UV plumage color is an honest signal of quality in male budgerigars

Elaborate and colorful feathers are important traits in female mate choice in birds. Plumage coloration can result from pigments deposited in feathers such as carotenoids and melanins, or can be caused by nano-scale reflective tissues (structurally based coloration), usually producing ultraviolet (UV) coloration. Structural colorations remain the least studied of the three most important feather colorations. Previous studies have found a female preference for UV color in the budgerigar, Melopsittacus undulatus, but it is not clear what information this ornament conveys, nor what is the possible cost associated with its production. We investigated possible correlations between immune response and plumage color of wild-type (green) male budgerigars. In particular we measured the wing web swelling resulting from injection of phytohaemagglutinin (PHA). We did not detect any correlation between the sedimentation rate and morphological and color variables. We found that UV chroma is the best predictor for the cutaneous immune activity. Indeed, male budgerigars with high UV reflectance in the breast feathers showed stronger immune responses. These results are consistent with the idea that UV colors are special signals conveying information about a bird’s condition.     

Resource-dependent nuptial feeding in Panorpa vulgaris: an honest signal for male quality

In mating systems that are characterized by resource-dependentmale behavior like nuptial feeding, food limitation obviouslyplays a major role in male performance. In Panorpa vulgaris(Mecoptera: Panorpidae), the ability to produce nuptial giftshas major fitness consequences as the number of gifts determinescopulation duration, which then determines the number of eggsfertilized by a given male. In the present study, we are ableto show that males of P. vulgaris were limited in their productionof salivary secretions. The number of saliva secretions maleswere able to produce declined in successive matings. Moreover,males of nutritionally high status produced more gifts thanthose of nutritionally low status. The proximate factor determiningmale saliva secretion was the development of the salivary gland,which in turn depended on the amount of food a male could access.The degree of male mating effort corresponded to the size ofthe salivary gland, yet while absolute investment increasedwith gland size, the relative investment decreased. Mating costsfor males thus depend on nutritional status.     

Structurally based plumage coloration is an honest signal of quality in male blue grosbeaks

We investigated the signaling function of blue plumage in maleblue grosbeaks (Guiraca caerulea) to determine if structurallybased coloration may act as a reliable signal of quality toconspecifics. Blue plumage results from the microstructureof feather barbules rather than from pigment granules, andthus it is possible that structurally based plumage ornamentsmay function differently from sexually selected ornamental coloration that is pigment based. The plumage of male blue grosbeaksreflects maximally in the blue-ultraviolet range, so most variationin plumage coloration among males is invisible to human observers.In previous research, we showed that increased area of blueplumage on the body is associated with a shift in the wavelengthof maximum feather reflectance toward the ultraviolet and withhigh intensity of light reflected at that maximum, and thatextreme expression of the male ornament is condition dependent.These observations suggest that blue plumage may be an honestadvertisement of male quality. We tested this hypothesis ina wild population of blue grosbeaks. We quantified male qualityin three broad categories. (1) Physical condition was assessed from subcutaneous fat deposits, ectoparasite load, and bodysize. (2) Territory quality was assessed from territory area,prey abundance, and predation risk. (3) Paternal investmentwas assessed from male feeding rate. We found that the bluestmales have the largest body size, maintain the largest territorieswith the greatest prey abundance, and feed nestlings in thefirst nest of the season at the highest rates. We conclude that structurally based plumage coloration functions as an honest,intraspecific signal of quality.     

Population density and phenotypic attributes influence the level of nematode parasitism in roe deer

The impact of parasites on population dynamics is well documented, but less is known on how host population density affects parasite spread. This relationship is difficult to assess because of confounding effects of social structure, population density, and environmental conditions that lead to biased among-population comparisons. Here, we analyzed the infestation by two groups of nematodes (gastro-intestinal (GI) strongyles and Trichuris) in the roe deer (Capreolus capreolus) population of Trois Fontaines (France) between 1997 and 2007. During this period, we experimentally manipulated population density through changes in removals. Using measures collected on 297 individuals, we quantified the impact of density on parasite spread after taking into account possible influences of date, age, sex, body mass, and weather conditions. The prevalence and abundance of eggs of both parasites in females were positively related to roe deer density, except Trichuris in adult females. We also found a negative relationship between parasitism and body mass, and strong age and sex-dependent patterns of parasitism. Prime-age adults were less often parasitized and had lower fecal egg counts than fawns or old individuals, and males were more heavily and more often infected than females. Trichuris parasites were not affected by weather, whereas GI strongyles were less present after dry and hot summers. In the range of observed densities, the observed effect of density likely involves a variation of the exposure rate, as opposed to variation in host susceptibility.     

