Biology subjects

Rosvall, K. A.

Publications and source records attributed to Rosvall, K. A..

9 recordsLinked to original sources

bioRxiv2026

Sex and breeding stage differences in neurogenomic profiles reflect hormone signaling in a socially polyandrous shorebird

In sex-role reversed species, females are socially polyandrous and compete for multiple mates, whereas males conduct the majority of parental care. To understand the extent to which physiological differences between females and males are shaped by sex roles, we examined sex differences in gene expression in sex-role reversed northern jacanas (Jacana spinosa). Given that females compete for mating opportunities, and males cycle between courtship and parental care, we predicted that transcriptomic profiles would be more similar between females and courting males, in contrast to female and parenting males. Leveraging a high quality de novo genome assembly, we conducted RNA-seq on two brain regions associated with the regulation of social behavior: the preoptic area of the hypothalamus and the nucleus taeniae. The majority of genes differentially expressed between the sexes were male-biased. Of these male-biased genes, the majority were located on the Z-chromosome. Contrary to our prediction, the greatest difference in autosomal gene expression was between females and courting males, in the preoptic area of the hypothalamus. Several differentially expressed genes related to elements of hormone signaling that are likely to be behaviorally salient, including higher expression of androgen receptor in females relative to parenting males, and higher expression of prolactin receptor in males, regardless of breeding stage. Some sex-associated gene networks were also associated with competitive traits, whereas others were associated with aggressive behaviors, regardless of sex. Few genes were differentially expressed between courting and parenting males, yet some nonetheless had connections to behavioral endocrinology, including prolactin, thyroid and insulin-like growth factor pathways. Our investigation of sex differences in gene expression can help to reveal the molecular mechanisms underlying female competition and male parental care in socially polyandrous species. We conclude that social polyandry is not a simple reversal in the direction of sex-biased gene expression in the brain, but rather a result of complex genetic and hormonal interactions that warrants further study.

genomics↗

bioRxiv2025

How sex shapes transcriptome evolution in the songbird brain

Sex differences have long captivated scientists, yet the evolutionary rate of change in sex-biased gene expression has not been directly quantified. To address this issue, we introduce new options in CAGEE (Computational Analysis of Gene Expression Evolution), specifically unbounded Brownian motion and variable evolutionary rates among genes. We applied these features to brain transcriptomes of ten songbird species, half of which convergently evolved obligate cavity-nesting, an element of reproductive ecology linked to sex-specific changes in competitive behavior. We find that the degree of sex-bias - measured as male:female expression ratio for each gene - evolves twice as fast on the Z chromosome versus autosomes, but Z gene expression does not evolve at different rates among sexes. Most Z-linked genes are male-biased in their expression, but not all. These sex-balanced genes are not skewed in their rate of evolution, contrary to the hypothesis that some genes experience selection for balance and consequently evolve more slowly. Finally, the degree of sex-bias in gene expression evolves more quickly along obligate-cavity nesting lineages, suggesting that sex-specific selection may shape the evolution of brain sex differences, or lack thereof. Together, these results provide new insights into the interplay between sex and gene expression evolution.

evolutionary biology↗

bioRxiv2025

AI, citizen science, and the 2024 eclipse emphasize the importance of light for bird behavior

On April 8th 2024, a total solar eclipse disrupted light-dark cycles for North American birds during the lead-up to spring reproduction. Compiling over 10,000 community observations and AI analyses of nearly 100,000 vocalizations, we found that bird behavior was significantly affected by these few minutes of unexpected afternoon darkness. More than half of wild bird species changed their biological rhythms, with many producing a dawn chorus in the aftermath of the eclipse. This natural experiment demonstrates the power of technology-enabled and public science projects to understand our natural world. Further, it underscores the power of light in structuring animal behavior: even when night lasts for just four minutes, robust behavioral changes ensue.

animal behavior and cognition↗

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↗

bioRxiv2024

How altricial birds respond to a heat challenge: organismal perspectives on coping with a future climate scenario

