Scaling the risk landscape drives optimal life-history strategies and the evolution of grazing.
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ABSTRACT:
SUBMITTER: Bhat U
PROVIDER: S-EPMC6983398 | biostudies-literature | 2020 Jan
REPOSITORIES: biostudies-literature
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Project description:UNLABELLED:Marine bacteria in the Roseobacter and SAR11 lineages successfully exploit the ocean habitat, together accounting for ~40% of bacteria in surface waters, yet have divergent life histories that exemplify patch-adapted versus free-living ecological roles. Here, we use a phylogenetic birth-and-death model to understand how genome content supporting different life history strategies evolved in these related alphaproteobacterial taxa, showing that the streamlined genomes of free-living SAR11 were gradually downsized from a common ancestral genome only slightly larger than the extant members (~2,000 genes), while the larger and variably sized genomes of roseobacters evolved along dynamic pathways from a sizeable common ancestor (~8,000 genes). Genome changes in the SAR11 lineage occurred gradually over ~800 million years, whereas Roseobacter genomes underwent more substantial modifications, including major periods of expansion, over ~260 million years. The timing of the first Roseobacter genome expansion was coincident with the predicted radiation of modern marine eukaryotic phytoplankton of sufficient size to create nutrient-enriched microzones and is consistent with present-day ecological associations between these microbial groups. We suggest that diversification of red-lineage phytoplankton is an important driver of divergent life history strategies among the heterotrophic bacterioplankton taxa that dominate the present-day ocean. IMPORTANCE:One-half of global primary production occurs in the oceans, and more than half of this is processed by heterotrophic bacterioplankton through the marine microbial food web. The diversity of life history strategies that characterize different bacterioplankton taxa is an important subject, since the locations and mechanisms whereby bacteria interact with seawater organic matter has effects on microbial growth rates, metabolic pathways, and growth efficiencies, and these in turn affect rates of carbon mineralization to the atmosphere and sequestration into the deep sea. Understanding the evolutionary origins of the ecological strategies that underlie biochemical interactions of bacteria with the ocean system, and which scale up to affect globally important biogeochemical processes, will improve understanding of how microbial diversity is maintained and enable useful predictions about microbial response in the future ocean.
| S-EPMC3735120 | biostudies-literature
Project description:BackgroundConsiderable attention has focused on how selection on dispersal and other core life-history strategies (reproductive effort, survival ability, colonization capacity) may lead to so-called dispersal syndromes. Studies on genetic variation in these syndromes within species could importantly increase our understanding of their evolution, by revealing whether traits co-vary across genetic lineages in the manner predicted by theoretical models, and by stimulating further hypotheses for experimental testing. Yet such studies remain scarce. Here we studied the ciliated protist Tetrahymena thermophila, a particularly interesting organism due to cells being able to transform into morphs differing dramatically in swim-speed. We investigated dispersal, morphological responses, reproductive performance, and survival in ten different clonal strains. Then, we examined whether life history traits co-varied in the manner classically predicted for ruderal species, examined the investment of different strains into short- and putative long-distance dispersal, while considering also the likely impact of semi-sociality (cell aggregation, secretion of 'growth factors') on dispersal strategies.ResultsVery significant among-strain differences were found with regard to dispersal rate, morphological commitment and plasticity, and almost all core life-history traits (e.g. survival, growth performance and strategy), with most of these traits being significantly intercorrelated. Some strains showed high short-distance dispersal rates, high colonization capacity, bigger cell size, elevated growth performance, and good survival abilities. These well performing strains, however, produced fewer fast-swimming dispersal morphs when subjected to environmental degradation than did philopatric strains performing poorly under normal conditions.ConclusionStrong evidence was found for a genetic covariation between dispersal strategies and core life history traits in T. thermophila, with a fair fit of observed trait associations with classic colonizer models. However, the well performing strains with high colonization success and short-distance dispersal likely suffered under a long-distance dispersal disadvantage, due to producing fewer fast-swimming dispersal morphs than did philopatric strains. The smaller cell size at carrying capacity of the latter strains and their poor capacity to colonize as individual cells suggest that they may be adapted to greater levels of dependency on clone-mates (stronger sociality). In summary, differential exposure to selection on competitive and cooperative abilities, in conjunction with selective factors targeting specifically dispersal distance, likely contributed importantly to shaping T. thermophila dispersal and life history evolution.
| S-EPMC1997130 | biostudies-literature
Project description:Plant mortality and birth rates are critical components of plant life history affecting the stability of plant populations and the ecosystems they form. Although allometric theory predicts that both plant birth and mortality rates should be size-dependent, this prediction has not yet been tested across plants ranging the full size spectrum. Here we show that both population mortality and population birth rates scale as the -(1/4) power and plant lifespan as the (1/4) power of plant mass across plant species spanning from the tiniest phototrophs to the largest trees. Whereas the controls on plant lifespans are as yet poorly understood, our findings suggest that plant mortality rates have evolved to match population birth rates, thereby helping to maintain plant communities in equilibrium and optimizing plant life histories.
