Summer Survival Research Articles

Ocean warming and novel species interactions boost growth and persistence of range‐extending tropical fishes but challenge that of sympatric temperate species in temperate waters

AbstractAimClimate change can have a broad range of impacts on the physiology and behaviour of animals. These effects can be mediated by the presence of other species in the community, but current forecasts of species responses to climate change largely ignore biological interactions. This is particularly true for novel interactions between range‐extending and native species, as this is often considered as noise and excluded from predictive models. Here we simulate how a tropical range‐extending and a local temperate fish species respond to the independent and combined effects of future ocean warming (RCPs 4.5 and 8.5) and novel ecological interactions in temperate ecosystems.LocationEast coast of Australia, along a ~ 2,000 km latitudinal gradient in a global climate warming hotspot.TaxonAbudefduf vaigiensis (tropical) and Atypicthys strigatus (temperate) fishes.MethodsWe use a dynamic energy budget model to simulate the length growth (i.e., increases in body length of individuals over time) and population persistence of juveniles of a tropical and a temperate fish species that form mixed‐species shoals, under different climate scenarios with and without the effects of novel ecological interactions.ResultsOur model forecasts that length growth of the juvenile tropical species will increase under ocean warming across subtropical to temperate regions. This increased length growth will be more drastic in temperate regions than in the subtropics, as winter warming will allow the tropical species to overwinter more frequently and show positive growth throughout the year. In contrast, warmer summer temperatures in the subtropics will likely exceed the optimal temperature of the juvenile temperate species at their trailing edge, resulting in reduced length growth under climate warming. Novel species interactions increased length growth of the juvenile tropical species but did not affect its winter or summer survival. In contrast, novel species interactions with tropical species were forecast to reduce length growth of the juvenile temperate species.Main ConclusionsOur study suggests that for some coastal fish species future warming will likely reverse body size dominance between temperate and tropical fish species, with increased novel interactions in temperate ecosystems (due to range extensions) but decreased novel interactions in the subtropics (due to range contractions). Novel species interactions and warming effects on body size and species survival are likely to reshuffle temperate fish communities and their competitive interactions.

Temporal and Spatial Influences on Fawn Summer Survival in Pronghorn Populations: Management Implications from Noninvasive Monitoring.

Monitoring vital rates allows managers to estimate trends in growth rates of ungulate populations. However, connecting the influence of nutrition on ungulate demography is challenging. Noninvasive sampling offers a low-cost, low-effort alternative for measuring nutritional indices, allowing for an increased understanding of the mechanistic relationships between environmental factors, nutrition, and specific population vital rates. We examined the temporal influence of intrinsic and extrinsic factors on pronghorn (Antilocapra americana) fawn recruitment. We collected fresh fecal samples from adult female pronghorn in five subpopulations spanning three sampling periods associated with critical maternal life-history stages (late gestation, early lactation, breeding season) for 2 years to investigate both intra- and interannual influences. Intrinsic factors were fecal glucocorticoid metabolites (FGMs), nutritional indices (fecal nitrogen (FN) and 2,6-diaminopimelic acid (DAPA)), and dietary composition (protein intake of forbs, graminoids, legumes, other, shrubs), while the extrinsic factor was vegetative greenness (normalized difference vegetation index (NDVI)). We found variations in DAPA, protein intake of forbs, variation in forb protein intake, and protein intake of legumes during late gestation positively influenced fawn recruitment. Fecal nitrogen during early lactation showed the strongest positive influence on the recruitment of any measured parameter. Finally, breeding season NDVI and the variation in DAPA values positively influenced the subsequent year's fawn recruitment. Our longitudinal study enabled us to investigate which parameter was most important to specific periods of fawn development and recruitment. We combined the results across five subpopulations, but interpretation and subsequent management decisions should be made at the subpopulation level such that pronghorn subpopulations with low recruitment can be positively influenced by increasing nitrogen on the landscape available to adult females during the early lactation period. As the use of noninvasive monitoring methods continues to expand, we believe our methodologies and results can be broadly applied to other ungulate monitoring programs.

