Survival Trade-off Research Articles

Life-history evolution in response to foraging risk, modelled for Northeast Arctic cod (Gadus morhua)

Foraging behaviour is known to be a key element in ecology and evolution. Increased foraging intensity increases energy intake, which is useful for growth and reproduction but comes at the cost of higher mortality risk due to increased exposure to predators. Here, we investigate these trade-offs through an individual-based, mechanistic modelling framework adapted to the Northeast Arctic Cod. The model incorporates a series of life-history traits, survival trade-offs, and heritability, which allow evolution to occur and optimal strategies to emerge due to individual trait combinations and their fitness consequences. By altering the relationship between foraging intensity and mortality risk, we find that increased risk causes evolution towards lower foraging effort leading to lower growth and in turn, earlier maturation and a faster pace of life. These results build on previous studies by demonstrating behavioural evolution without direct anthropogenic stressors. Natural mortality among fish is poorly understood, and these results highlight an interesting point of further research that could help future modelling approaches make more accurate assumptions about natural mortality and its components.

Anthropogenic impacts on threatened species erode functional diversity in chelonians and crocodilians

The Anthropocene is tightly associated with a drastic loss of species worldwide and the disappearance of their key ecosystem functions. The orders Testudines (turtles and tortoises) and Crocodilia (crocodiles, alligators, and gharials) contain numerous threatened, long-lived species for which the functional diversity and potential erosion by anthropogenic impacts remains unknown. Here, we examine 259 (69%) of the existing 375 species of Testudines and Crocodilia, quantifying their life history strategies (i.e., trade-offs in survival, development, and reproduction) from open-access data on demography, ancestry, and threats. We find that the loss of functional diversity in simulated extinction scenarios of threatened species is greater than expected by chance. Moreover, the effects of unsustainable local consumption, diseases, and pollution are associated with life history strategies. In contrast, climate change, habitat disturbance, and global trade affect species independent of their life history strategy. Importantly, the loss of functional diversity for threatened species by habitat degradation is twice that for all other threats. Our findings highlight the importance of conservation programmes focused on preserving the functional diversity of life history strategies jointly with the phylogenetic representativity of these highly threatened groups.

Trade-off for survival: Microbiome response to chemical exposure combines activation of intrinsic resistances and adapted metabolic activity.

The environmental microbiota is increasingly exposed to chemical pollution. While the emergence of multi-resistant pathogens is recognized as a global challenge, our understanding of antimicrobial resistance (AMR) development from native microbiomes and the risks associated with chemical exposure is limited. By implementing a lichen asa bioindicatororganism and model for a native microbiome, we systematically examined responses towards antimicrobials (colistin, tetracycline, glyphosate, and alkylpyrazine). Despite an unexpectedly high resilience, we identified potential evolutionary consequences of chemical exposure in terms of composition and functioning of native bacterial communities. Major shifts in bacterial composition were observed due to replacement of naturally abundant taxa; e.g. Chthoniobacterales by Pseudomonadales. A general response, which comprised activation of intrinsic resistance and parallel reduction of metabolic activity at RNA and protein levels was deciphered by a multi-omics approach. Targeted analyses of key taxa based on metagenome-assembled genomes reflected these responses but also revealed diversified strategies of their players. Chemical-specific responses were also observed, e.g., glyphosate enriched bacterial r-strategists and activated distinct ARGs. Our work demonstrates that the high resilience of the native microbiota toward antimicrobial exposure is not only explained by the presence of antibiotic resistance genes but also adapted metabolic activity as a trade-off for survival. Moreover, our results highlight the importance of native microbiomes as important but so far neglected AMR reservoirs. We expect that this phenomenon is representative for a wide range of environmental microbiota exposed to chemicals that potentially contribute to the emergence of antibiotic-resistant bacteria from natural environments.

Impact of Azo Dyes and Ibuprofen on the Proteome of Serratia nematodiphila sp. MB307.

