Beak Size Research Articles

Interannual variability of body size and beak morphology of the squid Ommastrephes bartramii in the North Pacific Ocean in the context of climate change

Oceanic squids are typical species that sensitive to the environment change. Previous studies on oceanic squids mainly focus on its annually fluctuated abundance under the background of climate change. The changes of individual morphological sizes, including body and beak, have been observed in recent years. In this study, Ommastrephes bartramii, an important cephalopod species in North Pacific Ocean, has been selected to analyze the annual morphological changes of body and beak under different scales of climate events. Geometric morphometrics was used to analyze the shape variations of both upper beak and lower beak. The possible phenotypic plasticity of body and beak was also discussed in different aspects. Body size showed different variations among different climatic years. The size at the maturity stage in 2015 (El Niño year) was much smaller than that in other years for both sexes. The centroid size representing the beak size showed the significant difference between two types of Pacific Decadal Oscillation phases. The shapes of upper and lower beaks showed significant differences between small-scale climatic patterns in which El Niño or La Niña event occurred, displaying different growth patterns.

Ontogenetic variation of trophic habitat for sympatric benthic octopods in East China Sea derived from isotopic analysis on beaks

Sympatry is commonly observed in marine species, and always accompanied by high competition. Octopus consists of large amount of species and also widely distributed in the neritic area of the sea. As typical benthic species, octopus tend to live in the similar habitat with less movement during its lifetime. It is important to understand the trophic ecology of sympatric octopod species, which play an irreplaceable role in marine ecosystem. In this study, four neritic octopus species in the East China Sea (Amphioctopus fangsiao, Amphioctopus ovulum, Octopus minor and Octopus sinensis) were chose, we used stable isotope analysis (SIA) to analyze the variation of δ13C and δ15N derived from beak to assess the trophic variation among species and maturity stages. O. sinensis has the largest body and beak size than other species, and this species also had highest mean δ13C, δ15N value among species. The result of ANOVA showed that significant differences existed among four species for isotopic values. The overlaps among species were also calculated by standard ellipse area (SEAc). Isotopic overlap was decreased from immature stage to mature stage. The trophic niches were shrunk from immature to mature for all the four octopods species except for A. ovulum, which presented an expansion tendency. Trophic overlaps between specific two species in different groups were also calculated with distribution and mean values based on Bayesian model. The highest and lowest isotopic overlap occurred between O. minor and A. ovulum in immature group, A. fangsiao and O. sinensis in mature group, respectively. The four octopods species had very different trophic niches during ontogeny.

Effects of Feed Form and Amino Acid Density on Productive and Processing Performance of Broilers

Limitations in beak size of newly hatched chicks have led the majority of broiler integrators in the United States to feed crumbles during the starter period. Previous research has reported improved growth performance on birds fed micro pellets during the starter period. However, research evaluating the effects of feeding micro pellets in the grower and finisher periods of broilers is sparse. Two experiments were conducted to determine the effects of feeding varying feed forms on growth performance and carcass characteristics of broilers during the starter, grower and finisher periods. In experiment 1, birds were fed diets with 3 feed forms: mash, crumbles, and 3.3 mm micro pellets during the starter period from 1 to 14 d (25 birds/pen; 8 replicate pens/treatment). In experiment 2, a 3 × 2 factorial arrangement of 3 feed forms (mash, 4.4 mm pellets, and 3.3 mm micro pellets) and 2 amino acid (AA) densities (88% and 96% of Aviagen recommendations Ross® 708 2014) were provided from 1 to 42 d (24 birds/pen; 7 replicate pens/treatment). In both experiments, birds fed 3.3 mm micro pellets during the starter period had lower feed conversion ratio compared with those that received mash and crumbles from 1 to 14 d (P< 0.05). In experiment 2, birds fed diets with 96% of AA recommendations had higher body weight, carcass yield, carcass and breast meat weight, and lower FCR than birds fed diets with 88% (P< 0.05). These data indicated that broilers can be fed 3.3 mm micro pellets during the starter and/or during the whole production period of broilers.