Physiological and biochemical response analysis of Styrax tonkinensis seedlings to waterlogging stress

Climate change is increasing flooding in provinces of the south of the Yangtze River, posing challenges for promoting Styrax tonkinensis seedlings in these areas. To understand the physiological reasons for this species' intolerance to waterlogging, we observed biochemical parameters in one-year-old S. tonkinensis seedlings during two seasons. For 4 and 12 days in summer and winter experiments, respectively, we subjected seedlings to a pot-in-pot waterlogging treatment. Control groups were established at 0 h and 0 days. We examined indicators related to root vigor, reactive oxygen species (ROS), antioxidant enzymes, fermentative pathways, and more. The results displayed that decreased abscisic acid accumulation in roots inhibited water transport. Increased dehydrogenase and lactate dehydrogenase activity in roots promoted alcohol and lactate fermentation, causing toxic damage and reduced root vigor, impeding water absorption. In leaves, high ROS levels led to lipid peroxidation, exacerbating water loss from continuous transpiration. The high relative electric conductivity and low leaf relative water content indicated water loss, causing leaf wilting and shriveling. Conversely, winter seedlings, devoid of leaves, significantly reduced transpiration, and dormancy delayed root fermentation. With less ROS damage in roots, winter seedlings exhibited greater waterlogging tolerance. In summary, excessive water loss from leaves and inhibited vertical water transport contributed to low summer survival rates, while winter leafless dormancy and reduced ROS damage enhanced tolerance. Our findings provide insights for enhancing waterlogging resistance in S. tonkinensis amidst climate change challenges.

Climate change-induced shifts in survival and size of the worlds' northernmost oviparous snake: A 68-year study.

Because of their dependence on ambient temperature ectothermic animals can serve as sentinels of conservation problems related to global warming. Reptiles in temperate areas are especially well suited to study such effects, as their annual and daily activity patterns directly depend on ambient temperature. This study is based on annual data spanning 68 years from a fringe population of Grass Snakes (Natrix natrix), which is the world's northernmost oviparous (egg-laying) reptile, and known to be constrained by temperature for reproduction, morphology, and behavior. Mark-recapture analyses showed that survival probability was generally higher in males than in females, and that it increased with body length. Body condition (scaled mass index) and body length increased over time, indicative of a longer annual activity period. Monthly survival was generally higher during winter (i.e., hibernation) than over the summer season. Summer survival increased over time, whilst winter survival decreased, especially during recent decades. Winter survival was lower when annual maximum snow depth was less than 15 cm, implying a negative effect of milder winters with less insulating snow cover. Our study demonstrates long-term shifts in body length, body condition and seasonal survival associated with a warming climate. Although the seasonal changes in survival ran in opposite directions and though changes were small in absolute terms, the trends did not cancel out, but total annual survival decreased. We conclude that effects of a warming climate can be diverse and pose a threat for thermophilic species in temperate regions, and that future studies should consider survival change by season, preferably in a long-term approach.

Overwintering and summer survival of Ulva prolifera in sediments: Indoor simulation of temperature impacts

Green tides, a globally prevalent marine ecological anomaly observed in coastal regions, have received substantial attention. However, there is limited research on the burial of Ulva prolifera in sediments during the late stages of green tide outbreaks. This study investigates the effect of temperature on U. prolifera buried in sediment over 30 days. The measurements included the length, biomass, relative growth rate, chlorophyll composition and maximum quantum yield (Fv/Fm) of PS II at different stages. The results indicate that at −20 °C, numerous seedlings emerged after 14 days of recovery culture, suggesting the release of spores or gametes; survival was possible from −2 °C to 15 °C; but at 20 °C and 30 °C, all U. prolifera died. The U. prolifera buried in sediment during the late stage of green tide outbreaks may serve as one of the sources for the subsequent year's green tide eruption. This research provides insights into the origins of green tide outbreaks in the southern Yellow Sea.