O_LIThe ability to cope with heatwaves is likely to influence species success amidst climate change. However, relatively little is known about heat-coping mechanisms in endotherms, which are increasingly pushed to their thermoregulatory limits. We experimentally elevated nest temperatures by 4.5{degrees}C for 4 hours, focused on 12-day-old tree swallows (Tachycineta bicolor). C_LIO_LINestlings exposed to sub-lethal heat moved towards cooler air at the nest box entrance, they panted more, and they weighed less than controls, suggesting panting-induced water loss. They also exhibited higher heat shock protein (HSP) gene expression in the blood, alongside widespread transcriptional differences related to antioxidant defenses, inflammation, and apoptosis. Nestlings exposed to milder heat were more likely to recruit into the breeding population, suggesting these coping mechanisms may be quite effective. C_LIO_LIWe also tested hypotheses on the drivers of variation in HSP gene expression, which was especially marked after heat-exposure. Even siblings in the same nest differed in HSP gene expression by over 14-fold. Heat-induced HSP levels were unrelated to individual body mass, or among-nest differences in brood size, temperature, and behavioral thermoregulation. However, nest ID explained a significant amount of HSP variation, which was larger between nests than within nests, pointing to genetic or early developmental factors C_LIO_LIThese results fill key knowledge gaps on thermoregulatory mechanisms in birds. We document ample individual variation upon which selection may act in the context of climate change and we underscore the need to understand intra-specific variation, an oft-ignored element that nevertheless shapes what is possible for future adaptation or acclimation to heat. C_LI

physiology↗

bioRxiv2021

Plasticity in female timing may explain current shifts in breeding phenology of a North American songbird

O_LIClimate change has driven changes in breeding phenology. Identifying the magnitude of phenological shifts and whether selection in response to climate change drives these shifts is key for determining species reproductive success and persistence in a changing world. C_LIO_LIWe investigated reproductive timing in a primarily sedentary population of the dark-eyed junco (Junco hyemalis) over 32 years. We predicted that juncos would breed earlier in warmer springs in response to selection favouring earlier breeding. C_LIO_LITo test this prediction, we compared the annual median date for reproductive onset (i.e., egg one date) to monthly spring temperatures and examined evidence for selection favouring earlier breeding and for plasticity in timing. C_LIO_LIEgg one dates occurred earlier over time, with the timing of breeding advancing up to 24 days over the 32-year period. Breeding timing also strongly covaried with maximum April temperature. We found significant overall selection favouring earlier breeding (i.e., higher relative fitness with earlier egg one dates) that became stronger over time, but strength of selection was not predicted by temperature. Lastly, individual females exhibited plastic responses to temperature across years. C_LIO_LIOur findings provide further evidence that phenotypic plasticity plays a crucial role in driving phenological shifts in response to climate change. For multi-brooded bird populations, a warming climate might extend the breeding season and provide more opportunities to re-nest rather than drive earlier breeding in response to potential phenological mismatches. However, as plasticity will likely be insufficient for long-term survival in the face of climate change, further research in understanding the mechanisms of female reproductive timing will be essential for forecasting the effects of climate change on population persistence. C_LI

ecology↗

bioRxiv2021

The telomere regulatory gene POT1 responds to stress and predicts performance in nature: implications for telomeres and life history evolution

Long telomeres have become nearly synonymous with a variety of fitness-related traits and may be mediators of ecologically relevant variation in life history strategies. Growing evidence suggests that telomere dynamics are more predictive of performance than length itself, but very little work considers how telomere regulatory mechanisms respond to environmental challenges or influence performance in nature. Here, we combine observational and experimental datasets from free-living tree swallows (Tachycineta bicolor) to assess how performance is predicted by the telomere regulatory gene POT1, which encodes a shelterin protein that sterically blocks telomerase from repairing the telomere. First, we show that lower POT1 gene expression was associated with higher female quality, i.e. earlier breeding, and heavier body mass. We next challenged mothers with an immune stressor (lipopolysaccharide injection) that led to sickness in mothers and 24h of food restriction in their offspring. While POT1 did not respond to maternal injection, females with lower constitutive gene expression were better able to maintain feeding rates following treatment. Maternal injection also generated a one-day stressor for chicks, who responded with decreased POT1 gene expression and elongated telomeres. Other putatively stress-responsive mechanisms (i.e. glucocorticoids, antioxidants) were not significantly different between control and stress-exposed chicks. Model comparisons indicated that POT1 mRNA abundance was a largely better predictor of performance than telomere dynamics, indicating that telomere regulators may be powerful modulators of variation in life history strategies.

