Demographic history and genomic signatures of selection in a widespread vertebrate ectotherm.

Environmental conditions vary greatly across large geographic ranges, and yet certain species inhabit entire continents. In such species, genomic sequencing can inform our understanding of colonization history and the impact of selection on the genome as populations experience diverse local environments. As ectothermic vertebrates are among the most vulnerable to environmental change, it is critical to understand the contributions of local adaptation to population survival.

Age Predicts Risky Investment Better Than Residual Reproductive Value.

AbstractLife-history theory predicts that investment in reproduction should increase as future reproductive potential (i.e., residual reproductive value [RRV]) decreases.

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.

Becoming creatures of habit: Among- and within-individual variation in nesting behaviour shift with age.

The quantification of repeatability has enabled behavioural and evolutionary ecologists to assess the heritable potential of traits. For behavioural traits that vary across life, age-related variation should be accounted for to prevent biasing the microevolutionary estimate of interest. Moreover, to gain a mechanistic understanding of ontogenetic variation in behaviour, among- and within-individual variance should be quantified across life.

Joint estimation of growth and survival from mark-recapture data to improve estimates of senescence in wild populations.

Understanding age-dependent patterns of survival is fundamental to predicting population dynamics, understanding selective pressures, and estimating rates of senescence. However, quantifying age-specific survival in wild populations poses significant logistical and statistical challenges. Recent work has helped to alleviate these constraints by demonstrating that age-specific survival can be estimated using mark-recapture data even when age is unknown for all or some individuals.

Energy demand and the context-dependent effects of genetic interactions underlying metabolism.

Genetic effects are often context dependent, with the same genotype differentially affecting phenotypes across environments, life stages, and sexes. We used an environmental manipulation designed to increase energy demand during development to investigate energy demand as a general physiological explanation for context-dependent effects of mutations, particularly for those mutations that affect metabolism. We found that increasing the photoperiod during which larvae are active during development phenocopies a temperature-dependent developmental delay in a mitochondrial-nuclear genotype with disrupted metabolism.

Altered spring phenology of North American freshwater turtles and the importance of representative populations.

Globally, populations of diverse taxa have altered phenology in response to climate change. However, most research has focused on a single population of a given taxon, which may be unrepresentative for comparative analyses, and few long-term studies of phenology in ectothermic amniotes have been published. We test for climate-altered phenology using long-term studies (10-36 years) of nesting behavior in 14 populations representing six genera of freshwater turtles (, , , , , and ).

Sex-specific growth, shape, and their impacts on the life history of a long-lived vertebrate.

Background: Individual growth rates both comprise and determine life-history phenotypes. Despite decades of interest in understanding the relationship between individual growth and life history, chelonian longevity has limited our ability to robustly estimate individual growth curves that span the life of both sexes.

Questions: (1) Do patterns of growth in size and shape differ between the sexes of the painted turtle, ? (2) Does individual variation in size and shape affect female reproductive effort?

Methods: Using 30 years of field data on shell morphology of a single population of painted turtles, we used principal components analysis to summarize multivariate size and shape.

Pleiotropic effects of a mitochondrial-nuclear incompatibility depend upon the accelerating effect of temperature in Drosophila.

Interactions between mitochondrial and nuclear gene products that underlie eukaryotic energy metabolism can cause the fitness effects of mutations in one genome to be conditional on variation in the other genome. In ectotherms, the effects of these interactions are likely to depend upon the thermal environment, because increasing temperature accelerates molecular rates. We find that temperature strongly modifies the pleiotropic phenotypic effects of an incompatible interaction between a Drosophila melanogaster polymorphism in the nuclear-encoded, mitochondrial tyrosyl-transfer (t)RNA synthetase and a D.

Inducing extra copies of the Hsp70 gene in Drosophila melanogaster increases energetic demand.

Background: Mutations that increase gene expression are predicted to increase energy allocation to transcription, translation and protein function. Despite an appreciation that energetic tradeoffs may constrain adaptation, the energetic costs of increased gene expression are challenging to quantify and thus easily ignored when modeling the evolution of gene expression, particularly for multicellular organisms. Here we use the well-characterized, inducible heat-shock response to test whether expressing additional copies of the Hsp70 gene increases energetic demand in Drosophila melanogaster.

Novel insights into the echinoderm nervous system from histaminergic and FMRFaminergic-like cells in the sea cucumber Leptosynapta clarki.

Understanding of the echinoderm nervous system is limited due to its distinct organization in comparison to other animal phyla and by the difficulty in accessing it. The transparent and accessible, apodid sea cucumber Leptosynapta clarki provides novel opportunities for detailed characterization of echinoderm neural systems. The present study used immunohistochemistry against FMRFamide and histamine to describe the neural organization in juvenile and adult sea cucumbers.

Critical thermal maxima in knockdown-selected Drosophila: are thermal endpoints correlated?

To explore the correlation of traits linked to thermotolerance, we compared three thermal endpoints (knockdown temperature and two critical thermal maxima) among replicate populations of Drosophila melanogaster selected for high, or low, knockdown temperature. The high knockdown flies maintain normal posture and locomotor ability within a knockdown column at temperatures >or=40 degrees C, whereas the low knockdown flies fall out of the column at much cooler temperatures (approximately 35 degrees C, on average). The critical thermal maximum (CT(max)) for respiratory control in the selected knockdown populations was determined by analyzing CO(2) output of individuals during exposure to a temperature ramp (from 30 degrees C to >45 degrees C) and was indicated by an abrupt alteration in the pattern of CO(2) release.