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642 results for “ornaments”
Data from: Divergent color signals from homologous unfeathered ornaments in two congeneric grouse
Color-based visual signals are important aspects of communication throughout the animal kingdom. Individuals evaluate color to obtain information about age and condition and to behave accordingly. Birds display a variety of striking, conspicuous colors and make ideal subjects for the study of color signaling. While most studies of avian color focus on plumage, bare unfeathered body parts also display a wide range of color signals. Mate choice and intrasexual competitive interactions are easily observed in lekking grouse, which also signal with prominent unfeathered color patches. Most male grouse have one pair of colorful bare part ornaments (combs), and males of several species also have inflatable air sacs in their throat. Previous studies have mostly focused on comb color and size, but little is known about the signaling role of air sac color. We measured comb size and the color properties of combs and air sacs in the Lesser and Greater Prairie-Chicken (Tympanuchus pallidicinctus and T. cupido, respectively), and investigated whether these properties varied with age and mass. We found that mass predicted color properties of air sacs and that age predicted comb size in the Greater Prairie-Chicken, suggesting that these ornaments indicate condition-dependence. No conclusive relationships between color and age or size were detected in the Lesser Prairie-Chicken. Color properties of both ornaments differed between the two species. Further research is needed to determine mechanisms that link condition to color and whether the information advertised by color signals from these ornaments is intended for males, females, or both.
Data from: The middle Smithian (Early Triassic) ammonoid Arctoceras blomstrandi: Conch morphology and ornamentation in relation to stratigraphy
<p class="MsoNoSpacing">The ammonoid genus <i>Arctoceras</i> (Hyatt, 1900) occurs across all palaeolatitudes, and is a key genus for middle Smithian (Early Triassic) biostratigraphic correlations at a global scale. In this study, intraspecific variations in conch morphology, ornamentation and allometry are examined in relation to stratigraphic position. <i>Arctoceras </i>is the most abundant ammonoid genus in the middle Smithian of Svalbard, Arctic Norway. Originally, seven <i>Arctoceras </i>species were described from Svalbard, but their practical use in fossil identification was questionable. Later, as the importance of intraspecific variation was recognized, six of the <i>Arctoceras</i> species from Svalbard were declared junior synonyms of <i>Arctoceras blomstrandi </i>(Lindström, 1865). Yet, the variations in <i>A. blomstrandi </i>conch morphology remain poorly quantified and the dependence on stratigraphic position unknown. Our research quantifies the intraspecific variation in conch morphology, ornamentation and allometry in relation to stratigraphy of the Svalbard <i>Arctoceras</i>. The results support the assignment of all <i>Arctoceras</i> morphotypes from Svalbard to a single species <i>A. blomstrandi</i>. The new data allow for an updated species description and opens for the use in biostratigraphy of the endmember morphology <i>A. blomstrandi </i>var<i> costatus</i>. We document consistent changes in both conch morphology and ornamentation in the studied stratigraphic interval with a distinct shift towards more evolute and ornate conchs in the top. The trends seen in the strength of ornamentation are partly explained by a covariation with the conch morphology, as wider and more evolute conchs tend to be more ornate (Buckman's law of covariation). The middle Smithian was characterized by a thermal maximum and low δ<sup>13</sup>C<sub>org</sub> values which shifted towards less negative values in the late Smithian and culminated in a positive carbon isotope excursion at the Smithian–Spathian boundary. The most marked shift in the conch morphology and allometric development of <i>A. blomstrandi</i> coincides with the onset of the positive carbon isotope excursion at the end of the middle Smithian, but predates the mid late Smithian cooling of the sea surface.</p>
Female ornaments: is red skin color attractive to males and related to condition in rhesus macaques?
