Biology subjects

Roulin, A.

Publications and source records attributed to Roulin, A..

25 records · Page 2Linked to original sources

bioRxiv2021

Landscape and climatic variations of the Quaternary shaped multiple secondary contacts among barn owls (Tyto alba) of the Western Palearctic

The combined actions of climatic variations and landscape barriers shape the history of natural populations. When organisms follow their shifting niches, obstacles in the landscape can lead to the splitting of populations, on which evolution will then act independently. When two such populations are reunited, secondary contact occurs in a broad range of admixture patterns, from narrow hybrid zones to the complete dissolution of lineages. A previous study suggested that barn owls colonized the Western Palearctic after the last glaciation in a ring-like fashion around the Mediterranean Sea, and conjectured an admixture zone in the Balkans. Here, we take advantage of whole-genome sequences of 94 individuals across the Western Palearctic to reveal the complex history of the species in the region using observational and modeling approaches. Even though our results confirm that two distinct lineages colonized the region, one in Europe and one in the Levant, they suggest that it predates the last glaciation and identify a narrow secondary contact zone between the two in Anatolia. Nonetheless, we also show that barn owls re-colonized Europe after the glaciation from two distinct glacial refugia: a western one in Iberia and an eastern one in Italy. Both glacial lineages now communicate via eastern Europe, in a wide and permeable contact zone. This complex history of populations enlightens the taxonomy of Tyto alba in the region, highlights the key role played by mountain ranges and large water bodies as barriers and illustrates the power of population genomics in uncovering intricate demographic patterns.

evolutionary biology↗

bioRxiv2021

Unexpected post-glacial colonisation route explains the white colour of barn owls (Tyto alba) from the British Isles

The climate fluctuations of the Quaternary shaped the movement of species in and out of glacial refugia. In Europe, the majority of species followed one of the described traditional postglacial recolonization routes from the southern peninsulas towards the north. Like most organisms, barn owls are assumed to have colonized the British Isles by crossing over Doggerland, a land bridge that connected Britain to northern Europe. However, while they are dark rufous in northern Europe, barn owls in the British Isles are conspicuously white, a contrast that could suggest selective forces are at play on the islands. However, analysis of known candidate genes involved in colouration found no signature of selection. Instead, using whole genome sequences and species distribution modelling, we found that owls colonised the British Isles soon after the last glaciation, directly from a white coloured refugium in the Iberian Peninsula, before colonising northern Europe. They would have followed a yet unknown post-glacial colonization route to the Isles over a westwards path of suitable habitat in now submerged land in the Bay of Biscay, thus not crossing Doggerland. As such, they inherited the white colour of their Iberian founders and maintained it through low gene flow with the mainland that prevents the import of rufous alleles. Thus, we contend that neutral processes likely explain this contrasting white colour compared to continental owls. With the barn owl being a top predator, we expect future research will show this unanticipated route was used by other species from its paleo community.

evolutionary biology↗

bioRxiv2020

A comprehensive framework for handling location error in animal tracking data

Animal tracking data are being collected more frequently, in greater detail, and on smaller taxa than ever before. These data hold the promise to increase the relevance of animal movement for understanding ecological processes, but this potential will only be fully realized if their accompanying location error is properly addressed. Historically, coarsely-sampled movement data have proved invaluable for understanding large scale processes (e.g., home range, habitat selection, etc.), but modern fine-scale data promise to unlock far more ecological information. While GPS location error can often be ignored in coarsely sampled data, fine-scale data require more care, and tools to do this have not kept pace. Current approaches to dealing with location error largely fall into two categories--either discarding the least accurate location estimates prior to analysis or simultaneously fitting movement and error parameters in a hidden-state model. In some cases these approaches can provide a level of correction, but they have known limitations, and in some cases they can be worse than doing nothing. Here, we provide a general framework to account for location error in the analysis of triangulated and trilatcralizcd animal tracking data, which includes GPS, Argos Doppler-shift, triangulated VHF, trilatcralized acoustic and cellular location data. We apply our error-modelselection framework to 190 GPS, cellular, and acoustic devices representing 27 models from 14 manufacturers. Collectively, these devices were used to track a wide range of taxa comprising birds, fish, reptiles, and mammals of different sizes and with different behaviors, in urban, suburban, and wild settings. In almost half of the tested device models, error-model selection was necessary to obtain the best performing error model, and in almost a quarter of tested device models, the reported DOP values were actually misinformative. Then, using empirical tracking data from multiple species, we provide an overview of modern, error-informed movement analyses, including continuous-time path reconstruction, home-range distribution, home-range overlap, speed, and distance estimation. Adding to these techniques, we introduce new error-informed estimators for outlier detection and autocorrelation visualization. Because error-induced biases depend on many factors--sampling schedule, movement characteristics, tracking device, habitat, etc.--differential bias can easily confound biological inference and lead researchers to draw false conclusions. We demonstrate how error-informed analyses on calibrated tracking data can provide more accurate estimates are that are insensitive to location error, and allow researchers to use all of their data.