Interdependent Phenotypic and Biogeographic Evolution Driven by Biotic Interactions.

Biotic interactions are hypothesized to be one of the main processes shaping trait and biogeographic evolution during lineage diversification. Theoretical and empirical evidence suggests that species with similar ecological requirements either spatially exclude each other, by preventing the colonization of competitors or by driving coexisting populations to extinction, or show niche divergence when in sympatry. However, the extent and generality of the effect of interspecific competition in trait and biogeographic evolution has been limited by a dearth of appropriate process-generating models to directly test the effect of biotic interactions. Here, we formulate a phylogenetic parametric model that allows interdependence between trait and biogeographic evolution, thus enabling a direct test of central hypotheses on how biotic interactions shape these evolutionary processes. We adopt a Bayesian data augmentation approach to estimate the joint posterior distribution of trait histories, range histories, and coevolutionary process parameters under this analytically intractable model. Through simulations, we show that our model is capable of distinguishing alternative scenarios of biotic interactions. We apply our model to the radiation of Darwin's finches-a classic example of adaptive divergence-and find limited support for in situ trait divergence in beak size, but stronger evidence for convergence in traits such as beak shape and tarsus length and for competitive exclusion throughout their evolutionary history. These findings are more consistent with presympatric, rather than postsympatric, niche divergence. Our modeling framework opens new possibilities for testing more complex hypotheses about the processes underlying lineage diversification. More generally, it provides a robust probabilistic methodology to model correlated evolution of continuous and discrete characters. [Bayesian; biotic interactions; competition; data augmentation; historical biogeography; trait evolution.].

Young Broiler Feeding Kinematic Analysis as A Function of the Feed Type.

Simple SummaryThe present study aims to compare the kinematic feeding variables of 3–4 days old broiler chickens using three different feed types: fine mash (F1), coarse mash (F2), and crumbled (F3); size was 476 µm, 638 µm, and 1243 µm, respectively. The head displacement and the maximum beak gape were automatically calculated by computational image analysis to find the feeding behavior of broilers. The results did not show strong correlations between birds’ weight, beak size (length and width), and the kinematic variables. The “catch-and-throw” movements in F1 (the smallest feed particle) generally occurred in the first mandibulation, while in F3 (the largest feed particle) occurred in the latest mandibulation. It can be suggested that the adoption of “catch-and-throw” in the latest mandibulations increases with larger particles.Past publications describe the various impact of feeding behavior of broilers on productivity and physiology. However, very few publications have considered the impact of biomechanics associated with the feeding process in birds. The present study aims at comparing the kinematic variables of young broiler chicks (3–4 days old; 19 specimens) while feeding them with three different feed types, such as fine mash (F1), coarse mash (F2), and crumbled feed (F3). The feeding behavior of the birds was recorded using a high-speed camera. Frames sequences of each mandibulation were selected manually and classified according to the temporal order that occurred (first, second, third, or fourth, and further). The head displacement and the maximum beak gape were automatically calculated by image analysis. The results did not indicate strong correlations between birds’ weight, beak size (length and width), and the kinematic variables of feeding. The differences between the tested feed were found mostly in the first and second mandibulations, probably explained by the higher incidence of “catch-and-throw” movements in F3 (33%) and F1 (26%) than F2 (20%). The “catch-and-throw” movements in F1 (the smallest feed particle) mostly occurred in the first mandibulation, as in F3 (the largest feed particle) also occurred in the latest mandibulations. It might be suggested that the adoption of “catch-and-throw” in the latest mandibulations increases with larger particles. The kinematic variables in the latest mandibulations (from the third one on) seem to be similar for all feed types, which represent the swallowing phase. It might be inferred that the temporal sequence of the mandibulations should be essential to describe the kinematics of a feeding scene of broiler chickens, and the first and second mandibulations are potentially the key factors for the differences accounted by the diverse feed particle sizes.

