Natural variation in the sexually selected feather ornaments of crested auklets (Aethia cristatella) does not predict future survival

We evaluated whether sexually selected crest and auricular plumefeather ornaments of crested auklet (Aethia cristatella) adultscovaried with individual local survival over 11 years (1991–2001).Crested auklets (n = 364 total) were captured near breedingsites, marked with color rings, and local survival estimateswere based on color ring resightings at a breeding colony. Survivalestimates and relationships among local survival and crest length,auricular plume length, mass and tarsus were evaluated usingthe program MARK. The best models included four groups, definedby sex and ease of resighting, that differed in resighting rate(p) but not local survival rate (). This model structure effectivelyexplained sources of variation in local survival and resightabilityamong individuals. The best fitting model showed local survivalrate varying annually, while accounting for differences in resightabilityof marked individuals between the sexes and groups ([t], p[sex*easeof resighting]). Annual local survival varied from 0.940 ±0.029 (SE) in 1993–1994 to 0.767 ± 0.034 in 1997–1998and averaged 0.859 ± 0.019. We found no evidence thatcrested auklet local survival covaried with continuous variationin individuals' ornaments. Simulations indicated that our dataset was sufficient to detect a relationship between local survivaland a covariate that equaled or exceeded a range of 8%. Theimplications for competing sexual selection mechanisms of empiricallymeasured survival–ornament relationships are controversial,but our study emphasizes that survival estimates for such investigationsmust control for confounding factors such as resighting rateas well as have sufficient statistical power and time scaleto be biologically meaningful. Our results are most consistentwith the idea that the conspicuous variation in crested auklet'sshowy ornaments is arbitrary with respect to individual viabilityas quantified by their long-term survival.     

Vocal and Optical Indicators of Individual Quality in a Social Seabird,the Crested Auklet (Aethia cristatella)

Indicators of individual quality in ornamentation or in vocalizations have been reported for different animal species. However, no studies have jointly investigated ornamentation and vocalizations in one species. The crested auklet (Aethia cristatella, Alcidae) is a small colonial seabird of the North Pacific and is unusual for a bird in using optical, vocal, and olfactory signals. We estimated the potential for coding individual quality in vocalizations and plumage ornamentation and the relationship between vocal and optical traits in crested auklets. During the summer seasons of 2008–2009, we recorded 359 trumpet calls from 28 individually marked males and measured indices of body size, condition, and plumage patterns of 58 male and 48 female crested auklets from a breeding colony on Talan Island, Sea of Okhotsk. We found strong interindividual differences in trumpet call characteristics. Furthermore, we found that the maximum fundamental frequency of the loudest notes of the trumpet call is negatively correlated with body condition, and head crest length is positively correlated with body size. However, we found no relationship between vocal and ornamental traits. The results suggest that advertising calls of crested auklets signal caller individuality and quality, but future experimental studies should test whether or not this is indeed case.     

Breeding Biology of the Crested Auklet (Aethia cristatella,Alcidae, Charadriiformes) in the Northern Part of the Sea of Okhotsk

Biology Bulletin - The breeding biology of the crested auklet, Aethia cristatella, was studied over the period 1989–2019 on Talan Island, Tauiskaya Bay, Sea of Okhotsk. In the early 1990s,...     

Seasonal covariation in progesterone and odorant emissions among breeding crested auklets (Aethia cristatella)

Crested auklets emit a citrus-like odorant that is seasonally modulated, suggesting that it is a secondary sexual trait. We hypothesized that expression of the chemical odorant is facilitated by steroid hormones, similar other secondary sexual traits in birds. Therefore we examined variation in concentrations of hormones in blood plasma and odor production during incubation and early chick rearing. A novel method was used to obtain and measure chemical emissions of crested auklets. Blood plasma samples were analyzed by radioimmunoassay. Progesterone was detected in all birds, and it varied during the breeding season. Octanal emissions covaried with progesterone levels in males but not in females. No seasonal patterns were detected in testosterone, estrogen or DHT, and these hormones were not detected in all breeding adults. Covariance of progesterone and octanal emissions in males suggests there could be at least an indirect relationship between odor emissions and steroid hormones in this species. Thus expression of the citrus-like odorant of crested auklets, like other secondary sexual traits in birds, could be regulated by steroid hormones.     