ecology↗

bioRxiv2019

Survival of adult barn owls is linked to corticosterone levels

Glucocorticoid hormones, such as corticosterone, are fundamental in the translation of external stimuli into physiological adjustments that promote the survival of an organism in face of changes in its environment. At baseline levels, corticosterone is crucial in regulating daily life metabolism and energy expenditure, whereas the acute corticosterone response promotes short-term physiological and behavioral responses to unpredictable environmental challenges. Given their different physiological effects and their role in mediating fitness components, it is still unclear whether and how inter-individual variation in baseline corticosterone levels and acute stress-response levels can affect the survival of organisms. We used 13 years of capture-recapture and dead recovery data combined with 11 years of corticosterone measurements taken on breeding barn owls (Tyto alba) to investigate how survival probability varies in relation to baseline and stress-induced corticosterone levels. Our study shows that males with a higher level of both baseline and stress-induced corticosterone levels have a higher probability of surviving than individuals with lower corticosterone levels. In females, survival probability was higher in individuals presenting elevated stress-induced corticosterone levels but was not significantly associated to baseline corticosterone levels. Our results suggest that in the barn owl the stress-induced corticosterone response is a better proxy of adult survival than baseline corticosterone levels. Further studies investigating the link between corticosterone levels and different fitness components as well as the environmental factors (e.g. weather, development conditions, disease and predation risk) leading to such endocrine phenotypes are needed to identify the costs and benefits of presenting high and low corticosterone profiles.

evolutionary biology↗

bioRxiv2019

Reproductive success in the barn owl is linked to partner compatibility in glucocorticoid levels

In biparental species, reproductive success depends not only on the quality of the parents, the care they each provide and many environmental factors such as territory quality and food availability, but also on the ability of the parents to collaborate and divide reproductive tasks. Because hormones, such as corticosterone (CORT), modulate physiological and behavioural functions that are associated to reproductive success, hormonal compatibility between pair members is likely to have consequences on reproductive success. Here, we investigated in the barn owl (Tyto alba) whether baseline and stress-induced CORT levels are correlated between breeding partners and whether this correlation is associated to fitness parameters (i.e., clutch size, offspring number and body mass). We found that the combination of CORT levels in the two partners predicts reproductive parameters. Pairs with similar baseline CORT levels during incubation produced more fledglings than pairs with dissimilar baseline CORT levels. On the other hand, pairs showing dissimilar stress-induced CORT responses during the period of offspring rearing produced more fledglings than pairs with similar stress-induced responses. Offspring body mass was associated only with maternal (baseline and stress-induced) CORT levels and depended on the context with baseline CORT being potentially adjusted to environmental conditions but also to the energetic demand of reproduction. Hence, to produce large broods good quality mothers might increase their baseline CORT to meet the energetic demand of the brood, while mothers in unfavourable habitats may have smaller broods but still need to increase baseline CORT to cope with the environmental challenges. Taken together, the results show that the association between parental CORT levels and reproductive success are context-dependent and rely on the combination of parental CORT levels. Assuming that CORT levels reflect investment in parental care, our study suggests that parents coordinate their reproductive activities in a complex way to ensure a high reproductive success.

evolutionary biology↗

bioRxiv2019

Expression of glucocorticoid and mineralocorticoid receptor genes co-vary with a stress-related colour signal in barn owls

Glucocorticoid hormones are important intermediates between an organism and its environment. They enable an organism to adjust its behavioural and physiological processes in response to environmental changes by binding to mineralocorticoid receptors (MR) and glucocorticoid receptors (GR) expressed in many tissues, including the integument. The regulation of glucocorticoids covaries with melanin-based colouration in numerous species, an association that might result from the melanocortin system and evolve within a signalling context. Most studies have focused on the circulating levels of glucocorticoids disregarding the receptors that mediate their action and could partly account for the covariation between the regulation of stress and melanin-based coloration. We investigated the association between melanin-based coloration and the gene expression levels of GR and MR but also of the melanocortin system and melanogenesis in the growing feathers of nestling barn owls (Tyto alba). We also considered the expression of genes related to the melanocortin system and melanogenesis to better understand the origin of the link between the expression of receptors to which corticosterone binds and melanin-based coloration. Nestling barn owls displaying larger black feather spots expressed GR and MR at lower levels than did smaller-spotted individuals. Because the expression of the GR and MR genes was positively, rather than negatively, correlated with the expression of melanogenic genes, we suggest that the link between melanin-based coloration, GR and MR is not directly associated to melanogenesis. The finding that the expression of GR and MR was positively associated with the expression of the PCSK2 gene (encoding the protein convertase responsible for post-translational modification of the proopiomelanocortin hormone) suggests that the melanocortin system may be implicated in the establishment of the covariation between melanism and the expression of receptors to which glucocorticoids bind. Together with previous studies, our results suggest that coloration is not only related to the production of glucocorticoids but also to the sensitivity of the integument to glucocorticoids.

physiology↗

bioRxiv2018

A novel cell-based sensor detecting the activity of individual basic proprotein convertases

The basic proprotein convertases (PCs) furin, PC1/3, PC2, PC5/6, PACE4, PC4, and PC7 are promising drug targets for human diseases. However, developing selective inhibitors remains challenging due to overlapping substrate recognition motifs and limited structural information. Classical drug screening approaches for basic PC inhibitors involve homogeneous biochemical assays using soluble recombinant enzymes combined with fluorogenic substrate peptides and do not accurately recapitulate the complex cellular context of the basic PC-substrate interaction. We report here PCific, a novel cell-based molecular sensor that allows rapid screening of candidate inhibitors and their selectivity toward individual basic PCs within mammalian cells. PCific consists of Gaussia luciferase linked to a sortilin-1 membrane anchor via a cleavage motif that allows efficient release of luciferase specifically if individual basic PCs are provided in cis. Screening of selected candidate peptidomimetic inhibitors revealed that PCific can readily distinguish between general and selective PC inhibitors in a high-throughput screening format.

biochemistry↗