Evaluating survival after heat challenges and investigating their correlations with field summer survival for the juvenile Pacific oyster (Crassostrea gigas)

Mass mortalities of juvenile Pacific oysters (Crassostrea gigas) in aquaculture operations have been associated with sustained high temperatures during the summer months. Selective breeding programs to improve field survival in the C. gigas are expensive, labor-intensive, and often rely on prolonged field trials. Therefore, controlled challenge methods for improving selection response towards increased summer mortality resistance are required. The purpose of this study was to verify whether juvenile survival after heat challenges predicts field summer survival for full-sib families of C. gigas. We thermally challenged juveniles from 59 families using two separate methods (chronic heat stress and acute heat shock) and monitored their survival rates. Oysters were also deployed in two major oyster farms and then survival rates were compared between the two conditions. In this study, families from different genetic backgrounds differed in heat tolerance and field survival. Correlations between heat challenges and field trials were low to moderate and positive (0.321–0.346 for acute heat shock and 0.472–0.491 for chronic heat stress). Our results suggest that although current heat challenge trials cannot completely replace field trails in selective breeding programs, selection for heat tolerance is expected to indirectly improve field survival. An important outcome of this study is that heat challenges can discriminate some families that are resistant or susceptible to summer mortality at an early age, and that selection efficiency can be improved by identifying and eliminating poor-performing families prior to planting. In a separate experiment, we found that juvenile oysters had significantly higher summer survival when they were exposed to heat challenges than oysters that were not exposed earlier. We conclude that heat challenge of oysters is a useful method for assessing the survival capacity of hatchery-produced spat used by the oyster industry.

Effects of large carnivores, hunter harvest, and weather on the mortality of moose calves in a partially migratory population

Survival of juvenile ungulates represents an important demographic parameter that influences population dynamics within ecosystems. In many ecological systems, the mortality of juvenile ungulates is influenced by various factors, including predation by large carnivores, human hunting activities and weather. While wolves Canis lupus are known to prey on moose Alces alces throughout all seasons, brown bears Ursus arctos primarily engage in predation during early summer, while human harvest primarily occurs in autumn and early winter. Hence, understanding the impacts of predation, harvest, and weather on the survival of juvenile moose is crucial for adaptive population management and the determination of sustainable harvest rates. To investigate the summer and autumn–winter survival of moose calves in relation to carnivore occurrence (wolf presence and bear density), summer habitat productivity, winter severity, human harvest, and migratory behaviour (migratory versus resident), we analysed data collected from 39 GPS‐collared female moose in south‐central Scandinavia. Our findings revealed significant interannual variation in summer survival rates, with areas with relatively higher bear densities exhibiting calf mortality rates twice as high as those in regions with low bear density. During the autumn–winter period, calf survival was lowest in the presence of wolves and deep snow, and it exhibited a negative correlation with the proportion of clearcuts and young forests within the mother's home range. Additionally, calf survival was negatively correlated with the risk of human hunting, and calves of stationary females displayed ten times higher survival rates compared to migratory individuals. Our study provides valuable insights into the survival of moose calves coexisting with two large carnivores and humans. Improving our understanding of the mechanisms causing calf survival to fluctuate has become increasingly important as many local moose populations in Scandinavia are declining and exposed to expanding predator populations, intense hunting pressure, and other threats associated with climate change.

Temperature variation generates interspecific synchrony but spatial asynchrony in survival for freshwater fish communities.