Sexual selection produces extravagant male traits, such as colorful ornaments, via female mate choice. More rarely, in mating systems in which males allocate mating effort between multiple females, female ornaments may evolve via male mate choice. Females of many anthropoid primates exhibit ornaments that indicate intra-individual cyclical fertility, but which have also been proposed to function as inter-individual quality signals. Rhesus macaque females are one such species, exhibiting cyclical facial color variation that indicates ovulatory status, but in which the function of inter-individual variation is unknown. We collected digital images of the faces of 32 rhesus macaque adult females. We assessed mating rates, and consortship by males, according to female face coloration. We also assessed whether female coloration was linked to physical (skinfold fat, BMI) or physiological (fecal glucocorticoid metabolite fGCM, urinary C-peptide concentrations) condition. We found that redder-faced females were mated more frequently, and consorted for longer periods by top-ranked males. Redder females had higher fGCM concentrations, perhaps related to their increased mating activity and consequent energy mobilization, and blood-flow. Prior analyses have shown that female facial redness is a heritable trait, and that redder-faced females have higher annual fecundity, while other evidence suggests that color expression is likely to be a signal rather than a cue. Collectively, the available evidence suggests that female coloration has evolved at least in part via male mate choice. Its evolution as a sexually-selected ornament attractive to males is probably attributable to the high female reproductive synchrony found in this species.
Data from: Fecundity selection on ornamental plumage colour differs between ages and sexes and varies over small spatial scales
Avian plumage colours are some of the most conspicuous sexual ornaments, and yet standardized selection gradients for plumage colour have rarely been quantified. We examined patterns of fecundity selection on plumage colour in blue tits (Cyanistes caeruleus L.). When not accounting for environmental heterogeneity, we detected relatively few cases of selection. We found significant disruptive selection on adult male crown colour and yearling female chest colour and marginally nonsignificant positive linear selection on adult female crown colour. We discovered no new significant selection gradients with canonical rotation of the matrix of nonlinear selection. Next, using a long-term data set, we identified territory-level environmental variables that predicted fecundity to determine whether these variables influenced patterns of plumage selection. The first of these variables, the density of oaks within 50 m of the nest, influenced selection gradients only for yearling males. The second variable, an inverse function of nesting density, interacted with a subset of plumage selection gradients for yearling males and adult females, although the strength and direction of selection did not vary predictably with population density across these analyses. Overall, fecundity selection on plumage colour in blue tits appeared rare and inconsistent among sexes and age classes.
Data from: Sex-specific patterns of aging on sexual ornaments and gametes
Sex differences in age-dependent mortality and reproductive success are predicted to drive the evolution of sexually dimorphic patterns of reproductive investment over life. However, this prediction has not been fully explored because it is difficult to measure primary and secondary sexual traits over the life spans of males and females. Here we studied a population of fowl, Gallus gallus, to gain longitudinal data on a sexual ornament (the comb), quantity of gametes produced, and gamete quality (sperm velocity and egg mass) of males and females. Our results reveal pronounced differences between the sexes in age-specific patterns of reproductive investment. In males, comb size decreased linearly with age, high sperm quality early in life was associated with reduced sperm quality late in life, and high sperm production was related to early death. In contrast, female comb size and egg mass were maximized at intermediate ages, and fecundity was independent of life span. Finally, the way traits were related in males did not change over life, whereas in females the association between fecundity and comb size changed from positive to negative over the lifetime of a female, indicating that aging may lead to trade-offs in investment between traits in females. These results show that males and females differ in reproductive investment with age, in terms of both the expression of individual traits and their phenotypic covariance.