Morphological trophic variation of the cyprinid Megalobrama pellegrini (Tchang, 1930) with different keratinized beaks from upper reaches of the Yangtze River, China

Megalobrama pellegrini, a cyprinid endemic to the upper Yangtze River China, has thick keratinized beaks on the jaws and feeds on algae and molluscs. The size of keratinized beaks varies among different individuals. In the present study, two populations, from Longxihe (LXH) and Chishui (CSH) Rivers, were examined in order to explore the morphological variation of keratinized beaks, together with an analysis of intestine length and of stable isotopes. The results showed that the ratio of upper to lower keratinized beaks varied from 0.84 to 2.06. We defined the ratio 1.26 as thicker upper beak (TUB) form. In the LXH population, there were more TUB forms, while EB forms dominated in CSH population. Intestine length showed a negative relationship with the upper to lower beak ratio (Pearson correlation coefficient = −0.697, P < 0.01) indicating the possible adaptation of beak size to food type. In addition, analysis of stable isotope showed that these two populations differed in their food, and there was a positive relationship between trophic niche and size of beaks (R = 0.5530 and 0.4927, respectively). This further supported the suggestion that the beak size was possibly adapted to food type, with the TUB form to a higher trophic niche and the EB form to a lower trophic niche.

Temporally varying disruptive selection in the medium ground finch (Geospiza fortis).

Disruptive natural selection within populations exploiting different resources is considered to be a major driver of adaptive radiation and the production of biodiversity. Fitness functions, which describe the relationships between trait variation and fitness, can help to illuminate how this disruptive selection leads to population differentiation. However, a single fitness function represents only a particular selection regime over a single specified time period (often a single season or a year), and therefore might not capture longer-term dynamics. Here, we build a series of annual fitness functions that quantify the relationships between phenotype and apparent survival. These functions are based on a 9-year mark-recapture dataset of over 600 medium ground finches (Geospiza fortis) within a population bimodal for beak size. We then relate changes in the shape of these functions to climate variables. We find that disruptive selection between small and large beak morphotypes, as reported previously for 2 years, is present throughout the study period, but that the intensity of this selection varies in association with the harshness of environment. In particular, we find that disruptive selection was strongest when precipitation was high during the dry season of the previous year. Our results shed light on climatic factors associated with disruptive selection in Darwin's finches, and highlight the role of temporally varying fitness functions in modulating the extent of population differentiation.

Beak morphology predicts apparent survival of crossbills: due to selective survival or selective dispersal?

Dozens of morphologically differentiated populations, subspecies and species of crossbills (genus Loxia) exist. It has been suggested that this divergence is due to variation in the conifer cones that each population specialises upon, requiring a specific beak size to efficiently separate the cone scales. If so, apparent survival should depend on beak size. To test this hypothesis, we undertook multievent capture–recapture modelling for 6844 individuals monitored during 27 years in a Pyrenean common crossbill L. curvirostra population in a forest of mountain pine Pinus uncinata. Apparent survival was indeed related to beak width, resulting in stabilizing selection around an optimum that was close to the observed mean beak width, indicating that local crossbill beak morphology is adapted to the conifer they feed upon. Both natural selection (selective mortality) and selective emigration of maladapted individuals may explain our findings. As is often the case in capture–recapture analyses but rarely recognised, we could not formally decompose apparent survival into selective mortality versus selective permanent emigration. Nonetheless, there are several indications that selective permanent emigration should not be fully excluded. First, natural selection by itself would have to be unusually strong compared to other empirical estimates to create the observed pattern of apparent survival. Second, the observed mean beak width was a bit lower than the estimated optimum beak width. This can be explained by immigration of crossbills with smaller beaks originating from southern populations, which may subsequently have left the study area permanently in response to low food intake. This is in line with a detected transient effect in the data, yet apparently little influx from crossbills from northern Europe. When permanent emigration is phenotypically selective this will have ecological and evolutionary consequences, so this possibility deserves more attention in general.

Insights about the toxicity of tannery effluent on chicken (Gallus gallus domesticus) embryos.