Identifying environmental drivers of demographic variation is key to predicting community-level impacts in response to global change. Climate conditions can synchronize population trends and can occur both spatially for populations of the same species, and across multiple species within the same local community. The aim of this study was to investigate patterns of temporal variation in survival for freshwater fish communities in two geographically close but isolated sites and to understand the amount of variation accounted for by abiotic covariates including metrics of water temperature and stream flow. Using mark-recapture data, we estimated bi-monthly apparent survival in a Bayesian Cormack-Jolly-Seber framework. The model included random effects to quantify temporal variance to understand species synchrony with the rest of the fish community and between sites. Study species included bluehead chub (Nocomis leptocephalus), creek chub (Semotilus atromaculatus), and striped jumprock (Moxostoma rupiscartes) in the southeastern USA. Results showed that survival varied over time and periods of low survival were associated with higher mean water temperature. However, temporal patterns of survival differed among species and between sites, where survival was synchronous among species within a site but asynchronous between sites for the same species despite their spatial proximity. Study streams differed in summer thermal regimes, which resulted in contrasting summer survival patterns, suggesting sensitivity of these fishes to warming. We found that interspecific synchrony was greater than spatial synchrony, where regional drivers such as temperature may interact with local habitat leading to differences in survival patterns at fine spatial scales. Finally, these findings show that changes in the timing and magnitude of environmental conditions can be critical in limiting vital rates and that some populations may be more resilient to climate variation than others.

Environmental influence on summer survival of Manila Clam Ruditapes philippinarum: A case study in an aquaculture bay

The aquaculture of Manila clam (Ruditapes philippinarum) is under threat due to its high mortality in summer. To investigate the environmental influence on mortality of the species, we have conducted field surveys in the aquaculture area in Laizhou Bay, during the summers of 2019 and 2020. Environmental and biological data were collected. The results of data analysis have shown that in 2020, large-scale mortality events were not recorded and spatial variations of environmental variables were no significant within the survey area. However, in August 2019, significant variations of environmental variables were detected in the middle tidal area. This area was charactered with relatively high-water temperature (with maximum temperature of 31.49 °C and mean value of 26.17 ± 1.62 °C), elevated hydrogen sulfide concentrations (with a maximum concentration of 24.72 μmol/L and a mean concentration of 7.89 ± 4.14 μmol/L), and low dissolved oxygen concentrations (with a minimum concentration of 3.35 mg/L and a mean concentration of 6.27 ± 0.42 mg/L). Correspondingly, high mortality of the clam was recorded in the area, the abundance of live Manila clams has decreased by 80%. No significant abnormalities of environmental variables and clam growth were observed in other regions in 2019. Glycogen content and condition index of the clam were analyzed to investigate the relationship between environmental stress and the health of the clam. Compared to the condition index, glycogen content is a more sensitive indicator of the health status of the clam because changes in glycogen content appeared earlier than changes in condition index and mortality. A principal component analysis further indicated that the high mortality of the clam corresponds with a few environmental variables, including elevated temperature, hypoxia and the concentration of hydrogen sulfide. The simultaneous presence of these multiple environmental stressors could have triggered alterations in the physiological responses of the clam.

Drivers of post‐fire resprouting success in restored Banksia woodlands

AbstractDisturbances can alter persistence trajectories of restored ecosystems. Resprouting is a common response of plants to disturbances such as fire or herbivory. Therefore, understanding a plant's resprouting response can inform successful restoration. We investigated patterns and drivers of resprouting following fire in fire‐prone Banksia woodlands restored after sand mining in the Mediterranean‐climate region of Western Australia. We applied experimental fire to samples of nine species with different resprouting types (rhizome, root crown, root sucker and lignotuber) across a 4‐ to 27‐year‐old restoration chronosequence. We investigated the influence of pre‐fire plant size, restoration age and soil conditions on resprouting success, defined by: (i) the probability of resprouting (measured ~5 months after fire), (ii) the probability of surviving the first summer and, (iii) vigour (both measured ~12 months post‐fire). We found that the probability of initial resprouting was high across most species, but summer survival was lower but comparable to that in other post‐mining restored ecosystems following fire. Generally, pre‐fire plant size did not influence probability of resprouting, while size and soil conditions were important for two species survival. Pre‐fire plant size was a significant predictor of vigour for all species with soil conditions influencing four species. Restoration age significantly influenced survival of three species. However, as our models explained low amounts of variation in probabilities of resprouting and survival (R2 = <0.11), other factors influencing resprouting success remain unidentified. Resprouting response to fire disturbance in restored Banksia woodlands are species and resprouter type specific, with plant size and soil conditions potentially more informative for understanding responses to disturbances than restoration age alone.

