Biology subjects

Liker, A.

Publications and source records attributed to Liker, A..

9 recordsLinked to original sources

bioRxiv2024

Demographic pathways linking sex-chromosome system to adult sex ratio variation across tetrapods

Sex chromosomes determine male and female phenotypes, and the resulting sex differences can have significant impacts on ecology and life history. One manifestation of this link is that ZZ/ZW sex-determination systems are associated with more male-skewed adult sex ratio (ASR, proportion of males in the adult population) than XY/XX systems across tetrapods (amphibians, reptiles, birds, and mammals). Here we investigate four demographic processes: male and female offspring production, sex differences in juvenile and adult mortalities and in timing of maturation that can contribute to ASR variation between XY/XX and ZZ/ZW systems, using phylogenetic analyses of a large dataset collected from tetrapod species in the wild. We show that sex differences in adult mortality reliably predict ASR, and it is also more male-biased in XY/XX species than in ZZ/ZW species. Sex differences in juvenile mortality or in maturation time also contribute to ASR skews, but do not differ consistently between XY/XX and ZZ/ZW systems. Phylogenetic path analyses confirm an influence of sex-determination system on ASR through sex-biased adult mortality. Thus, these results infer that sex chromosomes can impact, via demographic pathways, frequency-dependent selection emerging from the relative number of males and females. We call for follow-up studies to uncover the potentially complex web of associations between sex determination, population dynamics, and social behaviour.

evolutionary biology↗

bioRxiv2024

Continent-wide drivers of spatial synchrony in age structure across wild great tit populations

Spatio-temporal variation in age structure influences population dynamics, yet we have limited understanding of the spatial scale at which its fluctuations are synchronised between populations. Using 32 great tit populations, spanning 3200km and >130,000 birds across 67 years, we quantify spatial synchrony in breeding age structure and its drivers. We show that larger clutch sizes, colder winters and summers, and larger beech crops lead to younger populations. We report distant-dependent spatial synchrony of age structure, which is maintained at approximately 650km. Despite covariation with age structure, reproductive and environmental variables do not influence the scale of synchrony, except for a moderate effect of beech masting. We suggest that local ecological and density-dependent dynamics impact how environmental variation interacts with age structure, influencing estimates of the environments effect on spatial synchrony. Our analyses demonstrate the operation of synchrony in age structure over large scales, with implications for age-dependent demography in populations.

ecology↗

bioRxiv2022

Carotenoid-dependent plumage coloration is associated with reduced male care in passerine birds

The immense diversity of plumage coloration exhibited by birds is the result of either pigments deposited in the feathers or microstructural arrangements of feather barbules. Some of the most common pigments are carotenoids that produce bright yellow, orange and red colors. Carotenoids differ from other pigments since birds cannot synthesize them de novo and must obtain them from the diet. Carotenoid pigments are usually associated with signaling and sexual selection, although they also have antioxidant properties and play a role in the immune response. Here we hypothesize that carotenoid-dependent plumage coloration functions as a signal of a males tendency to invest in offspring care because they play an important role in the self-maintenance and may provide key information about individual quality; allowing females to obtain information about a males tendency to invest in offspring care. Using phylogenetic comparative analyses across 350 passerine birds we show that species that consume carotenoid-rich foods have more carotenoid-dependent plumage coloration than species with carotenoid-poor diets. In addition, carotenoid-dependent plumage coloration is associated with a decreased male investment in offspring care. Our results suggest investment into carotenoid-dependent plumage coloration trades off against male investment into offspring care and will likely have broad implications for our understanding of the ecological contexts that facilitate various evolutionary processes such as sexual selection or signaling associated with plumage colors.

evolutionary biology↗

bioRxiv2020

How do ecological and social environments reflect parental roles in birds? A comparative analysis

Parental roles are highly diverse in animal taxa. Since caring is an important determinant of fitness, understanding the origin and maintenance of various parental care strategies is a key question in evolutionary biology. Here we investigate parental care patterns in birds, which exhibit a remarkable diversity of parental sex roles. By means of phylogenetically informed comparative analyses we investigate whether and how care provisioning is predicted by ecology and social environment. Making use of the most comprehensive dataset including 1101 species that represent 126 avian families, we show that sex differences in parental care are neither related to food type nor to nest type, two key ecological factors. However, we found an effect of the social environment, as males tend to care relatively more in in colonial species than in non-colonial species. Taken together, these results highlight the importance of social effects for evolution of diverse parental sex roles.

evolutionary biology↗

bioRxiv2020

Does offspring sex ratio differ between urban and forest populations of great tits (Parus major)?

Since male and female offspring may have different costs and benefits, parents may use sex ratio adjustment to increase their fitness under different environmental conditions. Urban habitats provide poorer conditions for nestling development in many birds. Therefore, we investigated whether great tits (Parus major) produce different brood sex ratios in urban and natural habitats. We determined the sex of nestlings of 126 broods in two urban and two forest habitats between 2012 and 2014 by molecular sexing. We found that brood sex ratio did not differ significantly between urban and forest habitats either at egg-laying or near fledging. Male offspring were larger than females in both habitats. This latter result suggests that male offspring may be more costly to raise than females, yet our findings suggest that urban great tits do not produce more daughters despite the unfavourable breeding conditions. This raises the possibility that other aspects of urban life, such as better post-fledging survival, might favour males and thereby compensate for the extra energetic costs of producing male offspring.

ecology↗

bioRxiv2020

Effects of extreme hot weather on the reproductive output of great tits (Parus major, L.) in urban and natural habitats

