Extreme temperatures compromise male and female fertility in a large desert bird

Comparative Genomics Supports Ecologically Induced Selection as a Putative Driver of Banded Penguin Diversification

The relative importance of genetic drift and local adaptation in facilitating speciation remains unclear. This is particularly true for seabirds, which can disperse over large geographic distances, providing opportunities for intermittent gene flow among distant colonies that span the temperature and salinity gradients of the oceans. Here, we delve into the genomic basis of adaptation and speciation of banded penguins, Galápagos (Spheniscus mendiculus), Humboldt (Spheniscus humboldti), Magellanic (Spheniscus magellanicus), and African penguins (Spheniscus demersus), by analyzing 114 genomes from the main 16 breeding colonies. We aim to identify the molecular mechanism and genomic adaptive traits that have facilitated their diversifications. Through positive selection and gene family expansion analyses, we identified candidate genes that may be related to reproductive isolation processes mediated by ecological thermal niche divergence. We recover signals of positive selection on key loci associated with spermatogenesis, especially during the recent peripatric divergence of the Galápagos penguin from the Humboldt penguin. High temperatures in tropical habitats may have favored selection on loci associated with spermatogenesis to maintain sperm viability, leading to reproductive isolation among young species. Our results suggest that genome-wide selection on loci associated with molecular pathways that underpin thermoregulation, osmoregulation, hypoxia, and social behavior appears to have been crucial in local adaptation of banded penguins. Overall, these results contribute to our understanding of how the complexity of biotic, but especially abiotic, factors, along with the high dispersal capabilities of these marine species, may promote both neutral and adaptive lineage divergence even in the presence of gene flow.

Adaptation to fluctuating temperatures across life stages in endotherms

Accelerating rates of climate change have intensified research on thermal adaptation. Increasing temperature fluctuations, a prominent feature of climate change, means that the persistence of many species depends on both heat and cold tolerance across the entire life cycle. In endotherms, research has focused on specific life stages, with changes in thermoregulation across life rarely being examined. Consequently, there is a need to (i) analyse how heat and cold tolerance mechanisms coevolve, and (ii) test whether antagonistic effects between heat and cold tolerance across different life stages limit thermal adaptation. Information on genes influencing heat and cold tolerance and how they are expressed through life will enable more accurate modelling of species vulnerabilities to future climatic volatility.

Understanding the role of temperature in seasonal timing: Effects on behavioural, physiological and molecular phenotypes

Organisms adapt to daily and seasonal environmental changes to maximise their metabolic and reproductive fitness. For seasonally breeding animals, photoperiod is considered the most robust cue to drive these changes. It, however, does not explain the interannual variations in different seasonal phenotypes. Several studies have repeatedly shown the influence of ambient temperature on the timing of different seasonal physiologies including the timing of migration, reproduction and its associated behaviours, etc. In the present review, we have discussed the effects of changes in ambient temperature on different seasonal events in endotherms with a focus on migratory birds as they have evolved to draw benefits from distinct but largely predictable seasonal patterns of natural resources. We have further discussed the physiological and molecular mechanisms by which temperature affects seasonal timings. The primary brain area involved in detecting temperature changes is the hypothalamic preoptic area. This area receives thermal inputs via sensory neurons in the peripheral ganglia that measure changes in thermoregulatory tissues such as the skin and spinal cord. For the input signals, several thermal sensory TRP (transient receptor potential ion channels) channels have been identified across different classes of vertebrates. These channels are activated at specific thermal ranges. Once perceived, this information should activate an effector function. However, the link between temperature sensation and the effector pathways is not properly understood yet. Here, we have summarised the available information that may help us understand how temperature information is translated into seasonal timing.

Effects of meteorology and lunar cycle on the post-thawing quality of avian sperm

Introduction

Various climatological and lunar cycle parameters have a direct impact on animal reproduction, and in the case of the avian species, spermatozoa are extremely sensitive to heat stress. These parameters could influence sperm freezability, which will ultimately affect post-thawing semen quality, being sperm motility in roosters a relevant indicator of this quality as it is highly related to fertility. Therefore, the objective of the present study is to determine which are the climatological and lunar cycle parameters that have a greater effect on sperm freezability in roosters.

Methods

Sperm was obtained from 16 Utrerana breed roosters and a total of 27 replicates were performed. A pool was made with those ejaculates that met the minimum quality criteria for each replicate, and four freezing-thawing samples per replicate were analyzed. The straws were thawed, and sperm motility was evaluated, classifying the results obtained into four seminal quality groups according to the guidelines of the Food and Agriculture Organization of the United Nations (Group 1: Good, Group 2: Satisfactory, Group 3: Acceptable but undesirable and Group 4: Unsatisfactory). The following traits were recorded for each day of semen collection: maximum temperature, minimum temperature, maximum barometric pressure, minimum barometric pressure, maximum gust, wind direction, mean wind speed, sunshine hours, rainfall, moon phase, and percentage of illuminated lunar surface over the total area.