Comparative transcriptome and gene co-expression network analysis identifies key candidate genes associated with resistance to summer mortality in the Pacific oyster (Crassostrea gigas)

The global oyster industry is severely hampered by frequent outbreaks of summer massive mortalities. Selective breeding of disease-resistant broodstock is considered as a key strategy to address this problem, and marker-assisted selection programs would help develop oyster lines that are resistance to summer mortality. However, there is currently a need to identify candidate genes associated with disease resistance and to develop molecular markers based on these genes. To identify candidate genes associated with summer mortality resistance, we selected three most resistant and three most susceptible oyster families and compared their basal transcriptomes. A total of 59 families were tested in two sites, and there were significant differences in summer survival among families of different genetic backgrounds. Principal component analysis showed that there was significant clustering of different resistant families, suggesting that the molecular mechanisms underlying the development of resistance characteristics in different resistant families may be similar. Interestingly, transcriptome results showed that the highly expressed genes in resistant families were mainly associated with innate immunity, especially some pattern recognition receptors, including C-type lectins, fibrinogen-related proteins and scavenger receptors. Some transient receptor potential family genes showed differential expression in the both resistant and susceptible families, which may be related to the thermal tolerance of oysters. Notably, some genes related to antioxidant responses and detoxification were highly expressed in resistant families, such as glutathione S-transferase and Cytochrome P450, suggesting that oysters with summer mortality resistance may have greater antioxidant and detoxification capacities. In addition, weighted gene co-expression network analysis (WGCNA) identified three modules that were significantly positively associated with summer survival. The network map of key modules allows us to identify a series of hub genes, such as PEAR1, MCT12, RPL23, TRPM2, MFAP4, TLN1, SCARF1, GAL9 and ACOD. Overall, our study provides new insight into summer mortality resistance by employing comparative transcriptome and WGCNA, and the genes identified in this study should be further investigated for use in marker-assisted selection breeding programs.

Group selection cutting for regenerating Mediterranean Pinus pinaster plantations: Gap effects on seedling survival

Diversification of forests, both in terms of structure and species, has been identified as one of the main strategies for adapting forests to climate change. Among the different options available for managers to promote diversification, regeneration cuttings are a suitable option to meet these objectives in adult stands close to rotation ages. The regeneration of maritime pine (Pinus pinaster Ait.) stands is a major issue throughout its distribution area, with summer survival being the main bottleneck for seedling establishment and development. Group selection cutting system may be the best option to promote uneven-aged and mixed structures in shade intolerant species, such as maritime pine. Gaps generate different regeneration niches for species of contrasting shade tolerance while creating uneven-aged stands, which are potentially more resilient to the impacts of climate change.In our experiment, gaps of two different sizes (1.5 and 2.5 times the dominant height of the stand, both sizes being smaller than those proposed in literature) were opened up to test the effects on natural regeneration success in a planted 53-year-old maritime pine stand in Central Spain. There were nine gaps of each size, along with nine control plots, containing 1-m radius subplots distributed within them to record natural regeneration of maritime pine and other species, in addition to several ecological factors and seedling characteristics. A survival model was fitted to highlight the main factors driving seedling survival. Gaps were found to have a significant positive effect on seedling survival, as well as mid-shade positions within the gaps and the age of the seedlings. Summer was found to have a negative effect on seedling survival. No effect of inter-species competition (scrub or herbs), litter coverage or geomorphological characteristics (slope, aspect or altitude) was found. Our results indicate, therefore, that group selection system cuttings, even with small gap sizes (1.5 and 2.5 times the dominant height), would provide a suitable method for the regeneration of Mediterranean maritime pine plantations.

