Does avian conspicuous colouration increase or reduce predation risk?

Animals often announce their unprofitability to predators through conspicuous coloured signals. Here we tested whether the apparently conspicuous colour designs of the four European Coraciiformes and Upupiformes species may have evolved as aposematic signals, or whether instead they imply a cost in terms of predation risk. Because previous studies suggested that these species are unpalatable, we hypothesized that predators could avoid targeting them based on their colours. An experiment was performed where two artificial models of each bird species were exposed simultaneously to raptor predators, one painted so as to resemble the real colour design of these birds, and the other one painted using cryptic colours. Additionally, we used field data on the black kite's diet to compare the selection of these four species to that of other avian prey. Conspicuous models were attacked in equal or higher proportions than their cryptic counterparts, and the attack rate on the four species increased with their respective degree of contrast against natural backgrounds. The analysis of the predator's diet revealed that the two least attacked species were negatively selected in nature despite their abundance. Both conspicuous and cryptic models of one of the studied species (the hoopoe) received fewer attacks than cryptic models of the other three species, suggesting that predators may avoid this species for characteristics other than colour. Globally, our results suggest that the colour of coraciiforms and upupiforms does not function as an aposematic signal that advises predators of their unprofitability, but also that conspicuous colours may increase predation risk in some species, supporting thus the handicap hypothesis.

An analysis of continent-wide patterns of sexual selection in a passerine bird.

Patterns of selection are widely believed to differ geographically, causing adaptation to local environmental conditions. However, few studies have investigated patterns of phenotypic selection across large spatial scales. We quantified the intensity of selection on morphology in a monogamous passerine bird, the barn swallow Hirundo rustica, using 6495 adults from 22 populations distributed across Europe and North Africa. According to the classical Darwin-Fisher mechanism of sexual selection in monogamous species, two important components of fitness due to sexual selection are the advantages that the most attractive males acquire by starting to breed early and their high annual fecundity. We estimated directional selection differentials on tail length (a secondary sexual character) and directional selection gradients after controlling for correlated selection on wing length and tarsus length with respect to these two fitness components. Phenotype and fitness components differed significantly among populations for which estimates were available for more than a single year. Likewise, selection differentials and selection gradients differed significantly among populations for tail length, but not for the other two characters. Sexual selection differentials differed significantly from zero across populations for tail length, particularly in males. Controlling statistically for the effects of age reduced the intensity of selection by 60 to 81%, although corrected and uncorrected estimates were strongly positively correlated. Selection differentials and gradients for tail length were positively correlated between the sexes among populations for selection acting on breeding date, but not for fecundity selection. The intensity of selection with respect to breeding date and fecundity were significantly correlated for tail length across populations. Sexual size dimorphism in tail length was significantly correlated with selection differentials with respect to breeding date for tail length in male barn swallows across populations. These findings suggest that patterns of sexual selection are consistent across large geographical scales, but also that they vary among populations. In addition, geographical patterns of phenotypic selection predict current patterns of phenotypic variation among populations, suggesting that consistent patterns of selection have been present for considerable amounts of time.

Sexual selection, germline mutation rate and sperm competition.

BACKGROUND: An important component of sexual selection arises because females obtain viability benefits for their offspring from their mate choice. Females choosing extra-pair fertilization generally favor males with exaggerated secondary sexual characters, and extra-pair paternity increases the variance in male reproductive success. Furthermore, females are assumed to benefit from 'good genes' from extra-pair sires. How additive genetic variance in such viability genes is maintained despite strong directional selection remains an evolutionary enigma. We propose that sexual selection is associated with elevated mutation rates, changing the balance between mutation and selection, thereby increasing variance in fitness and hence the benefits to be obtained from good genes sexual selection. Two hypotheses may account for such elevated mutation: (1) Increased sperm production associated with sperm competition may increase mutation rate. (2) Mutator alleles increase mutation rates that are revealed by the expression of condition-dependent secondary sexual characters used by choosy females during their mate choice. M Petrie has independently developed the idea that mutator alleles may account for the maintenance of genetic variation in viability despite strong directional selection. RESULTS: A comparative study of birds revealed a positive correlation between mutation rate at minisatellite loci and extra-pair paternity, but not between mutation rate and relative testes mass which is a measure of relative sperm production. Minisatellite mutation rates were not related to longevity, suggesting a meiotic rather than a mitotic origin of mutations. CONCLUSION: We found evidence of increased mutation rate in species with more intense sexual selection. Increased mutation was not associated with increased sperm production, and we suggest that species with intense sexual selection may maintain elevated mutation rates because sexual selection continuously benefits viability alleles expressed in condition-dependent characters. Sexual selection may increase mutational input, which in turn feeds back on sexual selection because of increased variance in viability traits.