Results

A discriminant canonical analysis was performed to determine which of these parameters offered the most information when classifying an ejaculate in each quality group, with minimum temperature, the new moon as moon phase, minimum barometric pressure, and rainfall being the most significant variables.

Discussion

According to the results obtained, semen quality decreases when temperature and precipitation are lower, pressure is higher, and when there is a new moon phase. Therefore, these environmental conditions should be avoided for sperm collection and processing.

Positive selection footprints and haplotype distribution in the genome of dromedary camels

Dromedary camels are a domestic species characterized by various adaptive traits. Limited efforts have been employed toward identifying genetic regions and haplotypes under selection that might be related to such adaptations. These genetic elements are considered valuable sources that should be conserved to maintain the dromedaries' adaptability. Here, we have analyzed whole genome sequences of 40 dromedary camels from different Arabian Peninsula populations to assess their genetic relationship and define regions with signatures of selection. Genetic distinction based on geography was observed, classifying the populations into four groups: (1) North and Central, (2) West, (3) Southwest, and (4) Southeast, with substantial levels of genetic admixture. Using the de-correlated composite of multiple signal approach, which combines four intra-population analyses (Tajima's D index, nucleotide diversity, integrated haplotype score, and number of segregating sites by length), a total of 36 candidate regions harboring 87 genes were identified to be under positive selection. These regions overlapped with 185 haplotype blocks encompassing 1 340 haplotypes, of which 30 (∼2%) were found to be approaching fixation. The defined candidate genes are associated with different biological processes related to the dromedaries' adaptive physiologies, including neurological pathways, musculoskeletal development, fertility, fat distribution, immunity, visual development, and kidney physiology. The results of this study highlight opportunities for further investigations at the whole-genome level to enhance our understanding of the evolutionary pressures shaping the dromedary genome.

Diurnal temperature variation impacts energetics but not reproductive effort across seasons in a temperate dung beetle

Temperature varies on multiple timescales and ectotherms must adjust to these changes to survive. These adjustments may lead to energetic trade-offs between self-maintenance and reproductive investment. However, we know little about how diurnal and seasonal temperature changes impact energy allocation. Here we used a combination of empirical data and modeling of both thermoregulatory behaviors and body temperature to examine potential energetic trade-offs in the dung beetle Onthophagus taurus. Beginning in March 2020, universities and laboratories were officially closed due to the COVID-19 pandemic. We thus performed experiments at a private residence near Knoxville, Tennessee, USA, leveraging the heating, ventilation and air conditioning of the home to manipulate temperature and compare beetle responses to stable indoor temperatures versus variable outdoor temperatures. We collected O. taurus beetles in the early-, mid-, and late-breeding seasons to examine energetics and reproductive output in relation to diurnal and seasonal temperature fluctuations. We recorded the mass of field fresh beetles before and after a 24-h fast and used the resulting change in mass as a proxy for energetic costs of self-maintenance across seasons. To understand the impacts of diurnal fluctuations on energy allocation, we held beetles either indoors or outdoors for 14-day acclimation trials, fed them cow dung, and recorded mass change and reproductive output. Utilizing biophysical models, we integrated individual-level biophysical characteristics, microhabitat-specific performance, respirometry data, and thermoregulatory behaviors to predict temperature-induced changes to the allocation of energy toward survival and reproduction. During 24 h of outdoor fasting, we found that beetles experiencing reduced temperature variation lost more mass than those experiencing greater temperature variation, and this was not affected by season. By contrast, during the 14-day acclimation trials, we found that beetles experiencing reduced temperature variation (i.e., indoors) gained more mass than those experiencing greater temperature variation (i.e., outdoors). This effect may have been driven by shifts in the metabolism of the beetles during acclimation to increased temperature variation. Despite the negative relationship between temperature variation and energetic reserves, the only significant predictor of reproductive output was mean temperature. Taken together, we find that diurnal temperature fluctuations are important for driving energetics, but not reproductive output.

