Immaculate tits: head plumage pattern as an indicator of quality in birds

Great tits, Parus major, display their white cheek patches to one another during intraspecific encounters. We measured the size of these patches and the regularity of their borders (immaculateness) as part of an investigation into their function as signals. Patch size was not significantly related to any of our measures of fitness, but male great tits with more immaculate cheek patches had significantly greater access to a safer feeding site in winter and produced heavier chicks in small woods. Females with more immaculate patches bred significantly earlier in 2 of the 3 years of the study in both large and small woods. We decreased the immaculateness of both sexes with dye and found that competition with other tits significantly increased their exposure to danger when feeding. Factors resulting in reduced immaculateness included ectoparasites, fighting with conspecifics, faster feather wear in young birds and the timing of the autumn moult. Selection for immaculateness by conspecifics may be one mechanism responsible for the evolution of regular head and body patterns in several species of birds and in other animals.     

Inheritance of the snakeskin color pattern in the guppy, Poecilia reticulata

We made single-pair reciprocal crosses between the Green Snakeskin and Yellow Snakeskin domesticated strains of the guppy, Poecilia reticulata. The two snakeskin strains differ by a single autosomal gene, with the Green Snakeskin strain having the wild-type background coloration caused by the dominant gene (B), whereas the Yellow Snakeskin is homozygous for the recessive blond allele (bb). The snakeskin body and tail patterns characterizing males of these two strains are determined by two genes--Ssb and Sst--that are closely linked on the Y chromosome. The greenish-yellow tail color of the Green Snakeskin strain is mediated by an X-linked dominant gene, Grt. The recessive wild-type allele, Grt+, gives the hyaline tail color. In the Yellow Snakeskin strain, the Grt gene is expressed as a golden-yellow color as a result of the presence of the bb homozygous condition. The putative genotypes of the males and females of the Green Snakeskin strain are BB XGrt YSsb,Sst and BB XGrt XGrt, respectively. Males and females of the Yellow Snakeskin strain have the putative genotypes bb XGrt YSsb,Sst and bb XGrtXGrt, respectively. As a result of crossing over between the X and Y chromosomes, a few males and females of these two snakeskin strains may carry one or both snakeskin pattern genes (Ssb and Sst) on the X chromosome.     

Inheritance pattern of familial hypercholesterolemia and markers of cardiovascular risk

Studies in children and adults have resulted in conflicting evidence in the quest for the answer to the hypothesis that offspring from hypercholesterolemic mothers might have an increased cardiovascular risk. Previous studies might have suffered from limitations such as cohort size and clinical sampling bias. We therefore explored this hypothesis in large cohorts of both subjects with familial hypercholesterolemia (FH) and unaffected siblings in a wide age range. In three cohorts (cohort 1: n = 1,988, aged 0–18 years; cohort 2: n = 300, 8–30 years; cohort 3: n = 369, 18–60 years), we measured lipid and lipoproteins as well as carotid intima-media thickness (c-IMT) in offspring from FH mothers versus FH fathers. For LDL cholesterol, triglycerides (TGs), and c-IMT, we performed a pooled analysis. No significant differences could be observed in c-IMT, lipid, or lipoprotein levels from offspring of FH mothers versus FH fathers. Pooled analyses showed no significant differences for either LDL cholesterol [mean difference 0.02 (−0.06,0.11) mmol/l, P = 0.60], TGs [mean difference 0.07 (0.00,0.14) mmol/l, P = 0.08], or c-IMT [mean difference −0.00 (−0.01,0.01) mm, P = 0.86]. Our data do not support the hypothesis that cardiovascular risk markers are different between offspring from FH mothers and FH fathers.     