[Interactive morphometry and densitometry for the study of epidermoid carcinoma of the larynx. Preliminary results]. / Aplicación de la morfometría y densitometría interactivas al estudio del carcinoma epidermoide laríngeo. Resultado preliminar.

At present the utilization of quantitative techniques in anatomopathological studies is becoming more and more frequent, so adding the possibility of gaining measures and numerical assessments in front of conventional quantitative evaluations. In the paper the AA. report their first attempt with conventional slides of epidermoid carcinomas of the larynx, taken from the files. The aim has been to check out the contribution of this procedure compared with other traditional pathological techniques.

[A comparative study of the prognostic value of morphometric data and of conventional pathological anatomy in laryngeal epidermoid carcinoma]. / Estudio comparativo del valor pronóstico de los datos morfofotométricos y de la anatomía patológica convencional en el carcinoma epidermoide de laringe.

At the moment the use of quantitative techniques is not very frequent in standard anatomopathologic studies of epidermoid carcinoma of the larynx. By "multiple linear regression" the authors show a closed relationship between survival and conventional anatomopathologic data as grade of differentiation and of lymphoid infiltration of the primary tumor.

[The importance of laryngeal compartmentation in the limitation of tumor extension]. / Importancia de la compartimentación laríngea en la limitación de la extensión tumoral.

Histologic specimens from 75 patients with squamous cell carcinoma of the larynx treated exclusively by surgery were studied with special attention paid to the growth of the tumor in relation with the different laryngeal compartments. Some aspects traditionally admitted are discussed. The result show a not very close relation between the classic anatomic descriptions and the tumoral growing.

[A morpho-photometric study of laryngeal epidermoid carcinoma]. / Estudio morfofotométrico del carcinoma epidermoide de laringe.

At the moment the use of quantitative techniques in anatomopathology is more and more frequent. In this study the authors use for the first time the morpho-photometry approach in epidermoid carcinomas of the larynx coming from filed material. In this way they are checking if this method adds anything to conventional anatomopathology.

[Study of histological preparations of laryngeal epidermoid carcinoma using image analysis]. / Estudio de preparaciones histológicas de carcinoma epidermoide laríngeo mediante análisis de imagen.

At the present application of quantitative techniques in anatomopathologic studies is becoming more and more frequent, adding the possibility of numeric and quantitative evaluation. In this study the authors make a first attempt with one of these methods, the image analysis using conventional slides of epidermoid carcinomas from larynx.

[Prognostic value of the grade of malignancy in epidermoid carcinoma of the larynx]. / Valor pronóstico del grado de malignidad en el carcinoma epidermoide de la laringe.

At the moment the use of quantitative techniques in anatomopathology are becoming more and more frequent. In this study, with the mathematical transformation of morphometric data obtained from cell populations of epidermoid carcinoma of the larynx, the authors arrive at the "grade of malignancy" for every patient which has in itself prognostic value without taking into account the other anatomopathologic or clinical parameters.

[Use of morphophotometry in the study of the kinetics of cell populations in laryngeal epidermoid carcinoma]. / Aplicación de la morfofotometría al estudio de la cinética de poblaciones celulares en el carcinoma epidermoide laríngeo.

The use of morpho-photometric techniques in anatomopathology is, on the whole, not very frequent at the moment. In this study the authors show the possible applications of these quantitative methods for the evaluation of kinetics characteristics of cell population in epidermoid carcinomas of the larynx.

