in the commercial refrigeration and residential air conditioning systems, made possible by shifting towards more environmentally friendly refrigerants in the US, are presented. First, the current LCCP of the most common commercial refrigeration and residential air conditioning systems is calculated. Then, the LCCP of the baseline systems, when using the potential low GWP alternative refrigerants, is presented. This helps to determine the systems which have the highest potential for emission reductions.

Results and discussion

By shifting from the baseline refrigerants, R-404A and R-410A, to the suggested low GWP refrigerants, N-40 and L-41a, in the commercial refrigeration and residential HVAC systems, respectively, a combined drop of 30.43 % in the total emissions (i.e., total equivalent mass of emissions in kg CO_2eq) is obtained. This results from a 50.5 and 28.01 % drop in total emissions from supermarket refrigeration systems and residential air conditioning, respectively.

Conclusions

Shifting to lower GWP refrigerants in the refrigeration and air conditioning systems helps to reduce the total emissions and negative environmental impacts of these systems. Shifting to a secondary circuit commercial refrigeration system using N-40/L-40 and residential air conditioning and heat pump systems using L-41a helps in reducing the total emissions.

     

LCA study of air conditioners with an alternative refrigerant

In the refrigeration and air conditioning industry, technologies to reduce environmental impacts, such as global warming, ozone-layer depletion, and discharging industrial wastes, are getting much attention nowadays. This paper reports the Life Cycle Assessment conducted to comparatively analyze two air conditioner units for residential use. One is a traditional type with HCFC22 being used for its refrigerant and the other is with HFC410A. Because the main focus of this analysis is on the comparison of the refrigerants, data of the refrigerants used are taken from the actual measurements in their production and disposal stages. As a result, the ozone layer depleting effect can be eliminated completely by using HFC410A. On the other hand, the global warming effect doesn’t get reduced extensively by using HFC410A. However, it does so by treating used refrigerants with a proper waste management. Moreover, it can be proved that using HFC410A reduces environmental impacts in all the other impact categories assessed, which are acidification, air pollution, water pollution, and energy consumption. To conclude this case study, replacing HCFC22 with HFC410A for the refrigerant is certainly one of the effective methods for reducing environmental impacts given by air conditioners.     

An environmental evaluation of mechanical systems using environmentally acceptable refrigerants

New hydrofluorocarbon refrigerant gases in domestic refrigerators require the use of the newly developed synthetic lubricants. Research carried out so far indicates that the hermetic compressor used in these refrigerating systems is one component that is likely to be directly influenced by this change in working fluid. This may affect system performance as well as system durability such that a potential environmental improvement may result in a shift in environmental pollution. An environmental evaluation, using a life cycle assessment (LCA) computational tool, is carried out to study the influence of the individual components on the overall product environmental contribution. The manufacture and the recovery of the refrigerants addressed in this study were also included in this evaluation. In this LCA study, the hermetic compressor was found to contribute significantly to a number of impact categories as compared to other product components of concern. This becomes of primal environmental significance in view of the possibility that tribological characteristics, due to the presence of the new refrigerant/lubricant combinations, may influence its performance.     

Heterozygosity–fitness correlations in blue tit nestlings (<Emphasis Type="Italic">Cyanistis caeruleus</Emphasis>) under contrasting rearing conditions

Understanding the relation between genetic variation and fitness remains a key question in evolutionary biology. Although heterozygosity has been reported to correlate with many fitness-related traits, the strength of the heterozygosity–fitness correlations (HFCs) is usually weak and it is still difficult to assess the generality of these associations in natural populations. It has been suggested that HFCs may become meaningful only under particular environmental conditions. Moreover, existing evidence suggests that HFCs may also differ between sexes. The aim of this study was to investigate correlations between heterozygosity in neutral markers (microsatellites) and fitness-related traits in a natural population of blue tits (Cyanistes caeruleus). Additionally, we tested whether sex and environmental conditions may influence the magnitude and direction of HFCs. We found a positive relationship between heterozygosity and body mass of 14 days post-hatching nestlings, but only among females. Our results suggest that the correlation between heterozygosity and nestling body mass observed among female offspring could be attributed to within-brood effects. We failed to find any evidence that environmental conditions as simulated by brood size manipulation affect HFCs.     

