Biology subjects

Szekely, T.

Publications and source records attributed to Szekely, T..

15 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↗

bioRxiv2023

Urbanization spreads antimicrobial resistant enteric pathogens in wild bird microbiomes

Human behaviour is dramatically changing global ecology. Nowhere is this more apparent than in urbanization, where novel high human density habitats are disrupting long established ecotones. Resultant changes to the transitional areas between organisms, especially enhanced contact between humans and wild animals, provides new opportunities for the spread of zoonotic pathogens, posing a serious threat to global public health. Here, by studying the multi-host enteric pathogen Campylobacter jejuni isolated from the gut of 30 bird species in 8 countries, we investigated how proximity to urbanization influenced the spread of antimicrobial resistant (AMR) strains. Generalized linear models compared multiple behavioural and ecological traits and confirmed a positive correlation between proximity to urbanization and the number of C. jejuni genotypes and AMR genes in wild bird hosts. Wild birds from highly urban areas harboured up to four times more C. jejuni genotypes and six times more AMR genes. This is consistent with increased frequency of transition events. Quantifying zoonotic transmission and gene pool spread is essential for quantitative one health surveillance and control measures against future zoonosis emergences.

genomics↗

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↗

bioRxiv2022

A life-history perspective on the evolutionary interplay of sex ratios and parental sex roles

Parental care is one of the most diverse social behaviours, and caring by the male, female or both parents is essential for successful reproduction of many organisms. Theoretical and empirical studies suggest that parental sex roles are associated with biased sex ratios. However, there is considerable debate on the causal relationship between parental sex roles and sex ratio biases and on the relative importance of the operational sex ratio (OSR), the adult sex ratio (ASR), and the maturation sex ratio (MSR). Here we use individual-based evolutionary simulations to investigate the joint evolution of sex-specific parental behaviour and the various sex ratios in several life history scenarios. We show that sex differences in maturation time or mortality rates at various life-history stages predict the evolution of parental sex roles relatively well: typically, but not always, parental care is biased toward the sex with the lower mortality or the faster maturation. The association of parental sex roles with the various sex ratios is more intricate. In our simulations, the operational sex ratio at evolutionary equilibrium was typically biased toward the less-caring sex. However, the direction and strength of OSR biases often changed drastically in the course of evolution, implying that, rather than being a driver of parental sex roles, OSR biases emerge as a consequence of sex-biases in parental care. When the MSR or the ASR is biased, this bias is generally associated with a bias in parental care: the overrepresented sex does most of the caring. However, the opposite pattern (that the underrepresented sex did most of the caring) also occurs in some scenarios. Moreover, pronounced parental sex roles may also evolve in the absence of an MSR or ASR bias. Taken together, we conclude that none of the sex ratios can be viewed as drivers of a parental care bias; they rather co-evolve with parental care bias in a subtle manner.

evolutionary biology↗

bioRxiv2022

Breeding in an agricultural landscape: conservation actions increase nest survival in a ground-nesting bird

Agricultural intensification has affected wildlife across Europe, usually prompting steep declines and regional extinctions in farmland birds. Effective conservation activities are essential for preservation of biodiversity in agricultural landscape, but despite the efforts, the halting (or reversing) the decline of farmland species are still rare. Here we investigate a ground-nesting shorebird, the Collared Pratincole (Glareola pratincola) that has switched its habitat preferences in Central Europe in the last 20 years from alkaline grasslands to intensively managed agricultural landscapes. We show that nest success was different between three habitat types, with the highest nest success in fallow lands whereas nests in row crops showed the lowest hatching success. Nest success was also associated with timing of breeding and breeding density, since nests produced early in the breeding season and those in dense breeding sites hatched more successfully than those later in the season and low breeding density, respectively. Importantly, since 2012 direct conservation measures have been implemented that include the marking of nests and negotiating with farmers to avoid the usage of agricultural machinery around the marked areas, controlling nest predators and most recently creating suitable nesting sites and foraging areas for the Pratincoles. Due to these direct conservation actions, the probability of both nest survival increased from 0.11 in 2012 to 0.83 in year 2021, and the size of breeding population increased from 16 pairs in 2013 to 56 in 2021. Taken together, agricultural areas can continue providing important habitats for various organisms, and with targeted conservation actions we can reduce or even halt the decline of farmland species.

zoology↗

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

How do sex biases in demography and disease characteristics affect the spread of sexually transmitted infections?

