Biology subjects

Hauber, M. E.

Publications and source records attributed to Hauber, M. E..

12 recordsLinked to original sources

bioRxiv2025

Yolk steroid concentrations decline in Japanese Quail (Coturnix japonica) eggs throughout incubation

The development of avian embryos is dependent not only on their genetic background but also on both external conditions and the maternal resources deposited into eggs. Specifically, maternally derived steroids in egg yolks have been shown to influence morphological development in avian offspring, but the effect of most yolk steroid hormones and their metabolites on embryonic growth and development remain poorly explored. We tested relationships between eggshell maculation, surface temperature, hormone concentrations before and during incubation, and embryonic growth in Japanese Quail (Coturnix japonica) eggs developing while artificially incubated in duplicate incubators. We detected 10 steroid hormones in the yolks during development and concentrations of all hormones declined to Day 15 ([~]2 days before hatch). Steroid declines at Day 9 of incubation were related to eggshell surface temperature, with warmer eggs having higher concentrations of androgens and progestogens, and incubator assignment, as eggs were warmer on average in one incubator than the other. However, eggshell surface temperature was not related to eggshell maculation, embryonic size, or embryonic heart rate during development. These results provide evidence of yolk steroid concentration declines through incubation and suggest that environmental conditions (such as temperature or light) could alter embryonic hormone uptake and/or metabolism.

physiology↗

bioRxiv2025

Comparative population genomics reveals convergent adaptation across independent origins of avian obligate brood parasitism

Parental care evolved as a strategy to enhance offspring survival at the cost of reduced fecundity. While most birds provide parental care, obligate brood parasites circumvent this tradeoff by exploiting the parental behavior of other species. This radical life history shift has occurred independently seven times in birds, offering an outstanding opportunity to test for convergent patterns of adaptation in the genome. To investigate genomic adaptations underlying this transition, we analyzed population resequencing data from five brood-parasitic species across three independent origins of brood parasitism -- three parasitic finches (family Viduidae), a honeyguide, and a cowbird -- alongside related non-parasitic (parental) outgroups. Using the McDonald-Kreitman framework, we found evidence for repeated adaptation in genes involved in spermatogenesis and sperm function in multiple parasitic clades, but not in the matched outgroup parental species. This is consistent with evidence for increased male-male competition in parasitic lineages as a result of the loss of parental care. In addition, we detected selective sweeps near genes associated with nervous system development in parasitic lineages, perhaps associated with improved spatial cognition that aids brood parasites in locating, monitoring, and laying eggs in host nests. Finally, we found more selective sweeps in host-specific brood parasites as compared to parental outgroups, perhaps reflecting ongoing host-parasite coevolutionary arms races.

evolutionary biology↗

bioRxiv2024

Phylotranscriptomics reveals convergent behavioral evolution associated with shared and unique mechanisms in cavity-nesting songbirds

Uncovering the genomic bases of phenotypic adaptation is a major goal in biology, but this has been hard to achieve for complex behavioral traits. Here, we leverage the repeated, independent evolution of obligate cavity-nesting in birds to test the hypothesis that pressure to compete for a limited breeding resource has facilitated convergent evolution in behavior, hormones, and gene expression. We used an integrative approach, combining aggression assays in the field, testosterone measures, and transcriptome-wide analyses of the brain in wild-captured females and males. Our experimental design compared species pairs across five avian families, each including one obligate cavity-nesting species and a related species with a more flexible nest strategy. We find behavioral convergence, with higher levels of territorial aggression in obligate cavity-nesters, particularly among females. Across species, levels of testosterone in circulation were not associated with nest strategy, nor aggression. Phylogenetic analyses of individual genes and co-regulated gene networks revealed more shared patterns of brain gene expression than expected by drift, but the scope of convergent gene expression evolution was limited to a small percent of the genome. When comparing our results to other studies that did not use phylogenetic methods, we suggest that accounting for shared evolutionary history may reduce the number of genes inferred as convergently evolving. Altogether, we find that behavioral convergence in response to shared ecological pressures is associated with largely independent gene expression evolution across different avian families, punctuated by a narrow set of convergently evolving genes.