Although tannery effluent (TE) toxicity has already been demonstrated in different vertebrate models, our knowledge about their effects on birds remains significantly incipient. Thus, the aim of the current study was to evaluate the impact of ephemeral exposure of Gallus gallus domesticus eggs to environmental predictive TE dilutions (1.4% and 6.5%). Eggs at E6 developmental stage were opened in order to assess embryos' external morphology and genotoxic biomarkers. Based on our data, embryos exposed in ovo to TE recorded higher mortality rate, lower biomass and different morphological abnormalities such as optic vesicle depigmentation, pericardial and encephalic edemas, as well as body rotation error. Embryos exposed to TE showed lower crown-rump length head and anterior-posterior length, as well as reduced beak size. Embryos exposed to the highest TE dilution (6.5%) also showed greater lower/upper limb development, larger optic vesicle area and smaller crystalline lens area than the other groups. On the other hand, differences in mitotic index were not observed between groups; however, total erythrocyte chromosomal abnormalities, mainly in metaphase and anaphase, were higher in embryos exposed to TE. These phases presented chromosome fragments formed from typical chromosome breakage, laggard chromosome and chromosome bridge. Higher Cr, Mn and Zn concentrations in embryos exposed to TE strongly suggest that the observed abnormalities were directly associated with the absorption of chemical constituents. The present study is pioneer in investigating the morphotoxic and genotoxic potential of TE (a complex mixture of various xenobiotics) in bird embryos in order to better understand the eco (toxicological) magnitude of this pollutant in aquatic ecosystems.

The skull evolution of oviraptorosaurian dinosaurs: the role of niche partitioning in diversification.

Oviraptorosaurs are bird-like theropod dinosaurs that thrived in the final pre-extinction ecosystems during the latest Cretaceous, and the beaked, toothless skulls of derived species are regarded as some of the most peculiar among dinosaurs. Their aberrant morphologies are hypothesized to have been caused by rapid evolution triggered by an ecological/biological driver, but little is known about how their skull shapes and functional abilities diversified. Here, we use quantitative techniques to study oviraptorosaur skull form and mandibular function. We demonstrate that the snout is particularly variable, that mandibular form and upper/lower beak form are significantly correlated with phylogeny, and that there is a strong and significant correlation between mandibular function and mandible/lower beak shape, suggesting a form-function association. The form-function relationship and phylogenetic signals, along with a moderate allometric signal in lower beak form, indicate that similar mechanisms governed beak shape in oviraptorosaurs and extant birds. The two derived oviraptorosaur clades, oviraptorids and caenagnathids, are significantly separated in morphospace and functional space, indicating that they partitioned niches. Oviraptorids coexisting in the same ecosystem are also widely spread in morphological and functional space, suggesting that they finely partitioned feeding niches, whereas caenagnathids exhibit extreme disparity in beak size. The diversity of skull form and function was likely key to the diversification and evolutionary success of oviraptorosaurs in the latest Cretaceous.

Genetics of Inheritance and Interrelationship of Various Agronomic Traits of F2 Population in Cotton (Gossypium hirsutum L.)

Background: Cotton (Gossypium hirsutum L.) is grown in more than sixty countries worldwide. It is an important fiber crop in the world. It plays a vital role in our national economy being the source of earning of foreign exchange, therefore, it is considered to be the backbone of the economy of Pakistan. In Pakistan, millions of families are associated with cotton and textile industry for their livelihood.&#x0D; Results: In this experiment F2 population of the cross L. A. Frego Bract x CIM-600 and their parents was sown in randomized complete block design with three replications during normal growing season of the year 2014 to sort out best performing genotypes for yield related traits. Analysis of variance (ANOVA) revealed that parental and their F2 population showed significant differences for all the observed agronomic traits (plant height, number of monopodia branches, number of sympodial branches, number of bolls per plant, boll weight, ginning out turn, bract type, boll shape, beak size, seed cotton yield, staple length, fiber strength and fiber fineness). Estimation of correlation revealed that seed cotton yield was found positively correlated sympodial branches, fiber fineness and boll weight while ginning out turn, bract type, beak size, staple length and fiber strength were negatively associated with seed cotton yield. Epistasis was not found to be involved in any of the traits.&#x0D; Conclusion: The correlation and genetics study of various yield related traits provides us useful information for effective selection and sustainable breeding programs. Estimation of broad sense heritability ( ) in F2 populations for different traits vary as following order; ginning out turn&gt;plant height&gt;seed cotton yield&gt;sympodia branches&gt;fiber length&gt;fiber strength&gt;bolls per plant&gt;monopodia branches&gt;boll weight&gt;fiber fineness with heritability 0.90, 0.79, 0.78, 0.75, 0.73, 0.71 0.67, 0.64, 0.63 and 0.50 respectively. Results suggested form heritability and correlation that these traits can be improved either through appropriate selection method or hybrid breeding programme.