Cradle-to-gate study of red clay for use in the ceramic industry

Background, Goal and Scope  The ceramic tile industry is one of the most important industries in Spain, with the highest concentration of firms to be found in the province of Castellón on the Mediterranean coast. The basic input material for this industry is red clay. The aim of this study was to carry out an LCA of the process of mining, treating and marketing this clay in order to identify the stages and unit processes that have the greatest impact on the environment. This LCA examines all the stages of the red clay from cradle to the customer’s gate, including the process of mining and treating the clay in the mining facilities and its later distribution to end users. Methods  Life cycle inventory (LCI): An exhaustive LCI was performed by collecting data from the mine run by Watts Blake Bearne Spain, S.A. (WBB-Spain) in Castellón. Inputs and outputs were collected for all the unit processes involved in the mining, treatment and marketing of the clay:

The Resource Basis of Magnetic Refrigeration

Emerging economies such as China and India are currently experiencing a “refrigeration revolution.” Energy spent for domestic cooling is expected to outreach that for heating worldwide over the course of the twenty‐first century. Magnetic refrigeration is an alternative cooling technology that works without gas‐based refrigerants and has the potential to be significantly more energy efficient. We evaluate to what extent the raw materials needed to produce this kind of technology on a mass‐market scale are critical in terms of demand and supply, thus identifying potential supply bottlenecks that might hinder the breakthrough of this promising technology. We assess the criticality of three promising magnetocaloric materials, that is, Gd₅(SiGe)₄, La(FeSi)₁₃, and (MnFe)₂P), as well as of Nd₂Fe₁₄B, as the candidate permanent magnet material to drive the cooling cycle. The Gd‐based alloys are disqualified as a mass‐market refrigerant in terms of resource criticality, whereas La‐ and Mn‐based alloys are much less problematic. Given the current state of technology and projected resource supply, Nd in Nd₂Fe₁₄B magnets would experience a significant bottleneck only at a later innovation stage, that is, when magnetic cooling technology would largely dominate the domestic refrigerator and air‐conditioning market.     

HETEROZYGOSITY‐FITNESS CORRELATIONS: A TIME FOR REAPPRAISAL

Owing to the remarkable progress of molecular techniques, heterozygosity‐fitness correlations (HFCs) have become a popular tool to study the impact of inbreeding in natural populations. However, their underlying mechanisms are often hotly debated. Here we argue that these “debates” rely on verbal arguments with no basis in existing theory and inappropriate statistical testing, and that it is time to reconcile HFC with its historical and theoretical fundaments. We show that available data are quantitatively and qualitatively consistent with inbreeding‐based theory. HFC can be used to estimate the impact of inbreeding in populations, although such estimates are bound to be imprecise, especially when inbreeding is weak. Contrary to common belief, linkage disequilibrium is not an alternative to inbreeding, but rather comes with some forms of inbreeding, and is not restricted to closely linked loci. Finally, the contribution of local chromosomal effects to HFC, while predicted by inbreeding theory, is expected to be small, and has rarely if ever proven statistically significant using adequate tests. We provide guidelines to safely interpret and quantify HFCs, and present how HFCs can be used to quantify inbreeding load and unravel the structure of natural populations.     

Linking genetic mechanisms of heterozygosity-fitness correlations to footprints of selection at single loci

Investigations of heterozygosity-fitness correlations (HFCs) are central to the understanding how genetic diversity is maintained in natural populations. Advanced genome-wide approaches will enrich the number of functional loci to be tested. We argue that a combined analysis of the genetic mechanisms of HFCs and selection signals at single loci will allow researchers to better understand the micro-evolutionary basis of HFCs. Different dominance relationships among the alleles at the locus can lead to positive, negative or null HFCs depending on the allele frequency distribution. These scenarios differ in the temporal stability of the HFCs and in the patterns of allele frequency changes over time. Here, we describe a simple theoretical framework that links the analyses of heterozygosity-fitness associations (ecological timescale) with tests for selection signals (evolutionary timescale). Different genomic footprints of selection can be expected for the different underlying genetic mechanisms of HFCs, and this information can be independently used for the classification of HFCs. We suggest that in addition to inbreeding and single-locus overdominant effects also loci under directional selection could play a significant role in the development of heterozygosity-fitness effects in large natural populations under recent or fluctuating ecological changes.     

