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PubMed2003

Correlation of ultrasonographic observations with anatomic features and radiography of the elbow joint in dogs.

OBJECTIVE: To define the ultrasonographic appearance of the elbow joint of dogs and to develop an ultrasonographic imaging protocol to reliably accomplish complete evaluation of that joint. ANIMALS: 11 clinically normal mixed-breed dogs. PROCEDURE: Ultrasonographic observations (by use of a 5 to 10 MHz linear array probe) were made of 22 elbow joints in cadaveric forelimbs from clinically normal dogs. Images in standard anatomic planes were recorded with a multi-image camera, on videotape, or onto a computer. The anatomic plane of the ultrasonographic beam and position of the ultrasonographic probe were also recorded. Dissection of each elbow joint was performed, and anatomic features were correlated with ultrasonographic images. RESULTS: Structures clearly identified ultrasonographically included the lateral and medial humeral epicondyles, the humeroradial and humeroulnar joints, anconeal process, medial coronoid process, hyaline cartilage covering the proximal articular surface of the radius, collateral ligaments, tendons of triceps brachii and supinator muscles, and the supinator tendon and sesamoid in the supinator cartilage. An ultrasonographic imaging protocol for examination of the elbow joint was developed. CONCLUSIONS AND CLINICAL RELEVANCE: Precise correlations were established between the gross anatomic appearance of the elbow joint and the ultrasonographic images of its component structures. The ultrasonographic imaging protocol will enable complete examination of all regions of the joint for detection of pathologic lesions.

Animals↗
PubMed2002

Marker-assisted introgression of favorable alleles at quantitative trait loci between maize elite lines.

This article reports the marker-assisted introgression of favorable alleles at three quantitative trait loci (QTL) for earliness and grain yield among maize elite lines. The QTL were originally detected in 1992 by means of ANOVA in a population of 96 recombinant inbred lines (RILs). Introgression started from a selected RIL, which was crossed three times to one of the original parents and then self-fertilized, leading to BC(3)S(1) progenies. Markers were used to assist both foreground and background selection at each generation. At the end of the program, the effect of introgression was assessed phenotypically in agronomic trials, and QTL detection was performed by composite interval mapping among BC(3)S(1) progenies. The marker-assisted introgression proved successful at the genotypic level, as analyzed by precision graphical genotypes, although no emphasis was put on the reduction of linkage drag around QTL. Also, QTL positions were generally sustained in the introgression background. For earliness, the magnitude and sign of the QTL effects were in good agreement with those expected from initial RIL analyses. Conversely, for yield, important discrepancies were observed in the magnitude and sign of the QTL effects observed after introgression, when compared to those expected from initial RIL analyses. These discrepancies are probably due to important genotype-by-environment interactions.

Alleles↗
PubMed1995

Genetics of the interval from weaning to estrus in first-litter sows: distribution of data, direct response of selection, and heritability.

A selection experiment with a selection and a control line maintained for eight generations was set up to study efficacy of selection for a short interval from weaning to estrus after weaning the first litter and to estimate genetic variation in the Dutch Landrace population. Intervals were recorded without truncation (i.e., intervals up to 234 d were observed). A mating scheme with 10 mating groups was used to avoid inbreeding. Distribution of intervals from weaning to estrus was described by a mixture of a normal and an exponential distribution. Between lines, both underlying distributions were similar, but the contribution to the total distribution was different. From generation 4 onward, intervals were significantly shorter in the selection line than in the control line. Variances within lines, generations, and mating groups varied to a large extent. Response per unit selection differential was calculated for original data and three sets of transformed data, both with and without correction for unequal subclass numbers. Standardized responses were more precise and linear, when data were log-transformed, and when corrected for unequal subclass numbers. The assumed best estimate of the realized heritability was .17. The heritability in the foundation population was estimated at .36 +/- .05, using an animal model including all genetic relationships in the data. It was concluded that genetic selection decreases the average interval from weaning to estrus by reducing the number of sows with a record in the exponential part of the distribution.

Algorithms↗
PubMed2026

CRISPR/Cas9-Mediated Mutagenesis of OsERF94 Enhances Pre-Harvest Sprouting in Rice.

