Persistent maternal effects on juvenile survival in North American red squirrels

Maternal effects can have lasting fitness consequences for offspring, but these effects are often difficult to disentangle from associated responses in offspring traits. We studied persistent maternal effects on offspring survival in North American red squirrels (Tamiasciurus hudsonicus) by manipulating maternal nutrition without altering the post-emergent nutritional environment experienced by offspring. This was accomplished by providing supplemental food to reproductive females over winter and during reproduction, but removing the supplemental food from the system prior to juvenile emergence. We then monitored juvenile dispersal, settlement and survival from birth to 1 year of age. Juveniles from supplemented mothers experienced persistent and magnifying survival advantages over juveniles from control mothers long after supplemental food was removed. These maternal effects on survival persisted, despite no observable effect on traits normally associated with high offspring quality, such as body size, dispersal distance or territory quality. However, supplemented mothers did provide their juveniles an early start by breeding an average of 18 days earlier than control mothers, which may explain the persistent survival advantages their juveniles experienced.     

Ecological investigations to select mitigation options to reduce vehicle-caused mortality of a threatened butterfly

Whereas roads that bisect habitat are known to decrease population size through animal-vehicle collisions or interruption of key life history events, it is not always obvious how to reduce such impacts, especially for flying organisms. We needed a quick, cost-efficient and effective way to determine how best to decrease vehicle-caused mortality while maintaining habitat connectivity for the federally listed Oregon silverspot butterfly, Speyeria zerene hippolyta. Therefore, we gathered targeted ecological information that informed selection of a mitigation option prior to implementation. We sampled butterfly behavior and environmental conditions along a highway and conducted a small-scale experiment along a decommissioned road corridor used by these butterflies. Using our findings, we recommended vegetation management and helped managers eliminate options they were considering that would be ineffective such as increasing shade or wind in the road, and installing fencing or hedgerows aimed at directing flight above traffic. This quick and inexpensive approach of using ecological observations and small-scale experiments to evaluate the likely success of each available mitigation option can be used to determine effective, species-specific solutions for reducing traffic impacts on pollinators and other small, flying organisms of conservation concern.     

Developing sociopolitical consciousness of race and social class inequality in adolescents attending progressive and no excuses urban secondary schools

Sociopolitical consciousness refers to an individual’s ability to critically analyze the political, economic, and social forces shaping society and one’s status in it. A growing body of scholarship reports that high levels of sociopolitical consciousness are predictive in marginalized adolescents of a number of key outcomes including resilience and civic engagement. The present study explored the role that urban secondary schools can play in fostering adolescents’ sociopolitical consciousness through a longitudinal, mixed methods investigation of more than 400 adolescents attending “progressive” and “no excuses” charter high schools. Analyses revealed that, on average, students attending progressive high schools demonstrated sizeable shifts in their sociopolitical consciousness of racial inequality, and students attending no excuses high schools demonstrated sizeable shifts in their sociopolitical consciousness of social class inequality. Qualitative interviews with participating students offered insight into the curriculum, programming, and practices that these youth perceived as contributing to these differences in their sociopolitical consciousness.     

Offspring size–number tradeoffs and food quality feedbacks impact population dynamics in a Daphnia–algae system

Population fluctuations can be affected by both extrinsic (e.g. weather patterns, food availability) and intrinsic (e.g. life‐history) factors. A key life‐history tradeoff is the production of offspring size versus number, ranging from many small offspring to few large offspring. Models show that this life‐history tradeoff in offspring size and number, through maturation time, can have significant impacts on population dynamics. However, few manipulative experiments have been conducted that can isolate life‐history effects from impacts of extrinsic factors in consumer–resource systems. We experimentally tested the effect of an offspring size–number tradeoff on population stability and food availability in a consumer–resource system. Using Daphnia pulex, we created a shift from many, small offspring being produced to fewer, larger offspring. Two sets of experiments were performed to examine the interaction of an extrinsic factor (light levels) and intrinsic population structure on dynamics, and we controlled for the ingestion pressure on algal prey at the time of the manipulation. We predicted that the tradeoff would impact internal consumer population characteristics, including biasing the stage structure towards adults, increasing adult size, and increasing average population‐level reproduction. This adult‐dominated stage structure was predicted to then lead to instability and a low quantity–high quality food state. Under all light levels, the manipulated populations became dominated by large adults. Contrary to predictions, the amplitudes of fluctuations in Daphnia biomass were lower in populations shifted to few–large offspring, representing higher stability in these populations. Furthermore, in high light conditions, a stable low Daphnia – high algae biomass (low food quality) state was observed in few–large offspring treatments but not in control (many–small offspring) treatments. Our results show a strong link between light levels as an extrinsic factor and the life‐history tradeoff of consumer offspring size versus number that impacts consumer–resource population dynamics through feedbacks with resource quality.     