Intra-specific correlations between ejaculate traits and competitive fertilization success: a meta-analysis across species and fertilization modes

Understanding of how selection can act on traits that improve competitiveness and subsequent paternity has advanced, including the idea that internal and external fertilization presents different environments that may select differentially on ejaculate traits. However, no studies have quantitatively synthesized the intra-specific relationships between these traits and paternity. Therefore, we conducted a meta-analysis across 52 papers to determine which ejaculate traits positively correlate with paternity share and how these correlations vary with fertilization mode. Overall, most ejaculate traits were positively associated with paternity, with the notable exception of sperm length. Sub-analyses on sperm number, sperm length, and sperm velocity revealed no statistical differences between fertilization modes in the relationship between traits and paternity when all effect sizes across species were combined. However, in a sub-analysis on fish species only, we found evidence that sperm velocity may be more important in external fertilizers. We also observed differences in the importance of phylogenetic relatedness and some species-specific differences. Our results suggest that while most ejaculate traits should be under positive directional selection in both internal and external fertilizers, sperm length may be subject to more nuanced selection pressures. Overall, we highlight important patterns of intra-specific relationships between ejaculate traits and competitive fertilization success.

Season and temperature do not affect cumulative live birth rate and time to live birth in in vitro fertilization

Objective

To explore whether season and temperature on oocyte retrieval day affect the cumulative live birth rate and time to live birth.

Methods

This was a retrospective cohort study. A total of 14420 oocyte retrieval cycles from October 2015 to September 2019. According to the date of oocyte retrieval, the patients were divided into four groups (Spring(n=3634);Summer(n=4414); Autumn(n=3706); Winter(n=2666)). The primary outcome measures were cumulative live birth rate and time to live birth. The secondary outcome measures included the number of oocytes retrieved, number of 2PN, number of available embryos and number of high-quality embryos.

Results

The number of oocytes retrieved was similar among the groups. Other outcomes, including the number of 2PN (P=0.02), number of available embryos (p=0.04), and number of high-quality embryos (p<0.01) were different among the groups. The quality of embryos in summer was relatively poor. There were no differences between the four groups in terms of cumulative live birth rate (P=0.17) or time to live birth (P=0.08). After adjusting for confounding factors by binary logistic regression, temperature (P=0.80), season (P=0.47) and duration of sunshine(P=0.46) had no effect on cumulative live births. Only maternal age (P<0.01) and basal FSH (P<0.01) had an effect on cumulative live births. Cox regression analysis suggested no effect of season(P=0.18) and temperature(P=0.89) on time to live birth. Maternal age did have an effect on time to live birth (P<0.01).

Conclusion

Although season has an effect on the embryo, there was no evidence that season or temperature affect the cumulative live birth rate or time to live birth. It is not necessary to select a specific season when preparing for IVF.

Experimental evidence for stronger impacts of larval but not adult rearing temperature on female fertility and lifespan in a seed beetle

Temperature impacts behaviour, physiology and life-history of many life forms. In many ectotherms, phenotypic plasticity within reproductive traits could act as a buffer allowing adaptation to continued global warming within biological limits. But there could be costs involved, potentially affecting adult reproductive performance and population growth. Empirical data on the expression of reproductive plasticity when different life stages are exposed is still lacking. Plasticity in key components of fitness (e.g., reproduction) can impose life-history trade-offs. Ectotherms are sensitive to temperature variation and the resulting thermal stress is known to impact reproduction. So far, research on reproductive plasticity to temperature variation in this species has focused on males. Here, I explore how rearing temperature impacted female reproduction and lifespan in the bruchid beetle Callosobruchus maculatus by exposing them to four constant temperatures (17 °C, 25 °C, 27 °C and 33 °C) during larval or adult stages. In these experiments, larval rearing cohorts (exposed to 17 °C, 25 °C, 27 °C and 33 °C, from egg to adulthood) were tested in a common garden setting at 27 °C and adult rearing cohorts, after having developed entirely at 27 °C, were exposed to four constant rearing temperatures (17 °C, 25 °C, 27 °C and 33 °C). I found stage-specific plasticity in all the traits measured here: fecundity, egg morphological dimensions (length and width), lifespan and egg hatching success (female fertility). Under different larval rearing conditions, fecundity and fertility was drastically reduced (by 51% and 42%) at 17 °C compared to controls (27 °C). Female lifespan was longest at 17 °C across both larval and adult rearing: by 36% and 55% compared to controls. Collectively, these results indicate that larval rearing temperature had greater reproductive impacts. Integrating both larval and adult rearing effects, I present evidence that female fertility is more sensitive during larval development compared to adult rearing temperature in this system.