Data from: Female ornamentation and the fecundity trade-off in a sex-role reversed pipefish
Sexual ornaments found only in females are a rare occurrence in nature. One explanation for this is that female ornaments are costly to produce and maintain and, therefore, females must trade-off resources related to reproduction to promote ornament expression. Here, we investigate whether a trade-off exists between female ornamentation and fecundity in the sex-role reversed, wide-bodied pipefish, Stigmatopora nigra. We measured two components of the disk-shaped, ventral-striped female ornament, body width and stripe thickness. After controlling for the influence of body size, we found no evidence of a cost of belly width or stripe thickness on female fecundity. Rather, females that have larger ornaments have higher fecundity and thus accurately advertise their reproductive value to males without incurring a cost to fecundity. We also investigated the relationship between female body size and egg size and found that larger females suffered a slight decrease in egg size and fecundity, although this decrease was independent of female ornamentation. More broadly, considered in light of similar findings in other taxa, lack of an apparent fecundity cost of ornamentation in female pipefish underscores the need to revisit theoretical assumptions concerning the evolution of female ornamentation.
Evolution of a conspicuous melanin-based ornament in gulls Laridae
<p>Melanin- and carotenoid-based ornaments often signal different aspects of individual quality or similar aspects under different environmental conditions and, thus, they may become evolutionarily integrated into a composite sexual trait. On the other hand, functionally and developmentally different characters (e.g. coloration characters of different developmental origin) are more likely to evolve independently from each other than more similar traits. Here, we examined evolutionary correlations between the occurrence of a conspicuous melanin-based ornament (hood) and carotenoid-based bare-part ornaments within gull family. We also aimed to identify major ecological, life-history, and biogeographical predictors of hood occurrence and reconstruct evolutionary history of this ornament. We found that hood occurrence was associated with red or dark coloration of unfeathered traits (bill and legs), while combinations of hood with yellow carotenoid-based coloration of integument were evolutionarily avoided. Also, hood occurrence correlated negatively with the occurrence of other melanin-based plumage character (mantle). Breeding latitude and habitat were identified as major predictors of hood occurrence in gulls, as hoods were recorded more frequently in low-latitude and inland (rather than marine) species. Finally, our analysis provided support for evolutionary lability in hood occurrence, with a dominance of transitions towards hood loss in the evolutionary history of gulls. The results of our study provide one of the first evidence for a correlated evolution of melanin- and carotenoid-based ornaments in an avian lineage, which supports evolutionary modularity of developmentally and functionally different coloration traits.</p>
Data from: Conspicuous female ornamentation and tests of male mate preference in threespine sticklebacks (Gasterosteus aculeatus)
Sexual selection drives the evolution of exaggerated male ornaments in many animal species. Female ornamentation is now acknowledged also to be common but is generally less well understood. One example is the recently documented red female throat coloration in some threespine stickleback (Gasterosteus aculeatus) populations. Although female sticklebacks often exhibit a preference for red male throat coloration, the possibility of sexual selection on female coloration has been little studied. Using sequential and simultaneous mate choice trials, we examined male mate preferences for female throat color, as well as pelvic spine color and standard length, using wild-captured threespine sticklebacks from the Little Campbell River, British Columbia. In a multivariate analysis, we found no evidence for a population-level mate preference in males, suggesting the absence of directional sexual selection on these traits arising from male mate choice. Significant variation was detected among males in their preference functions, but this appeared to arise from differences in their mean responsiveness across mating trials and not from variation in the strength (i.e., slope) of their preference, suggesting the absence of individual-level preferences as well. When presented with conspecific intruder males, male response decreased as intruder red throat coloration increased, suggesting that males can discriminate color and other aspects of phenotype in our experiment and that males may use these traits in intrasexual interactions. The results presented here are the first to explicitly address male preference for female throat color in threespine sticklebacks.