Local effects drive heterozygosity–fitness correlations in an outcrossing long-lived tree

Heterozygosity–fitness correlations (HFCs) have been used to understand the complex interactions between inbreeding, genetic diversity and evolution. Although frequently reported for decades, evidence for HFCs was often based on underpowered studies or inappropriate methods, and hence their underlying mechanisms are still under debate. Here, we used 6100 genome-wide single nucleotide polymorphisms (SNPs) to test for general and local effect HFCs in maritime pine (Pinus pinaster Ait.), an iconic Mediterranean forest tree. Survival was used as a fitness proxy, and HFCs were assessed at a four-site common garden under contrasting environmental conditions (total of 16 288 trees). We found no significant correlations between genome-wide heterozygosity and fitness at any location, despite variation in inbreeding explaining a substantial proportion of the total variance for survival. However, four SNPs (including two non-synonymous mutations) were involved in significant associations with survival, in particular in the common gardens with higher environmental stress, as shown by a novel heterozygosity–fitness association test at the species-wide level. Fitness effects of SNPs involved in significant HFCs were stable across maritime pine gene pools naturally growing in distinct environments. These results led us to dismiss the general effect hypothesis and suggested a significant role of heterozygosity in specific candidate genes for increasing fitness in maritime pine. Our study highlights the importance of considering the species evolutionary and demographic history and different spatial scales and testing environments when assessing and interpreting HFCs.     

Population demography and heterozygosity–fitness correlations in natural guppy populations: An examination using sexually selected fitness traits

Heterozygosity–fitness correlations (HFCs) have been examined in a wide diversity of contexts, and the results are often used to infer the role of inbreeding in natural populations. Although population demography, reflected in population‐level genetic parameters such as allelic diversity or identity disequilibrium, is expected to play a role in the emergence and detectability of HFCs, direct comparisons of variation in HFCs across many populations of the same species, with different genetic histories, are rare. Here, we examined the relationship between individual microsatellite heterozygosity and a range of sexually selected traits in 660 male guppies from 22 natural populations in Trinidad. Similar to previous studies, observed HFCs were weak overall. However, variation in HFCs among populations was high for some traits (although these variances were not statistically different from zero). Population‐level genetic parameters, specifically genetic diversity levels (number of alleles, observed/expected heterozygosity) and measures of identity disequilibrium (g2 and heterozygosity–heterozygosity correlations), were not associated with variation in population‐level HFCs. This latter result indicates that these metrics do not necessarily provide a reliable predictor of HFC effect sizes across populations. Importantly, diversity and identity disequilibrium statistics were not correlated, providing empirical evidence that these metrics capture different essential characteristics of populations. A complex genetic architecture likely underpins multiple fitness traits, including those associated with male fitness, which may have reduced our ability to detect HFCs in guppy populations. Further advances in this field would benefit from additional research to determine the demographic contexts in which HFCs are most likely to occur.     

Evaluating the reduction in green house gas emissions achieved by the implementation of the household appliance recycling in Japan