Citizen science reveals waterfowl responses to extreme winter weather

Global climate change is increasing the frequency and severity of extreme climatic events (ECEs) which may be especially detrimental during late-winter when many species are surviving on scarce resources. However, monitoring animal populations relative to ECEs is logistically challenging. Crowd-sourced datasets may provide opportunity to monitor species' responses to short-term chance phenomena such as ECEs. We used 14 years of eBird-a global citizen science initiative-to examine distribution changes for seven wintering waterfowl species across North America in response to recent extreme winter polar vortex disruptions. To validate inferences from eBird, we compared eBird distribution changes against locational data from 362 GPS-tagged Mallards (Anas platyrhynchos) in the Mississippi Flyway. Distributional shifts between eBird and GPS-tagged Mallards were similar following an ECE in February 2021. In general, the ECE affected continental waterfowl population distributions; however, responses were variable across species and flyways. Waterfowl distributions tended to stay near wintering latitudes or moved north at lesser distances compared with non-ECE years, suggesting preparedness for spring migration was a stronger "pull" than extreme weather was a "push" pressure. Surprisingly, larger-bodied waterfowl with grubbing foraging strategies (i.e., geese) delayed their northward range shift during ECE years, whereas smaller-bodied ducks were less affected. Lastly, wetland obligate species shifted southward during ECE years. Collectively, these results suggest specialized foraging strategies likely related to resource limitations, but not body size, necessitate movement from extreme late-winter weather in waterfowl. Our results demonstrate eBird's potential to monitor population-level effects of weather events, especially severe ECEs. eBird and other crowd-sourced datasets can be valuable to identify species which are adaptable or vulnerable to ECEs and thus, begin to inform conservation policy and management to combat negative effects of global climate change.

Evolutionary interactions between thermal ecology and sexual selection

Thermal ecology and mate competition are both pervasive features of ecological adaptation. A surge of recent work has uncovered the diversity of ways in which temperature affects mating interactions and sexual selection. However, the potential for thermal biology and reproductive ecology to evolve together as organisms adapt to their thermal environment has been underappreciated. Here, we develop a series of hypotheses regarding (1) not only how thermal ecology affects mating system dynamics, but also how mating dynamics can generate selection on thermal traits; and (2) how the thermal consequences of mate competition favour the reciprocal co-adaptation of thermal biology and sexual traits. We discuss our hypotheses in the context of both pre-copulatory and post-copulatory processes. We also call for future work integrating experimental and phylogenetic comparative approaches to understand evolutionary feedbacks between thermal ecology and sexual selection. Overall, studying reciprocal feedbacks between thermal ecology and sexual selection may be necessary to understand how organisms have adapted to the environments of the past and could persist in the environments of the future.

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, which lives in variable environments in tropical and subtropical Africa. Both heat and cold tolerance were under selection and heritable, indicating the potential for evolutionary responses to mean temperature change. However, we found evidence for a negative, genetic correlation between heat and cold tolerance that should limit the potential for adaptation to fluctuating temperatures. Genetic constraints between heat and cold tolerance appear a crucial, yet underappreciated, factor influencing responses to climate change.

Egg-laying increases body temperature to an annual maximum in a wild bird

Most birds, unlike reptiles, lay eggs successively to form a full clutch. During egg-laying, birds are highly secretive and prone to disturbance and predation. Using multisensor data loggers, we show that average daily body temperature during egg-laying is significantly increased (1 °C) in wild eider ducks (Somateria mollissima). Strikingly, this increase corresponds to the annual maximum body temperature (40.7 °C), representing a severe annual thermogenic challenge. This egg-laying-induced rise in body temperature may prove to be a common feature of wild birds and could be caused by habitat-related thermoregulatory adjustments and hormonal modulation of reproduction. We conclude our findings with new perspectives of the benefits of high body temperature associated with egg-laying of birds and the potential effect of heat stress that may occur with the future advent of heatwaves.

Birds of different morphs use slightly different strategies to achieve similar reproductive performance following heatwave exposure

Responses to extreme climatic events may differ between individuals of distinct morphs which differ in life-history strategies, resulting in climate change 'winners' and 'losers' within species. We examined the reproductive performance and carry-over effects on offspring of black- and red-headed Gouldian finches Erythrura gouldiae after exposure to simulated heatwaves of moderate or severe intensity. We expected black-headed pairs' reproductive performance to decline after the severe heatwave because only the condition of black-headed females deteriorates during such a heatwave. Supporting the fact that Gouldian finches of different morphs use alternative reproductive strategies, we found that black-headed females initiated egg-laying a month earlier than red-headed females after experiencing a severe heatwave. We also found that this severe heatwave resulted in shorter spermatozoa in males irrespective of their morph. Despite these effects associated with heatwave intensity, the overall reproductive performance of both morphs was not affected by this factor, which was possibly due to an increased nestling provisioning rate by parents after exposure to the severe heatwave. However, offspring still bore the cost of parental exposure to the severe heatwave, as they showed a reduced condition (lower plasma antioxidant capacity and transient lower breathing rate) and higher oxidative damage (at least in fledglings with black-headed parents). These results suggest that inter-morph phenotypic variability in the Gouldian finch does not result in clear differences in reproductive performance following heatwave exposure, despite basal phenotypic differences between morphs. Whether animals using alternative reproductive strategies are, in the end, differently affected by climate changes will likely depend on the capacity of their offspring to recover from altered developmental conditions.