Data from: The effects of climate warming and disturbance on the colonization potential of ornamental alien plant species
1. A large number of alien plant species have been introduced as ornamental garden plants to Europe, but relatively few have become invasive. Low climatic suitability may be limiting the current invasion potential of many alien ornamental species. However, with ongoing disturbance and climate change, this barrier may be reduced for some species. 2. Here we tested how colonization ability (a prerequisite for invasion) of frequently planted alien ornamentals depends on disturbance and heating, and on their species characteristics. We sowed seeds of 37 non-naturalized alien herbaceous garden-plant species into native grassland plots with and without disturbance, and with and without infrared heating lamps. To assess whether their responses differ from those within the regional wild flora, we also sowed 14 native species and 12 naturalized alien species. During two years, we assessed the likelihoods of germination, first-year survival, second-year survival and flowering of these 63 study species. 3. The heating treatment, which also reduced soil moisture, decreased all measures of colonization success, but more so for sown native species than for the non-naturalized and naturalized alien ones. The disturbance treatment increased colonization success, and because heating decreased productivity of the undisturbed grassland plots, it also increased invasibility of these plots. Average colonization success of non-naturalized aliens was reduced by heating, but some species were not affected or performed even better with heating, particularly those with an annual life span and a high seed mass. Winter hardiness improved colonization ability of non-naturalized aliens, but this advantage was reduced in the heated plots. 4. Synthesis. Disturbance increased and heating decreased the absolute colonization success of most of the 63 species sown. However, heating had stronger adverse effects on the resident grassland and sown native species than either type of sown alien species. Together, these results suggest that some alien plants may have greater colonization success relative to native plants under a warmer climate.
Data from: Intrasexual selection favours an immune-correlated colour ornament in a dragonfly
Sexual signalling is predicted to shape the evolution of sex-specific ornamentation, and establishing the costs and benefits of ornamentation and the information that ornamentation provides to receivers is necessary to evaluating this adaptive function. Here, we assessed the adaptive function of a common colour ornament in insects, melanin wing ornamentation, using the dragonfly Pachydiplax longipennis. We hypothesized that greater ornamentation would improve territory-holding success by decreasing aggression that males receive from territorial rivals, but that more ornamented males may have shorter lifespans. Using mark–recapture field observations, we found that more ornamented males had greater territory-holding success and that viability selection did not act on wing melanization. We then compared the aggression of territorial rivals to decoy males before and after experimentally augmenting wing melanization, finding that males significantly reduced aggression following the manipulation. We next hypothesized that wing melanization would signal fighting ability to territorial rivals by reflecting condition via investment in the costly melanin synthesis pathway. We observed a positive relationship between ornamentation and the likelihood of winning territorial disputes, suggesting that wing melanization provides information about fighting ability to rivals. We also found a positive relationship between melanin-based immune defence and ornamentation, supporting a link between the signal and condition. We conclude that wing melanization is a condition-related signal of fighting ability and suggest that this may be a common mechanism promoting the evolution of melanin ornamentation.
Data from: MHC variation is related to a sexually selected ornament, survival and parasite resistance in common yellowthroats
Hamilton and Zuk (1982) proposed that females choose mates based on ornaments whose expression is dependent on their genetically based resistance to parasites. The Major Histocompatibility Complex (MHC) plays an important role in pathogen recognition and is a good candidate for testing the relationships between immune genes and both ornament expression and parasite resistance. We tested the hypothesis that female common yellowthroats prefer to mate with more ornamented males, because it is a signal of their MHC-based resistance to parasites and likelihood of survival. In this species, females prefer males that have larger black facial masks as extra-pair mates. Using pyrosequencing, we found that mask size was positively related to the number of different MHC class II alleles, as predicted if greater variation at the MHC allows for the recognition of a greater variety of pathogens. Furthermore, males with more MHC class II alleles had greater apparent survival, and resistance to malaria infection was associated with the presence of a particular MHC class II allele. Thus, extra-pair mating may provide female warblers with immunity genes that are related to parasite resistance, survival and the expression of a male ornament, consistent with good genes models of sexual selection.
