Current and time-lagged effects of climate on innate immunity in two sympatric snake species.

Changing environments result in alterations at all levels of biological organization, from genetics to physiology to demography. The increasing frequency of droughts worldwide is associated with higher temperatures and reduced precipitation that can impact population persistence via effects on individual immune function and survival.We examined the effects of annual climate variation on immunity in two sympatric species of garter snakes from four populations in California over a seven-year period that included the record-breaking drought.

Embryonic heart rate correlates with maternal temperature and developmental stage in viviparous snakes.

Interactions between the environment and maternal and embryonic physiology can have critical ramifications for early-life phenotypes and survival in a range of species. A major component of the environment-maternal-embryonic nexus is the regulation of embryonic heart rate, which can have important ramifications for developmental phenology, but remains relatively unexplored in viviparous reptiles. The goal of this study was to test for a relationship between embryonic heart rate and maternal body temperature in two species of viviparous garter snakes.

The untapped potential of reptile biodiversity for understanding how and why animals age.

1. The field of comparative aging biology has greatly expanded in the past 20 years. Longitudinal studies of populations of reptiles with a range of maximum lifespans have accumulated and been analyzed for evidence of mortality senescence and reproductive decline.

The utility of reptile blood transcriptomes in molecular ecology.

Reptiles and other nonmammalian vertebrates have transcriptionally active nucleated red blood cells. If blood transcriptomes can provide quantitative data to address questions relevant to molecular ecology, this could circumvent the need to euthanize animals to assay tissues. This would allow longitudinal sampling of animals' responses to treatments, as well as sampling of protected taxa.

Convergence in reduced body size, head size, and blood glucose in three island reptiles.

Many oceanic islands harbor diverse species that differ markedly from their mainland relatives with respect to morphology, behavior, and physiology. A particularly common morphological change exhibited by a wide range of species on islands worldwide involves either a reduction in body size, termed island dwarfism, or an increase in body size, termed island gigantism. While numerous instances of dwarfism and gigantism have been well documented, documentation of other morphological changes on islands remains limited.

Use of field-portable ultrasonography reveals differences in developmental phenology and maternal egg provisioning in two sympatric viviparous snakes.

A thorough understanding of the life cycles underlying the demography of wild species is limited by the difficulty of observing hidden life-history traits, such as embryonic development. Major aspects of embryonic development, such as the rate and timing of development, and maternal-fetal interactions can be critical features of early-life fitness and may impact population trends via effects on individual survival. While information on development in wild snakes and lizards is particularly limited, the repeated evolution of viviparity and diversity of reproductive mode in this clade make it a valuable subject of study.

Integrating behaviour into the pace-of-life continuum: Divergent levels of activity and information gathering in fast- and slow-living snakes.

An animal's life history, physiology, and behaviour can be shaped by selection in a manner that favours strong associations among these aspects of an integrated phenotype. Recent work combining animal personality and life-history theory proposes that animals with faster life-history strategies (i.e.

Geographic variation and within-individual correlations of physiological stress markers in a widespread reptile, the common garter snake (Thamnophis sirtalis).

Characterizing the baseline and stress-induced hormonal, metabolite, and immune profiles of wild animals is important to assess the impacts of variable environments, including human-induced landscape changes, on organismal health. Additionally, the extent to which these profiles are coordinated across physiological systems within individuals remains an important question in understanding how stressors can differentially affect aspects of an individual's physiology. Here, we present data from wild populations of the common garter snake (Thamnophis sirtalis) on both baseline and stress-induced biomarkers: plasma corticosterone (CORT) concentration, plasma glucose concentration, and whole blood heterophil:lymphocyte ratio.

Physiological indices of stress in wild and captive garter snakes: correlations, repeatability, and ecological variation.

Glucocorticoids and leukocyte ratios have become the most widespread variables employed to test hypotheses regarding physiological stress in wild and captive vertebrates. Little is known, however, regarding how these two indices of stress covary in response to stressors, their repeatability within individuals, and differences in response time upon capture. Furthermore, few studies compare stress indices between captive and wild populations, to assess potential alteration of stress physiology in captivity.