Background, Aim and Scope The Home Appliance Recycling Law (hereunder referred to as the Law) for used cathode ray tube (CRT) TVs, air conditioners, refrigerators and washing machines was enacted in April 2001 in Japan. The Law requires that retailers reclaim, and manufacturers and importers recycle such home appliances. Consumers are required to pay collection and recycling fees incurred in disposing of any of the four home appliances. Home appliances must, as a general rule, be managed in accordance with the Law. In reality, other routes exist, such as via local authorities, scrap processors, illegal dumping and exporting. At about the time the Law was enacted, the refrigerant used for air conditioners and refrigerators was replaced by more environmentally friendly substances such as isobutene. Local authorities had the responsibility of disposing of the appliances of households before the enactment of the Law. It was general practice for local authorities to dispose of home appliances in landfills after breaking them up and recovering valuable resources such as iron, copper and aluminum. Although they made efforts to recover refrigerant fluorocarbons, there were not required to do so. Materials and Methods This study analyzed the material flow resulting from the Law and other processing flows to quantify the global warming effect caused by home appliance recycling using the life cycle assessment (LCA) method. To evaluate the Law and to develop policy planning, the challenges of future efforts will be considered using time series data. For these reasons, we have assessed the Project Scenario, which corresponded to the present reality; the Baseline Scenario, which assumed that measures such as the Law were not implemented after 2000, and the Ideal Scenario, where all used products were recycled as prescribed by the Law. The environmental impacts for each scenario were estimated using value, which was obtained from multiplying the amount of reproduction and waste treatment by each inventory data. Results It is estimated that emission reductions of 4.7E+4 t CO₂e, subtracted the Project Scenario from the Baseline Scenario, were reduced for TVs in 2001 through recycling. The impact from recycling glass from cathode ray tube (CRT) televisions is significant. An improvement of 2.3E+4 t CO₂e could be anticipated by upgrading to the Ideal Scenario in 2001. It was estimated that there was a reduction of 9.2E+5 t CO₂e in 2001 for air conditioners. Although the effect of the recovery for refrigerants contributed greatly, some fluorocarbons that are still discharged have had a considerable impact on greenhouse gas emissions. Hypothetically, a reduction of 3.2E+6 t CO₂e could be anticipated with the Ideal Scenario in 2001. A reduction of 2.6E+6 t CO₂e was achieved for refrigerators in 2001. Although a further reduction can be anticipated through the Ideal Scenario, there will not be much difference with the Project Scenario by 2010. It was estimated that 3.8E+4 t CO₂e were reduced for washing machines in 2001. Only a small improvement can be expected through the Ideal Scenario. Discussion Since many assumptions were used in this study, a sensitivity analysis was carried out in order to grasp their impact. The findings of the sensitivity analysis are that the uncertainties are large, but the number of the greenhouse gas (GHG) reductions is still clear except for the difference between the Project Scenario and the Ideal Scenario for TVs. This analysis gives authenticity to the findings. Conclusions Establishing a system for liquid crystal display and plasma display panel TVs is desirable because the absolute amount of used LCD/PDP TVs will rapidly increase as the usage of CRT TVs rapidly decreases from 2007. With regard to refrigerant recovery from air conditioners, a significant decrease in GHG emissions has been recorded. There is, however, still ample room for improvement. It will be necessary to switch to refrigerants with low global warming potentials (GWPs) or work more on improving the recovery rate in the future. Alternatives and recovery of fluorocarbons from refrigerators contributed greatly to GHG reductions. The GHG emissions from refrigerator recycling will be minimal whether used refrigerator will be processed legally or not because most used refrigerators will contain natural refrigerants in the near future. The improvement for washing machines was low because it was assumed that their main constituent steel has been previously recycled, and that the plastic recycling rate will not change significantly in the future. An improvement in the recycling technology itself is required. This study was carried out on four home appliance products, and it was found that the Home Appliance Recycling Law has brought significant reductions in GHG emissions. There is also room to make GHG reductions through improving the processing methods further. Recommendations and Perspectives The impact on GHG emissions by fluorocarbons of air conditioners and refrigerators is the greatest. Adequate measures are particularly required for air conditioners that may continue to discharge GHGs in the future. ESS-Submission Editor: Dr. Lindita Bushi (lindita.bushi@ghgm.com)     

Evaluation of liquid nitrogen and dry ice–alcohol refrigerants for freeze marking three mammal species

Degus (Octodon degus), Patagonian cavies (Dolichotis patagonum), and mouflon (Ovis musimon) were freeze marked with instruments refrigerated in liquid nitrogen or a mixture of dry ice and alcohol. The instruments were pressed against the skin of the animal for various trial durations. Recommended exposure durations with dry ice-alcohol refrigerant were: degus—28 sec; cavies—≈ 18 sec (estimated); mouflon—12 sec. While unsatisfactory results were obtained with the liquid nitrogen refrigerant on degus and cavies, an exposure duration of 8 sec was recommended for mouflon. With mouflon, the site of the mark influenced the appropriate exposure duration for both refrigerants. With degus, moderate overexposure resulted in acceptable marks as much of the length of peripheral white hairs was exposed due to the lack of hair in the central bare area. The dry ice-alcohol refrigerant yielded much greater exposure latitude and consistency, indicating its superiority for freeze marking, especially in a zoo setting.     

Heterozygosity-fitness correlations within inbreeding classes: local or genome-wide effects?