Micropollutants comprise organic/mineral substances that cause an undesirable impact on the environment, by affecting life at all scales. In this study, we explored the changes they impart on the global proteome of a soil bacterium Serratia nematodiphila MB307, for two classes of pollutants, i.e., Azo dyes (Methyl orange, Congo red) and a pharmaceutical (Ibuprofen). The 100 μg pollutant supplemented alteration of pure S. nematodiphila MB307 culture after 24 hours of incubation at 37 °C and its control was analyzed using a differential proteomics approach. MaxQuant software with the Perseus package was used for data analysis purposes. Prominently, ribosomal proteins and chaperones were up or downregulated in the whole cell and membranous fraction. This illustrates dynamic protein production adaptation of bacteria, to cope with stress and cell growth/division trade-off for survival. A collective pattern of survival under stress or pollution resistance could not be decrypted for all classes of pollutants, portraying dissimilar mechanisms of coping with differently structured pollutant moieties.

Genome Resource of Colletotrichum spaethianum, the Causal Agent of Leaf Anthracnose in Polygonatum falcatum

Genome Resource of <i>Colletotrichum spaethianum</i>, the Causal Agent of Leaf Anthracnose in <i>Polygonatum falcatum</i>

Inconsistent evolution and growth-survival tradeoffs in Gambusia affinis.

Growth-survival tradeoffs may be a generalizable mechanism influencing trajectories of prey evolution. Here, we investigate evolutionary contributions to growth and survival in western mosquitofish (Gambusia affinis) from 10 populations from high- and low-predation ancestral environments. We assess (i) the degree to which evolutionary components of growth and survival are consistent or inconsistent across populations within ancestral predation environments, and (ii) whether growth and survival trade off at the population level. We measure growth and survival on groups of common-reared mosquitofish in pond mesocosms. We find that evolution of growth is consistent, with fish from low-predation ancestral environments showing higher growth, while the evolution of survival is inconsistent, with significant population-level divergence unrelated to ancestral predation environment. Such inconsistency prevents a growth-survival tradeoff across populations. Thus, the generalizability of contemporary evolution probably depends on local context of evolutionary tradeoffs, and a continued focus on singular selective agents (e.g. predators) without such local context will impede insights into generalizable evolutionary patterns.

Habitat specific tradeoffs in growth and survival by hogfish Lachnolaimus maximus in southeast Florida

The hogfish Lachnolaimus maximus, an economically important, reef-associated protogynous teleost, has gained additional interest from fisheries managers due to evidence of overfishing in the southeastern United States. This study collected data on age and growth of hogfish in southeast Florida (SEFL), an understudied part of the species' range. Hogfish (n = 227) were collected from three reef tracts at different depths between January 2016 and August 2017. The average maximum potential length (L∞) was 414 mm overall and showed evidence of Lee's Phenomenon occurring relative to the eastern Gulf of Mexico, an area of presumed lower fishing pressure, where L∞ was 920 mm. Hogfish growth was also found to vary significantly by reef location in SEFL. Otolith-based aging revealed that SEFL hogfish growth past age 3 significantly decreased as reef depth increased between the three reef tracts [length at age 9 (L9) = 564, 405, 351 mm FL]. By L9, hogfish from the shallowest reef tract (4–6 m) were on average 61% longer and four times the weight of individuals collected from the deepest reef tract (15–25 m). Annual survival also increased with depth (42%, 65%, 73%), with a linear relationship to growth at L9 where R2 = 1.0, indicating there are inherent tradeoffs between growth and longevity in hogfish of southeast Florida.

The Sovereign's Dilemma: State Capacity and Ruler Survival in Imperial China

China's state development was shaped by elite network structures that characterized state–society relations, rather than representative institutions or bellicist competition. For the 2,000 years of its existence, its rulers faced the sovereign's dilemma: a coherent elite that could take collective action to strengthen the state could also overthrow the ruler. When elites were in geographically broad and densely interconnected networks, they preferred a strong state capable of protecting their far-flung interests, and their cohesiveness constituted a threat to the ruler's survival. Yet when elites relied on local bases of power and were not tightly connected, they instead sought to hollow out the central state from within; their internal divisions enabled the ruler to play competing factions against each other to secure his personal survival. This capacity–survival tradeoff explains China's historical state development and highlights the importance of elite social relations in understanding alternative paths of state development outside Europe.