Patterns of fluctuating asymmetry in sexual ornaments predict female choice

Extravagant secondary sexual characters are assumed to have arisen and be maintained by sexual selection. While traits like horns, antlers and spurs can be ascribed to intrasexual competition, other traits such as extravagant feather ornaments, displays and pheromones have to be ascribed to mate choice. A number of studies have tested whether females exert selection on the size of male ornaments, but only some of these have recorded female preferences for the most extravagantly ornamented males. Here I demonstrate that female choice can be directly predicted from the relationship between the degree of fluctuating asymmetry and the size of a secondary sexual character. Fluctuating asymmetry is an epigenetic measure of the ability of individuals to cope with stress, and it occurs when an individual is unable to undergo identical development of an otherwise bilaterally symmetric trait on both sides of its body. There is a negative relationship between the degree of fluctuating asymmetry and the absolute size of an ornament in those bird species with a female preference for the largest male sex trait, while there is a flat or U-shaped relationship among species without a female preference. These results suggest that females prefer exaggerated secondary sexual characters if they reliably demonstrate the ability of males to cope with genetic and environmental stress. Some species may demonstrate a flat or U-shaped relationship between the degree of fluctuating asymmetry and the absolute size of an ornament because (i) the genetic variance in viability signalled by the secondary sex trait has been depleted; (ii) the secondary sex trait is not particularly costly and therefore does not demonstrate condition dependence; or because (iii) the sex traits can be considered arbitrary traits rather than characters reflecting good genes.     

Geographic variation in the function of ornaments in the common yellowthroat Geothlypis trichas

We used controlled aviary experiments to study the role of male ornaments in male-male competition and female choice in the common yellowthroat Geothlypis trichas , a sexually dichromatic warbler. Previous aviary studies in Wisconsin, USA, indicated that males with larger black facial masks were dominant over males with smaller masks and preferred by females in mate choice experiments. In this study, we replicated those experiments in a population in New York, USA, where male mating success was related more consistently to the size of the yellow bib (throat, breast, and belly) than to the size of the mask. Similar to the study in Wisconsin, we found that males with larger masks were more likely to be dominant in New York, however, we found that males with larger bibs were preferred by females in New York, and there was no significant preference for males with larger masks. These results are consistent with the hypothesis that carotenoid-based ornaments are selected by female choice and melanin-based ornaments are selected by male-male competition. However, the pattern of female choice appears to vary between New York and Wisconsin. This geographic difference could be related to a variety of environmental factors (habitat, carotenoid and parasite abundance) that affect the costs and benefits of choosing males with particular ornaments in each location.     

Maintenance of genetic variation in sexual ornaments: a review of the mechanisms

Female preferences for elaborate male sexual traits have been documented in a number of species in which males contribute only genes to the next generation. In such systems, mate choice has been hypothesised to benefit females genetically. For the genetic benefits to be possible there must be additive genetic variation (V(A)) for sexual ornaments, such that highly ornamented males can pass fitter genes on to the progeny of choosy females. Here, I review the mechanisms that can contribute to the maintenance of this variation. The variation may be limited to sexual ornaments, resulting in Fisherian benefits in terms of the increased reproductive success of male progeny produced by choosy females. Alternatively, ornaments may capture V(A) in other life-history traits. In the latter case, "good genes" benefits may apply in terms of improved performance of the progeny of either sex. Some mechanisms, however, such as negative pleiotropy, sexually antagonistic variation or overdominance, can maintain V(A )in ornaments and other life-history traits with little variation in total fitness, leaving little room for any genetic benefits of mate choice. Distinguishing between these mechanisms has consequences not only for the theory of sexual selection, but also for evolution of sex and for biological conservation. I discuss how the traditional ways of testing for genetic benefits can usefully be supplemented by tests detecting benefits resulting from specific mechanisms maintaining V(A )in sexual ornaments.     