molecular biology↗

bioRxiv2020

Nesting strategy shapes territorial aggression but not testosterone: a comparative approach in female and male birds

Our understanding of the proximate and ultimate mechanisms shaping competitive phenotypes primarily stems from research on male-male competition for mates, even though female-female competition is also widespread. Obligate secondary cavity-nesting has evolved repeatedly across avian lineages, providing a useful comparative context to explore how competition over limited nest cavities shapes aggression and its underlying mechanisms across species. Although evidence from one or another cavity-nesting species suggests that territorial aggression is adaptive in both females and males, this has not yet been tested in a comparative framework. We tested the hypothesis that cavity-nesting generates more robust territorial aggression, in comparison to close relatives with less restrictive nesting strategies. Our focal species were two obligate secondary cavity-nesting species and two related species with more flexible nesting strategies in the same avian family: tree swallow (Tachycineta bicolor) vs. barn swallow (Hirundo rustica); Eastern bluebird (Sialia sialis) vs. American robin (Turdus migratorius). We assayed conspecific territorial aggression, and found that cavity-nesting species physically attacked a simulated intruder more often than their close relatives. This pattern held for both females and males. Because territorial aggression is often associated with elevated testosterone, we also hypothesized that cavity-nesting species would exhibit higher testosterone levels in circulation. However, cavity-nesting species did not have higher testosterone in circulation for either sex, despite some correlative evidence that testosterone is associated with higher rates of physical attack in female tree swallows. Our focus on a competitive context that is relevant to both sexes - competition over essential breeding resources - provides a useful comparative framework for co-consideration of proximate and ultimate drivers of reproductive competition in females and males.

animal behavior and cognition↗

bioRxiv2019

Testosterone secretion varies in a sex- and stage-specific manner: insights on the regulation of competitive traits from a sex-role reversed species

Testosterone (T) mediates a variety of traits that function in competition for mates, including territorial aggression, ornaments, armaments, and gametogenesis. The link between T and mating competition has been studied mainly in males, but females also face selection pressures to compete for mates. Sex-role reversed species, in which females are the more competitive sex, provide a unique perspective on the role of T in promoting competitive traits. Here, we examine patterns of T secretion in sex-role reversed Northern Jacanas (Jacana spinosa) during breeding, when females are fertile and males are either seeking copulations or conducting parental care. We measured baseline levels of T in circulation along with a suite of behavioral and morphological traits putatively involved in mating competition. We evaluated hypotheses that levels of T track gonadal sex and parental role, and we begin to investigate whether T and competitive traits co-vary in a sex- and stage-specific manner. Although females had higher expression of competitive traits than males at either breeding stage, we found that females and incubating males had similar levels of T secretion, which were lower than those observed in copulating males. T was correlated with wing spur length in females and testes mass in copulating males, but was otherwise uncorrelated with other competitive traits. These findings suggest that levels of T in circulation alone do not predict variation in competitive traits across levels of analysis, including gonadal sex and parental role. Instead, our findings coupled with prior research indicate that selection for female mating competition and male care may generate different physiological regulation of competitive traits in jacanas. HighlightsO_LIIn role reversed species, females face stronger competition and males care for offspring C_LIO_LIWe examine testosterone (T) and competitive traits in female and male jacanas C_LIO_LICirculating T is similar in females and incubating males, but higher in copulating males C_LIO_LIBoth gonadal sex and parental role shape patterns of T secretion C_LIO_LIPhysiological regulation of competitive traits may differ in female and male jacanas C_LI

physiology↗