Pre-harvest sprouting (PHS), where seeds germinate on panicles before harvest under humid conditions, is a serious global issue in cereal crop production, including rice. Fine-mapping of the previously reported chromosome 4 locus identified OsERF94 as a strong candidate gene for functional validation. In this study, we investigated the role of OsERF94 in PHS using CRISPR/Cas9 gene editing. The CRISPR/Cas9-mediated mutagenesis of OsERF94 induced frameshift mutations, resulting in a loss-of-function of OsERF94 in the 1-I-ET and 2-D-ET lines. The 1-I-ET and 2-D-ET lines exhibited significantly higher germination rates under PHS conditions compared to the wild type, indicating increased susceptibility to PHS. Whole-genome re-sequencing confirmed that few or no mutations could be detected at off-target candidate sites in both edited lines, ensuring the precision of the CRISPR/Cas9 gene editing. A transcriptome analysis revealed altered expression patterns of several GA-related genes, including OsLOL1, OsKO3, OsGA3ox2, and OsGA2ox5 in the OsERF94 mutant lines. The up-regulation of GA biosynthetic genes and the down-regulation of GA deactivation genes observed in both the OsERF94 mutant lines suggest possible alterations in GA metabolism during the early stages of PHS. Transient luciferase reporter assays using a single-luciferase system suggested that OsERF94 may be associated with changes in the promoter activities of several GA- and ethylene-related genes. These findings suggest that OsERF94 may contribute to the regulation of PHS, potentially through moderation of GA- and ethylene-related pathways. Overall, this study improves our understanding of the molecular role of OsERF94 in PHS and highlights its potential as a target for the genetic improvement of PHS resistance in rice-breeding programs.

OsERF94↗
PubMed1993

Detection of bicarbonate administration (milkshake) in standardbred horses.

Total plasma carbon dioxide (TCO2) concentrations were measured in Standardbred horses to determine criteria to discriminate between normal horses and horses with excessive TCO2 concentrations on raceday. TCO2 concentrations from stabled horses were distributed normally with a mean of 30.2 mmol/L and a standard deviation of 1.2 (n = 192) while pre-race TCO2 concentrations were not normally distributed. The results indicate that about 50 horses per million are likely to have TCO2 concentrations greater than or equal to 35 mmol/L and that it is extremely unlikely that a normal horse would have a resting TCO2 concentration above 36 mmol/L. These values were associated with sensitivities of 67% and 59%, respectively, and with a specificity of 100%. TCO2 concentrations were relatively stable in blood samples stored at 4 degrees C for 4 days, whereas the TCO2 in specimens stored at room temperature (25 degrees C) and at ambient temperature (16-28 degrees C) declined progressively over 5 days. The accuracy and precision of the Beckman EL-ISE Auto Analyser were acceptable and within the manufacturers specified range. Paired specimens analysed using a Beckman EL-ISE Auto Analyser and a Kodak Dry Chemistry Analyser were not significantly different. However, the measurements made using the Kodak Dry Chemistry Analyser averaged 0.5 mmol/L higher than those analysed on the Beckman EL-ISE. The significance of these sources of variation in TCO2 concentration in relation to the testing of horses for 'milkshake' administration are discussed.

Administration, Oral↗
PubMed2006

Genetic control of conventional labeling through the bovine meat production chain by single nucleotide polymorphisms using real-time PCR.

Since January 2002, the European Union has adopted precise guidelines aimed at protecting the safety of meat and controlling the production chain. To this purpose, the conventional traceability of livestock and meat represents the main tool, but verification of traceability requires genetic support. At present, single nucleotide polymorphisms (SNPs) represent the most innovative molecular markers in genotyping studies. The aim of this study was to verify correct labeling in a bovine meat production chain by a real-time PCR protocol based on SNP analysis. Reference hair samples from 5,000 animals were randomly collected from 22 farms. Twelve hundred meat samples were collected at different steps of the bovine meat production chain. In particular, 1,000 meat samples were collected at the slaughterhouse and 200 samples from the same animals directly at the butcher's shop. The protocol was optimized and validated by testing a set of 16 SNP markers on 95 DNA samples from bovine sires of different breeds. Thereafter, the genotyping of 2,200 samples was conducted with a set of 12 selected SNPs to verify traceability of the meat production chain at three different stages: farm, slaughterhouse, and butcher's shop. Irregularities in conventional traceability were evidenced directly in 1.87% of the samples at the slaughterhouse. This percentage increased to 3.25% when sampling was conducted at the butcher's shop. This study demonstrates that despite the precautions adopted over the meat production chain, some critical points still exist that cause the loss of a correct association between registration numbers and samples.

Animal Identification Systems↗
PubMed1991

Comparison of Henderson's Method I and restricted maximum likelihood estimation of genetic parameters of reproductive traits.