| S-EPMC1989662 | biostudies-literature
Project description:Human life history (LH) strategies are theoretically regulated by developmental exposure to environmental cues that ancestrally predicted LH-relevant world states (e.g., risk of morbidity-mortality). Recent modeling work has raised the question of whether the association of childhood family factors with adult LH variation arises via (i) direct sampling of external environmental cues during development and/or (ii) calibration of LH strategies to internal somatic condition (i.e., health), which itself reflects exposure to variably favorable environments. The present research tested between these possibilities through three online surveys involving a total of over 26,000 participants. Participants completed questionnaires assessing components of self-reported environmental harshness (i.e., socioeconomic status, family neglect, and neighborhood crime), health status, and various LH-related psychological and behavioral phenotypes (e.g., mating strategies, paranoia, and anxiety), modeled as a unidimensional latent variable. Structural equation models suggested that exposure to harsh ecologies had direct effects on latent LH strategy as well as indirect effects on latent LH strategy mediated via health status. These findings suggest that human LH strategies may be calibrated to both external and internal cues and that such calibrational effects manifest in a wide range of psychological and behavioral phenotypes.
| S-EPMC10638872 | biostudies-literature
Project description:The ubiquitous oceanic copepod Calanus finmarchicus is the major link between primary producers and important fish stocks in the North Atlantic Ocean and adjacent seas. Despite over a century of research on growth and development of this key species, the effect of predation risk on these processes remains elusive. We tested how food level and chemical cues from a fish predator influence growth and development of C. finmarchicus, using a predator naïve laboratory population. Copepods reached adult stage earlier both in response to high food and to predator cues in our experiment. High food also increased growth and lipid accumulation. In contrast, perceived predation risk triggered reduced size and lipid fullness, indicating a decoupling of growth and development rates. Our results demonstrate that chemical predator cues can influence life history strategies in C. finmarchicus, and suggest that present and future patterns in oceanic zooplankton size and population dynamics may also reflect differences in predation risk.
| S-EPMC7816270 | biostudies-literature
Project description:According to life-history theory, the development of immune function should be balanced through evolutionary optimization of the allocation of resources to reproduction and through mechanisms that promote survival. We investigated interspecific variability in cell-mediated immune response (CMI), as measured by the phytohaemagglutinin (PHA) assay, in relation to clutch size, longevity and other life-history traits in 50 species of birds. CMI exhibited significant repeatability within species, and PHA responses in chicks were consistently stronger than in adults. Univariate tests showed a variety of significant relationships between the CMI of both chicks and adults with respect to size, development period and lifespan, but not clutch size or prevalence of blood parasites in adults. Multivariate analyses confirmed these patterns but independent variables were too highly correlated to isolate unique influences on CMI. The positive relationship of chick CMI to nestling period is further complicated by a parallel relationship of chick CMI to the age at testing. However, multivariate analysis showed that chick CMI varies uniquely with length of the nestling period. Adult CMI was associated with a strong life-history axis of body size, development rate and longevity. Therefore, adult CMI may be associated with prevention and repair mechanisms related to long lifespan, but it also may be allometrically related to body size through other pathways. Neither chick CMI nor adult CMI was related to clutch size, contradicting previous results linking parasite-related mortality to CMI and the evolution of clutch size (reproductive investment) in birds.
| S-EPMC1690995 | biostudies-literature
Project description:Factors influencing the hominoid life histories are poorly understood, and little is known about how ecological conditions modulate the pace of their development. Yet our limited understanding of these interactions underpins life history interpretations in extinct hominins. Here we determined the synchronisation of dental mineralization/eruption with brain size in a 20th century museum collection of sympatric Gorilla gorilla and Pan troglodytes from Central Cameroon. Using ?13C and ?15N of individuals' hair, we assessed whether and how differences in diet and habitat use may have impacted on ape development. The results show that, overall, gorilla hair ?13C and ?15N values are more variable than those of chimpanzees, and that gorillas are consistently lower in ?13C and ?15N compared to chimpanzees. Within a restricted, isotopically-constrained area, gorilla brain development appears delayed relative to dental mineralization/eruption [or dental development is accelerated relative to brains]: only about 87.8% of adult brain size is attained by the time first permanent molars come into occlusion, whereas it is 92.3% in chimpanzees. Even when M1s are already in full functional occlusion, gorilla brains lag behind those of chimpanzee (91% versus 96.4%), relative to tooth development. Both bootstrap analyses and stable isotope results confirm that these results are unlikely due to sampling error. Rather, ?15N values imply that gorillas are not fully weaned (physiologically mature) until well after M1 are in full functional occlusion. In chimpanzees the transition from infant to adult feeding appears (a) more gradual and (b) earlier relative to somatic development. Taken together, the findings are consistent with life history theory that predicts delayed development when non-density dependent mortality is low, i.e. in closed habitats, and with the "risk aversion" hypothesis for frugivorous species as a means to avert starvation. Furthermore, the results highlight the complexity and plasticity of hominoid/hominin development.
