Biology subjects

Perez-Tris, J.

Publications and source records attributed to Perez-Tris, J..

8 recordsLinked to original sources

bioRxiv2026

Blackcaps (Sylvia atricapilla) with blood parasites have impaired oxidative status during autumn migration

Parasites decrease host fitness, more so during physiologically challenging life stages such as migration. However, parasites are unevenly distributed among individuals, and hosts with different physiological condition may face different costs of migration with infections. We tested whether the relationship between infection by haemosporidian parasites and oxidative balance during autumn migration in blackcaps depends on individual age and sex, two major sources of variation in prevalence and physiological condition. We captured blackcaps at stopover in central Spain and measured infection status and physiological parameters. Blackcaps physiologically more prepared to depart from stopover had lower antioxidant capacity of plasma, probably because of physiological adjustments prior to the upcoming flight stage. Plasmodium parasites occurred only in coinfections, which were more frequent among young blackcaps. Regardless of individual sex and age, coinfected birds had lower antioxidant capacity of plasma, and blackcaps coinfected with Plasmodium had more oxidative damage to lipids in their red blood cells. Our results support the idea that haemosporidian infections impair the oxidative balance of blackcaps during autumn migration, which could impair individual performance and ultimately fitness, with increased population impacts during the first year of life when a larger proportion of individuals migrate coinfected with harmful Plasmodium parasites.

evolutionary biology↗

bioRxiv2026

Broad scale environmental conditions, not urbanisation, explain geographic variation in great tit feather microstructure

Urbanisation imposes novel environmental conditions that can shape phenotypic traits including plumage, yet, its effects on characteristics beyond colouration remain poorly understood. Feather microstructure plays an important role in thermoregulation, protection from solar radiation and waterproofing, and its expression is sensitive to environmental conditions. Here, we quantified feather barbule density, a key component of feather microstructure, in great tits (Parus major) from five urban-rural paired populations across Europe to assess its association with urbanisation, temperature and elevation. We found no significant effects of the urban environment or temperature. However, feather microstructure significantly varied between the studied areas and was positively associated with elevation and ultraviolet B (UV-B) radiation, suggesting a potential adaptive response to variation in solar radiation.

ecology↗

bioRxiv2026

From migrants to residents: Genomic insights into adaptive strategies in European robins (Erithacus rubecula)

Bird migration evolved as an adaptation to seasonally changing habitats. Migratory behaviour can vary within the same species in case of partial migratory behaviour, i.e. one population (or individual) is migratory and another one is resident. Species that exhibit a wide variety of migratory phenotypes provide valuable systems to understand the evolutionary drivers behind different phenotypes and how populations adapt to habitats with distinct seasonality. The European robin (Erithacus rubecula) expresses migratory behaviour in central and northern areas of the species distribution range, whereas populations in the South and on the Macaronesian islands are predominantly resident, providing a suitable system to investigate these questions. We use high coverage whole genome re-sequencing data of 125 European robins to investigate how migration behaviour affects population structure and demography, and how it affects the selection landscape in the genome. Genetic structure in European robins coincides with migratory phenotype and geography and populations are characterised by distinct demographic histories. Our results suggest that both the continental resident population as well as the Macaronesian island populations have derived independently from an ancestral migratory population. Unexpectedly, tests for differential selection revealed extensive positive selection pressure acting across all chromosomes in the resident populations, while selective sweeps are largely absent from migrants. We speculate that this might be an analytical artifact due to mismatching timescales between what population genomics methods can detect and the scale on which migration behaviour likely evolved in the robin. We suggest that future studies on the genomics of migration should more focally account for different time scales on which these processes happen, such as including the wider phylogenomic background of the target species, to capture the full evolutionary history of migratory traits.

evolutionary biology↗

bioRxiv2026

Sex- and age-specific body condition decline under warmer and drier breeding conditions in European robins

O_LILocal environmental conditions during the breeding season can limit bird populations. Identifying which variables, when, and how they affect key biological traits such as body condition is crucial for understanding long-term population trends under ongoing climate change. C_LIO_LIWe analysed the relationships between environmental variables and body condition during the breeding season in European robins (Erithacus rubecula), aiming to uncover links between short-term environmental influences and long-term trends in body condition in the context of local climate change. C_LIO_LIUsing data from a robin population monitored between 2007 and 2021, we applied weather sliding-window analyses to identify periods when temperature, soil moisture, and vegetation productivity best predicted individual body condition. For each variable, we identified critical time windows (CTWs) influencing (1) body condition across the season and (2) individual changes within two weeks. Juveniles and adults were analysed separately, with adult males and females distinguished during pre- and post-fledging periods. We also assessed long-term trends in environmental variables and body condition, and examined how body condition was correlated with apparent survival. C_LIO_LIBody condition variation across the season was explained by different environmental variables depending on age, sex, and period. Body condition declined with increasing minimum temperatures in adult males and juveniles, and with low soil moisture in adults of both sexes. We did not identify reliable CTWs explaining short-term within-individual changes in body condition. Across 2007-2021, body condition in adult males during the post-fledging period declined with rising minimum temperatures, while fledging dates advanced. Apparent survival was positively associated with body condition only in juvenile robins. C_LIO_LIOur results reveal multiple seasonal environmental influences that may contribute to short- and long-term declines in body condition in European robins, with effects particularly strong (or most detectable) in adult males. Reduced body condition may have demographic consequences by lowering juvenile survival, although shifts in breeding phenology could mitigate this impact. Overall, these findings highlight how environmental effects on body condition can shape long-term population trends and species vulnerability to climate change. C_LI