Genetic parameters of simulated reproductive traits were estimated with Henderson's Method I or restricted maximum likelihood (REML). Each of the 25 samples consisted of 2,667 birds from 50 sires. When reproductive traits were measured on all birds, the means of both sets of estimates were equal to the true value; however, precision was higher with REML. When they were only measured on the 60 (20%) heaviest birds, Henderson's Method I was severely biased by selection (up to 40% for estimates of heritability of reproductive traits and up to 45% for estimates of genetic correlation between reproductive traits and body weight). This bias, as well as the variance of estimates, increased with selection rate and absolute value of genetic correlation between body weight and reproductive traits (or another criterion of selection). Conversely, REML was not biased by selection. It should therefore be preferred when sequential selection occurs.

Analysis of Variance↗
PubMed1995

The interactive effects of low pH, toxic metals, and DOC on a simulated temporary pond community.

The effects of pH, potentially toxic metals, and dissolved organic carbon (DOC) on a freshwater, palustrine wetland assemblage (three amphibian species, one mosquito genus, and 18 genera of algae) were examined in 500 liter outdoor mesocosms. The design was fully factorial and exposure levels were set to represent concentrations that occur naturally in temporary ponds in central Pennsylvania, an acid-impacted region of the USA. Water chemistry was precisely regulated by use of an artificial pond water rather than using stream water or well water with partially unknown composition. Jefferson (Ambystoma jeffersonianum) and spotted salamanders (A. maculatum) were negatively impacted by low pH and high metal concentrations. Wood frogs (Rana sylvatica) were negatively impacted by high DOC and low pH. These negative effects included increased time to metamorphosis and decreased survival and wet body mass at metamorphosis. Mosquito emergence was unaffected by pH, metals, or DOC. All three abiotic factors (metals, pH, and DOC) interacted to determine algal taxonomic composition. Hence, abiotic conditions may determine amphibian reproductive success both directly and indirectly, via effects on algae, since a primary food source of salamanders, zooplankton, are affected by changes in algal composition. These complex interactions should be considered in evaluating the possible toxicity of pond waters to fauna and flora. Until now, pH alone has been considered the primary limiting factor for amphibians breeding in temporary ponds.

Journal Article↗
PubMed1999

Estimating the effective number of breeders from heterozygote excess in progeny.

The heterozygote-excess method is a recently published method for estimating the effective population size (Ne). It is based on the following principle: When the effective number of breeders (Neb) in a population is small, the allele frequencies will (by chance) be different in males and females, which causes an excess of heterozygotes in the progeny with respect to Hardy-Weinberg equilibrium expectations. We evaluate the accuracy and precision of the heterozygote-excess method using empirical and simulated data sets from polygamous, polygynous, and monogamous mating systems and by using realistic sample sizes of individuals (15-120) and loci (5-30) with varying levels of polymorphism. The method gave nearly unbiased estimates of Neb under all three mating systems. However, the confidence intervals on the point estimates of Neb were sufficiently small (and hence the heterozygote-excess method useful) only in polygamous and polygynous populations that were produced by <10 effective breeders, unless samples included > approximately 60 individuals and 20 multiallelic loci.

Animals↗
PubMed2004

BREED: Generating novel inhibitors through hybridization of known ligands. Application to CDK2, p38, and HIV protease.

In this work we describe BREED, a method for the generation of novel inhibitors from structures of known ligands bound to a common target. The method is essentially an automation of the common medicinal chemistry practice of joining fragments of two known ligands to generate a new inhibitor. The ligand-bound target structures are overlaid, all overlapping bonds in all pairs of ligands are found, and the fragments on each side of each matching bond are swapped to generate the new molecules. Since the method is automated, it can be applied recursively to generate all possible combinations of known ligands. In an application of this method to HIV protease inhibitors and protein kinase inhibitors, hundreds of new molecular structures were generated. These included known inhibitor scaffolds not included in the initial set, entirely novel scaffolds, and novel substituents on known scaffolds. The method is fast, and since all of the ligand functional groups are known to bind the target in the precise position and orientation present in the novel ligand, the success rate of this method should be superior to more traditional de novo design techniques. In an era of increasingly high-throughput structural biology, such methods for high-throughput utilization of structural information will become increasingly valuable.

Crystallization↗
PubMed2002

Animal models of endocrine/organ-specific autoimmune diseases: do they really help us to understand human autoimmunity?