Marker-based studies of inbreeding may lead to an enhanced understanding of inbreeding depression in natural populations, which is a major concern in conservation genetics. Correlations between marker heterozygosity and variation in fitness-associated traits—‘heterozygosity-fitness correlations’ (HFCs)—are of particular importance and have been widely applied in natural populations. In partially inbred populations, HFCs can be driven by selection against inbred individuals and thus reflect inbreeding depression. However, other explanations for HFCs also exist, such as functional effects of the markers per se or that the markers reveal selection on linked fitness genes due to extended linkage disequilibrium (LD) in the population. Accordingly, HFCs do not only arise in partially inbred populations, they may also occur within inbreeding classes such as families, i.e. in situations when there is no variation in the inbreeding coefficient. In this study we focus on the importance of LD for within-family HFCs, thereby aiming at enhancing our general understanding of HFCs. For non-coding markers, within-family HFCs have been proposed to be caused in two ways: either by ‘local effects’ at linked fitness genes in LD with the markers, or by ‘general effects’ due to a correlation between proportion of heterozygous markers (H _M ) and heterozygosity at genome-wide distributed fitness genes (H _GW ). To evaluate these contrasting hypotheses for within-family HFCs, we analysed simulated data sets of sexually reproducing populations with varying levels of LD. The results confirmed that segregation induces variation in both H _M and H _GW at a fixed level of inbreeding; as expected, the variation in H _M declined with increasing number of markers, whereas the variation in H _GW declined with decreasing LD. However, less intuitively, there was no positive correlation between the variation in H _M and H _GW within inbreeding classes when the local component of H _GW was accounted for (i.e. when the part of the chromosome in LD with the markers was excluded). This strongly suggests that within-family HFCs are not caused by general effects. Instead, our results support the idea that HFCs at a known level of inbreeding can be driven by local effects in populations with high to moderate LD. Note however that we define the local component of H _GW as the part of the chromosomes in LD with the markers. This implies that when LD is high, the local component will consist of a substantial part of the genome and thus provides a rather ‘genome-wide’ view. We caution against routinely interpreting positive HFCs as evidence of inbreeding depression and non-significant HFCs as lack thereof, especially when few markers are used.     

Sex-Specific Correlations of Individual Heterozygosity,Parasite Load,and Scalation Asymmetry in a Sexually Dichromatic Lizard

Heterozygosity-fitness correlations (HFCs) provide insights into the genetic bases of individual fitness variation in natural populations. However, despite decades of study, the biological significance of HFCs is still under debate. In this study, we investigated HFCs in a large population of the sexually dimorphic lizard Takydromus viridipunctatus (Lacertidae). Because of the high prevalence of parasitism from trombiculid mites in this lizard, we expect individual fitness (i.e., survival) to decrease with increasing parasite load. Furthermore, because morphological asymmetry is likely to influence individuals'' mobility (i.e., limb asymmetry) and male biting ability during copulation (i.e., head asymmetry) in this species, we also hypothesize that individual fitness should decrease with increasing morphological asymmetry. Although we did not formally test the relationship between morphological asymmetry and fitness in this lizard, we demonstrated that survival decreased with increasing parasite load using a capture-mark-recapture data set. We used a separate sample of 140 lizards to test the correlations between individual heterozygosity (i.e., standardized mean d² and HL based on 10 microsatellite loci) and the two fitness traits (i.e., parasite load and morphological asymmetry). We also evaluated and excluded the possibility that single-locus effects produced spurious HFCs. Our results suggest male-only, negative correlations between individual heterozygosity and parasite load and between individual heterozygosity and asymmetry, suggesting sex-specific, positive HFCs. Male T. viridipunctatus with higher heterozygosity tend to have lower parasite loads (i.e., higher survival) and lower asymmetry, providing a rare example of HFC in reptiles.     

Defluorination of 1,1,1,2-tetrafluoroethane (R-134a) by rat hepatocytes

As part of its toxicological evaluation we assessed the in vitro metabolism of 1,1,1,2-tetrafluoroethane (R-134a), a non-ozone-depleting chemical likely to replace dichlorodifluoromethane (R-12) as an air-conditioning refrigerant. Hepatocyte suspensions in sealed flasks produced increasing quantities of F- (detected in the liquid media) as the headspace concentration of R-134a increased from 1% to 50% (balance of atmosphere 95% O2-5% CO2); the kinetics of defluorination suggested substrate-saturation. Little F- was detected in cultures without R-134a or in cell suspensions heated prior to addition of R-134a. Halothane (1,1,1-trichloro-2-bromo-2-chloro-ethane), although not defluorinated by hepatocytes maintained with 95% O2, inhibited defluorination of R-134a. Hepatocytes from phenobarbital-treated rats dehalogenated high (greater than or equal to 25%) concentrations of R-134a at greater rates than cells from untreated rats. These findings are consistent with the hypothesis that oxidative metabolism of R-134a by cytochrome P-450 can occur in vivo.     

