Biology subjects

Cornwallis, C. K.

Publications and source records attributed to Cornwallis, C. K..

12 recordsLinked to original sources

bioRxiv2026

Development shapes molecular responses to thermal extremes in a desert bird

Thermal extremes are among the most immediate environmental challenges faced by animals. Coping with these conditions across life is complex because growth changes body size, heat exchange and thermoregulatory demands. Consequently, adaptive responses in young, small individuals may be maladaptive, or require adjustment, later in life. However, in endotherms we know very little about how thermoregulatory responses to hot and cold temperatures change during development, or about the molecular mechanisms regulating responses. We examined the molecular responses to acute heat (40{degrees}C), cold (12{degrees}C) and benign (23{degrees}C) conditions in 1- and 8-week-old ostrich chicks (Struthio camelus), a rapidly growing species exposed to strong daily and seasonal temperature variation. We found that in 1-week-old chicks, 44% of temperature-related genes were involved in both heat and cold responses, indicating that responses to opposing temperatures involve overlapping molecular pathways. However, the response of 76% of these genes changed during development. For example, some genes that increased with heat exposure when young decreased with heat exposure later in development, and vice versa. Such opposing selection pressures may maintain genetic variation in thermoregulatory pathways. Consistent with this prediction, comparisons between ostrich subspecies adapted to different thermal environments revealed patterns of genomic variation compatible with balancing selection in differentially expressed genes. Our results show that hot and cold temperatures trigger overlapping molecular responses that change during development, which shape genetic variation in the thermoregulatory system.

evolutionary biology↗

bioRxiv2024

Latent infection of an active giant endogenous virus in a unicellular green alga

Latency is a common strategy in a wide range of viral lineages, but its prevalence in giant viruses remains unknown. Here we describe the activity and viral production from a 617 kbp integrated giant viral element in the model green alga Chlamydomonas reinhardtii. We resolve the integrated viral region using long-read sequencing and show that viral particles are produced and released in otherwise healthy cultures. A diverse array of viral-encoded selfish genetic elements are expressed during GEVE reactivation and produce proteins that are packaged in virions. In addition, we show that field isolates of Chlamydomonas sp. harbor latent giant viruses related to the C. reinhardtii GEVE that exhibit similar infection dynamics, demonstrating that giant virus latency is prevalent in natural host communities. Our work reports the largest temperate virus documented to date and the first active GEVE identified in a unicellular eukaryote, substantially expanding the known limits of viral latency.

microbiology↗

bioRxiv2024

Reproductive and ecological adaptations to climate underpin the evolution of sociality in lizards

Identifying the environmental factors associated with group living is important for understanding how social systems originate, persist and diversify. In endothermic birds and mammals, living in social groups is associated with habitat constraints and harsh climatic conditions. We use phylogenetic comparative analyses to test whether climate and habitat have played similar roles in the evolution of social grouping in a globally distributed clade of ectothermic vertebrates, lizards (Nspecies = 1696). Social grouping was strongly associated with cool, dry climates across the lizard phylogeny. However, this climatic signature arose indirectly, by association with live birth (common in cool climates) and a reliance on rock crevices (common in dry climates), traits which increase parent-offspring associations and reduce offspring dispersal. In contrast, direct effects of cool temperature on the evolution of social grouping were marginal and restricted to live bearing species. Our results demonstrate that relationships between climate and sociality may result from climatic adaptations that go on to promote the emergence of grouping behaviour.

evolutionary biology↗

bioRxiv2022

A thermal radiator underlies plasticity to extreme temperatures in the world's largest bird

Organisms inhabiting extreme thermal environments, such as desert birds, have evolved spectacular adaptations to thermoregulate during hot and cold conditions. However, our knowledge of selection for thermoregulation and the potential for evolutionary responses is limited, particularly for large organisms experiencing extreme temperature fluctuations. Here we use thermal imaging to quantify selection and genetic variation in thermoregulation in ostriches (Struthio camelus), the worlds largest bird species that is experiencing increasingly volatile temperatures. We found that females that are better at regulating their head temperatures ( thermoregulatory capacity) had higher egg-laying rates under hotter conditions. Thermoregulatory capacity was both heritable and showed signatures of local adaptation: females originating from more unpredictable climates were better at regulating their head temperatures in response to temperature fluctuations. Together these results reveal that past and present evolutionary processes have shaped genetic variation in thermoregulatory capacity, which appears to protect critical organs, such as the brain, from extreme temperatures during reproduction. Impact SummaryLarge animals inhabiting extreme thermal environments, such as deserts, are predicted to be particularly vulnerable to the increasing temperature fluctuations expected in the future. However, previous work on the evolutionary potential of thermoregulation has primarily focused on the effect of hot temperatures on the survival of small ectotherms. We know little about how large endothermic vertebrates, such as birds, will respond to changing temperatures. Here we study the ostrich (Struthio camelus), the worlds largest bird, that inhabits some of the hottest and driest regions on Earth. We show that the ability of females to reproduce during hot conditions is associated with the regulation of their head temperatures ( thermoregulatory capacity). Furthermore, variation in thermoregulation is heritable and related to past climatic conditions: females originating from parts of Africa with more extreme temperature fluctuations were better able to thermoregulate, indicating local adaptation to different climatic conditions. Together, these results suggest that thermoregulation in this large desert bird has evolved in response to past climatic conditions, remains genetically variable and is currently under selection through its effect on reproduction.