Organ-specific or endocrine autoimmune diseases are complex, polygenic afflictions the penetrance of which is heavily dependent on various environmental influences. Important target tissues are the thyroid, the islets of Langerhans, gastric parietal cells and steroid-producing cells in the adrenal and ovary. The etiology of these diseases remains to be clarified. The pathogenesis is strongly associated with autoimmune phenomena. None of the current treatment approaches provides a cure; rather they represent replacement therapy. An important objective in the treatment of endocrine/organ-specific autoimmune diseases is the detection of individuals at risk for the development of such diseases and the development of interventions to prevent an outbreak of the diseases. This requires an exquisite knowledge of the early etio-pathogenic stages of these diseases. This review concentrates on the usefulness of animal models for a precise understanding of these very early stages. It must be emphasized that studying animal models cannot answer all the problems presented by endocrine/organ-specific autoimmune diseases as seen in the clinic. It must be expected - considering the different etiologies in the different animal models (see below) - that the causes of the diseases in the human and the involvement of various genes and environmental factors may also vary. Yet, particularly in the study of the pre-autoimmune phases of the diseases, there is hardly any alternative to the study of animal models. Only limited series of experiments can be carried out in human subjects at risk to develop such diseases. Moreover, a general semblance (blueprint) of the etio-pathogenesis found in the animal models can lead the way for human studies. Efforts to understand the patho-physiology of the early stages of endocrine/organ-specific autoimmune diseases have mainly involved animal models that "spontaneously" develop such diseases. Of these the bio-breeding diabetes-prone (BB-DP) rat and the non-obese diabetes (NOD) mouse are the most well studied, yet many studies have also been carried out in the obese strain (OS) chicken. Apart from these spontaneous models there are animal models that are induced by environmental perturbations (viruses, toxic substances), by thymectomy procedures or by genetic manipulations, e.g., the RIP-LCMV model and the BDC 2.5 TCR mouse model. A general blueprint has emerged from the studies into the early stages of the pathogenesis of endocrine/organ-specific autoimmune diseases in these animal models: animals at risk to develop endocrine/organ-specific autoimmune diseases show various pre-autoimmune aberrancies in their target glands, T cells, macrophages (Mphi) and dendritic cells (DC). The presumably aberrant target cells, T cells, DC and Mphi need to interact abnormally before autoimmune disease can fully develop. In this abnormal interaction additional aberrancies in other regulatory systems may play a role in a further exacerbation of the self-directed immune response, such as defects in the hypothalamus pituitary adrenal (HPA) axis system. The various aberrancies are partly genetically determined by a variety of separate genes, particularly MHC-related genes, but they may also be environmentally induced (e.g., via viruses, high iodine diet, and other experimental manipulations). Recently evidence has been gathered for pre-autoimmune aberrancies similar to the animal models in the DC/ Mphi compartment and the HPA axis in humans at risk to develop endocrine/organ-specific autoimmune diseases. However, analogous pre-autoimmune abnormalities in human target glands or in T cell function have not yet been found with certainty. We believe that animal models of endocrine/organ-specific autoimmune disease still hold immense promise for the discovery of pathways, genes and environmental factors that determine the development of endocrine/organ-specific autoimmune diseases. Animals affected by such diseases provide a unique opportunity to uncover disease-associated pathways, which are complicated to define in man.

Animals↗
PubMed1995

Endogenous opioid peptides control the amplitude and shape of gonadotropin-releasing hormone pulses in the ewe.

This study was designed to test the hypothesis that endogenous opioid peptides (EOP) mediate the negative feedback action of estradiol on GnRH pulse size in breeding season ewes. If this hypothesis is correct, one would predict that an EOP antagonist should increase GnRH pulse size in estradiol-treated ovariectomized (OVX+E), but not in OVX, ewes. We, therefore, examined the effects of naloxone on GnRH pulse profiles in the hypophyseal portal blood of OVX and OVX+E ewes (n = 6/group). Samples were collected every 10 min for 6 h before, 6 h during, and 4 h after naloxone infusion. Estradiol treatment decreased GnRH pulse size and increased GnRH pulse frequency. Naloxone treatment had no effect on GnRH pulse frequency, but significantly increased GnRH pulse size. However, this stimulatory action of naloxone on GnRH pulse size was evident in both OVX and OVX+E ewes. These results are thus not consistent with the hypothesis that EOP mediate the negative feedback action of estradiol. Interestingly, naloxone not only increased GnRH pulse amplitude, but also prolonged the duration of GnRH release during a pulse. To obtain a more precise characterization of the effects of naloxone on the dynamics of GnRH release, pulse profiles in six OVX ewes were examined in hypophyseal portal blood sampled every minute for 4 h before and 4 h during naloxone infusion. Naloxone again increased both the amplitude and duration of GnRH pulses. The increase in GnRH pulse duration was caused by a prolongation of both the plateau and declining phases of the GnRH pulse. In addition to these effects on GnRH release during a pulse, naloxone increased the amount of GnRH collected between pulses in both experiments. The stimulatory effects of naloxone on GnRH release in OVX ewes indicate that the role of EOP in the control of GnRH is not limited to mediating the feedback actions of steroids. In particular, the dramatic effects of naloxone on GnRH pulse shape and interpulse GnRH levels raise the possibility that EOP play an important role in synchronizing the activity of the GnRH neurons involved in episodic GnRH secretion.