The epidemiology of sexually transmitted infections (STIs) is inherently linked to host mating dynamics. Studies across many taxa show that adult sex ratio, a major determinant of host mating dynamics, is often skewed - sometimes strongly - toward males or females. However, few predictions exist for the effects of skewed sex ratio on STI epidemiology, and none when coupled with sex biased disease characteristics. Here we use mathematical modelling to examine how interactions between sex ratio and disease characteristics affect STI prevalence in males and females. Notably, we find that while overall disease prevalence peaks at equal sex ratios, prevalence per sex peaks at skewed sex ratios. Furthermore, disease characteristics, sex-biased or not, drive predictable differences in male and female STI prevalence as sex ratio varies, with higher transmission and lower virulence generally increasing differences between the sexes for a given sex ratio. These findings may be due to a balance between increased per-capita mating in the less common sex, and a reduction in mating rate - hence disease prevalence - at the population level. Our work reveals new insights into how STI prevalence in males and females depends on a complex interaction between host population sex ratio and disease characteristics.

animal behavior and cognition↗

bioRxiv2019

Making the best of a bad job? Chick mortality and flexible female brood care in Snowy Plovers

Offspring desertion represents a trade-off between current and future reproductive success. Its timing is crucial as the termination of parental care has profound consequences for the fitness of the parents and their offspring. However, the decision process involved with termination of care is still poorly understood. Snowy Plovers Charadrius nivosus show highly flexible brood care with females either deserting the brood early or providing care for an extended period. Deserting females often quickly remate and start a new breeding attempt. Using a dynamic modelling framework, we investigated the decision-making process for continuation or termination of care by females over a seven-year period. The length of female care increased over the season likely reflecting lower re-mating opportunities for deserting females late in the season. Present brood size, assessed daily during the brood care period, was strongly related to the length of female care: females were more likely to stay and care for larger than for smaller broods. Chick death and desertion frequently coincided, suggesting that poor offspring condition served as a trigger for female desertion. Overall, deserting females had a similar number of fledglings to caring females. This suggests that for many females, desertion was not a strategy to escape the shackles of monogamy and secure higher reproductive success through sequential polygamy. Rather, most deserting females made the best of a bad job when conditions were poor and their continued presence did not make a difference for the survival of their young. We conclude that when making the decision to continue or terminate care, Snowy Plover females monitor the condition of their offspring closely and adjust their care flexibly to the value and needs of their young.

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

Responses of global waterbird populations to climate change vary with latitude

While climate change continues to present a major threat to global biodiversity and ecosystems, most research on climate change impacts do not have the resolution to detect changes in species abundance and are often limited to temperate ecosystems. This limits our understanding of global responses in species abundance--a determinant of ecosystem function and services--to climate change including in the highly-biodiverse tropics. We address this knowledge gap by quantifying abundance responses to climate change in waterbirds, an indicator taxon of wetland biodiversity, at 6,822 sites between -55{degrees} and 64{degrees}. Using 1,303,651 count records since 1990 of 390 species, we show that with temperature increase, the abundance of species and populations decreased at lower latitudes, particularly in the tropics, but increased at higher latitudes. These contrasting responses to temperature increase according to latitude indicate potential global-scale poleward shifts of species abundance under climate change, providing empirical support for predictions by earlier studies. The negative responses to temperature increase in tropical species and populations are of conservation concern, as they are often also threatened by other anthropogenic factors. Our results suggest that existing biases in studies towards temperate regions could underestimate the impact of climate change on waterbirds and other species.

ecology↗

bioRxiv2019

Phylogeny, transposable element and sex chromosome evolution of the basal lineage of birds

Sex chromosomes of mammals and most birds are heteromorphic, while those of many paleognaths (ratites and tinamous) are inexplicably homomorphic. To dissect the mechanisms underlying the different tempo of sex chromosome evolution, we produced high-quality genomes of 12 paleognathous species, and reconstructed their phylogeny based on alignments of the non-coding sequences extending to nearly 40% of the genome. Our phylogenomic tree grouped the South American rheas and tinamous together, and supported the independent evolution of gigantism and loss of flight among ratites. The small-bodied tinamous have much higher rates of genome-wide substitutions and transposon turnovers. Yet majorities of both have retained exceptionally long recombining regions occupying over half of the entire sex chromosome, with the rest sex-linked regions diverging from each other at a much lower rate relative to neognathous birds. Each species exhibits a punctuated sequence divergence pattern between sex chromosomes termed evolutionary strata, because of stepwise suppression of recombination. We concluded that all paleognaths share one evolutionary stratum with all other birds, and convergently formed between one to three strata after their rapid speciation. Contrary to the classic notion, we provided clear evidence that the youngest stratum of some tinamous formed without chromosomal inversion. Intriguingly, some of the encompassing W-linked genes have upregulated their expression levels in ovary, probably due to the female-specific selection. We proposed here that the unique male-only parental care system of paleognaths has reduced the intensity of sexual selection, and contributed to these species low rates of sex chromosome evolution. We also provided novel insights into the evolution of W-linked genes at their early stages.

evolutionary biology↗

bioRxiv2019

Demographic histories and genome-wide patterns of divergence in incipient species of shorebirds