evolutionary biology↗

bioRxiv2022

Microstructural and crystallographic evolution of palaeognath (Aves) eggshells

The avian palaeognath phylogeny has been recently revised significantly due to the advancement of genome-wide comparative analyses and provides the opportunity to trace the evolution of the microstructure and crystallography of modern dinosaur eggshells. Here, eggshells of all major clades of Palaeognathae (including extinct taxa) and selected eggshells of Neognathae and non-avian dinosaurs are analysed with electron backscatter diffraction. Our results show the detailed microstructures and crystallographies of (previously) loosely categorized ostrich-, rhea-, and tinamou-style morphotypes of palaeognath eggshells. All rhea-style eggshell appears homologous, while respective ostrich-style and tinamou-style morphotypes are best interpreted as homoplastic morphologies (independently acquired). Ancestral state reconstruction and parsimony analysis additionally show that rhea-style eggshell represents the ancestral state of palaeognath eggshells both in microstructure and crystallography. The ornithological and palaeontological implications of the current study are not only helpful for the understanding of evolution of modern and extinct dinosaur eggshells, but also aid other disciplines where palaeognath eggshells provide useful archive for comparative contrasts (e.g. palaeoenvironmental reconstructions, geochronology, and zooarchaeology).

evolutionary biology↗

bioRxiv2021

Caste, sex, and parasitism influence brain plasticity in a social wasp

Phenotypic plasticity is the capacity of a single genotype to exhibit different phenotypes, and can be an adaptive response to specific environmental and social conditions. Social insects are particularly well-suited to study plasticity, because the division of labor amongst females and the different life histories of males and females are associated with specific sensory needs. Here, we take advantage of the social wasp Polistes dominula to explore if brain plasticity is influenced by caste and sex, and the exploitation by the parasite Xenos vesparum. Within sexes, males had proportionally larger optic lobes, while females, regardless of caste, had larger antennal lobes, which is consistent with sensory needs of sex-specific life histories. Within castes, reproductive females had larger calyces, as predicted by their sensory needs for extensive within-colony interactions and forming winter aggregations, than workers who spend more time foraging for nest material and prey. Surprisingly, parasites had different effects on female and male hosts. Female workers were castrated and behaviorally manipulated by female or male parasites, but only showed moderate differences in relative allocation of different brain tissue compared to non-parasitized workers. In contrast, the testes and behavior of parasitized males were essentially unaffected, but they had smaller brains and greater relative volume of most sensory brain regions than non-parasitized males. Our results are consistent with caste and sex mediating brain plasticity in P. dominula and that the parasites manipulation can also drive differential allocation of brain regions depending on host sex.

neuroscience↗

bioRxiv2021

Pressure for rapid and accurate mate recognition promotes avian-perceived plumage sexual dichromatism in true thrushes (genus: Turdus)

Ecological conditions limiting the time to find a compatible mate or increasing the difficulty in doing so likely promote the evolution of traits used for species and mate recognition. Conspicuous traits that signal an individuals species, sex, and breeding status reduce the challenge of identifying a compatible conspecific mate, and should be more common in migratory rather than sedentary species, species with shorter breeding seasons, and species breeding under high sympatry with many closely-related heterospecifics. Here, we tested this recognition hypothesis for promoting plumage sexual dichromatism in the true thrushes (Turdus spp.), a large and diverse genus of passerine birds. We used receptor-noise limited models of avian vision to quantify avian-perceived chromatic and achromatic visual contrasts between male and female plumage patches and tested the influence of breeding season length, spatial distribution, and sympatry with other Turdus species on plumage dichromatism. As predicted, we found that 1) true thrush species with migratory behaviour have greater plumage sexual dichromatism than non-migratory species, 2) species with longer breeding seasons have less plumage sexual dichromatism, and 3) greater numbers of Turdus thrush species breeding in sympatry is associated with more plumage sexual dichromatism. These results suggest that social recognition systems, including species and mate recognition, play a prominent role in the evolution of plumage sexual dichromatism in true thrushes.