Animals↗
PubMed2026

Deciphering the mosaic genome of sugarcane cultivars through polyploid admixture inference with AdmixPoly.

BACKGROUND: Characterizing population structure and admixture events between ancestral groups plays a key role in understanding the evolutionary history of species and crops. Most tools for inferring admixture have been developed for diploids and are not suitable for polyploids, in particular those with high and mixed ploidy such as Saccharum. RESULTS: Here we present AdmixPoly, an R-package designed to infer admixture in polyploid species both at the genome-wide scale and locally along chromosomes. We compare AdmixPoly with state-of-the-art methods using simulations, demonstrating its precision and computational efficiency. Notably, local admixture inference in complex scenarios, such as high ploidy levels, large numbers of ancestral groups and alleles per marker is enabled through efficient approximations of emission and transition probabilities within a hidden Markov model framework. We apply this approach to characterize the contributions of wild Saccharum species to the complex polyploid genome of modern sugarcane cultivars. A panel of wild and cultivated Saccharum accessions is genotyped for 80K genomic regions, each revealing approximately 50 read-scale haplotypes. CONCLUSIONS: The results reveal that most of the approximately 12 copies of each basic chromosome in modern cultivars are derived from the domesticated species Saccharum officinarum, with one to four copies typically contributed by distinct subgroups of the wild species Saccharum spontaneum. In addition, contributions from an unknown wild Saccharum group originating from the Pacific were identified in most cultivars. The conserved pattern of these introgressions suggests that they can be traced back to the early stages of sugarcane breeding approximately a century ago.

Saccharum↗
PubMed1981

Periparturient and postpartum endocrine changes of conceptus and maternal units in Jersey cows bred for milk yield.

Control cows, sired and bred by bulls of zero estimated breeding value, and selected cows, sired by and bred to bulls of high predicted differences for milk yield, were used to evaluate maternal endocrine changes from 14 days prepartum to 28 days postpartum. Examined were concentrations in plasma of 13, 14 dihydro-15 keto-prostaglandinF2 alpha, progesterone, estrone sulfate, estrone, luteinizing hormone, and prolactin. Ability of cows to release prolactin and luteinizing hormone on day 10 postpartum was evaluated after a simultaneous injection of thyrotropin releasing hormone (100 microgram) and gonadotropin releasing hormone (100 microgram). Changes in progesterone and estrogens prepartum lead to peak concentrations of prolactin and prostaglandin at parturition and 3 days postpartum, respectively. Higher basal concentrations of prolactin for control cows prepartum were associated with a higher prolactin release by thyrotropin releasing hormone at 10 days postpartum. Although release of luteinizing hormone in response to gonadotropin releasing hormone did not differ between groups on day 10 postpartum, a subsequent increase in progesterone to above 1 ng/ml was earlier and more precisely synchronized among control cows (16 +/- .43 versus 23 +/- 2.33 days). Within cow concentrations of F2 alpha 13, 14 dihydro-15-keto-prostaglandin-F2 alpha were correlated with size of previous gravid uterine horn (.67) and milk yield (-.39). Selection for milk yield influenced postpartum endocrine function.

Animals↗
PubMed2004

Bovine umbilical hernia maps to the centromeric end of Bos taurus autosome 8.