Understanding how incipient species are maintained with gene flow is a fundamental question in evolutionary biology. Whole genome sequencing of multiple individuals holds great potential to illustrate patterns of genomic differentiation as well as the associated evolutionary histories. Kentish (Charadrius alexandrinus) and the white-faced (C. dealbatus) plovers, which differ in their phenotype, ecology and behaviour, are two incipient species and parapatrically distributed in East Asia. Previous studies show evidence of genetic diversification with gene flow between the two plovers. Under this scenario, it is of great importance to explore the patterns of divergence at the genomic level and to determine whether specific regions are involved in reproductive isolation and local adaptation. Here we present the first population genomic analysis of the two incipient species based on the de novo Kentish plover reference genome and resequenced populations. We show that the two plover lineages are distinct in both nuclear and mitochondrial genomes. Using model-based coalescence analysis, we found that population sizes of Kentish plover increased whereas white-faced plovers declined during the Last Glaciation Period. Moreover, the two plovers diverged allopatrically, with gene flow occurring after secondary contact. This has resulted in low levels of genome-wide differentiation, although we found evidence of a few highly differentiated genomic regions in both the autosomes and the Z-chromosome. This study illustrates that incipient shorebird species with gene flow after secondary contact can exhibit discrete divergence at specific genomic regions and provides basis to further exploration on the genetic basis of relevant phenotypic traits.

evolutionary biology↗

bioRxiv2018

Divergence in the face of gene flow in two Charadrius plovers along the Chinese coast

Speciation with gene flow is an alternative to the nascence of new taxa in strict allopatric separation. Indeed, many taxa have parapatric distributions at present. It is often unclear if these are secondary contacts, e.g. caused by past glaciation cycles or the manifestation of speciation with gene flow, which hampers our understanding of how different forces drive diversification. Here we studied genetic, phenotypic and ecological aspects of divergence in a pair of incipient species, the Kentish (Charadrius alexandrinus) and the white-faced Plovers (C. dealbatus), shorebirds with parapatric breeding ranges along the Chinese coast. We assessed divergence based on molecular markers with different modes of inheritance and quantified phenotypic and ecological divergence in aspects of morphometric, dietary and climatic niches. These analyses revealed small to moderate levels of genetic and phenotypic distinctiveness with symmetric gene flow across the contact area at the Chinese coast. The two species diverged approximately half a million years ago in dynamical isolation and secondary contact due to cycling sea level changes between the Eastern and Southern China Sea in the mid-late Pleistocene. We found evidence of character displacement and ecological niche differentiation between the two species, invoking the role of selection in facilitating divergence despite gene flow. These findings imply that the ecology can indeed counter gene flow through divergent selection and thus contribute to incipient speciation in these plovers. Furthermore, our study highlights the importance of using integrative datasets to reveal the evolutionary history and underlying mechanisms of speciation.

evolutionary biology↗

bioRxiv2017

Demographic causes of adult sex ratio variation and their consequences for parental cooperation

The adult sex ratio (ASR) is a fundamental concept in population biology, sexual selection, and social evolution. However, it remains unclear which demographic processes generate ASR variation and how biases in ASR in turn affect social behaviour. Here, we evaluate the demographic mechanisms shaping ASR and their consequences for parental cooperation using detailed survival, fecundity, and behavioural data on 6,119 individuals from six wild shorebird populations exhibiting flexible parental strategies. We show that these closely related populations express strikingly different ASRs, despite having similar ecologies and life histories, and that ASR variation is largely driven by sex differences in the apparent survival of juveniles. Furthermore, families in populations with biased ASRs were predominantly tended by a single parent, suggesting that parental cooperation breaks down with unbalanced sex ratios. Taken together, our results indicate that sex biases emerging during early life have profound consequences for social behaviour.

ecology↗

bioRxiv2017

Adult sex ratio bias in snowy plovers is driven by sex-specific early survival: implications for mating systems and population growth

Adult sex ratio (ASR) is a central concept in population biology and a key factor in sexual selection, yet why do most demographic models ignore sex-biases? Vital rates often vary between the sexes and across life history, but their relative contributions to ASR variation remain poorly understood--an essential step to evaluate sex ratio theories in the wild and inform conservation. Here we combine structured two-sex population models with individual-based mark-recapture data from an intensively monitored polygamous population of snowy plovers. We show that a strongly male-biased ASR is primarily driven by sex-specific survival of juveniles, rather than adults or dependent offspring. This provides empirical support for theories of unbiased sex allocation when sex-differences in survival arise after the period of parental investment. Importantly, a conventional model ignoring sex-biases significantly overestimated population viability. We suggest that sex-specific population models are essential to understand the population dynamics of sexual organisms: reproduction and population growth is most sensitive to perturbations in survival of the limiting sex. Overall, our study suggests that sex-biased early survival may contribute towards mating system evolution and population persistence, with implications for both sexual selection theory and biodiversity conservation.\n\nSIGNIFICANCE STATEMENTSex biases are widespread in nature and represent a fundamental component of sexual selection and population biology--but at which point in life history do these biases emerge? Here we report a detailed individual-based demographic analysis of an intensively studied wild bird population to evaluate the origins of sex biases and their consequences on mating strategies and population dynamics. We document a strongly male-biased adult sex ratio, which is consistent with behavioral observations of female-biased polygamy. Notably, sex-biased juvenile, rather than adult survival, contributed most to the adult sex ratio. Sex-biases also strongly influenced population viability, which was significantly overestimated when sex ratio and mating system were ignored. Our study therefore has implications for both sexual selection theory and biodiversity conservation.

ecology↗