Different ornaments signal male health and MHC variation in two populations of a warbler

Male traits that signal health and vigour are used by females to choose better quality mates, but in some cases the male trait selected by females differs among populations. Multiple male traits can be maintained through female mate choice if both traits are equally honest indicators of male quality, but tests of this prediction are rare. By choosing males based on such traits, females could gain direct benefits from males (assistance with parental care), but when females choose extra‐pair mates based on these traits, females gain only male sperm, and potentially indirect genetic benefits for their offspring. In common yellowthroats (Geothylpis trichas), female choice of extra‐pair mates targets two different plumage ornaments: the black mask in a Wisconsin population and the yellow bib in a New York population. Previously, we found that the black mask in Wisconsin is related to greater major histocompatibility complex (MHC) class II variation, which in turn signals better survival and disease resistance. In this study, we examined the signalling function of the yellow bib in New York to test whether it signals the same aspects of male quality as the black mask in Wisconsin. As predicted, we found that the yellow bib in New York is most closely associated with MHC variation, which also signals survival and resistance to blood parasites. Thus, the ornament preferred by females differs between the two populations, but the different ornaments signal similar aspects of male health and genetic quality, specifically information regarding MHC variation and potential indirect genetic benefits to females.     

Expression of sexual ornaments in a polymorphic species: phenotypic variation in response to environmental risk

Secondary sexual traits may evolve under the antagonistic context of sexual and natural selection. In some polymorphic species, these traits are only expressed during the breeding period and are differently expressed in alternative phenotypes. However, it is unknown whether such phenotypes exhibit phenotypic plasticity of seasonal ornamentations in response to environmental pressures such as in the presence of fish (predation risk). This is an important question to understand the evolution of polyphenisms. We used facultative paedomorphosis in newts as a model system because it involves the coexistence of paedomorphs that retain gills in the adult stage with metamorphs that have undergone metamorphosis, but also because newts exhibit seasonal sexual traits. Our aim was therefore to determine the influence of fish on the development of seasonal ornamentation in the two phenotypes of the palmate newt (Lissotriton helveticus). During the entire newt breeding period, we assessed the importance of phenotype and fish presence with an information‐theoretic approach. Our results showed that paedomorphs presented much less developed ornamentation than metamorphs and those ornamentations varied over time. Fish inhibited the development of sexual traits but differently between phenotypes: in contrast to metamorphs, paedomorphs lack the phenotypic plasticity of sexual traits to environmental risk. This study points out that internal and external parameters act in complex ways in the expression of seasonal sexual ornamentations and that similar environmental pressure can induce a contrasted evolution in alternative phenotypes.     

Patterns of allozyme variation in Nordic Pilosella

Patterns of allozyme variation have been investigated in 101 clones representing most of the morphological variation (and taxa) found in the amphi-apomictic genus Pilosella Hill. in the Nordic countries. Levels of variation were very high, both within narrowly defined taxa and within the whole data-set, but the correlation between a morphology-based taxonomy and patterns of allozyme variation was very weak. Almost all enzyme bands were found in more than one taxon and the differences between broadly defined species in terms of the frequency of bands were generally small. Cluster analyses did not perfectly recover any taxon but there were some tendencies for samples of some broadly defined taxa (e.g. P. officinarum s. l., and P. cymosa ssp. cymosa) to cluster together. It is concluded that there is considerable gene-flow among virtually all Nordic morpho-types of Pilosella and this is considered an argument for applying a very broad species concept in this genus.Financial support for the present study has been recieved from Stiftelsen Harald E. Johanssons minnesfond at the Royal Swedish Academy of Sciences.     

Phenotypic variation and fluctuating asymmetry in sexually dimorphic feather ornaments in relation to sex and mating system

Secondary sexual characters have been hypothesized to demonstrate increased phenotypic variation between and within individuals as compared to ordinary morphological traits. We tested whether this was the case by studying phenotypic variation, expressed as the coefficient of variation (CV), and developmental instability, measured as fluctuating asymmetry (FA), in ornamental and non-ornamental traits of 70 bird species with feather ornamentation while controlling for similarity among species due to common descent. Secondary sexual characters differed from ordinary morphological traits by showing large phenotypic CV and FA. This difference can be explained by the different mode of selection operating on each kind of trait: a history of intense directional (ornaments) and stabilizing selection (non-ornaments). Phenotypic variation is reduced in the sex with more intense sexual selection (males), but does not differ among species with different mating systems. The strength of stabilizing selection arising from natural selection is associated with decreased CV (wing CV is smaller than tarsus or tail CVs). We found evidence of FA being reduced in ornamental feathers strongly affected by aerodynamics (tail feathers) compared to other ornaments, but only in females. In conclusion, CV and FA were not related, suggesting mat phenotypic plasticity and developmental instability are independent components of phenotypic variation.     