Population Fluctuations of the Deer Mouse (Peromyscus maniculatus) in Old-Field and Bunchgrass–Sagebrush Habitats: The Role of Agricultural Setting and Optimum Habitat

In semiarid regions, the deer mouse (Peromyscus maniculatus) is a major small mammal species occupying perennial grassland habitats that include old-fields, native bunchgrass–sagebrush, and some agricultural settings. We investigated population changes in deer mouse populations in perennial grasslands, both natural and old-field, from 1982 to 2003 in southern British Columbia, Canada. Hypotheses (H) predicted that P. maniculatus populations will have (H1) multiannual fluctuations in abundance driven by population increases from extended breeding in summer and winter; (H2) relaxed spring reorganization events in some years leading to higher overall recruitment and survival; and (H3) interspecific competition with montane voles that causes deer mice to be lower in density when voles are higher. P. maniculatus populations in old-field and grass–sagebrush sites had clearly defined periods of high “peak” mean numbers (32–52/ha) and other times of low mean numbers (20–22/ha). Based on mean annual peak density in autumn, deer mouse populations exhibited fluctuations of 3–4 years in both habitats, but this pattern was not always present. The greater numbers of P. maniculatus in high than low years was directly related to population increases from extended breeding seasons and an increased number of lactating females, thereby supporting H1. Spring breeding season declines occurred but were similar or less in high than low years of mean abundance and were relaxed in comparison to forest populations of deer mice in other studies. Thus, H2 was supported for recruitment with high numbers of young-of-the-year breeding and total number of juvenile recruits but for survival was equivocal. Total summer survival was consistently higher in high than low population years but juvenile productivity in all years was poor. Mean abundance of P. maniculatus and M. montanus in old-field sites were highly correlated, and hence H3 was not supported. This latter result is the first, to our knowledge, of P. maniculatus coexisting in a similar pattern of population fluctuations with a Microtus species in a mainland grassland habitat. Higher than average precipitation in the year preceding a peak population of deer mice may have enhanced herbaceous vegetation and contributed to population increases in both habitats. We conclude that the old-field habitat associated with this agricultural setting provides optimum habitat for P. maniculatus and facilitates multiannual population fluctuations in this species.

Phenotypic evaluation of two genetically improved strains selected from the reciprocal hybrids of Crassostrea gigas and C. angulata

The Pacific oyster (Crassostrea gigas) is one of the most economically important aquaculture shellfish in China, but further development of its industry is constrained by germplasm degradation and summer mass mortality episodes. To this end, a three-generation mass selection on the reciprocal hybrids, GA-C. gigas ♀ × C. angulata ♂ and AG-C. angulata ♀ × C. gigas ♂, was conducted to develop two strains (GA and AG selected strain) with fast-growing and warm-adapted characteristics. The aim of the present study was to determine whether the genetic improvement in growth, survival and thermal tolerance could be achieved by mass selection. For shell height, a genetic gain of 7.77–14.60%, a selection response of 0.67–0.91, and a realized heritability of 0.39–0.57 were observed in the selected strains after three generations of selection; for total weight, a genetic gain of 11.33–14.85%, a selection response of 0.73–1.06, and a realized heritability of 0.41–0.67 were observed in the selected strains after three generations of selection. The significant selection response of growth traits suggests the potential for genetic improvement of growth traits in both strains. With selection, the LT50 increased from 41.81 °C to 42.10 °C in the GA selected strain and from 41.61 °C to 42.06 °C in the AG selected strain. By the F3 generation, the summer survival rates of the GA and AG selected strain were 10.53% and 8.98% higher than that of the control strain, respectively, and 20.80% and 18.14% higher than that of the C. gigas strain, respectively. The consistent results of LT50 and summer survival suggest that thermotolerance selection may provide a viable strategy for improving summer survival in oysters. After three generations of selection, the total yield of the two strains increased by 29.63% and 19.78%, respectively, compared to C. gigas strain. This study provides a source of superior strains for the sound development of the oyster industry and can be used as a reference for shellfish breeding strategies.

Is flight initiation distance associated with longer-term survival in yellow-bellied marmots, Marmota flaviventer?