Local heterozygosity-fitness correlations with global positive effects on fitness in threespine stickleback

The complex interactions between genetic diversity and evolution have important implications in many biological areas including conservation, speciation, and mate choice. A common way to study these interactions is to look at heterozygosity-fitness correlations (HFCs). Until recently, HFCs based on noncoding markers were believed to result primarily from global inbreeding effects. However, accumulating theoretical and empirical evidence shows that HFCs may often result from genes being linked to the markers used (local effect). Moreover, local effect HFCs could differ from global inbreeding effects in their direction and occurrence. Consequently, the investigation of the structure and consequences of local HFCs is emerging as a new important goal in evolutionary biology. In this study of a wild threespine stickleback (Gasterosteus aculeatus) population, we first tested the presence of significant positive or negative local effects of heterozygosity at 30 microsatellites loci on five fitness components: survival, mating success, territoriality, length, and body condition. Then, we evaluated the direction and shape of total impact of local HFCs, and estimated the magnitude of the impacts on fitness using regression coefficients and selection differentials. We found that multilocus heterozygosity was not a reliable estimator of individual inbreeding coefficient, which supported the relevance of single-locus based analyses. Highly significant and temporally stable local HFCs were observed. These were mainly positive, but negative effects of heterozygosity were also found. Strong and opposite effects of heterozygosity are probably present in many populations, but may be blurred in HFC analyses looking for global effects only. In this population, both negative and positive HFCs are apparently driving mate preference by females, which is likely to contribute to the maintenance of both additive and nonadditive genetic variance.     

Mapping the UDP-glucuronic acid binding site in UDP-glucuronosyltransferase-1A10 by homology-based modeling: confirmation with biochemical evidence

The UDP-glucuronosyltransferase (UGT) isozyme system is critical for protecting the body against endogenous and exogenous chemicals by linking glucuronic acid donated by UDP-glucuronic acid to a lipophilic acceptor substrate. UGTs convert metabolites, dietary constituents, and environmental toxicants to highly excretable glucuronides. Because of difficulties associated with purifying endoplasmic reticulum-bound UGTs for structural studies, we carried out homology-based computer modeling to aid analysis. The search found structural homology in Escherichia coli UDP-galactose 4-epimerase. Consistent with predicted similarities involving the common UDP moiety in substrate/inhibitor, UDP-glucose and UDP-hexanol amine caused competitive inhibition by Lineweaver-Burk plots. Among predicted binding sites N292, K314, K315, and K404 in UGT1A10, two informative sets of mutants K314R/Q/A/E/G and K404R/E had null activities or 2.7-fold higher/50% less activity, respectively. Scatchard analysis of binding data of the affinity ligand, 5-azidouridine-[beta- (32)P]diphosphoglucuronic acid, to purified UGT1A10-His or UGT1A7-His revealed high- and low-affinity binding sites. 2-Nitro-5-thiocyanobenzoic acid-digested UGT1A10-His bound with the radiolabeled affinity ligand revealed an 11.3 and 14.3 kDa peptide associated with K314 and K404, respectively, in a discontinuous SDS-PAGE system. Similar treatment of 1A10His-K314A bound with the ligand lacked both peptides; 1A10-HisK404R- and 1A10-HisK404E showed 1.3-fold greater and 50% less label in the 14.3 kDa peptide, respectively, compared to 1A10-His without affecting the 11.3 kDa peptide. Scatchard analysis of binding data of the affinity ligand to 1A10His-K404R and -K404E showed a 6-fold reduction and a large increase in K d, respectively. Our results indicate that K314 and K404 are required UDP-glcA binding sites in 1A10, that K404 controls activity and high-affinity sites, and that K314 and K404 are strictly conserved in 70 aligned UGTs, except for S321, equivalent to K314, in UGT2B15 and 2B17 and I321 in the inactive UGT8, which suggests UGT2B15 and 2B17 contain suboptimal activity. Hence our data strongly support UDP-glcA binding to K314 and K404 in UGT1A10.     