Antler size in red deer: heritability and selection but no evolution

We present estimates of the selection on and the heritability of a male secondary sexual weapon in a wild population: antler size in red deer. Male red deer with large antlers had increased lifetime breeding success, both before and after correcting for body size, generating a standardized selection gradient of 0.44 (+/- 0.18 SE). Despite substantial age- and environment-related variation, antler size was also heritable (heritability of antler mass = 0.33 +/- 0.12). However the observed selection did not generate an evolutionary response in antler size over the study period of nearly 30 years, and there was no evidence of a positive genetic correlation between antler size and fitness nor of a positive association between breeding values for antler size and fitness. Our results are consistent with the hypothesis that a heritable trait under directional selection will not evolve if associations between the measured trait and fitness are determined by environmental covariances: In red deer males, for example, both antler size and success in the fights for mates may be heavily dependent on an individual's nutritional state.     

Female goats use courtship display as an honest indicator of male quality

Due to the differential cost of reproduction in promiscuous species, like domesticated goat(s) (Capra hircus), it is expected that females should mate with higher quality males, while males should mate with a greater number of females. Females may use conspicuous secondary sexual characteristics of males such as courtship display to distinguish among high and low quality males. Testosterone (T) controls a large suite of secondary sexual characteristics and variation in T concentrations may account of differences in courtship rates. Two studies were conducted to examine the relationship between T concentrations and courtship rate and its role in mammalian female mate choice. Experiment 1 utilized bucks (intact males) and Experiment 2 utilized T-replaced wethers (castrated pre-pubertally). During the first year of Experiment 2, T-replaced wethers received either vehicle control (CON), 25 mg or 100 mg testosterone propionate (TP). During the second year of Experiment 2, T-replaced wethers were treated with either 5 mg, 15 mg or 25 mg TP. For all experiments, mean courtship rates and circulating T concentrations were measured, as well as female preference for males displaying different courtship frequencies. T concentrations and courtship rate were positively correlated for bucks and estrous females preferred high courting bucks. Males receiving 25 mg and 100 mg TP courted females at a similar rate, but both were significantly higher than courtship rates of the CON wethers. Courtship rates of the 25 mg, 15 mg and 5 mg TP-treated males were all significantly different. Females did not show a preference between the 100 mg or 25 mg TP-treated wethers, however both were preferred in comparison to the CON wethers. Females did not show preference between the 25 mg or 15 mg TP-treated wethers, however both were preferred in comparison to the 5 mg TP-treated wethers. Taken together, these studies suggest that courtship rate is T-dependent. Further, females can use courtship rate to distinguish among males.     

Unexpected population genetic structure of European roe deer in Poland: an invasion of the mtDNA genome from Siberian roe deer

Introgressive hybridization is a widespread evolutionary phenomenon which may lead to increased allelic variation at selective neutral loci and to transfer of fitness‐related traits to introgressed lineages. We inferred the population genetic structure of the European roe deer (Capreolus capreolus) in Poland from mitochondrial (CR and cyt b) and sex‐linked markers (ZFX, SRY, DBY4 and DBY8). Analyses of CR mtDNA sequences from 452 individuals indicated widespread introgression of Siberian roe deer (C. pygargus) mtDNA in the European roe deer genome, 2000 km from the current distribution range of C. pygargus. Introgressed individuals constituted 16.6% of the deer studied. Nearly 75% of them possessed haplotypes belonging to the group which arose 23 kyr ago and have not been detected within the natural range of Siberian roe deer, indicating that majority of present introgression has ancient origin. Unlike the mtDNA results, sex‐specific markers did not show signs of introgression. Species distribution modelling analyses suggested that C. pygargus could have extended its range as far west as Central Europe after last glacial maximum. The main hybridization event was probably associated with range expansion of the most abundant European roe deer lineage from western refugia and took place in Central Europe after the Younger Dryas (10.8–10.0 ka BP). Initially, introgressed mtDNA variants could have spread out on the wave of expansion through the mechanism of gene surfing, reaching high frequencies in European roe deer populations and leading to observed asymmetrical gene flow. Human‐mediated introductions of C. pygargus had minimal effect on the extent of mtDNA introgression.     

Dominance is not always an honest signal of male quality,but females may be able to detect the dishonesty

Females prefer dominant males as mating partners in numerous species. Male dominance rank is considered as an honest signal of male quality, because only healthy males in good condition are thought to be able to win fights with other males. Here, we tested whether activation of the immune system influences the success of males in male–male competition and mating in the field cricket, Gryllus integer. We activated the immune system of males with a nylon monofilament (to mimic a parasitoid larva), and arranged fights between male pairs to assess male dominance and associated mating success. Activation of the immune system with nylon monofilament substantially enhanced the fighting success of males during male–male competition but had no effect on mating success. However, sham-manipulation (a wound only) did not have any effect on fighting success although females mated more often with dominant males. Our study suggests that when male crickets meet an apparent survival threat they may behave more dominantly, probably owing to terminal investment. Male success during male–male competition is not always an honest signal of males’ quality, but females may be able to detect this dishonesty.     