The distance at which animals move away from threats, flight initiation distance (FID), is often used to study antipredator behaviour and risk assessment. Variation in FID is explained by a variety of internal and external biotic and physical factors, including anthropogenic activities. Most prior studies focused on unidentified individuals, so our understanding of the fitness consequences of FID is relatively limited. We asked whether consistent individual differences in variation in flight initiation distance is associated with variation in summer survival and/or winter survival in an individually marked population of yellow-bellied marmots. We found no clear association between flight initiation distance and summer survival or winter survival. This suggests that FID decisions, while demonstrably optimizing current survival, may not have longer-term fitness consequences. Our results may be explained by the relatively modest repeatability of FID or it may have emerged from our attempt to explain longer-term measures of fitness. Future studies of the fitness consequences of personality traits should pay particular attention to the time interval between measuring the individuality of a trait and examining its fitness consequences.

Genetic diversity and structure in a selected strain of hybrid oysters between Crassostrea gigas and C. angulata evaluated from microsatellites and mitochondrial COI sequences

Summer mass mortality is a main problem affecting the production of Pacific oyster (Crassostrea gigas). Selective breeding represents a promising method to improve the summer survival rate and growth of the oyster. However, the pitfall is that selection may significantly decrease genetic diversity, leading to inbreeding depression. The current study presented an analysis of genetic diversity in one hybrid oyster (GA - C. gigas ♀ × C. angulata ♂), parental populations (C. gigas ♀ × C. gigas ♂ and C. angulata ♀ × C. angulata ♂) and three generations of mass-strain GA strain (GAF1, GAF2 and GAF3) as well as four wild populations of C. gigas (RC, QD, LY and ZS) using 18 microsatellite loci and mitochondrial COI sequences. Heterozygosity levels of GA (He = 0.69) demostrated an increased genetic diversity in hybrids compared to the parental populations. Heterozygosity (He: 0.64–0.67) and COI haplotypes (Hd: 0.195–0.279) revealed no significant (P > 0.05) loss of genetic diversity in selected strains over three generations. However, the average number of alleles (Na ranging from 8.06 to 7.61), polymorphic information content (I ranging from 1.53 to 1.43), heterozygosity (Ho ranging from 0.72 to 0.55) and effective population size (Ne-lin ranging from 144.1 to 51.2) exhibited a tendency to decrease with selection. Moderate genetic structuring (FST: 0.059–0.124; Nei's D: 0.140–0.326) was found among the selected strains and wild populations (QD, LY and ZS). These results indicate that breeders need to be cautious about artificial selection beyond the third generation and work to improve effective population sizes to maintain genetic gains. The results obtained in this study is that it provides important inference and guidance concerning future genetic improvement project.

Endurance Swimming Is Related to Summer Lake Survival of Rainbow Trout in a Warm Lake with Avian Piscivores

Fitness of fish is assumed to be influenced by locomotion performance, but empirical evidence linking swimming capacity to survival in nature remains sparse. Poor triploid (3N) fish aerobic swimming performance in conjunction with production of sibling diploid (2N) and 3N populations of genetically identical origin to minimize variability among compared populations make 3N trout an informative system to test hypotheses about fitness consequences of fish locomotion. Here, we ask if reduced survival of 3N relative to 2N trout in natural ecosystems during periods of high temperature relate to a lower aerobic swimming capacity and aerobic scope of 3N compared with 2N conspecifics. Three-yearly cohorts of conspecific 2N and 3N hatchery-reared, yearling rainbow trout were ranked for swimming endurance, externally marked for their endurance quantile, and then stocked into two lakes as yearlings to quantify their survival in the wild over summer as a function of ploidy, temperature and endurance; all while tracking temperature and depth habitat utilization via telemetry. As expected, 3N swimming endurance was lower than that of 2N, but with considerable individual overlap. Aerobic swimming endurance, especially for 3N, was predictive of summer survival in a warm lake where piscivorous birds potentially exerted high predation pressure, resulting in low fish survival. This empirical evidence of a connection between swimming endurance and fitness provides support for long held assumptions of this relationship and could inform future sport fishing stocking industry practices to match fish strains to ideal habitats.