[Vascular microinvasion in laryngeal epidermoid carcinoma]. / Microinvasión vascular en el carcinoma epidermoide laríngeo.

Microvascular invasion by carcinoma cells is one of the first steps for the potential development of metástasis. The presence of squamous cell carcinoma within capillaries and/or venules in the immediate vicinity of primary lesions of the oral cavity and oropharynx may be related to regional lymph node metastasis. To evaluate this possibility in laryngeal carcinomas we have reviewed the histopathologic features of 48 cases of this type of tumor with simultaneous surgical treatment of the primary neoplasms and the neck. In our opinion the histologic finding of such invasion is not pathognomonic for establishment of regional metástasis in epidermoid carcinoma of the larynx.

[Prognostic value of lymph node histologic pattern in epidermoid carcinoma of the larynx]. / Interés pronóstico del patrón histológico ganglionar en el carcinoma epidermoide de laringe.

Histologic specimens from 48 patients with squamous cell carcinoma of the larynx treated exclusively by surgery were studied with special attention paid to the reactivity of regional lymph nodes. The lymph nodes were classified into four microscopic patterns of immune response: lymphocytic predominance, sinus histiocytosis, germinal center predominance and unstimulated or lymphocytic depletion. As a result no correlation were then made between the patterns and survival rate at 5 year follow-up.

[Prognostic value of the degree of differentiation and the peri-tumor lymphoid infiltration in epidermoid carcinoma of the larynx]. / Valor pronóstico del grado de diferenciación y el infiltrado linfoide peritumoral en el carcinoma epidermoide de laringe.

By multiple linear regression the authors show a closed relationship between survival and conventional anatomopathologic data as grade of differentiation and of lymphoid infiltration of the primary tumor. This retrospective pathological study showed that various degrees of squamous cell differentiation may be recognized for malignant laryngeal lesions and that such distinction may be of prognostic significance.

SPECIATION AND FEATHER ORNAMENTATION IN BIRDS.

The hypothesis that sexual selection promotes speciation has rarely been tested. We identified 70 evolutionarily independent events of feather ornaments in birds. For each focal species we noted the number of ornamented and nonornamented species belonging to its genus and its number of subspecies, as well as its mating system and the extent of its geographic range. For purposes of comparison, we randomly chose a second, nonornamented species for which we obtained information on the number of subspecies, and in cases in which the nonornamented species was in the same genus, we chose a third, nonornamented species in a related genus and obtained the same information. We then noted the number of species in each genus and the difference in numbers of species, or species richness, between paired genera. For the genera of the focal ornamented species, we regressed number of ornamented species on number of nonornamented species and found a positive relationship. As number of species per genus rose, number of ornamented species per genus rose more rapidly, indicating that more speciose genera have a higher proportion of ornamented species than less speciose genera. We then took the deviations from this regression, the residual number of species, and regressed them on the differences in species richness between the paired genera. This relationship was positive indicating that ornamented genera with more than the expected number of ornamented species were more speciose with respect to their paired genera than were genera with fewer than the expected number of ornamented species. Finally, we compared the deviations from this regression, the residual number of ornamented species, with species' mating system and found a greater residual number of ornamented species among species whose mating system is associated with greater skew in male mating success and thus more intense sexual selection. Ornamented species had more subspecies than nonornamented species, even when controlling for geographic range, suggesting an association between subspeciation and ornaments.

[Bone marrow biopsy in myeloproliferative syndromes: prognostic value of cellular quantification]. / Biopsia medular en los síndromes mieloproliferativos: valor pronóstico de la cuantificación celular.

The proportion of granulocytes, erythroblasts, immature cells and megakaryocytes was evaluated when revising the bone-marrow biopsy specimens of 36 patients with myeloproliferative syndromes. These proportions were compared between themselves, a so-called Z value being thus attained; such value resulted from summing the proportion of granulocytes, megakaryocytes and immature cells and subtracting the proportion of erythroblasts. According to its value, above or below the mean, the Z figure correlates with the survival, the difference between both groups appearing as statistically significant (p = 0.02).