Data from: Odor is linked to adrenocortical function and male ornament size in a colonial seabird
Crested auklets (Aethia cristatella), colonial seabirds of Alaska and Siberia, emit a citrus-like odorant from wick-like feathers. We examined whether the odorant emission is linked to adrenocortical function and correlated with size of the crest feather ornament. Conventional signals like the size of crest ornament are inexpensive to produce and thus may be prone to deception. However, assessment signals such as the odorant could be more reliable if they impose costs and more proximate since they are continually produced. This may be the case for the crested auklet's volatile aldehyde odorant. The signal is composed of highly volatile chemicals that appear to be products of fatty acid metabolism. Adrenocortical function helps to mobilize endogenous resources for metabolism. Elevation of corticosterone may be needed to sustain a reliable chemical signal, but there are physiological costs for prolonged elevation of circulating corticosterone. We predicted that higher odorant emissions would be correlated with larger crest ornaments. Furthermore, we predicted that odorant emissions would be linked to adrenocortical response. Octanal, the most abundant compound in the citrus-like odorant, was positively correlated with crest size in males, and adrenocortical response explained 42% of the variation in octanal emissions, after controlling for stage of the breeding period. Adrenocortical response was positively correlated with octanal emissions (rs = 0.57) in females. We conclude that dominant individuals with greater capacity to mount a more robust stress response may have greater capacity to sustain odorant secretions.
Data from: The relationship between blood parasites and ornamentation depends on the level of analysis in the common yellowthroat
The Hamilton–Zuk hypothesis predicts that ornament expression is a signal of the ability of individuals to resist parasite infection. Thus, across a population (i.e. between-individuals) more ornamented individuals should have lower levels of parasitism. Numerous studies have tested this prediction and the results are mixed. One reason for these conflicting results may be that many studies have examined this relationship at the between-individual level, which may be affected by confounding factors such as selective mortality. Using within-subject centering we examined the relationship between male ornamentation and avian blood parasites at both the between- and within-individual levels. These relationships focus on differences in genetically-based resistance to parasites and the trade-off in resource allocation between parasite resistance and ornament expression within an individual, respectively. We studied male common yellowthroats Geothlypis trichas, which have two plumage ornaments, a yellow, carotenoid-based bib (throat and chest) and a black, melanin-based facial mask. Surprisingly, within-individuals, an increase in parasitism between years was associated with an increase in mask size and, potentially, greater concentration of carotenoids in the yellow feathers. This suggests that males may be able to tolerate an increase in parasitism and still increase ornament expression. In contrast, ornamentation was not related to parasitism at the between-individual level. Thus, our study revealed relationships between ornaments and parasitism at the within-individual level that were not present at the between-individual level. Our results highlight the importance of examining both within- and between-individual relationships as correlations between variables, such as ornaments and parasites, may depend on the level of analysis (i.e. within- or between-individuals).
Data from: Shell ornamentation as a likely exaptation: evidence from predatory drilling on Cenozoic bivalves
Predation is an important process in modern oceans and in the evolutionary history of marine ecosystems. Consequently, it has been hypothesized that shelled prey modified their ornamentation in response to predation. However, bivalve ornamentation has also been argued to be important in maintaining a stable life position in the sediment and in burrowing. To test whether concentric ribs were effective against drilling by carnivorous gastropods, we examined drill hole position and completeness for four Cenozoic bivalve species that differ in rib strength (Astarte radiata, A. goldfussi, Lirophora glyptocyma, and L. latilirata). The percentage of drill holes located between the ribs increases with increasing rib strength, whereas the percentage of drill holes on top of ribs decreases. This result suggests that gastropods select the drill hole site more effectively as rib strength increases, thereby saving time and energy, and that natural selection favors gastropods that select drill hole sites between ribs. Because of this greater stereotypy, the percentage of drill holes that are incomplete is generally lower in strongly ribbed species. The proportion of drill holes located on top of ribs is greater for incomplete than complete holes, implying that ribs can be effective against predators, but only when selected as the drilling location. We show that ribs are most effective against drilling predation for bivalves with moderately sized ribs, between which gastropods have difficulty siting drill holes. Concentric ribs are unlikely to have evolved as an adaptation against drilling predation because concentric ribs evolved in the Paleozoic and were already common in the Mesozoic, whereas drilling frequency increased later, in the Late Cretaceous–Paleogene. Moreover, rib strength of North American Astarte did not change through this time interval. Thus, the ribs considered here are a likely exaptation to drilling given their effectiveness at deterring drilling predation on bivalves with moderate ribs.