Does coat colour influence survival? A test in a cyclic population of snowshoe hares.

Some mammal species inhabiting high-latitude biomes have evolved a seasonal moulting pattern that improves camouflage via white coats in winter and brown coats in summer. In many high-latitude and high-altitude areas, the duration and depth of snow cover has been substantially reduced in the last five decades. This reduction in depth and duration of snow cover may create a mismatch between coat colour and colour of the background environment, and potentially reduce the survival rate of species that depend on crypsis. We used long-term (1977-2020) field data and capture-mark-recapture models to test the hypothesis that whiteness of the coat influences winter apparent survival in a cyclic population of snowshoe hares (Lepus americanus) at Kluane, Yukon, Canada. Whiteness of the snowshoe hare coat in autumn declined during this study, and snowshoe hares with a greater proportion of whiteness in their coats in autumn survived better during winter. However, whiteness of the coat in spring did not affect subsequent summer survival. These results are consistent with the hypothesis that the timing of coat colour change in autumn can reduce overwinter survival. Because declines in cyclic snowshoe hare populations are strongly affected by low winter survival, the timing of coat colour change may adversely affect snowshoe hare population dynamics as climate change continues.

An infectious disease outbreak and increased mortality in wild alpine reindeer

AbstractClimate changes may lead to tipping points where the epidemiological characteristics of infectious wildlife diseases suddenly change, leading to outbreaks. However, empirically documented cases of the extent to which emerging infectious diseases (EIDs) affect populations of large vertebrates are few, partly because of the limited surveillance of remote wildlife populations. EIDs may potentially lead to higher mortality than mean mortality levels. Here, we quantified the likely impact of digital necrobacillosis on the survival and population dynamics of wild alpine reindeer (Rangifer tarandus) in Hardangervidda National Park (NP), Norway. The outbreak of digital necrobacillosis in 2019 contributed to a decrease in the summer survival rate of juveniles to 51% compared to an average of 88% in 2005–2018 and 77% in 2020. However, since the outbreak mainly reduced juvenile survival, the impact on short‐term population dynamics was moderate, lowering the population growth rate (λ) before harvest from an average value of 1.18 (2005–2018) to 1.08 (2019) before harvest. In 2019, anomalous climate conditions with a high daily mean temperature combined with the highest recorded daily precipitation in late summer were observed. Further studies are required to document the pathological development of digital necrobacillosis across demographic groups and proximate and ultimate causes of mortality.

Genetic parameters and response to selection for thermal tolerance, summer survival and growth in hybrid oyster (Crassostrea gigas ♀ × C. angulata ♂)

The Pacific oyster Crassostrea gigas is the most commonly farmed mollusks worldwide, while its production has been hindered by massive mortalities linked to high temperatures. Selective breeding focusing on thermal tolerance is an attractive option for reducing the impact of massive mortalities, but the genetic basis underlying this trait is currently unknown. Hybridization between C. gigas and C. angulata was conducted and followed by one generation of family selection for thermal tolerance. The genetic parameters for thermal resistance, summer survival and growth and selection response were investigated by using 50 full-sibling families. The mean survival of all families ranged from 30.2 to 69.5%, reflecting the large variation of thermal tolerance in the hybrid population. The estimates of heritability for thermal tolerance were low to moderate, ranging from 0.19 ± 0.03 to 0.27 ± 0.05, confirmed that there is genetic basis for thermal tolerance. The phenotypic (r = 0.537, P < 0.01) and genetic correlations (r = 0.546, P < 0.01) between thermal tolerance and summer survival were positive and significant, while the phenotypic and genetic correlations between growth and survival (including thermal tolerance and summer survival) were positive but low (P > 0.05). High response to selection (ΔG = 36.33%) was observed after one generation of selection for thermal tolerance, and there was also corresponding response (ΔG = 14.46%) for summer survival. These results demonstrated that genetic selection to improve summer survival of oyster may be facilitated by selecting highly heat-tolerant lines.