Tree mode of death and mortality risk factors across Amazon forests

The carbon sink capacity of tropical forests is substantially affected by tree mortality. However, the main drivers of tropical tree death remain largely unknown. Here we present a pan-Amazonian assessment of how and why trees die, analysing over 120,000 trees representing > 3800 species from 189 long-term RAINFOR forest plots. While tree mortality rates vary greatly Amazon-wide, on average trees are as likely to die standing as they are broken or uprooted—modes of death with different ecological consequences. Species-level growth rate is the single most important predictor of tree death in Amazonia, with faster-growing species being at higher risk. Within species, however, the slowest-growing trees are at greatest risk while the effect of tree size varies across the basin. In the driest Amazonian region species-level bioclimatic distributional patterns also predict the risk of death, suggesting that these forests are experiencing climatic conditions beyond their adaptative limits. These results provide not only a holistic pan-Amazonian picture of tree death but large-scale evidence for the overarching importance of the growth–survival trade-off in driving tropical tree mortality.

Right phenotype, wrong place: predator-induced plasticity is costly in a mismatched environment.

Like many animals, tadpoles often produce different, predator-specific phenotypes when exposed to risk of predation. It is generally assumed that such plasticity enhances survival in the presence of the predator and is costly elsewhere, but evidence remains surprisingly scarce. We measured (1) the survival trade-off of opposing phenotypes developed by Dendropsophus ebraccatus tadpoles when exposed to different predators and (2) which specific aspects of morphology drive any potential survival benefit or cost. Tadpoles developed predator-specific phenotypes after being reared with caged fish or dragonfly predators for two weeks. In 24 h predation trials with either a fish or a dragonfly, survival was highest in the groups with their matched predator, and lowest among with those the mismatched predator, with predator-naive controls being relatively intermediate. Then, using a large group of phenotypically variable predator-naive tadpoles, we found that increased survival rates are directly related to the morphological changes that are induced by each predator. This demonstrates that induced phenotypes are indeed adaptive and the product of natural selection. Furthermore, our data provide clear evidence of an environmental cost for phenotypic plasticity in a heterogeneous environment. Such costs are fundamental for understanding the evolution and maintenance of inducible phenotypes.

Generalism in Nature…The Great Misnomer: Aphids and Wasp Parasitoids as Examples.

In the present article we discuss why, in our view, the term ‘generalism’ to define the dietary breadth of a species is a misnomer and should be revised by entomologists/ecologists with the more exact title relating to the animal in question’s level of phagy—mono-, oligo, or polyphagy. We discard generalism as a concept because of the indisputable fact that all living organisms fill a unique ecological niche, and that entry and exit from such niches are the acknowledged routes and mechanisms driving ecological divergence and ultimately speciation. The term specialist is probably still useful and we support its continuing usage simply because all species and lower levels of evolutionary diverge are indeed specialists to a large degree. Using aphids and parasitoid wasps as examples, we provide evidence from the literature that even some apparently highly polyphagous agricultural aphid pest species and their wasp parasitoids are probably not as polyphagous as formerly assumed. We suggest that the shifting of plant hosts by herbivorous insects like aphids, whilst having positive benefits in reducing competition, and reducing antagonists by moving the target organism into ‘enemy free space’, produces trade-offs in survival, involving relaxed selection in the case of the manicured agro-ecosystem.

Weak biofilm formation among carbapenem-resistant Klebsiella pneumoniae

Biofilm formation of multidrug and extensively drug resistant Klebsiella pneumoniae isolates is poorly understood. We investigated 139 diverse clinical K. pneumoniae isolates that possess various resistance patterns to evaluate the relationship between biofilm formation and resistance. Antimicrobial resistance was compared among a diverse collection of weak versus strong biofilm-forming K. pneumoniae, and predictors of strong biofilm formation were identified. Multi-drug resistant isolates were more common among weak (97.9%) versus strong biofilm formers (76%; P = 0.002). Carbapenem-resistant K. pneumoniae were 91% less likely to form strong biofilm (odds ratio 0.09; 95% confidence interval 0.02–0.33). The statistically significant inverse relationship between biofilm formation and antibiotic resistance suggests that virulence may be a trade-off for survival.