Heterozygosity is linked to the costs of immunity in nestling great tits (Parus major)

There is growing evidence that heterozygosity–fitness correlations (HFCs) are more pronounced under harsh conditions. Empirical evidence suggests a mediating effect of parasite infestation on the occurrence of HFCs. Parasites have the potential to mediate HFCs not only by generally causing high stress levels but also by inducing resource allocation tradeoffs between the necessary investments in immunity and other costly functions. To investigate the relative importance of these two mechanisms, we manipulated growth conditions of great tit nestlings by brood size manipulation, which modifies nestling competition, and simultaneously infested broods with ectoparasites. We investigated under which treatment conditions HFCs arise and, second, whether heterozygosity is linked to tradeoff decisions between immunity and growth. We classified microsatellites as neutral or presumed functional and analyzed these effects separately. Neutral heterozygosity was positively related to the immune response to a novel antigen in parasite‐free nests, but not in infested nests. For nestlings with lower heterozygosity levels, the investments in immunity under parasite pressure came at the expenses of reduced feather growth, survival, and female body condition. Functional heterozygosity was negatively related to nestling immune response regardless of the growth conditions. These contrasting effects of functional and neutral markers might indicate different underlying mechanisms causing the HFCs. Our results confirm the importance of considering marker functionality in HFC studies and indicate that parasites mediate HFCs by influencing the costs of immune defense rather than by a general increase in environmental harshness levels.     

Heterozygosity-fitness correlations in a migratory bird: an analysis of inbreeding and single-locus effects

Studies in a multitude of taxa have described a correlation between heterozygosity and fitness and usually conclude that this is evidence for inbreeding depression. Here, we have used multilocus heterozygosity (MLH) estimates from 15 microsatellite markers to show evidence of heterozygosity-fitness correlations (HFCs) in a long-distance migratory bird, the light-bellied Brent goose. We found significant, positive heterozygosity-heterozygosity correlations between random subsets of the markers we employed, and no evidence that a model containing all loci as individual predictors in a multiple regression explained significantly more variation than a model with MLH as a single predictor. Collectively, these results lend support to the hypothesis that the HFCs we have observed are a function of inbreeding depression. However, we do find that fitness correlations are only detectable in years where population-level productivity is high enough for the reproductive asymmetry between high and low heterozygosity individuals to become apparent. We suggest that lack of evidence of heterozygosity-fitness correlations in animal systems may be because heterozygosity is a poor proxy measure of inbreeding, especially when employing low numbers of markers, but alternatively because the asymmetries between individuals of different heterozygosities may only be apparent when environmental effects on fitness are less pronounced.     

DOES LINKAGE DISEQUILIBRIUM GENERATE HETEROZYGOSITY‐FITNESS CORRELATIONS IN GREAT REED WARBLERS?

Heterozygosity-fitness correlations (HFCs) at noncoding genetic markers are commonly assumed to reflect fitness effects of heterozygosity at genomewide distributed genes in partially inbred populations. However, in populations with much linkage disequilibrium (LD), HFCs may arise also as a consequence of selection on fitness loci in the local chromosomal vicinity of the markers. Recent data suggest that relatively high levels of LD may prevail in many ecological situations. Consequently, LD may be an important factor, together with partial inbreeding, in causing HFCs in natural populations. In the present study, we evaluate whether LD can generate HFCs in a small and newly founded population of great reed warblers (Acrocephalus arundinaceus). For this purpose dyads of full siblings of which only one individual survived to adult age (i.e., returned to breed at the study area) were scored at 19 microsatellite loci, and at a gene region of hypothesized importance for survival, the major histocompatibility complex (MHC). By examining siblings, we controlled for variation in the inbreeding coefficient and thus excluded genome-wide fitness effects in our analyses. We found that recruited individuals had significantly higher multilocus heterozygosity (MLH), and mean d2 (a microsatellite-specific variable), than their nonrecruited siblings. There was a tendency for the survivors to have a more diverse MHC than the nonsurvivors. Single-locus analyses showed that the strength of the genotype-survival association was especially pronounced at four microsatellite loci. By using genotype data from the entire breeding population, we detected significant LD between five of 162 pairs of microsatellite loci after accounting for multiple tests. Our present finding of a significant within-family multilocus heterozygosity-survival association in a nonequilibrium population supports the view that LD generates HFCs in natural populations.