Indrikis Krams

Indrikis Krams
University of Latvia | LU · Department of Zoology and Animal Ecology

PhD

About

242
Publications
124,277
Reads
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4,528
Citations
Citations since 2017
73 Research Items
2759 Citations
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20172018201920202021202220230100200300400500
20172018201920202021202220230100200300400500
Additional affiliations
January 2016 - June 2016
University of Tartu
Position
  • Senior Researcher
January 2016 - June 2016
University of Tartu
Position
  • Senior Researcher
August 2015 - April 2016
University of Tennessee
Position
  • Researcher

Publications

Publications (242)
Article
Full-text available
Nests are structures built to support and protect eggs and/or offspring from predators, parasites, and adverse weather conditions. Nests are mainly constructed prior to egg laying, meaning that parent birds must make decisions about nest site choice and nest building behavior before the start of egg-laying. Parent birds should be selected to choose...
Article
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Body height and other body attributes of humans may be associated with a diverse range of social outcomes such as attractiveness to potential mates. Despite evidence that each parameter plays a role in mate choice, we have little understanding of the relative role of each, and relationships between indices of physical appearance and general health....
Article
The resources available to an individual in any given environment are finite, and variation in life history traits reflect differential allocation of these resources to competing life functions. Nutritional quality of food is of particular importance in these life history decisions. In this study we tested trade-offs among growth, immunity and surv...
Article
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Cuticle melanism in insects is linked to a number of life history traits: a positive relationship is hypothesized between melanism, immune function, fecundity and lifespan. However, it is not clear how activation of the immune system affects trade-offs between life history traits in female mealworm beetles (Tenebrio molitor) differing in cuticle me...
Article
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Factors such as temperature, habitat, larval density, food availability and food quality substantially affect organismal development. In addition, risk of predation has a complex impact on the behavioural and morphological life history responses of prey. Responses to predation risk seem to be mediated by physiological stress, which is an adaptation...
Article
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Evolutionary approaches to human mating strategies have associated facial and physical attractiveness with cues of health, fertility, and personality traits both in men and women. In this study, we tested the hypothesis that these associations may be mediated by psychological flexibility (an indicator of mental health) and/or sociosexual orientatio...
Article
Hormones are key factors in determining the response of organisms to their environment. For example, the juvenile hormone (JH) coordinates the insects' development, reproduction, and survival. However, it is still unclear how the impact of juvenile hormone on insect immunity varies depending on the sex and reproductive state of the individual, as w...
Article
Invertebrates' immune priming or innate immune memory is an analogous response to the vertebrates' adaptive memory. We investigated if honey bees have immune memory. We compared survival and immune response between bees that were: 1) manipulated (Naïve), 2) challenged twice with the same pathogen Escherichia coli (Memory), 3) challenged twice with...
Article
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Schizophrenia has been an evolutionary paradox: it has high heritability, but it is associated with decreased reproductive success. The causal genetic variants underlying schizophrenia are thought to be under weak negative selection. To unravel this paradox, many evolutionary explanations have been suggested for schizophrenia. We critically discuss...
Article
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Objective Findings on the associations between sex hormones and immune function are scarce and mixed, especially in women. To contribute to the understanding on how sex hormones and immune function interact, we analyzed relationships between testosterone, estradiol, and immune responses in women.Methods Two doses of hepatitis B vaccine were adminis...
Article
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Blood parasites are considered to have strong negative effects on host fitness. Negative fitness consequences may be associated with proximity to areas where blood parasite vectors reproduce. This study tested for relationships between haemosporidian infection prevalence, parasitemia, and fitness parameters of breeding Pied Flycatchers (Ficedula hy...
Article
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Background Parasites are among the main factors that negatively impact the health and reproductive success of organisms. However, if parasites diminish a host’s health and attractiveness to such an extent that finding a mate becomes almost impossible, the parasite would decrease its odds of reproducing and passing to the next generation. There is e...
Article
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Free-living organisms face multiple stressors in their habitats, and habitat quality often affects development and life history traits. Increasing pressures of agricultural intensification have been shown to influence diversity and abundance of insect pollinators, and it may affect their elemental composition as well. We compared reproductive succe...
Article
Avian species often use anti‐predator calls such that the costs and benefits of vigilance are distributed within the group. Some species respond differentially to graded risk by attending to relevant predator cues, such as head orientation and gaze direction. One benefit of graded‐risk sensitivity is fewer missed foraging opportunities. It is not k...