evolutionary biology↗

bioRxiv2022

Experimental evidence that animal societies vary in size due to sex differences in cooperation

Cooperative breeding societies allow the costs of reproduction to be shared. However, as groups become larger, such benefits often decrease and competition increases. This is predicted to select for an optimal group size, yet variation in groups is a ubiquitous feature of cooperative breeding animals. Here we experimentally established groups (ngroups=96) of cooperative breeding ostriches, Struthio camelus, with different numbers of males and females and manipulated the potential for cooperation over incubation. There was a clear optimal group size for males. Their reproductive success was maximized in groups with four or more females and no other males, irrespective of cooperation over incubation. Conversely, female reproductive success was strongly dependent on the benefits of cooperating over incubation, being maximized in groups with either many males or many females. In intermediate sized groups, both male and female reproductive success was reduced by sexual conflict over the timing of mating and incubation. Our experiments show that sex differences in the opposing forces of cooperation and competition can explain why variation in cooperative groups is widespread.

evolutionary biology↗

bioRxiv2021

Evolutionary trade-offs between heat and cold tolerance limit responses to fluctuating climates

The evolutionary potential of species to cope with short-term temperature fluctuations during reproduction is critical to predicting responses to future climate change. Despite this, vertebrate research has focused on reproduction under high or low temperatures in relatively stable temperate climates. Here, we characterize the genetic basis of reproductive thermal tolerance to temperature fluctuations in the ostrich that lives in tropical and sub-tropical Africa. Both heat and cold tolerance are under selection and heritable, indicating that evolutionary responses to mean temperature change are possible. However, a negative, genetic correlation between heat and cold tolerance limits the potential for adaptation to fluctuating temperatures. Genetic constraints between heat and cold tolerance appears a crucial, yet underappreciated, factor influencing responses to climate change. One-sentence summaryReproductive success in fluctuating climates is constrained by a negative genetic correlation between heat and cold tolerance

evolutionary biology↗

bioRxiv2021

Behavioural adaptations in egg laying ancestors facilitate evolutionary transitions to live birth

Live birth is a key innovation that has evolved from egg laying ancestors over 100 times in reptiles. However, egg-laying lizards and snakes often possess preferred body temperatures that are lethal to developing embryos, which should select against egg retention. Here, we demonstrate that thermal mismatches between mothers and offspring are widespread across the squamate phylogeny. This mismatch is resolved by gravid females adjusting their body temperature towards the thermal optimum of embryos. Importantly, phylogenetic reconstructions suggest this thermoregulatory behaviour evolved in egg-laying species prior to the evolution of live birth. Maternal thermoregulatory behaviour therefore bypasses the constraints imposed by a slowly evolving thermal physiology and has likely been a key facilitator in the repeated transitions to live birth.

evolutionary biology↗

bioRxiv2021

Living with relatives offsets the harm caused by pathogens in natural populations

Living with relatives can be highly beneficial, enhancing reproduction and survival. However, high relatedness can increase susceptibility to pathogens, a phenomenon known as the monoculture effect. Here we examine if the benefits of living with relatives offsets the harm caused by pathogens, and if this depends if species typically live with kin. Using comparative meta-analysis across plants, animals and bacteria (nspecies= 56), we show that high within-group relatedness increases mortality when pathogens are present. Contrastingly, mortality decreased with relatedness when pathogens were rare, particularly in species that live with kin. Variation in pathogen abundances was lower across groups of relatives, but rates of mortality were more unpredictable. The effects of within-group relatedness were only evident when pathogens were manipulated, suggesting that the harm caused by pathogens is masked by the benefits of living with relatives. These results highlight the importance of kin selection for understanding disease spread in natural populations.

ecology↗

bioRxiv2019

Early-life gut dysbiosis linked to mass mortality in ostriches

Dysbiosis in the vertebrate gut microbiome has been associated with several diseases. However, it is unclear whether particular gut regions or specific time periods during ontogeny are responsible for the development of dysbiosis, especially in non-model organisms. Here we examine the microbiome associated with dysbiosis in different parts of the gastrointestinal tract (ileum, caecum, colon) in a long-lived bird with high juvenile mortality, the ostrich. Individuals that died of gut disease (n=68) had substantially different microbial composition from age-matched controls (n=50) throughout the gut. Several taxa were associated with mortality (Enterobacteriaceae, Peptostreptococcaceae, Porphyromonadaceae, Clostridium) and some with survival (Lachnospiraceae, Ruminococcaceae, Erysipelotrichaceae, Turicibacter). Repeated faecal sampling showed that pathobionts were already present shortly after hatching and proliferated in individuals with low diversity, resulting in mortality weeks later. The factors influencing seeding of the gut microbiota may therefore be key to understanding dysbiosis and host development.