evolutionary biology↗

bioRxiv2021

Differential investment in visual and olfactory brain regions mirrors the sensory needs of a paper wasp social parasite and its host

Obligate social parasites evolve traits to effectively locate and then exploit their hosts, whereas hosts have complex social behavioral repertoires, which include sensory recognition to reject potential conspecific intruders and heterospecific parasites. While social parasite and host behaviors have been studied extensively, less is known about how their sensory systems function to meet their specific selective pressures. Here, we compare investment in visual and olfactory brain regions in the paper wasp Polistes dominula, and its obligate social parasite P. sulcifer, to explore the link between sensory systems and brain plasticity. Our results show opposite and significant differences, consistent with their very different life-histories, in the sensory investments between these two closely-related species. Social parasites initially invest in the optic lobes to likely locate their hosts. After host colony usurpation, the parasite increases its brain volume, with specific investment in antennal lobes, which mirrors the behavioral switch from a usurping parasite to an integrated parasitic queen of the host colony. Contrastingly, hosts initially invest in the antennal lobes and sensory processing compared to social parasites, as predicted by their need to maintain social cohesion, allocate colony tasks, and recognize con- and heterospecific intruders. Host queens show a trend of higher investment in all sensory brain regions compared to workers, paralleling differences in task allocations. Our work provides novel insights into how intraspecific brain plasticity can facilitate the unique sensory adaptations needed to perform specific tasks by the host or to transition from searching to successful host exploitation by the social parasite.

neuroscience↗

bioRxiv2020

Visual acuity and egg spatial chromatic contrast predict egg rejection behavior of American robins

Color and spatial vision are critical for recognition and discrimination tasks affecting fitness, including finding food and mates and recognizing offspring. For example, as a counter defense to avoid the cost of raising the unrelated offspring of obligate interspecific avian brood parasites, many host species routinely view, recognize, and remove the foreign egg(s) from their nests. Recent research has shown that host species visually attend to both chromatic and spatial pattern features of eggs; yet how hosts simultaneously integrate these features together when recognizing eggs remains an open question. Here, we tested egg rejection responses of American robins (Turdus migratorius) using a range of 3D-printed model eggs covered with blue and yellow checkered patterns differing in relative square sizes. We predicted that robins would reject a model egg if they could visually resolve the blue and yellow squares as separate features or accept it if the squares blended together and appeared similar in color to the natural blue-green color of robin eggs as perceived by the avian visual system. As predicted, the probability of robins rejecting a model egg increased with greater sizes of its blue and yellow squares. Our results suggest that chromatic visual acuity and viewing distance have the potential to limit the ability of a bird to recognize a foreign egg in its nest, thus providing a limitation to host egg recognition that obligate interspecific avian brood parasites may exploit.

animal behavior and cognition↗

bioRxiv2020

Loss of graded enemy recognition in a Whitehead population allopatric with brood parasitic Long-tailed Cuckoos

Many avian hosts of brood parasitic birds discriminate between different types of threats and may respond with categorically different, specifically anti-predatory or anti-parasitic behaviors. Alternatively, hosts may adjust their responses to threat level in a graded manner, responding more aggressively to brood parasites during the laying and incubation stages of nesting, when nests are most susceptible to parasitism, and more aggressively to nest predators during the nestling and fledgling stages when predation would be more costly than parasitism. In New Zealand, endemic host Whiteheads act inconspicuously around their nests in the presence of sympatric Long-tailed Cuckoos, their obligate brood parasite, perhaps to avoid disclosing nest location. We tested behavioral responses of a Whitehead population on Tiritiri Matangi Island that has been breeding allopatrically from cuckoos for 17 years. We presented models of the allopatric parasite, a sympatric predator (Morepork Owl), and a sympatric non-threatening heterospecific (Song Thrush) during the egg and chick stages, and to groups of cooperatively breeding Whiteheads. We compared responses across nest stage and stimulus type. We found that, unlike sympatric Whiteheads elsewhere in New Zealand, Whiteheads on Tiritiri Matangi produced alarm calls in response to the cuckoo model. Furthermore, the rate of alarm calling was similar towards the cuckoo and the owl and across egg and chick stage and higher than to the control stimulus. These results are consistent with allopatric Whiteheads having lost their specific anti-parasitic defense tactics in response to brood parasitic cuckoos.