Inheritance of finger pattern types in MZ and DZ twins

Digital patterns of a sample on twins were analyzed to estimate the resemblance between monozygotic (MZ) and dizygotic (DZ) twins and to evaluate the mode of inheritance by the use of maximum likelihood based variance decomposition analysis. MZ twin resemblance of finger pattern types appears to be more pronounced than in DZ twins, which suggests the presence of genetic factors in the forming of fingertip patterns. The most parsimonious model shows twin resemblance in count of all three basic finger patterns on 10 fingers. It has significant dominant genetic variance component across all fingers. In the general model, the dominant genetic variance component proportion is similar for all fingertips (about 60%) and the sibling environmental variance is significantly nonzero, but the proportion between additive and dominant variance components was different. Application of genetic model fitting technique of segregation analyses clearly shows mode of inheritance. A dominant genetic variance component or a specific genetic system modifies the phenotypic expression of the fingertip patterns. The present study provided evidence of strong genetic component in finger pattern types and seems more informative compared to the earlier traditional method of correlation analysis.     

Inheritance pattern of platelet membrane fluidity in Alzheimer disease.

The fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene in labeled platelet membranes, an index of membrane fluidity, is a stable, familial trait that is associated with a clinically distinct subtype of Alzheimer disease. Complex segregation analysis of this continuous variable was performed on 95 members of 14 pedigrees identified through probands who had autopsy-confirmed or clinically diagnosed Alzheimer disease. The results suggest that platelet membrane fluidity is controlled by a single genetic locus, PMF, with two alleles that have additive effects. The PMF locus appears to explain approximately 80% of the total variation in platelet membrane fluidity within the families of patients with Alzheimer disease.     

Inheritance of exine pattern in Nicotiana x sanderae (Solanaceae)

Two distinct exine patterns were found among plants of Nicotiana x sanderae; studies of the F1 generation, and the F₂ produced by self and cross bud-pollination showed one pattern to be recessive, the other dominant, perhaps controlled by two genes. The occurrence of the two patterns in these and other flowering plants and in spores of non-flowering plants is discussed in relation to genie control of exine pattern.     

Inheritance pattern of downy mildew resistance in advanced generations of sorghum*

In a project aimed to incorporate downy mildew resistance into sorghum hybrid seed parents, we screened F₄ and F₅ families for resistance to the ICRISAT Centre isolate of the pathogen using a greenhouse seedling screening technique. The families originated from a cross of 296B (susceptible) and IS 18757 [(QL-3) resistant]. The F₄s were obtained from agronomic selection in F₂s and F₃s, and the F₅ families from advancing plants identified as resistant in segregating F₄ families. The resistant plants were more than double the number of susceptible plants in the F₄ and almost so in the F₅ suggesting that resistance to downy mildew was dominant. Of the four genetic models examined (a single-locus model and three two-locus models with complementary, inhibitory, and a combination of complementary and inhibitory interactions), the two-locus model with independent segregation and a combination of complementary and inhibitory inter-allelic interaction appeared to be most appropriate in explaining the segregation patterns within and among F₄ and F₅ families. Accordingly, for resistance to P. sorghi, the suggested genotypes for IS 18757 is Pl_aPl_aPl_bPl_b and for 296B is Pl_aPl_aPl_bPl_b.     

Delayed maturation of plumage coloration and plumage spottedness in the Barn Owl (Tyto alba)

Summary The Barn Owl (Tyto alba) varies in plumage from dark reddish-brown to white, and from heavily marked with black spots to immaculate. Males are commonly lighter coloured and less spotted than females. I assessed whether male and female Barn Owls delay the full expression of plumage coloration and spottedness to the second year of life. In Switzerland, I quantified the two traits of birds captured at the nestling stage, first, second and third year of life. Males and females became lighter coloured only from the first to the second year. Males became less spotted only from the first to the second year, and females less spotted from the nestling stage to the first year but more spotted from the first to the second year. Females were also similarly spotted at the second and third year of age. By cutting off small pieces of feathers of females I could recognize which feathers had later been renewed. After a complete moult old females did not change in plumage characteristics.