Data from: 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.
Data from: Bacteria and the evolution of honest signals. The case of ornamental throat feathers in spotless starlings
1.Mechanisms guaranteeing reliability of messages are essential in understanding the underlying information and evolution of signals. Microorganisms may degrade signalling traits and therefore, influence the transmitted information and evolution of these characters. The role of microorganisms in animal signalling has, however, rarely been investigated. 2.Here, we explore a possible role for feather-degrading bacteria driving the design of ornamental throat feathers in male spotless starlings (Sturnus unicolor). We estimated length, bacterial load, degradation status, and susceptibility to degradation by keratinolytic bacteria in those feathers, compared to non-ornamental adjacent feathers in males, as well as to throat feathers in females. In addition, the volume of the uropygial gland and its secretion was measured, and the secretion extracted. We also experimentally evaluated the capacity of each secretion to inhibit growth of a keratinolytic bacterium. 3.The apical part of male ornamental throat feathers harboured more bacteria and degraded more quickly than the basal part; these patterns were not detected in female throat feathers or in non-ornamental male feathers. Moreover, degradation status of male and female throat feathers did not differ, but was positively associated with feather bacterial density. Finally, the size of the uropygial gland in both males and females predicted volume and the inhibitory capacity of secretion against feather-degrading bacteria. Only in males was uropygial gland size negatively associated with the level of feather degradation. 4.All results indicate differential susceptibility of different parts of throat feathers to keratinolytic bacterial attack, which supports the possibility that throat feathers in starlings reflect individual ability to combat feather-degrading bacteria honestly. This is further supported by the relationship detected between antimicrobial properties of uropygial secretion and the level of feather degradation. 5.Our results suggest that selection pressures exerted by feather-degrading bacteria on hosts may promote evolution of particular morphologies of secondary sexual traits with different susceptibility to bacterial degradation that reliably inform of their bacterial load. Those results will help to understand the evolution of ornamental signals.
Data from: Biotic resistance to tropical ornamental invasion
We examined invasive, casual (found occasionally outside cultivation) and non-invasive (found only in cultivation) species to investigate the role of species traits and two forms of biotic resistance (plant neighbours and herbivores) in limiting invasion in Hawaiian lowlands. Seeds of 21 species of common woody ornamentals from three plant families (Acanthaceae, Apocynaceae, Bignoniaceae) that are non-invasive, casual or invasive in Hawai'i were outplanted at two field sites. We measured germination of seeds and growth and survival of seedlings for one year in plots with and without neighbours from the naturally-assembled community. The presence of neighbours reduced survival in some species, mostly non-invasive or casual species and completely excluded two non-invasive species from community plots. Damage from the existing community of herbivores was correlated with lower survival in the Acanthaceae and Bignoniaceae, but not the Apocynaceae. Non-invasive and casual species had lower survival and growth rates than invasive species and lower photosynthetic rates in the presence of neighbours than invasive species. Non-invasives without neighbours also had lower specific leaf area than invasives and casuals. We found evidence for barriers to invasion in some non-invasive and casual species, including low growth rate, low survival, or low survival in the presence of neighbours. By contrast, five of the six invasives flowered and three began setting fruit within the duration of the experiment, as did one of the casual species. Synthesis: Our research demonstrates biotic resistance, presumably as a result of competition. Neighbouring plants reduced survival and growth for most species. For non-invasive species with low survival and growth even without competition from neighbouring plants, this resulted in complete exclusion from community plots or such low growth rates that exclusion over longer time frames was likely. We also provide evidence for traits-based barriers to invasion in non-invasive and casual species. However, no single barrier to invasion was shared across all non-invasive and casual species.