The sex- and duration-dependent effects of intermittent fasting on lifespan and reproduction of spider mite Tetranychus urticae

BackgroundIntermittent fasting (IF) is receiving increasing attention as an alternative to continuous restriction of calories because of its benefits in aging-related disease prevention and lifespan extension. However, whether both sexes with sexual dimorphism have similar response to IF have rarely been assayed. In this study, we determined how different durations of IF influence lifespan and whether males and females differed in their responses to IF. We also tested whether there is a trade-off between lifespan and lifetime reproduction in females under IF.MethodWe used spider mite Tetranychus urticae, with female-biased sexual size dimorphism (SSD), as our model species to investigate the survival and lifespan difference of both sexes at different durations of IF regimes, and explore the association between longevity and fecundity in females within and across treatments.ResultsThe lifespan of females increased before intermediate level of IF and then decreased afterwards, but males showed a decreasing trend in lifespan when subjected to IF. Within each treatment, female longevity was positively associated with their fecundity. However, the females fed ad libitum had a higher lifetime fecundity with a shorter lifespan, whereas mites fed 50% IF outlived ad libitum fed ones with lower fecundity because of the later onset of reproduction and lower daily fecundity, showing clear survival and reproduction trade-off when variation of resource availability enhanced across treatments.ConclusionWe showed sex-specific response to IF in lifespan, indicating that sexes with SSD have different optimal level of IF. These findings showed trade-off between survival and reproduction between treatments but not within treatments, suggesting that variation in resource availability is the necessary precondition for life history trade-off, and IF extends lifespan of females at the cost of reproductive success.

Directional selection on body size but no apparent survival cost to being large in wild New Zealand giraffe weevils.

When an individual's reproductive success relies on winning fights to secure mating opportunities, bearing larger weapons is advantageous. However, sexual selection can be extremely complex, and over an animal's life the opportunity to mate is influenced by numerous factors. We studied a wild population of giraffe weevils (Lasiorhynchus barbicornis) that exhibit enormous intra and intersexual size variation. Males bear an elongated rostrum used as a weapon in fights for mating opportunities. However, small males also employ sneaking behavior as an alternative reproductive tactic. We investigated sexual selection on size by tracking individual males and females daily over two 30-day periods to measure long-term mating success. We also assessed how survival and recapture probabilities vary with sex and size to determine whether there might be a survival cost associated with size. We found evidence for directional selection on size through higher mating success, but no apparent survival trade-off. Instead, larger individuals mate more often and have a higher survival probability, suggesting an accumulation of benefits to bigger individuals. Furthermore, we found evidence of size assortative mating where males appear to selectively mate with bigger females. Larger and more competitive males secure matings with larger females more frequently than smaller males, which may further increase their fitness.

Evolution of viviparity in mammals: what genomic imprinting tells us about mammalian placental evolution.

Genomic imprinting is an epigenetic mechanism of regulating parent-of-origin-specific monoallelic expression of imprinted genes in viviparous therian mammals such as eutherians and marsupials. In this review we discuss several issues concerning the relationship between mammalian viviparity and genomic imprinting, as well as the domestication of essential placental genes: why has the genomic imprinting mechanism been so widely conserved despite the evident developmental disadvantages originating from monoallelic expression? How have genomic imprinted regions been established in the course of mammalian evolution? What drove the evolution of mammalian viviparity and how have genomic imprinting and domesticated genes contributed to this process? In considering the regulatory mechanism of imprinted genes, reciprocal expression of paternally and maternally expressed genes (PEGs and MEGs respectively) and the presence of several essential imprinted genes for placental formation and maintenance, it is likely that complementary, thereby monoallelic, expression of PEGs and MEGs is an evolutionary trade-off for survival. The innovation in novel imprinted regions was associated with the emergence of imprinting control regions, suggesting that genomic imprinting arose as a genome defence mechanism against the insertion of exogenous DNA. Mammalian viviparity emerged in the period when the atmospheric oxygen concentration was the lowest (~12%) during the last 550 million years (the Phanerozoic eon), implying this low oxygen concentration was a key factor in promoting mammalian viviparity as a response to a major evolutionary pressure. Because genomic imprinting and gene domestication from retrotransposons or retroviruses are effective measures of changing genomic function in therian mammals, they are likely to play critical roles in the emergence of viviparity for longer gestation periods.