| S-EPMC4108342 | biostudies-literature
Project description:Different parasitic life strategies are described including four new life cycles: complex rebrooding, micro-male, mesoparasite and prey-predator transfer. Four new life cycle behaviours are named: nursery hiding, mid-moult stage, positive precursor (intraspecific antagonism) and negative precursor (ambush strategy). Further strategies discussed are opossum attack, double parasitism (doubling of the normal reproductive set), duplex arrangement (separated male-female pairs), simple rebrooding, and describing how displaced parasites and superinfections may partly elucidate life cycles. Proportional stunting masks life history effects of parasitism; cuckoo copepods are true parasites and not just associates; burrowing barnacles (acrothoracicans) are not parasites. Further findings based on life cycle information: branchiurans and pentastomes are possibly not related; firefly seed shrimp are not parasites; copepod pre-adult life cycle stages are common in the western pacific but rare in Caribbean; harpacticoids on vertebrates are not parasites; cuckoo copepods are true parasites; explained the importance of pennellid intermediate hosts. Crustacean parasite life cycles are largely unknown (1% of species). Most crustacean life cycles represent minor modifications from the ancestral free-living mode. Crustacean parasites have less complex and less modified life cycles than other major parasite groups. This limits their exploitation of, and effectiveness, in parasitism. However, these life cycles will be an advantage in Global Change. Most metazoan parasites will be eliminated while crustaceans (and nematodes) will inherit the new world of parasites.
| S-EPMC7124122 | biostudies-literature
Project description:New genes contribute substantially to adaptive evolutionary innovation, but the functional evolution of new mammalian genes has been little explored at a broad scale. Previous work established mRNA-derived gene duplicates, known as retrocopies, as useful models for the study of new gene origination. Here we combine extensive mammalian transcriptomic and epigenomic data to unveil the processes underlying the evolution of stripped-down retrocopies into complex new genes. We show that although some robustly expressed retrocopies are transcribed from preexisting promoters, the majority evolved new promoters from scratch or recruited proto-promoters in their genomic vicinity. In particular, many retrocopy promoters emerged from ancestral enhancers or bivalent regulatory elements, as well as from CpG islands not associated to other genes. Altogether, these mechanisms facilitated the birth of up to 280 retrogenes in each therian species. Furthermore, the regulatory evolution of the originally monoexonic retrocopies was frequently accompanied by exon gain, which facilitated the cooption of distant promoters and in many cases allowed the expression of alternative isoforms. While young retrogenes are often initially expressed in the testis, increased regulatory and structural complexities allowed retrogenes to functionally diversify and evolve somatic organ functions, sometimes as complex as those of their parents. Thus, some retrogenes evolved the capacity to temporarily substitute their parents during the process of male (meiotic) X inactivation, while others even rendered parental functions completely superfluous, allowing for parental gene loss. Overall, our reconstruction of the complete â??life historyâ?? of mammalian retrogenes highlights the usefulness of retroposition as a general model for understanding new gene birth and functional evolution. Assembly and expression of vertebrate retrogene transcripts
2015-12-16 | E-GEOD-72236 | biostudies-arrayexpress
Project description:Skeletal histology supports the hypothesis that primate life histories are regulated by a neuroendocrine rhythm, the Havers-Halberg Oscillation (HHO). Interestingly, subfossil lemurs are outliers in HHO scaling relationships that have been discovered for haplorhine primates and other mammals. We present new data to determine whether these species represent the general lemur or strepsirrhine condition and to inform models about neuroendocrine-mediated life history evolution. We gathered the largest sample to date of HHO data from histological sections of primate teeth (including the subfossil lemurs) to assess the relationship of these chronobiological measures with life history-related variables including body mass, brain size, age at first female reproduction, and activity level. For anthropoids, these variables show strong correlations with HHO conforming to predictions, though body mass and endocranial volume are strongly correlated with HHO periodicity in this group. However, lemurs (possibly excepting Daubentonia) do not follow this pattern and show markedly less variability in HHO periodicity and lower correlation coefficients and slopes. Moreover, body mass is uncorrelated, and brain size and activity levels are more strongly correlated with HHO periodicity in these animals. We argue that lemurs evolved this pattern due to selection for risk-averse life histories driven by the unpredictability of the environment in Madagascar. These results reinforce the idea that HHO influences life history evolution differently in response to specific ecological selection regimes.
| S-EPMC4534448 | biostudies-literature