Biology subjects

Bonier, F.

Publications and source records attributed to Bonier, F..

4 recordsLinked to original sources

bioRxiv2025

Divergent climate impacts despite similar response to temperature in a widespread aerial insectivore

Climate change is shifting when animals breed1,2, but it is still not clear why some populations keep pace with warming while others fall behind3,4. Differences could arise from variation in sensitivity to temperature3 or constraints on the ability to respond to temperature. Without knowing whether populations differ in sensitivity--or in their ability to act on that sensitivity--we cannot identify which are most at risk. Using 1,555 population-years from 123 populations of tree swallows (Tachycineta bicolor), we show that populations have similar sensitivity to local temperature, advancing breeding by about one day per degree of warming. However, northern populations face tighter time constraints and greater exposure to recent warming. Northern populations have advanced laying dates the most, but still experience stronger selection for earlier breeding, especially in warm years; they have also declined most in breeding abundance. These findings show that vulnerability to climate change can arise not just from different sensitivity to warming, but from when and where populations can respond effectively. By disentangling sensitivity from timing constraints, our results support a general mechanism by which even uniformly responsive species can show uneven impacts of climate change across their ranges.

ecology↗

bioRxiv2020

Cytonuclear discordance in the crowned-sparrows, Zonotrichia atricapilla and Zonotrichia leucophrys: a mitochondrial selective sweep?

The golden-crowned (Zonotrichia atricapilla) and white-crowned (Z. leucophrys) sparrows have been presented as a compelling case for rapid speciation. They display divergence in song and plumage with overlap in their breeding ranges implying reproductive isolation, but have almost identical mitochondrial genomes. Previous research proposed hybridization and subsequent mitochondrial introgression as an alternate explanation, but lacked robust nuclear gene trees to distinguish between introgression and incomplete lineage sorting. We test for signatures of these processes between Z. atricapilla and Z. leucophrys, and investigate the relationships among Z. leucophrys subspecies, using mitochondrial sequencing and a reduced representation nuclear genomic dataset. Contrary to the paraphyly evident in mitochondrial gene trees, we confirmed the reciprocal monophyly of Z. atricapilla and Z. leucophrys using large panels of single nucleotide polymorphism (SNPs). The pattern of cytonuclear discordance is consistent with limited, historical hybridization and mitochondrial introgression, rather than a recent origin and incomplete lineage sorting between recent sister species. We found evidence of nuclear phylogeographic structure within Z. leucophrys with two distinct clades. Altogether, our results support the true species status of Z. atricapilla and Z. leucophrys, and indicate deeper divergences between the two species than inferred using mitochondrial markers. Our results demonstrate the limitations of relying solely on mitochondrial DNA for taxonomy, and raise questions about the possibility of selection on the mitochondrial genome during temperature oscillations (e.g. during the Pleistocene). Historical mitochondrial introgression facilitated by past environmental changes could cause erroneous dating of lineage splitting in other taxa when based on mitochondrial DNA alone.

evolutionary biology↗

bioRxiv2018

Prenatal aromatase inhibition alters postnatal immune function in domestic chickens (Gallus gallus)

In birds, exposure to testosterone during embryonic development can suppress immune function; however, it is unclear whether this is caused by direct stimulation of androgen receptors. Estradiol is synthesized from testosterone by the enzyme aromatase, and this conversion is a necessary step in many signaling pathways that are ostensibly testosterone-dependent. Many lines of evidence in mammals indicate that estradiol can affect immune function. We tested the hypothesis that immunosuppressive effects of avian in ovo testosterone exposure are mediated by conversion to estradiol by aromatase, using Fadrozole to inhibit aromatization of endogenous testosterone during a crucial period of embryonic immune system development in domestic chickens (Gallus gallus). We then measured total IgY antibody count, response to PHA challenge, mass of thymus and bursa of Fabricius, and plasma testosterone post-hatch on days 3 and 18. We predicted that if immunomodulation by testosterone is dependent on aromatization, then Fadrozole treatment would lead to elevated immune activity by inhibiting estrogen production. Conversely, if testosterone inhibits immune function directly by binding to androgen receptors, then Fadrozole treatment would likely not alter immune function. Fadrozole treated birds had decreased day 3 plasma IgY antibody titers but there was a strong trend towards increased day 18 thymic mass. Furthermore, Fadrozole treatment generated a positive relationship between testosterone and thymic mass in males, and tended to increase day 18 IgY levels for a given bursal mass in females. There was no effect on PHA response, bursal mass, or plasma testosterone at either age. Overall, Fadrozole treated birds tended to have elevated indicators of immune function, implicating aromatization as a relevant pathway through which developmental exposure to testosterone can affect immunity.

developmental biology↗

bioRxiv2017

Male parental investment reflects the level of partner contributions and brood value in tree swallows

Biparental care presents an interesting case of cooperation and conflict between unrelated individuals. Several models have been proposed to explain how parents should respond to changes in each others parental care to maximize their own fitness, predicting no change, partial compensation, or matching effort as a response. Here, we present an experiment in tree swallows (Tachycineta bicolor) in which we increased the parental care of females by presenting them, but not their mates, with additional nestling begging calls using automated playbacks. We performed this experiment in two populations differing in future breeding opportunities and thus the intensity of conflict over current parental care. We found that in response to a temporary increase in female parental effort, males in the northern population with lower sexual conflict matched the increased effort, whereas males in the southern population did not. We also found that increases in parental care during playbacks were driven by the females (i.e., females initiated the increased effort and their mates followed them) in the northern population but not the southern population. These results support the idea that with incomplete information about the brood value and need, cues or signals from the partner might become important in coordinating parental care.

animal behavior and cognition↗