animal behavior and cognition↗

bioRxiv2019

Glucocorticoids mediate egg rejection in a brood parasite host

Avian brood parasites and their hosts are engaged in a coevolutionary battle that can result in the evolution of sophisticated trickery by parasites and novel defence behaviours in hosts. Despite the clear evolutionary and ecological significance of host behaviour, however, we know very little about the mechanisms that regulate host defences, which limits our understanding of both inter- and intraspecific variation in host responses to parasitism. Here we tested whether corticosterone, a hormone known to be upregulated in hosts exposed to parasitism, also mediates one of the most frequent host defences - the rejection of foreign eggs. We experimentally reduced corticosterone levels in free-living brood parasite hosts, American robins Turdus migratorius, using mitotane and found that the likelihood of model egg rejection was significantly lower in the mitotane-treated birds relative to the sham-treated birds. These results demonstrate a causal link between glucocorticoids and egg rejection in hosts of avian brood parasites, but the physiological and sensory-cognitive pathways that regulate this effect remain unknown.

animal behavior and cognition↗

bioRxiv2019

Shared transcriptional responses to con- and heterospecific behavioral antagonists in a wild songbird

The recognition of and differential responses to salient stimuli are among the main drivers of behavioral plasticity, yet, how animals evolve and modulate functional responses to novel classes of antagonistic stimuli remain poorly understood. We studied free-living male red-winged blackbirds (Agelaius phoeniceus) to test whether gene expression responses in blood are distinct or shared between patterns of aggressive behavioral responses directed at simulated conspecific versus heterospecific intruders. In this species, males defend territories against conspecific males and respond aggressively to female brown-headed cowbirds (Molothrus ater), a brood parasite that commonly lays eggs in blackbird nests. Both conspecific songs and parasitic calls elicited aggressive responses from focal subjects and caused a downregulation in genes associated with immune system response, relative to control calls of a second, harmless heterospecific species. In turn, only the conspecific song treatment elicited an increase in singing behavior and an upregulation of genes associated with metabolic processes relative to the two heterospecific calls. Our results suggest that aspects of antagonistic responses to both conspecifics and brood parasites can be based on similar physiological responses, suggestive of shared molecular and behavioral pathways involved in the recognition and reaction to both evolutionarily old and new enemies.

animal behavior and cognition↗

bioRxiv2018

Avian diet and foraging ecology constrain foreign egg recognition and rejection

Egg rejection is the most common defense against avian brood parasitism in which the host either removes the parasitic egg or deserts the parasitized clutch. The ability to recognize and reject a parasitic egg depends on bill morphology, sensory systems, and cognition, all of which are also shaped by other selective processes, such as foraging. This begs the question whether specific phenotypes associated with different foraging strategies and diets may constrain or facilitate egg recognition and rejection. Here, we propose a novel hypothesis that host species phenotypes related to foraging ecology and diet impose morphological and sensory constraints on the evolution of egg rejection. We conducted a comparative analysis of the adult diets and egg rejection rates of 165 current host and non-host species and found species that consume an animal and fruit dominated diet rather than seeds and grains, forage arboreally rather than aerially, and possess relatively larger body sizes have significantly higher egg rejection rates. As predicted, these results suggest that phenotypes related to specific diets and foraging strategies may differentially constrain or facilitate evolution of host egg rejection defenses against avian brood parasitism.

animal behavior and cognition↗