Article
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Significance In many monogamous species, a substantial proportion of offspring is sired by other males than the one providing care at the nest. Although females often solicit extra-pair mating, the benefits of extra-pair copulations to females are not fully understood. In this study on pied flycatchers, we tested whether extra-pair paternity in nei...
Article
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Bumblebees are key pollinators in agricultural landscapes. However, little is known about how gut microbial communities respond to anthropogenic changes. We used commercially produced colonies of buff-tailed bumblebees (Bombus terrestris) placed in three habitats. Whole guts (midgut, hindgut, and rectum) of B. terrestris specimens were dissected fr...
Article
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Objective Phenotypic markers associated with developmental stability such as fluctuating asymmetry, facial attractiveness, and reports of minor ailments can also act as indicators of overall physical health. However, few studies have assessed whether these markers might also be cues of mental health. We tested whether self- and other-perceived faci...
Article
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Modelling fertility decline in post-industrial populations in the context of life history theory has allowed us to better understand the environmental pressures that shape reduced family size. One such pressure, which has received relatively little attention from ecologists, is the movement of women into the labour market. Analyses of effects of em...
Article
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Ecological stoichiometry is important for revealing how the composition of chemical elements of organisms is influenced by their physiological functions and ecology. In this study, we investigated the elemental body composition of queens, workers, and males of the bumblebee Bombus terrestris, an important pollinator throughout Eurasia, North Americ...
Article
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Background The abundance of insects has decreased considerably during recent decades, resulting in current abundance showing 70–80% reductions in more than 15 studies across temperate climate zones. Dramatic reductions in the abundance of insects are likely to have consequences for other taxa at higher trophic levels such as predators and parasites...
Article
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Habitat quality has direct effects on the evolutionary fitness of breeding organisms, which is why it is believed that animals tend to have an evolved preference for the best possible habitats. However, some animals may mistakenly choose to reproduce in habitats that decrease their fitness, resulting in ‘ecological traps’. In this study, we tested...
Article
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The presence of pathogens has imposed constant threats to human survival and reproduction. Selective pressures exerted by pathogens have shaped our array of immune functions—including physiological, psychological, and behavioral immune systems. Pathogens and epidemics have plagued humankind and our ancestors from their dawn, yet despite advances in...
Article
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When organisms’ environmental conditions vary unpredictably in time, it can be advantageous for individuals to hedge their phenotypic bets. It has been shown that a bet-hedging strategy possibly underlies the high inter-individual diversity of phototactic choice in Drosophila melanogaster . This study shows that fruit flies from a population living...
Article
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Objective The ability of parasites to hijack the nervous system, manipulating the host’s physiology and behavior in ways that enhance the parasite’s fitness while damaging host fitness, is a topic of ongoing research interest in evolutionary biology, but is largely overlooked in mental health research. Nevertheless, recent evidence has shown that T...
Article
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The genes of the Major Histocompatibility Complex (MHC), which plays a fundamental role in the immune system, are some of the most diverse genes in vertebrates and have been connected to mate choice in several species, including humans. While studies suggest a positive relationship between MHC diversity and male facial attractiveness, the connectio...
Article
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The development of costly traits such as immune function and secondary sexual traits is constrained by resource availability. The quality of developmental conditions and the availability of resources in ontogeny may therefore influence immune system functions and other biological traits. We analyzed causal pathways between family socioeconomic posi...
Article
The immune response of animals, including insects, is overcome by some parasites. For example, dauer larvae (DL) of the obligate entomopathogenic nematodes (EPNs) Heterorhabditis and Steinernema can invade insects, evade their defenses, and cause death. Although DL were long assumed to be the only infective stage of nematodes, recent reports sugges...
Article
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While COVID-19 infection and mortality rates are soaring in Western countries, Southeast Asian countries have successfully avoided the second wave of the SARS-CoV-2 pandemic despite high population density. We provide a biochemical hypothesis for the connection between low COVID-19 incidence, mortality rates, and high visceral adiposity in Southeas...
Article
Bipolar disorder is a mental health disorder characterized by extreme shifts in mood, high suicide rate, sleep problems, and dysfunction of psychological traits like self-esteem (feeling inferior when depressed and superior when manic). Bipolar disorder is rare among populations that have not adopted contemporary Western lifestyles, which supports...