Contrasting female mate preferences for red coloration in a fish.

Understanding how animals select their mates requires knowing the factors that shape mate preferences. Recent theoretical and empirical considerations suggest that female mating status can influence the degree to which a female engages in mate choice, with virgin females predicted to be less choosy than mated females. In this study, we investigated mate choice in both virgin and mated females in the pygmy halfbeak Dermogenys collettei. Halfbeaks are small, live-bearing, internally fertilizing freshwater fish that live in mixed-sex groups where females have ample opportunity to engage in mate choice. Using a dichotomous choice assay, we quantified and contrasted in virgin and mated females mate preferences for differences in male body size, beak size, and area of yellow and red coloration. We also examined how mating status influenced the amount of time a female associated with the first male encountered and the relative amount of time a female associated with each male. We demonstrate that mate preferences of female halfbeaks are driven primarily by the size of red coloration present on males. Females showed contrasting preferences based on mating status, with virgin females preferentially associating with drab males whereas mated females preferentially associate with males possessing large areas of red. Contrary to expectations, female mating status did not influence how females associate with the first males encountered or how females biased their association time among males. Although the precise drivers of these effects need further studying, our finding highlights a possible explanation for how variation in male ornamentation can be maintained.

Do beak volume and bite force influence the song structure of sympatric species of seedeaters (Thraupidae: Sporophila)?

ABSTRACTSong structure can be constrained by morphological characters such as beak size. Studies have shown that songbirds with larger beaks produce songs with a lower frequency, narrower frequency range and lower note rates than birds with smaller beaks. We tested whether beak volume and bite force constrain song parameters in three Neotropical seedeaters that show a gradient of beak size and force (Sporophila beltoni, S. caerulescens and S. hypoxantha). We also determined the relationship between body size and song structure. We evaluated the song structure of these species, measuring differences that may help them to segregate the acoustic space, since they occur in sympatry. These birds can be predicted to segregate the acoustic space to reduce overlapping of their songs, which is a possible result of the force of sexual selection. Individuals of each species had their beaks and bite forces measured and their own territorial songs recorded in the field. Only S. caerulescens showed a positive relationship between beak volume and song parameters (maximum frequency and frequency bandwidth). No song parameters showed an association with bite force or body size. The use of acoustical space seemed to be unique to each species with respect to note rate and song duration. Sporophila beltoni and S. hypoxantha showed the most differences from each other in all song parameters analysed. In contrast to other studies of finch species with conical beaks, our findings suggested that for these three species, beak volume and bite force do not limit the song structure.

Role of sexual imprinting in assortative mating and premating isolation in Darwin’s finches

Global biodiversity is being degraded at an unprecedented rate, so it is important to preserve the potential for future speciation. Providing for the future requires understanding speciation as a contemporary ecological process. Phylogenetically young adaptive radiations are a good choice for detailed study because diversification is ongoing. A key question is how incipient species become reproductively isolated from each other. Barriers to gene exchange have been investigated experimentally in the laboratory and in the field, but little information exists from the quantitative study of mating patterns in nature. Although the degree to which genetic variation underlying mate-preference learning is unknown, we provide evidence that two species of Darwin's finches imprint on morphological cues of their parents and mate assortatively. Statistical evidence of presumed imprinting is stronger for sons than for daughters and is stronger for imprinting on fathers than on mothers. In combination, morphology and species-specific song learned from the father constitute a barrier to interbreeding. The barrier becomes stronger the more the species diverge morphologically and ecologically. It occasionally breaks down, and the species hybridize. Hybridization is most likely to happen when species are similar to each other in adaptive morphological traits, e.g., body size and beak size and shape. Hybridization can lead to the formation of a new species reproductively isolated from the parental species as a result of sexual imprinting. Conservation of sufficiently diverse natural habitat is needed to sustain a large sample of extant biota and preserve the potential for future speciation.