Condition-dependent skipped spawning in anadromous brown trout (Salmo trutta)

Repeat spawners of anadromous salmonids may contribute significantly to population resilience by providing multiple cohorts to both seawater and freshwater life stages. In this study, winter survival of sea trout (Salmo trutta Linnaeus, 1758) post spawners (kelts) was 89%. Sea survival increased linearly with female length with a return probability between 30% and 50%, whereas males attained a maximum return probability of 60% at 520 mm. Of the returning sea trout, 40% skipped spawning and they had significantly lower condition factor as kelts compared with those who returned after one summer. These results suggest that sex-specific differences in individual post-spawning growth–survival trade-off exist and that energetic status of descending kelts may influence the probability to skip spawning. We discuss to what extent hydropower may reduce post-spawning survival due to blocking of river descent opportunities, potentially altering the fitness landscape and favouring new life-history adaptations. From a management perspective, it is concluded that it is crucial to maintain connectivity in regulated rivers, allowing fish to complete repetitive spawning and feeding migrations, thus contributing to population productivity.

Experimental evaluation of the robustness of the growth–stress tolerance trade‐off within the perennial grass Dactylis glomerata

Abstract A core tenet of functional ecology is that the vast phenotypic diversity observed in the plant kingdom could be partly generated by a trade‐off between the ability of plants to grow quickly and acquire resources in rich environments vs. the ability to conserve resources and avoid mortality under stress. However, experimental demonstrations remain scarce and potentially blurred by phylogenetic constraints in cross‐species analyses. Here, we experimentally decoupled growth potential and stress survival by applying an off‐season stress on contrasting populations of the perennial grass Dactylis glomerata exhibiting a range of seasonal dormancy. Seventeen populations of D. glomerata, originating from a latitudinal gradient from Norway to Morocco, were subjected to three types of dehydration stress: winter frost in Norway, and summer drought and early spring (off‐season) drought stress in the south of France. Growth rate and two leaf traits (leaf width and leaf dry matter content) suspected to be involved in the adaptation to dehydration stress were monitored under optimal conditions. We quantified plant dehydration survival as the amount of plant recovery after a severe stress. Nordic populations were found to be winter‐dormant. Winter‐ and summer‐dormant populations better survived frost and summer drought, respectively. However, no trade‐off between growth potential and dehydration survival was detected in non‐dormant plants in early spring when dehydration occurred unseasonably for all populations. Furthermore, Mediterranean populations better survived an early spring drought. Our results highlight the importance of assessing plant growth potential as a response to seasonal environmental cues. They suggest that growth potential and stress survival trade off when plants exhibit seasonal dormancy but can be functionally independent at other seasons. Consequently, the growth–stress survival relationship could be better described as a dynamic linkage rather than a constant and general trade‐off. Moreover, leaf trait values, such as thinner and more lignified leaves reflecting drought adaptation, may have contributed to the improved drought‐stress survival without resulting in a cost to growth. Further exploration of the growth–stress survival relationship should permit deciphering the suite of plant traits and trait covariations involved in plants’ responses to increasing stress. A plain language summary is available for this article.

Between invaders and a risky place: Exotic grasses alter demographic tradeoffs of native forb germination timing

AbstractPriority effects are hypothesized to play an important role in community assembly and may promote suppression of native by exotic species. Work in a range of grassland systems has proved valuable for testing these effects, demonstrating that earlier germination by some exotic annual grasses contributes to their competitive dominance over natives. Yet few studies have measured native forb germination phenology under field conditions, and the demographic consequences of emergence timing for competitive interactions and native fitness are not well understood. We focused on three native annual species in a southern California grassland dominated by exotic Bromus spp. over three years, measuring (1) seedling emergence rates, for both early (October) and later (November and December) germinators; (2) effects of exotic grasses on native survival and reproduction, through a grass removal experiment; and (3) interactions between emergence timing and grass competitive effects on native mortality, survival, and flowering. We quantified tradeoffs of emergence timing, by estimating mortality experienced by early germinants until the late cohort emerged (early survival), and then for both cohorts from the time of late emergence to flowering (spring survival). The two most common focal natives, Amsinckia intermedia and Phacelia distans, varied substantially in germination phenology but primarily emerged early. The less abundant Clarkia purpurea germinated late. Late emergence reduced spring survival in control plots but not those where exotic grasses were reduced experimentally, supporting the importance of priority effects and benefits of early germination in competition with grasses. However, early emergence entailed a high cost of initial mortality risk in some years. We found no effect of emergence timing on size at flowering. Estimates of net survivorship to flowering suggest that late emergence consistently was associated with the highest survival when exotic grasses were reduced experimentally. Early emergence was more favored in control than in exotic grass reduction plots, but the survival tradeoffs differed substantially between years. These results suggest that priority effects contribute to suppression of native forbs, but may not consistently promote higher fitness for earlier germinators. Instead, exotic invasion may increase yearly variation in the fitness consequences of native germination phenology, with potential implications for bet hedging strategies.