Patterns of variation within self-incompatibility loci

Diverse self-incompatibility (SI) mechanisms permit flowering plants to inhibit fertilization by pollen that express specificities in common with the pistil. Characteristic of at least two model systems is greatly reduced recombination across large genomic tracts surrounding the S-locus, which regulates SI. In three angiosperm families, including the Solanaceae, the gene that controls the expression of gametophytic SI in the pistil encodes a ribonuclease (S-RNase). The gene that controls pollen SI expression is currently unknown, although several candidates have recently been proposed. Although each candidate shows a high level of polymorphism and complete allelic disequilibrium with the S-RNase gene, such properties may merely reflect tight linkage to the S-locus, irrespective of any functional role in SI. We analyzed the magnitude and nature of nucleotide variation, with the objective of distinguishing likely candidates for regulators of SI from other genes embedded in the S-locus region. We studied the S-RNase gene of the Solanaceae and 48A, a candidate for the pollen gene in this system, and we also conducted a parallel analysis of the regulators of sporophytic SI in Brassica, a system in which both the pistil and pollen genes are known. Although the pattern of variation shown by the pollen gene of the Brassica system is consistent with its role as a determinant of pollen specificity, that of 48A departs from expectation. Our analysis further suggests that recombination between 48A and S-RNase may have occurred during the interval spanned by the gene genealogy, another indication that 48A may not regulate SI expression in pollen.     

Patterns of morphological variation insesamum indicum

Cultivars of sesame from 20 countries were sampled for morphological variability. Taximetric methods, including factor, cluster, discriminant, and principal components analyses, established patterns of similarities and were used to generate groupings among the taxa. The complementary results of the analyses indicate that 8 major groups can be discerned. Plants with tetracarpellate capsules have a distinctive form and comprise the initial separation from the entire collection on the dendrogram. The second branch is a group of purple-tinged plants from India that also includes the proposed progenitor. A short, bushy, early maturing genotype consists of predominantly Turkish cultivars. Another group, composed primarily of Korean accessions, consists of unbranched plants with strap-shaped leaves. Other groups are less easily typified. This characterization of the genetic variation in sesame can be used to identify sources of genetic materials for crop improvement, as well as to provide information about the evolution and genetic differentiation of the crop.     

Patterns of genetic variation in anthropogenically impacted populations

Genetic variation is considered critical for allowing natural populations to adapt to their changing environment, and yet the effects of human disturbance on genetic variation in the wild are poorly understood. Different types of human disturbances may genetically impact natural populations in a predictable manner and so the aim of this study was to provide an overview of these changes using a quantitative literature review approach. I examined both allozyme and microsatellite estimates of genetic variation from peer-reviewed journals, using the mean number of alleles per locus and expected heterozygosity as standardized metrics. Populations within each study were categorized according to the type of human disturbance experienced (“hunting/harvest”, “habitat fragmentation”, or “pollution”), and taxon-specific, as well as time- and context-dependent disturbance effects were considered. I found that human disturbances are associated with weak, but consistent changes in neutral genetic variation within natural populations. The direction of change was dependent on the type of human disturbance experienced, with some forms of anthropogenic challenges consistently decreasing genetic variation from background patterns (e.g., habitat fragmentation), whereas others had no effect (e.g., hunting/harvest) or even slightly increased genetic variation (e.g., pollution). These same measures appeared sensitive to both the time of origin and duration of the disturbance as well. This suggests that the presence or absence, strength, type, as well as the spatial and temporal scale of human disturbance experienced may warrant careful consideration when conservation management plans are formulated for natural populations, with particular attention paid to the effects of habitat fragmentation.     

Patterns of genetic variation in Native America.

Allele frequencies from seven polymorphic red cell antigen loci (ABO, Rh, MN, S, P, Duffy, and Diego) were examined in 144 Native American populations. Mean genetic distances (Nei's D) and the fixation index FST are approximately equal for the North and South American samples but are reduced in the Central American geographic area. The relationship between genetic distance and geographic distance differs markedly across geographic areas. The correlation between geographic distance and genetic distance for the North and Central American data is twice as large as that observed for the South American samples. This geographic difference is confirmed in spatial autocorrelation analyses; no geographic structure is apparent in the South American data but geographic structure is prominent in North and Central American samples. These results confirm earlier observations regarding differences between North and South American gene frequency patterns.