Twelve bull calves were produced by mating elite Israeli cows to "Glenhapton Enhancer", a Canadian Holstein bull. The frequency of umbilical hernia (UH) in the progeny of the sons ranged from 1 to 21%, consistent with the hypothesis that Enhancer is the carrier of major dominant or codominant gene with partial penetrance for UH. Five sons of Enhancer produced progeny with >10% frequency of UH including sire 3259, whereas progeny of three sons had <3% UH. A total of 116 grand-progeny of Enhancer, all progeny of 3259, were genotyped for 59 microsatellites spanning the 29 bovine autosomes. Of these offspring, 41 were affected. Significant differences in paternal allele frequencies between the affected and unaffected progeny groups were found for marker BMS1591 on bovine chromosome 8 (BTA8). The UH-associated paternal allele originated from Enhancer. The chromosomal segment associated with UH was more precisely mapped between UWCA47, on the centromeric end of BTA8 and RM321, 12 cM from the centromere. A maximum LOD score of 3.84 was obtained 2.5 cM from the centromere with a support interval of 8 cM. Haplotype analysis of eight sons of Enhancer suggested that the UH gene is located in the centromeric end of BTA8 beyond ARO71/ARO72. Thus, by integrating the results from progeny of sire 3259 and sons of Enhancer the location of the UH gene was further refined to the BTA8 segment between ARO71/ARO72 and UWCA47.

Animals↗
PubMed2003

QTL analysis of an intervarietal set of substitution lines in Brassica napus: (i) Seed oil content and fatty acid composition.

Backcross breeding with marker-assisted selection was used to construct an intervarietal set of part chromosome substitution lines in Brassica napus, formed from a cross between two winter varieties of oilseed rape: Tapidor and Victor. A total of 22 lines from this substitution library were examined over a 3-year period, in a total of nine field trials, for seed oil fatty acid composition and seed oil content. Trialing of the substitution lines gave evidence for the existence of 13 quantitative trait loci (QTL). All 13 QTL affected fatty acid composition of the seed, and were distributed among linkage groups 1, 3, 6, 7, 8, 11, 13, 14, 18, and 19. Seven of these QTL, on linkage groups 3, 6, 8, 13, 14, 18, and 19, also affected total seed oil content. The positions of these QTL are compared to those in the published literature and with respect to erucic acid QTL previously identified in a backcross population of the same cross. The substitution line approach gives increased precision and sensitivity for QTL mapping compared to other methods.

Brassica napus↗
PubMed2004

Prediction of daily milk, fat, and protein production by a random regression test-day model.

Test-day genetic evaluation models have many advantages compared with those based on 305-d lactations; however, the possible use of test-day model (TDM) results for herd management purposes has not been emphasized. The aim of this paper was to study the ability of a TDM to predict production for the next test day and for the entire lactation. Predictions of future production and detection of outliers are important factors for herd management (e.g., detection of health and management problems and compliance with quota). Because it is not possible to predict the herd-test-day (HTD) effect per se, the fixed HTD effect was split into 3 new effects: a fixed herd-test month-period effect, a fixed herd-year effect, and a random HTD effect. These new effects allow the prediction of future production for improvement of herd management. Predicted test-day yields were compared with observed yields, and the mean prediction error computed across herds was found to be close to zero. Predictions of performance records at the herd level were even more precise. Discarding herds enrolled in milk recording for <1 yr and animals with very few tests in the evaluation file improved correlations between predicted and observed yields at the next test day (correlation of 0.864 for milk in first-lactation cows as compared with a correlation of 0.821 with no records eliminated). Correlations with the observed 305-d production ranged from 0.575 to 1 for predictions based on 0 to 10 test-day records, respectively. Similar results were found for second and third lactation records for milk and milk components. These findings demonstrate the predictive ability of a TDM.

Animals↗
PubMed2006

Parental effort and reproductive skew in coalitions of brood rearing female common eiders.

Members of breeding groups face conflicts over parental effort when balancing antipredatory vigilance and feeding. Empirical evidence has shown disparate responses to manipulations of parental effort. We develop a model in which we determine the evolutionarily stable effort of partners given their body conditions, allowing the benefits of shared care to be unevenly divided, and we test this model's predictions with data on common eiders (Somateria mollissima). Eiders show uniparental female care; females may share brood rearing, or they may tend alone, and their body condition at hatching of the young shows large environmentally induced variation. The model predicts that parental effort (vigilance) in a coalition is lower than when tending alone, controlling for parental condition; this prediction is supported by the data. The parental effort in a coalition should be positively correlated with body condition, and this prediction is also supported. Finally, parental effort should increase when partner condition decreases and vice versa; this prediction is partially supported. The Nash bargaining game may provide promising avenues by which to determine the precise settlement of reproductive skew and effort between coalition partners in the future.

Animals↗