Non-redundancy in seed dispersal and germination by native and introduced frugivorous birds: implications of invasive bird impact on native plant communities

Seed dispersal by vertebrate animals is important for the establishment of many fleshy-fruited plant species. Different frugivorous species can provide different seed dispersal services according to their specific dietary preferences as well as behaviour and body traits (e.g. body size and beak size of birds). Our aim was to study redundancies and complementarities in seed dispersal and germination between the two main native seed disperser birds and the introduced silver pheasant Lophura nycthemera in the temperate Patagonian forests. For this, we collected fresh droppings from the studied species and analyzed seed content. We conducted germination trials for four plant species common in bird droppings; two native species (Aristotelia chilensis and Rhaphithamnus spinosus) and two invasive non-native species (Rubus ulmifolius and Rosa rubiginosa). Both native frugivorous birds and the silver pheasant dispersed fruits of non- native fleshy-fruited plants, but their roles were non-redundant in terms of species dispersed and effect on seed germination. The silver pheasant dispersed a proportionally high number of non-native seeds, while native birds dispersed a high number of native seeds. In addition, the effect of gut treatment in seed germination differed between seed dispersers. Native birds promoted the germination for the two native plant species studied, while the silver pheasant promoted the germination of one non-native plant. This suggests that seed dispersal by the silver pheasant may contribute to the spread of some invasive fleshy-fruited plants in the ecosystems that otherwise would not be dispersed by any other bird. The understanding of redundancies and complementarities on seed dispersal and germination between native and introduced birds will allow improving the management of fleshy-fruited non-native plants.

Beak identification of four dominant octopus species in the East China Sea based on traditional measurements and geometric morphometrics

Octopus is the most abundant genus in the family Octopodidae and accounts for more than half of the total cephalopod landing in neritic fisheries. A taxonomic problem still exists due to synonymous scientific names and limited genetic information. The cephalopod beak is a stable structure that allows an effective solution to the problem of the species and stock identification. Beak shape variation has been more widely considered than beak measurements in recent years. In this study, with the beak as the experimental material, we combined geometric morphometrics (GM) with machine learning methods and compared the discrimination results obtained by traditional and GM methods in four Chinese neritic octopus species (Amphioctopus fangsiao, Amphioctopus ovulum, Octopus minor and Octopus sinensis). According to our analyses, Octopus sinensis has the larger beak size [both upper beak (UB) and lower beak (LB)] than other species. The results of ANOVA showed that all beak measurements differed significantly among the four species. Significant differences in both UB and LB shapes among four species were identified in MANOVA analysis based on the GM method. The results of GM-based discriminant analysis were better than those of traditional measurements, and machine learning methods also showed the higher correct classification rates than linear discriminant analysis. GM is a useful method to reconstruct the shape cephalopod beak and can also effectively distinguish different species. We should improve classification accuracy with machine learning methods for determining species structure in the future.