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Verzögerter Wechsel vom Juvenil- zum Adultgefieder bei der Schleiereule(Tyto alba)

Zusammenfassung Das Gefieder der Schleiereule (Tyto alba) variiert von rostbraun bis weiss und von dicht gefleckt bis fleckenlos. Die Männchen sind eher hell und weniger gefleckt als die Weibchen. Es wurde untersucht, ob männliche und weibliche Schleiereulen die volle Entfaltung ihrer Gefiederfarbe und -struktur auf das zweite Lebensjahr verlegen. In der Schweiz habe ich beide Gefiederpolymorphismen bei Jungvögeln, ein-, zwei- und dreijährigen Vögeln quantifiziert. Bei Männchen und Weibchen wurde das Auslichten der Gefiederfarbe nur zwischen dem 1. und 2. Lebensjahr beobachtet. Männchen wurden weniger dicht gefleckt nur zwischen dem 1. und 2. Lebensjahr, während Weibchen zwischen dem Nestlingstadium und dem 1. Lebensjahr weniger gefleckt wurden und zwischen dem 1. und 2. Lebensjahr wieder mehr Flecken hatten. Weibchen wurden also gleich gefleckt im 2. und 3. Lebensjahr. Um die erneuerten Federn zu erkennen, wurden bei Weibchen kleine Federstücke herausgeschnitten. Nach einer vollständigen Erneuerung der Brustfedern hatte sich die Farbe und die Anzahl Punkte bei alten Weibchen nicht geändert.

     

Air pollution fades the plumage of the Great Tit

1. Great Tits ( Parus major ) derive the carotenoid pigments for their yellow plumage via the prey items in their diet. Air pollution is known to affect the abundance of many forest insects, e.g. green caterpillars, which are an important source of food and pigments for tits. This study investigates whether air pollutants indirectly affected the intensity of the yellow colour in P. major plumage via the reduced access to carotenoid sources.
2. The intensity of the yellow colour in the plumage of P. major nestlings was scored and the relative abundance of green herbivorous larvae in territories around a polluting copper smelter in SW Finland was simultaneously measured.
3. Both the intensity of yellow colour in nestling plumage and caterpillar abundance increased with increasing distance from the pollution source. The colour intensity correlated significantly with the density of green herbivorous larvae in a territory.
4. Parus major nestlings were significantly heavier at distant sites than close to the pollution source which suggests that the future survival probability of pale nestlings may be lowered.
5. Young birds, after their first moult, were studied for the relationships between condition, size and plumage colour by the means of ptilochronology. The plumage colour intensity did not correlate with the size corrected width of the growth bars in fifth rectrix (condition at moult) but was correlated positively with the length of the rectrix (size).
6. The implications of colour change for survival and mate choice are discussed.     

Evolutionary genetics: the evolution of plumage patterns

The identification and sequencing of a gene affecting melanin production in the bananaquit, a bird species notable for its polymorphic plumage colour, paves the way for much greater understanding of the evolution of plumage patterns in birds, and the developmental modulations involved in producing new patterns.     

Contemporary divergence of island bird plumage

Although the diversity in avian plumage coloration is striking, there is little known about the rate with which colour diverges. Eastern bluebirds Sialia sialis bermudensis on the island of Bermuda are considered endemic based upon differences in coloration from the mainland, but recent molecular evidence suggests they established on the island only 400 yr ago. We explored sexual dichromatism and colour divergence in this isolated population, thus providing one of the few quantitative accounts of contemporary plumage change. Contrary to expectations that sexual dichromatism would decrease in this sedentary island population, we found that males and females have increased plumage ornamentation in a coordinated fashion that acts to preserve sexual dichromatism, while plumage colour is also altered to become brighter and bluer. These differences were in place at least 100 yr ago based upon a separate analysis of museum specimens. Our results provide insight into the divergence of plumage colour in an incipient species, and we show the remarkable extent to which plumage colour can change over contemporary time frames.