Article
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Predation is an essential factor affecting prey populations, yet attacks are notoriously difficult to observe in real time. Here, we provide descriptive data about the attack behavior of Eurasian Sparrowhawks (Accipiter nisus) and the escape tactics of their prey in coniferous forests in Latvia during the non-breeding season. Over a period of 36 ye...
Article
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Juvenile hormone has been suggested to be a potential mediator in the trade-off between mating and insects' immunity. Studies on various insect taxons have found that juvenile hormone interferes with humoral and cellular immunity. Although this was shown experimentally, studies using highly virulent parasites or pathogens are lacking so far. In thi...
Preprint
Abstract- Male mating signals are sexual traits that may provide females with information about the physiological quality of the individual. Males of the yellow mealworm beetle, Tenebrio molitor, use pheromones to attract mating partners. The level of pheromone production in males has been identified as a signal of the male condition. We tested wh...
Article
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Research Highlights: Studies on tree canopy dwelling species often require simple proxies of tree canopy volume estimated at a stand level. These include allometrically related tree crown parameters such as crown area and basal area, and canopy cover. Background and Objectives: In monoculture Scot's pine and mixed pine/Norway spruce forest, we aime...
Article
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Although obesity is known to be a risk factor for COVID-19 severity, there is an urgent need to distinguish between different kinds of fat – visceral and subcutaneous fat – and their inflammation status in COVID-19. These different fat types have partially diverging biochemical roles in the human body, and they are differentially associated with SA...
Article
Male mating signals are sexual traits that may provide females with information about the physiological quality of the individual. Males of the yellow mealworm beetle, Tenebrio molitor, use pheromones to attract mating partners. The level of pheromone production in males has been identified as a signal of the male condition. We tested whether male...
Article
We studied the relationship between temperature and the coexistence of great tit Parus major and blue tit Cyanistes caeruleus, breeding in 75 study plots across Europe and North Africa. We expected an advance in laying date and a reduction in clutch size during warmer springs as a general response to climate warming and a delay in laying date and a...
Article
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The elemental composition of organisms belongs to a suite of functional traits that change during development in response to environmental conditions. However, associations between adaptive variations in developmental speed and elemental body composition are not well understood. We compared body mass, elemental body composition, food uptake and fat...
Article
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Immune function, height and resource accumulation comprise important life history traits in humans. Resource availability models arising from life history theory suggest that socioeconomic conditions influence immune function, growth and health status. In this study, we tested whether there are associations between family income during ontogeny, ad...
Article
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We investigated the intra- and trans-generational effects of larval diet on immune function, body size and development time of the greater wax moth, Galleria mellonella (Lepidoptera : Pyralidae). We found that moths reared on a diet diluted with cellulose (a low-nutrition diet) were about one-third smaller, had about one-fifth longer development ti...
Article
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Only dominant individuals have unrestricted access to contested resources in group-living animals. in birds, subordinates with restricted access to resources may respond to intragroup contests by acquiring extra body reserves to avoid periods of food shortage. In turn, higher body mass reduces agility and increases predation and mortality risk to s...
Article
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Mixed-species animal groups (MSGs) are widely acknowledged to increase predator avoidance and foraging efficiency, among other benefits, and thereby increase participants' fitness. Diversity in MSG composition ranges from two to 70 species of very similar or completely different phenotypes. Yet consistency in organization is also observable in that...
Article
We present data from 122 nations showing that Baumard’s argument on the ecological predictors of life history strategies and innovation is incomplete. Our analyses indicate that wealth, parasite stress, and cold climate impose orthogonal effects on life histories, innovation, and industrialization. Baumard also overlooks the historical exploitation...
Article
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Before a population becomes extinct, there are hidden costs in the physiology at the individual level that provide valuable insights into their condition. Here, we study two dams with one species in common (Argia anceps Garrison, 1996) to evaluate whether their physiological condition differed (total protein quantity, prophenoloxidase (proPO) and p...
Article
Full-text available
Immune response is evolutionary costly, but it is not clear whether these costs affect energetic expenditure (short-term cost), growth (medium-term cost), or reproduction (long-term cost). We tested the costs of immune memory in Tenebrio molitor against Metarhizium brunneum. To do this, we used two groups of T. molitor larvae: (a) the control group...
Article
We present data from 122 nations showing that Baumard's argument on the ecological predictors of life history strategies and innovation is incomplete. Our analyses indicate that wealth, parasite stress, and cold climate impose orthogonal effects on life histories, innovation, and industrialization. Baumard also overlooks the historical exploitation...