ecology↗

bioRxiv2024

Delayed post-juvenile moult in malaria-infected European blackcaps

Parasites have their strongest impact on fitness when host defences limit the quantity of resources available for other critical life-history stages, such as development, breeding or migration. One greatly neglected stage that could be altered by parasites is the post-juvenile moult (PJM) of birds, through which inexperienced yearlings replace their weak and fast-generated juvenile feathers by adult-like feathers. The earlier juvenile birds complete PJM, the earlier they will be prepared to withstand forthcoming adverse conditions, especially if they migrate short after moulting. We used data from 435 juvenile European blackcaps (Sylvia atricapilla) sampled during three years in 26 localities spanning the wide range of environmental conditions across Iberian Spain to test whether haemosporidian infections (presence and abundance in blood of parasites of the genera Haemoproteus, Plasmodium and Leucocytozoon) were related to delayed PJM. Controlling for body condition, sex, year and date of capture, infected blackcaps (single-infected or coinfected) had lower moult scores indicative of delayed moult, especially when birds had Plasmodium infections or higher intensity of Haemoproteus parasites. Our results broaden the range of fitness costs that haemosporidian parasites may have on birds, as delayed plumage maturation prolongs the period during which juvenile birds lack a fully functional plumage.

ecology↗

bioRxiv2023

Host space, not energy or symbiont size, constrains feather mite abundance across passerine bird species

Comprehending symbiont abundance among host species is a major ecological endeavour, and the metabolic theory of ecology has been proposed to understand what constraints symbiont populations. We parameterized metabolic theory equations to predict how bird species body size and the body size of their feather mites relate to mite abundance according to four potential energy (microbial abundance, uropygial gland size) and space constraints (wing area, number of feather barbs). Predictions were compared with the empirical scaling of feather mite abundance from 26,604 birds of 106 passerine species, using phylogenetic modelling and quantile regression. Feather mite populations were strongly constrained by host space (number of feather barbs) and not energy. Moreover, feather mite species body size was unrelated to their abundance or to the body size of their host species. We discuss the implications of our results for our understanding of the bird-feather mite system and for symbiont abundance in general.

ecology↗

bioRxiv2022

Urbanisation impacts plumage colouration in a songbird across Europe: evidence from a correlational, experimental, and meta-analytical approach

Urbanisation is increasing at a phenomenal rate across the globe, transforming landscapes, presenting organisms with novel challenges, shaping phenotypic traits, and even impacting fitness. Among colour traits, urban individuals are widely claimed to have duller tones in carotenoid-based traits, the so-called "urban dullness" phenomenon. However, at the intra-specific level, this generalisation is surprisingly inconsistent and often based on examples from single urban/non-urban population pairs or a limited geographic area. Here, combining correlational, experimental, and meta-analytical results from a common songbird, the great tit (Parus major), we investigated carotenoid-based plumage coloration in urban and forest populations across Europe. We find that, as predicted, urban individuals are paler than forest individuals. Interestingly, we also find large population-specific differences in the magnitude of the urban-forest contrast in plumage colouration. Moreover, our meta-analysis indicates a non-significant effect of environmental pollution on carotenoid-based plumage for the species, suggesting that the observed differences across urban populations are not only driven by pollution. Finally, using one region as an example (Malmo, Sweden), we reveal population-specific processes behind plumage colouration differences, which are likely the result of variation in the spatial and temporal distribution of carotenoid-rich resources in anthropogenic environments. This is the first study to quantify the consistency of an oft-cited textbook example of the impact of urbanisation on wildlife; our results provide the most convincing evidence to date of the "urban dullness" phenomenon, but also highlight that the magnitude of the phenomenon depends on local urban characteristics.

evolutionary biology↗

bioRxiv2021

Recombination suppression and selection affect local ancestries in genomes of a migratory songbird

Genetic variation of the entire genome represents population structure, yet individual loci can show distinct patterns. Such deviations identified through genome scans have often been attributed to effects of selection instead of randomness. This interpretation assumes that long enough genomic intervals average out randomness in underlying genealogies, which represent local genetic ancestries. However, an alternative explanation to distinct patterns has not been fully addressed: too few genealogies to average out the effect of randomness. Specifically, distinct patterns of genetic variation may be due to reduced local recombination rate, which reduces the number of genealogies in a genomic window. Here, we associate distinct patterns of local genetic variation with reduced recombination rates in a songbird, the Eurasian blackcap (Sylvia atricapilla), using genome sequences and recombination maps. We find that distinct patterns of local genetic variation reflect haplotype structure at low-recombining regions either shared in most populations or found only in a few populations. At the former species-wide low-recombining regions, genetic variation depicts conspicuous haplotypes segregating in multiple populations. At the latter population-specific low-recombining regions, genetic variation represents variance among cryptic haplotypes within the low-recombining populations. With simulations, we confirm that these distinct patterns of haplotype structure evolve due to reduced recombination rate, on which the effects of selection can be overlaid. Our results highlight that distinct patterns of genetic variation can emerge through evolution of reduced local recombination rate. Recombination landscape as an evolvable trait therefore plays an important role determining the heterogeneous distribution of genetic variation along the genome.

evolutionary biology↗