Data from: Oxidative stress is related to both melanin- and carotenoid-based ornaments in the common yellowthroat
Male ornaments are hypothesized to signal the ability of males to produce an effective immune response without extensive oxidative stress and damage to DNA. We examined this hypothesis in male common yellowthroats (Geothlypis trichas), which have two ornaments, a black (eumelanin-based) facial mask and a yellow (carotenoid-based) bib. In our study population, only the black mask is sexually selected. As predicted by the oxidative stress hypothesis, males with larger black masks were more resistant to oxidative stress, as measured by an in vitro assay of the resistance of erythrocytes to haemolysis by free radicals. Furthermore, males with larger masks also tended to have lower levels of glutathione, which was predicted because glutathione inhibits eumelanin production. In contrast, mask size was not related to absolute levels of oxidative stress measured in the plasma. Although the yellow bib is not under sexual selection in our population, males with larger bibs and feathers with greater carotenoid chroma had lower levels of oxidative stress. The oxidative stress hypothesis was first proposed for carotenoid-based ornaments. However, our results suggest that, even in the same individuals, carotenoid and eumelanin-based plumage ornaments may both signal the ability of males to resist or manage oxidative stress.
Data from: Cope's rule and the universal scaling law of ornament complexity
Luxuriant, bushy antlers, bizarre crests, and huge, twisting horns and tusks are conventionally understood as products of sexual selection. This view stems from both direct observation and from the empirical finding that the size of these structures grows faster than body size (i.e., ornament size shows positive allometry). We contend that the familiar evolutionary increase in the complexity of ornaments over time in many animal clades is decoupled from ornament size evolution. Increased body size comes with extended growth. Since growth scales to the quarter power of body size, we predicted that ornament complexity should scale according to the quarter power law as well, irrespective of the role of sexual selection in the evolution and function of the ornament. To test this hypothesis, we selected three clades (ammonites, deer, and ceratopsian dinosaurs) whose species bore ornaments that differ in terms of the importance of sexual selection to their evolution. We found that the exponent of the regression of ornament complexity to body size is the same for the three groups and is statistically indistinguishable from 0.25. We suggest that the evolution of ornament complexity is a by-product of Cope's rule. We argue that although sexual selection may control size in most ornaments, it does not influence their shape.
Data from: Introduction bias affects relationships between the characteristics of ornamental alien plants and their naturalization success
Aim: Alien plants with certain characteristics may have been introduced earlier and more frequently than others. Such introduction bias may cause spurious associations between plant characteristics and naturalization (the establishment of self-sustaining populations in the wild). We aimed to disentangle direct and indirect (i.e. mediated by introduction history) effects of species characteristics on the naturalization success of alien plants introduced for horticulture. Location: Germany (non-native range); rest of the world (native range). Methods: We compiled a dataset of 435 alien plant species introduced in cultivation in Germany, including data on their year of introduction, the number of botanical gardens where they are planted, native range, biological traits and naturalization success. We used path analysis to estimate the direct effects of geographical origin and biological traits on naturalization, and their indirect effects mediated by year and/or frequency of introduction. Results: We found significant direct positive effects of native range size and winter hardiness on naturalization. Alien species native to other parts of Europe and species with a large native range were brought to the country earlier than other species. In addition, woody species, winter-hardy species and tall species were planted more frequently than others. Because the number of botanical gardens where a species is planted increased naturalization success directly, and residence time did so indirectly through a significant positive association with the number of botanical gardens, most of the species characteristics had indirect effects on naturalization. Main conclusions: Our approach allowed us to show that apparent effects of species characteristics on naturalization success can be at least partly indirect, due to introduction biases. This indicates that failure to recognize such introduction biases could impair our ability to explain the success of alien plant species.
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