Shared decision-making in ovarian cancer.

5549 Background: The value of shared decision-making in ovarian cancer is relatively unexplored. The goal of this study was to test a new decision aid, Patient Centered Outcome Aid (PCOA), that facilitates shared decision-making and helps ovarian cancer patients assimilate information and identify quality of life (QOL), toxicity and survival trade-offs between IP/IV therapy and IV therapy alone, based on their preferences and personal clinical characteristics. Methods: Participants were randomized to either PCOA (N=64) or usual care (N=59). Patient characteristics, QOL and shared decision-making data were collected at baseline and treatment initiation. Primary outcomes included satisfaction with treatment decision and decisional regret. Comparisons were made using t-tests and multivariate methods, adjusting for patient covariates. Multivariate linear models were used to investigate predictors of the primary outcomes. Results: Although satisfaction and decisional regret did not differ significantly by arm at any time point, the majority of PCOA patients indicated that the aid helped them understand treatment options and side effects. Notably, low shared decision-making and low QOL, were significant predictors of low satisfaction at treatment initiation (multiple r=0.76), six months (multiple r=0.48) and nine months (r=0.58). They were also significant predictors of decisional regret (multiple r=0.48 and 0.36 at 6 and 9 months). Patient covariates including age, stage, treatment and neoadjuvant status were not associated with differences in satisfaction or decisional regret. Conclusions: There were no clinically meaningful differences in satisfaction with the treatment decision, or decisional regret between the study arms. The absence of a difference may reflect the high degree of shared decision-making in both arms and greater disease severity in PCOA patients, who were more likely to report low baseline QOL and declining QOL over time. Both shared decision-making and quality of life were robust, independent predictors of satisfaction with the treatment decision over time. This implies that women who perceive themselves as less engaged in the decision process, and report poor QOL may benefit from a decision aid, in addition to physician counseling. Clinical trial information: NCT02259699.

The role of transcriptomes linked with responses to light environment on seedling mortality in a subtropical forest, China

Summary Differences in seedling survival in trees have a lasting imprint on seedling, juvenile and adult community structure. Identifying the drivers of these differences, therefore, is a critical research objective that ultimately requires knowledge regarding how organismal function interacts with the local environment to influence survival rates. In tree communities, differences in light use strategies are frequently invoked to explain differences in seedling demographic performance through growth and survival trade‐offs. For example, shade‐tolerant species grow slowly and have higher survival rates, whereas shade‐intolerant species grow quickly but have lower survival rates. Thus, functional traits related to photosynthesis should be strong predictors of demographic rates, but results in the literature are mixed indicating that additional or alternative information regarding organismal function should be considered. Here, we provide a community‐wide inventory of transcriptomes in a subtropical tree community. This information is utilized to determine the degree to which species share homologous genes related to gene ontologies for light use and harvesting. These species similarities are used in neighbourhood generalized linear mixed‐effects models of seedling survival that evaluated seedling survival as a function of the transcriptomic, functional trait and phylogenetic composition of the local neighbourhood. The results show neighbourhood similarity in three of the 15 gene ontologies evaluated are significantly related to survival rates based on neighbourhood composition. For two of these ontologies, survival rates increase when neighbours are similar in their gene tree composition indicating the importance of abiotic filtering and performance hierarchies. Synthesis. The present work takes a novel approach by sequencing the transcriptomes of naturally co‐occurring tree species in a subtropical forest in China. The results show that the transcriptomic similarity of species is a significant predictor of differential survival. The study demonstrates that exploring the functional genomic similarity of non‐model species in nature has the potential to increase the breadth and depth of our understanding of how gene function influences species co‐occurrence and population dynamics in communities.