Influence of weather and phenotypic characteristics on pregnancy rates of female roe deer in central Italy

In many ungulates, female fecundity is influenced by weather, population density and body condition. Based on a six-year survey of the reproductive tracts of adult female roe deer (Capreolus capreolus) harvested in the province of Pisa (Tuscany, central Italy), we evaluated the influence of weather, population density and individual characteristics on pregnancy rates. Eighty-five percent of females were pregnant, with a median litter size of two (range one—three). We found that pregnancy rate was positively correlated with summer rainfall and body mass of females, whereas early-winter conditions, spring rainfall, the age of females and density-dependent factors did not appear to influence pregnancy rate. These results reflect the particular seasonal variation in the abundance and quality of resources in Mediterranean habitats and show that heavier females (high-quality mothers) are more productive than lighter females.     

A paretic condition in an Anaplasma phagocytophilum infected roe deer calf

This paper describes a case of Anaplasma phagocytophilum infection in a roe deer (Capreolus capreolus) calf in Norway. The calf was found deserted, paretic, and heavily infested with Ixodes ricinus ticks. It was euthanized and investigated postmortem. Anaplasma phagocytophilum was detected in several tissues by polymerase chain reaction (PCR) and 16S rRNA sequence analyses. Analyses for Borrelia burgdorferi sensu lato and tick-borne encephalitis (TBE) virus infections were negative. This is the first report of a possible paretic condition in A. phagocytophilum infected roe deer.     

Variation in cohort mandible size as an index of roe deer (Capredus capreolus) densities and population trends

This paper examines the effects of increasing population density on the skeletal development of roe deer as indexed by variation in the size of the mandible. We tested for density-dependence in total jaw length and minimum diastema height among cohorts in a single, intensively studied population in France. A strong relationship of average adult jaw length of both males and females with deer density in the year of birth of a given cohort was observed, and presumably reflects inadequate nutrition of juveniles at high population density. No such relationship was observed for the minimum diastema height which remained constant over the range of densities studied. This relationship was exploited to investigate population trends of roe deer in Britain. In nine populations, where equivalent data were available for between 16 and 28 separate cohorts, a consistent pattern of variation in cohort jaw size was observed, with a decrease in average total length, but not diastema height, towards the present. This trend is discussed in relation to changes in habitat structure in the coniferous forests of Britain. The utility of cohort jaw length as a management tool to index population trends of roe deer is highlighted.     

Distribution of an increasing roe deer population in a fragmented Mediterranean landscape

This paper describes roe deer Capreolus capreolus distribution in central Spain, where the species has spread from the mountains into peripheral agricultural areas In this region, it is more abundant in forest fragments near the mountains than in those further away, in pine and oak woodlands than in sclerophyllous forests, and in forests with open water than in those lacking this resource The paper also analyzes whether habitat quality and geographic location of forests with respect to roe deer source areas are the two basic causes of its distribution, as predicted by some models of the species distribution in fragmented landscapes The results corroborate this hypothesis revealing that roe deer abundance is linked negatively to sclerophyllous forest cover and distance from mountains We conclude that this type of farmland seems to be sub-optimal for roe deer in comparison with forested, moist mountains     

Colored nectar as an honest signal in plant-animal interactions

Many flowering plants obtain the services of pollinators by using their floral traits as signals to advertise the rewards they offer to visitors—such as nectar, pollen and other food resources. Some plants use colorful pigments to draw pollinators’ attention to their nectar, instead of relying on the appeal of nectar taste. Although this rare floral trait of colored nectar was first recorded by the Greek poet Homer in the Odyssey, it has only recently received the attention of modern science. This mini-review focuses on recent findings about some of the species that use colored nectar; topics include its function as an honest signal for pollinators, as well as the pigments responsible for the nectar coloration. Such research of the ecology and physiology of colored nectar expands our understanding of the role and evolution of pollinator signaling in plants.     

Courtship as an honest indicator of male parental quality in the bicolor damselfish, Stegastes partitus

Previous work on the bicolor damselfish, a species with exclusivemale parental care of eggs, suggested that female mate choicewas based on male characteristics. The aims of this study wereto determine whether females discriminate among potential mateson the basis of courtship and, if so, to determine whether courtshipserves as an indicator of male parental quality. Observationsmade over two reproductive cycles showed that courtship ratesand mating success of individual males are positively correlatedand that males begin courting several days before females beginlaying eggs. Experimental manipulations showed that a male'scourtship rate is indicative of the subsequent egg survivalfrom his nest. We suggest that observed differences betweenmales in their courtship rates and parental ability may be aresult of differences in their energy reserves. These resultsdemonstrate the operation of honest advertising and lend supportto adaptive models of sexual selection. [Behav Ecol 1991;2:295–300]