Article
Full-text available
Mitochondria have been increasingly recognized as a central regulatory nexus for multiple metabolic pathways, in addition to ATP production via oxidative phosphorylation (OXPHOS). Here we show that inducing mitochondrial DNA (mtDNA) stress in Drosophila using a mitochondrially-targeted Type I restriction endonuclease (mtEcoBI) results in unexpected...
Preprint
Full-text available
The elemental composition of organisms relates to a suite of functional traits that change during development in response to environmental conditions. It may be a part of a phenomenon known as ‘developmental programming’, which hypothetically creates phenotypes that are better adapted to their environments. However, associations between development...
Preprint
Full-text available
Eating disorders are evolutionarily novel conditions. They lead to some of the highest mortality rates of all psychiatric disorders. Several evolutionary hypotheses have been proposed for eating disorders, but only the intrasexual competition hypothesis is extensively supported by evidence. We present the mismatch hypothesis as a necessary extensio...
Article
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[Target Article.] Women’s capacity for sexual fluidity is at least as interesting a phenomenon from the point of view of evolutionary biology and behavioral endocrinology as exclusively homosexual orientation. Evolutionary hypotheses for female nonheterosexuality have failed to fully account for the existence of these different categories of nonhet...
Article
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Female sexual orientation and its various species-wide and species-specific manifestations comprise a topic to which one scientific article can hardly do justice. We have nevertheless attempted to analyze the topic more broadly than any one scientific article of which we are aware. To this end, we applied Tinbergen’s four questions and life history...
Article
(a) Objective. We explored relationships between male mortality and the sex ratio. (b) Methods. We tested relationships across 142 societies and in longitudinal data from Scotland. (c) Results. A male-biased sex ratio was associated with reduced mortality by intentional self-harm across 142 societies. This was replicated in longitudinal Scottish da...
Article
Full-text available
The elemental composition of organisms belongs to a suite of functional traits that may adaptively respond to fluctuating selection pressures. Life history theory predicts that predation risk and resource limitations impose selection pressures on organisms' developmental time and are further associated with variability in energetic and behavioral t...
Article
Full-text available
The strength of sexual selection on secondary sexual traits varies depending on prevailing economic and ecological conditions. In humans, cross-cultural evidence suggests women’s preferences for men’s testosterone dependent masculine facial traits are stronger under conditions where health is compromised, male mortality rates are higher and economi...
Preprint
Full-text available
[In press for Behavioral and Brain Sciences]. We present data from 122 nations showing that Baumard’s argument about the ecological predictors of life history strategies and innovation is incomplete. Our analyses indicate that wealth, parasite stress, and cold climate impose orthogonal effects on life histories, innovation, and industrialization....
Chapter
Rye was a basic and essential part of the daily diet in northern and eastern parts of Europe because of its great energy value and beneficial agricultural properties. Nowadays sufficient scientific evidence shows that rye, containing a mixture of biologically active substances, possesses a wide range of protective properties in the prevention and t...
Article
Objectives: Male height and health affect a diverse range of social and economic outcomes such as competition for resources and mates. Life history theory predicts that limited availability of bioenergetic resources curbs the development of central life history functions such as somatic growth, immunity, and investment in offspring. Although genet...
Article
Organisms in the wild are likely to face multiple immune challenges as well as additional ecological stressors, yet their interactive effects on immune function are poorly understood. Insects are found to respond to cues of increased infection risk by enhancing their immune capacity. However, such adaptive plasticity in immune function may be limit...
Article
Full-text available
Evidence suggests that brain serotonin (5-HT) is one of the central mediators of different types of animal personality. We tested this assumption in field crickets Gryllus integer using a selective serotonin reuptake inhibitor (SSRI). Crickets were selected for slow and rapid development and tested for their coping styles under non-stressful condit...
Article
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Many organisms adjust their reproductive phenology in response to climate change, but phenological sensitivity to temperature may vary between species. For example, resident and migratory birds have vastly different annual cycles, which can cause differential temperature sensitivity at the breeding grounds, and may affect competitive dynamics. Curr...
Article
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There is evidence of the relation of sex steroid hormones and sexual dimorphism in immune system response to infectious diseases. The aim of this review was to identify the role of sex hormones in immune function and sexual dimorphism of immune reactions. Gonadal hormones together with the immune system play an important role in process of immune r...