Rates of molecular evolution vary in vertebrates for insulin-like growth factor-1 (IGF-1), a pleiotropic locus that regulates life history traits.

Insulin-like growth factor-1 (IGF-1) is a member of the vertebrate insulin/insulin-like growth factor/relaxin gene family necessary for growth, reproduction, and survival at both the cellular and organismal level. Its sequence, protein structure, and function have been characterized in mammals, birds, and fish; however, a notable gap in our current knowledge of the function of IGF-1 and its molecular evolution is information in ectothermic reptiles. To address this disparity, we sequenced the coding region of IGF-1 in 11 reptile species-one crocodilian, three turtles, three lizards, and four snakes.

Corticosterone and pace of life in two life-history ecotypes of the garter snake Thamnophis elegans.

Glucocorticoids are main candidates for mediating life-history trade-offs by regulating the balance between current reproduction and survival. It has been proposed that slow-living organisms should show higher stress-induced glucocorticoid levels that favor self-maintenance rather than current reproduction when compared to fast-living organisms. We tested this hypothesis in replicate populations of two ecotypes of the garter snake (Thamnophis elegans) that exhibit slow and fast pace of life strategies.

Social and demographic effects of anthropogenic mortality: a test of the compensatory mortality hypothesis in the red wolf.

Whether anthropogenic mortality is additive or compensatory to natural mortality in animal populations has long been a question of theoretical and practical importance. Theoretically, under density-dependent conditions populations compensate for anthropogenic mortality through decreases in natural mortality and/or increases in productivity, but recent studies of large carnivores suggest that anthropogenic mortality can be fully additive to natural mortality and thereby constrain annual survival and population growth rate. Nevertheless, mechanisms underlying either compensatory or additive effects continue to be poorly understood.

Developmental plasticity of immune defence in two life-history ecotypes of the garter snake, Thamnophis elegans - a common-environment experiment.

1. Ecoimmunological theory predicts a link between life-history and immune-defence strategies such that fast-living organisms should rely more on constitutive innate defences compared to slow-living organisms. An untested assumption of this hypothesis is that the variation in immune defence associated with variation in life history has a genetic basis.

Helper effects on pup lifetime fitness in the cooperatively breeding red wolf (Canis rufus).

The evolutionary maintenance of cooperative breeding systems is thought to be a function of relative costs and benefits to breeders, helpers and juveniles. Beneficial effects of helpers on early-life survivorship and performance have been established in several species, but lifetime fitness benefits and/or costs of being helped remain unclear, particularly for long-lived species. We tested for effects of helpers on early- and late-life traits in a population of reintroduced red wolves (Canis rufus), while controlling for ecological variables such as home-range size and population density.

A test of life-history theories of immune defence in two ecotypes of the garter snake, Thamnophis elegans.

1. Life-history theorists have long observed that fast growth and high reproduction tend to be associated with short life span, suggesting that greater investment in such traits may trade off with self-maintenance. The immune system plays an integral role in self-maintenance and has been proposed as a mediator of life-history trade-offs.

Evolutionary ecology of endocrine-mediated life-history variation in the garter snake Thamnophis elegans.

The endocrine system plays an integral role in the regulation of key life-history traits. Insulin-like growth factor-1 (IGF-1) is a hormone that promotes growth and reproduction, and it has been implicated in the reduction of lifespan. IGF-1 is also capable of responding plastically to environmental stimuli such as resource availability and temperature.

An empirical test of evolutionary theories for reproductive senescence and reproductive effort in the garter snake Thamnophis elegans.

Evolutionary theory predicts that differential reproductive effort and rate of reproductive senescence will evolve under different rates of external mortality. We examine the evolutionary divergence of age-specific reproduction in two life-history ecotypes of the western terrestrial garter snake, Thamnophis elegans. We test for the signature of reproductive senescence (decreasing fecundity with age) and increasing reproductive effort with age (increasing reproductive productivity per gram female) in replicate populations of two life-history ecotypes: snakes that grow fast, mature young and have shorter lifespans, and snakes that grow slow, mature late and have long lives.