Haplotype Analysis of Hemochromatosis: Evaluation of Different Linkage-Disequilibrium Approaches and Evolution of Disease Chromosomes

We applied several types of linkage-disequilibrium calculations to analyze the hereditary hemochromatosis (hh) locus. Twenty-four polymorphic markers in the major histocompatibility complex (MHC) class I region were used to haplotype hh and normal chromosomes. A total of 169 hh and 161 normal chromosomes were analyzed. Disequilibrium values were found to be high over an unusually large region beginning 150 kb centro-meric of HLA-A and extending nearly 5 Mb telomeric of it. Recombination in this region was −28% of the expected value. This low level of recombination contributes to the unusually broad region of linkage disequilibrium found with hh. The strongest disequilibrium was found at locus HLA-H (d = .84) and at locus D6S2239 (d = .85), a marker −10 kb telomeric to HLA-H. All disequilibrium methods employed in this study found peak disequilibrium at HLA-H or D6S2239. The cys282tyr mutation in HLA-H, a candidate gene for hh, was found in 85% of disease chromosomes. A haplotype phylogeny for hh chromosomes was constructed and suggests that the mutation associated with the most common haplotype occurred relatively recently. The age of the hh mutation was estimated to be −60-70 generations. Disequilibrium was maintained over a greater distance for hh-carrying chromosomes, consistent with a recent mutation for hh. Our data provide a reasonable explanation for previous difficulties in localizing the hh locus and provide an evolutionary history for disease chromosomes.     

Oxytocin has dose-dependent developmental effects on pair-bonding and alloparental care in female prairie voles

The present study examines the developmental consequences of neonatal exposure to oxytocin on adult social behaviors in female prairie voles (Microtus ochrogaster). Female neonates were injected within 24 h of birth with isotonic saline or one of four dosages of oxytocin (OT). As adults, females were tested in an elevated plus-maze paradigm (a measure of anxiety and exploratory behavior), and for alloparental behavior and partner preferences. At 2 mg/kg OT, females took longer to approach pups, but were the only group to form a statistically significant within-group partner preference. At 4 mg/kg OT, females retrieved pups significantly more frequently but no longer displayed a partner preference; while females treated developmentally with 8 mg/kg spent significantly more time in side-to-side contact with a male stranger than any other treatment group. OT may have broad developmental consequences, but these effects are not linear and may both increase and decrease the propensity to display behaviors such as pair-bonding.     

Quantitative methods for defining mast‐seeding years across species and studies

Abstract: Although there is a quantitative method that is commonly used for identifying mast‐seeding behaviour of a plant population based on the coefficient of variation (i.e. CV is standard deviation/mean>1), there is no general quantitative method for delineating “mast” as opposed to “non‐mast” years. Mast years are, however, described qualitatively as years when “large”, “unusually large” and “high” seed production occurs. The use of a consistent and generally applicable method for delineating mast years across species and plant populations is important for synthesizing knowledge of the causes and consequences of mast seeding, which could be confounded by using different methods among studies. We examine six quantitative methods for identifying mast years: four methods from the literature and two methods developed here. We use 36 seed production datasets covering a variety of species with ≥10 years of data to test the performance of these six methods. For each method, we quantify the percentage of the datasets to which the method could be successfully applied, the magnitude of the mast year relative to the mean, the frequency of mast years and the occurrence of consecutive mast years. The majority of the methods failed to meet the criteria for a suitable method. The best method used the number of standard deviates (standardized deviate method) of the annual mean seed production from the long‐term mean of the dataset to identify mast‐seeding years. General results from the standardized deviate method include that the occurrence of mast‐seeding years is largely unrelated to plant population CV, but similar across species and data collection methods.