Morphological trait matching shapes plant–frugivore networks across the Andes

Interactions between resource and consumer species are organized in ecological networks. Species interactions in these networks are influenced by the functional traits of the interacting partners, but the generality of trait‐based interaction rules and the relationship between functional traits and a species’ specialization on specific interaction partners are not yet understood. Here we combine data on eight interaction networks between fleshy‐fruited plants and frugivorous birds sampled across the tropical and subtropical Andean range. We test which combinations of morphological plant and animal traits determine trait matching between resource and consumer species in these networks. In addition, we test which of the morphological traits influence functional specialization of plant and bird species. In a meta‐analysis across network‐specific fourth‐corner analyses, we found that plant–animal trait pairs related to size matching (fruit size–beak size) and avian foraging behavior (plant height–wing shape and crop mass–body mass) were positively related in these networks. The degree of functional specialization on specific interaction partners was positively related to crop mass in plants and to the pointedness of the wing in birds. Our findings show that morphological trait matching between fleshy‐fruited plants and frugivorous birds is a general phenomenon in plant–frugivore networks across the Andes and that specific plant and bird traits can be used to approximate the degree of functional specialization. These insights into the generality of interaction rules are the base for predictions of species interactions in ecological networks, for instance in novel communities in the future, and can be applied to identify plant and animal species that fulfill specialized functional roles in ecological communities.

Genomic Contingencies and the Potential for Local Adaptation in a Hybrid Species.

Hybridization is increasingly recognized as a potent evolutionary force. Although additive genetic variation and novel combinations of parental genes theoretically increase the potential for hybrid species to adapt, few empirical studies have investigated the adaptive potential within a hybrid species. Here, we address whether genomic contingencies, adaptation to climate, or diet best explain divergence in beak morphology using genomically diverged island populations of the homoploid hybrid Italian sparrow Passer italiae from Crete, Corsica, and Sicily. Populations vary significantly in beak morphology both between and within islands of origin. Temperature seasonality best explains population divergence in beak size. Interestingly, beak shape along all significant dimensions of variation was best explained by annual precipitation, genomic composition, and their interaction, suggesting a role for contingencies. Moreover, beak shape similarity to a parent species correlates with proportion of the genome inherited from that species, consistent with the presence of contingencies. In conclusion, adaptation to local conditions and genomic contingencies arising from putatively independent hybridization events jointly explain beak morphology in the Italian sparrow. Hence, hybridization may induce contingencies and restrict evolution in certain directions dependent on the genetic background.

Dissecting the roles of body size and beak morphology in song evolution in the “blue” cardinalids (Passeriformes: Cardinalidae)

ABSTRACT Certain vocal signals can be difficult or challenging to produce due to constraints on vocal mechanics. In the case of birdsong, both body size and beak morphology have been shown to constrain spectral and temporal song parameters. Therefore, variation within a clade in both these morphological traits could exert an important effect in vocal evolution and diversity. However, given the allometric relationship between body size and beak size, it is not always easy to separate the effects they may have. Additionally, different habitats impose different sources of sound attenuation and degradation, and birdsong seems to be adapted to minimize habitat-specific sound degradation. Here, we analyze vocal variation in relation to both body size and beak morphology in 13 of 14 species in the “blue” clade of the Cardinalidae, controlling for habitat characteristics. On one hand, we found the predicted negative correlation of body size with song frequencies, but no effect of body size on temporal variables. ...

Does beak size predict the pollination performance of hummingbirds at long and tubular flowers? A case study of a Neotropical spiral ginger

AbstractLong‐billed hummingbirds are assumed to be better adapted than short‐billed ones for the pollination of long tubular flowers. However, the majority of the empirical evidence is derived from surveys of pollinator feeding performance, which tend to ignore the implications for plant fitness. Here, we tested the long‐billed performance hypothesis from the perspective of the pollinated plant. We conducted a comparative survey to evaluate fecundity in relation to the length of the beak of the pollinating hummingbirds visiting the long and tubular flowers of Costus spiralis (Costaceae), in the Brazilian Atlantic forest. The flowers of C. spiralis were pollinated by three hummingbird species and their nectar was thieved by the bee Eulaema sp. There was no significant difference in the frequency of floral visits nor in the production of seeds among the three hummingbirds in fruits formed from flowers exposed to a single visit by each pollinator. Unexpectedly, our results indicate that the floral morphology of C. spiralis is equally compatible with long‐ and short‐billed pollinators, and is apparently incompatible with pollination by large insects. These findings emphasize the need to test the performance of each floral visitor with the simultaneous estimation of the intensity of the interactions, to increase the accuracy of the measurement of the pollinator's relative importance in studies of plant–pollinator interactions in ornithophilous systems.