Climate change and urbanization are among the most salient human-induced changes affecting Earths biota. Extreme weather events can have high biological impacts and are becoming more frequent recently. In cities, the urban heat island can amplify the intensity and frequency of hot weather events. However, the joint effects of heat events and urban microclimate on wildlife are unclear, as urban populations may either suffer more from increased heat stress or become adapted to warmer temperatures. Here we test whether the effects of hot weather on reproductive success of great tits (Parus major) are exacerbated or dampened in urban environments compared to forest habitats. By studying two urban and two forest populations over six years, we show that 14-16 days-old nestlings have smaller body mass and tarsus length, and suffer increased mortality when they experience a higher number of hot days during the nestling period. The negative effects of hot weather on body mass and survival are significantly stronger in forests than in urban areas, where these effects are dampened or even reversed. These results suggest that urban birds are less vulnerable to extreme hot weather conditions than their non-urban conspecifics, possibly by adaptively evolving or flexibly adjusting nestling physiology to tolerate heat stress, and/or by adjusting parental behavior in response to heat. This finding highlights that endothermic vertebrates may be able to adapt to heat stress, which may help their populations cope with the joint challenges of climate change and urbanization. Significance statementExtreme weather events are becoming more frequent due to climate change and can have substantial effects on reproduction and survival of wild animals. Urban heat island can amplify the frequency of extreme hot weather events, making it potentially more harmful for city-dwelling organisms. Alternatively, urban populations living in warmer environments may adapt to better tolerate heat. We investigated these alternatives by comparing nestling development and survival between urban and forest great tit (Parus major) populations. We found that urban populations are less vulnerable to heat: nestling body mass and survival decreased rapidly with the increasing number of hot days in forests, while these effects were dampened in urban broods. Thus, urban populations may become adapted to better tolerate heat events.

ecology↗

bioRxiv2019

Ecology, phylogeny, and the evolution of developmental duration in birds

The duration of the developmental period represents a fundamental axis of life history variation in animals, yet broad insights regarding the drivers of this diversity are currently lacking. Here using embryological data combined with information on incubation and fledging periods for 3096 species, we test key mechanistic and adaptive explanations for the evolutionary diversification of developmental durations in birds. First, using data on embryonic development for 20 model species, we show that developmental phases associated primarily with growth are longer and more variable than earlier phases, consistent with a role for allometric constraint in determining the duration of development. Second, using phylogenetic comparative methods, we find that avian developmental durations retain a strong imprint of deep evolutionary history, and that after accounting for these effects, body size differences among species explain less variation (5-22%) in developmental period lengths than previously thought. Finally, by collecting data for a suite of potential explanatory variables, our analyses reveal broad-scale ecological correlates of developmental durations, including variables associated with the relative safety of the developmental environment (e.g. nest height, insularity) and pressures of breeding phenology (e.g. migration). Overall, our results reveal that the combined effects of species body size, ecology, and phylogenetic history can account for 62-93% of the variation in developmental durations across birds, providing broad-scale quantitative insight into the relative importance of mechanistic constraints, adaptive evolution and evolutionary constraints in shaping the diversification of this key life-history trait.

evolutionary biology↗

bioRxiv2019

Higher frequency of extra-pair offspring in urban than forest broods of great tits (Parus major)

Urbanization increasingly changes the ecological conditions for wild animal populations, influencing their demography, reproduction, and behaviour. While studies on the ecological consequences of urbanization frequently document a reduced number and poorer body condition of offspring in urban than in non-urban bird populations, consequences for other components of reproduction are rarely investigated. Mating with partners outside the social pair-bond is widespread in birds, and although theory predicts that the occurrence of extra-pair fertilizations (EPF) may be sensitive to the altered ecological conditions of cities, the effect of urbanization on EPF is poorly known. Here we used data from two urban and two forest populations collected over three years to test whether the frequency of extra-pair offspring (EPO) in great tit broods differed between the habitats. We found that significantly more broods contained EPO in urban habitats (48.9 %) than in forests (24.4 %). In broods with EPO, the number and proportion of EPO was similar in urban and forest broods. These results suggest that females that live in urban habitats are more likely to engage in EPF than those living in forests. Urban environments may either 1) provide more spatiotemporal opportunities to EPF because of higher breeding density and lower or more constant caterpillar supply in cities compared to natural habitats, or 2) enhance the benefits of EPF via increased fertility or due to disrupted quality signals caused by anthropogenic pollution. In addition, 3) females with higher propensity to engage in EPF may more likely settle in urban habitats.

ecology↗

bioRxiv2018

Meta-analysis challenges a textbook example of status signalling: evidence for publication bias

The status signalling hypothesis aims to explain conspecific variation in ornamentation by suggesting that some ornaments signal dominance status. Here, we use multilevel meta-analytic models to challenge the textbook example of this hypothesis, the black bib of house sparrows (Passer domesticus). We conducted a systematic review, and obtained raw data from published and unpublished studies to test whether dominance rank is positively associated with bib size across studies. Contrary to previous studies, our meta-analysis did not support this prediction. Furthermore, we found several biases in the literature that further question the support available for the status signalling hypothesis. First, the overall effect size of unpublished studies was zero, compared to the medium effect size detected in published studies. Second, the effect sizes of published studies decreased over time, and recently published effects were, on average, no longer distinguishable from zero. We discuss several explanations including pleiotropic, population- and context-dependent effects. Our findings call for reconsidering this established textbook example in evolutionary and behavioural ecology, raise important concerns about the validity of the current scientific publishing culture, and should stimulate renewed interest in understanding within-species variation in ornamental traits.

evolutionary biology↗