microbiology↗

bioRxiv2018

The development of gut microbiota in ostriches and its association with growth

The development of gut microbiota during ontogeny in vertebrates is emerging as an important process influencing physiology, immune system, health, and adult fitness. However, we have little knowledge of how the gut microbiome is colonised and develops in non-model organisms, and to what extent microbial diversity and specific taxa influence changes in fitness-related traits. Here, we used 16S rRNA gene sequencing to describe the successional development of the faecal microbiota in juvenile ostriches (Struthio camelus; n = 71) over their first three months of life, during which time a five-fold difference in weight was observed. We found a gradual increase in microbial diversity with age, an overall convergence in community composition among individuals, multiple colonisation and extinction events, and major taxonomic shifts coinciding with the cessation of yolk absorption. In addition, we discovered significant but complex associations between juvenile growth and microbial diversity, and identified distinct bacterial groups that had positive (Bacteroidaceae) and negative (Enterobacteriaceae, Enterococcaceae, Lactobacillaceae) correlations with the growth of individuals at specific ages. These results have broad implications for our understanding of the development of gut microbiota and its association with juvenile growth.

microbiology↗

bioRxiv2017

Direct PCR offers a fast and reliable alternative to conventional DNA isolation methods for animal gut microbiomes

The gut microbiome of animals is emerging as an important factor influencing ecological and evolutionary processes. A major bottleneck in obtaining microbiome data from large numbers of samples is the time-consuming laboratory procedures, specifically the isolation of DNA and generation of amplicon libraries. Recently, direct PCR kits have been developed that circumvent conventional DNA extraction steps, thereby streamlining the laboratory process by reducing preparation time and costs. However, the reliability and efficacy of the direct PCR method for measuring host microbiomes has not yet been investigated other than in humans with 454-sequencing. Here, we conduct a comprehensive evaluation of the microbial communities obtained with direct PCR and the widely used MoBio PowerSoil DNA extraction kit in five distinct gut sample types (ileum - caecum - colon - faeces - cloaca) from 20 juvenile ostriches, using 16S rRNA Illumina MiSeq sequencing. We found that direct PCR was highly comparable over a range of measures to the DNA extraction method in caecal, colon, and faecal samples. However, the two methods recovered significantly different microbiomes in cloacal, and especially ileal samples. We also sequenced 100 replicate sample pairs to evaluate repeatability during both extraction and PCR stages, and found that both methods were highly consistent for caecal, colon, and faecal samples (rs > 0.7), but had low repeatability for cloacal (rs = 0.39) and ileal (rs = -0.24) samples. This study indicates that direct PCR provides a fast, cheap, and reliable alternative to conventional DNA extraction methods for retrieving 16S data, which will aid future gut microbiome studies of animals.

microbiology↗

bioRxiv2017

Measuring the gut microbiome in birds: comparison of faecal and cloacal sampling

The gut microbiomes of birds and other animals are increasingly being studied in ecological and evolutionary contexts. While methods for preserving samples and processing high-throughput sequence data to characterise bacterial communities have received considerable attention, there has been little evaluation of non-invasive sampling methods. Numerous studies on birds and reptiles have made inferences about gut microbiota using cloacal sampling, however, it is not known whether the bacterial community of the cloaca provides an accurate representation of the avian gut microbiome. We examined the accuracy with which cloacal swabs and faecal samples measure the microbiota in three different parts of the gastrointestinal tract (ileum, caecum, and colon) using a case study on juvenile ostriches, Struthio camelus, and high-throughput 16S rRNA sequencing. We found that faeces were significantly better than cloacal swabs in representing the bacterial community of the colon. Cloacal samples had a higher abundance of Gammaproteobacteria and fewer Clostridia relative to the gut and faecal samples. However, both faecal and cloacal samples were poor representatives of the microbial communities in the caecum and ileum. Furthermore, the accuracy of the sampling methods in measuring the abundance of different bacterial taxa was highly variable: Bacteroidetes was the most highly correlated phylum between all three gut sections and both methods, whereas colonic Actinobacteria correlated strongly only with faecal samples. This study demonstrates that sampling methods can have significant effects on the inferred gut microbiome in studies of birds. Based on our results, we recommend sampling faeces, whenever possible, as this provides the most accurate assessment of the colon microbiome. The fact that neither sampling technique portrayed the bacterial community of the ileum or the caecum illustrates the difficulty in non-invasively monitoring gut bacteria located further up in the gastrointestinal tract. These results have important implications for the interpretation of avian gut microbiome studies.

ecology↗