Stochastic population dynamics in populations of western terrestrial garter snakes with divergent life histories

Comparative evaluations of population dynamics in species with temporal and spatial variation in life-history traits are rare because they require long-term demographic time series from multiple populations. We present such an analysis using demographic data collected during the interval 1978–1996 for six populations of western terrestrial garter snakes (Thamnophis elegans) from two evolutionarily divergent ecotypes. Three replicate populations from a slow-living ecotype, found in mountain meadows of northeastern California, were characterized by individuals that develop slowly, mature late, reproduce infrequently with small reproductive effort, and live longer than individuals of three populations of a fast-living ecotype found at lakeshore locales. We constructed matrix population models for each of the populations based on 8–13 years of data per population and analyzed both deterministic dynamics based on mean annual vital rates and stochastic dynamics incorporating annual variation in vital rates. (1) Contributions of highly variable vital rates to fitness (λs) were buffered against the negative effects of stochastic variation, and this relationship was consistent with differences between the meadow (M-slow) and lakeshore (L-fast) ecotypes. (2) Annual variation in the proportion of gravid females had the greatest negative effect among all vital rates on λs. The magnitude of variation in the proportion of gravid females and its effect on λs was greater in M-slow than L-fast populations. (3) Variation in the proportion of gravid females, in turn, depended on annual variation in prey availability, and its effect on λs was 4–23 times greater in M-slow than L-fast populations. In addition to differences in stochastic dynamics between ecotypes, we also found higher mean mortality rates across all age classes in the L-fast populations. Our results suggest that both deterministic and stochastic selective forces have affected the evolution of divergent life-history traits in the two ecotypes, which, in turn, affect population dynamics. M-slow populations have evolved life-history traits that buffer fitness against direct effects of variation in reproduction and that spread lifetime reproduction across a greater number of reproductive bouts. These results highlight the importance of long-term demographic and environmental monitoring and of incorporating temporal dynamics into empirical studies of life-history evolution

Grounding robot motion in natural language and visual perception

The current state of the art in military and first responder ground robots involves heavy physical and cognitive burdens on the human operator while taking little to no advantage of the potential autonomy of robotic technology. The robots currently in use are rugged remote-controlled vehicles. Their interaction modalities, usually utilizing a game controller connected to a computer, require a dedicated operator who has limited capacity for other tasks. I present research which aims to ease these burdens by incorporating multiple modes of robotic sensing into a system which allows humans to interact with robots through a natural-language interface. I conduct this research on a custom-built six-wheeled mobile robot. First I present a unified framework which supports grounding natural-language semantics in robotic driving. This framework supports learning the meanings of nouns and prepositions from sentential descriptions of paths driven by the robot, as well as using such meanings to both generate a sentential description of a path and perform automated driving of a path specified in natural language. One limitation of this framework is that it requires as input the locations of the (initially nameless) objects in the floor plan. Next I present a method to automatically detect, localize, and label objects in the robot’s environment using only the robot’s video feed and corresponding odometry. This method produces a map of the robot’s environment in which objects are differentiated by abstract class labels. Finally, I present work that unifies the previous two approaches. This method detects, localizes, and labels objects, as the previous method does. However, this new method integrates natural-language descriptions to learn actual object names, rather than abstract labels

Merging the “Morphology–Performance–Fitness” Paradigm and Life-History Theory in the Eagle Lake Garter Snake Research Project

The morphology-performance-fitness paradigm for testing selection on morphological traits has seen decades of successful application. At the same time, life-history approaches using matrix methods and perturbation studies have also allowed the direct estimate of selection acting on vital rates and the traits that comprise them. Both methodologies have been successfully applied to the garter snakes of the long-term Eagle Lake research project to reveal selection on morphology, such as color pattern, number of vertebrae, and gape size; and life-history traits such as birth size, growth rates, and juvenile survival. Here we conduct a reciprocal transplant study in a common laboratory environment to study selection on morphology and life-history. To place our results in the ecomorphology paradigm, we measure performance outcomes (feeding rates, growth, insulin-like growth factor 1 titers) of morphological variation (body size, condition) and their fitness consequences for juvenile survival?a trait that has large fitness sensitivities in these garter snake populations, and therefore is thought to be subject to strong selection. To better merge these two complementary theories, we end by discussing our findings in a nexus of morphology-performance-fitness-life history to highlight what these approaches, when combined, can reveal about selection in the wild.Fil: Addis, Elizabeth A.. University of Iowa; Estados UnidosFil: Gangloff, Eric J.. University of Iowa; Estados UnidosFil: Palacios, María Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; Argentina. University of Iowa; Estados UnidosFil: Carr, Katherine E.. Gonzaga University; Estados UnidosFil: Bronikowski, Anne M.. University of Iowa; Estados Unido

Reaction dynamics of H + O2 at 1.6 eV collision energy

The hot hydrogen atom reaction, H + O2 yields OH + O, has been studied at a center of mass collision energy of 1.6 eV. H atoms were generated by 266 nm photolysis of HI in a mixture of HI and O2 at 293 K. The OH product was probed by laser induced fluorescence and the nascent OH vibrational, rotational, and fine structure distributions were determined. The OH(v=0/OH(v=1) vibrational branching ratio was measured to be 1.72 + or - 0.09. The data suggest that the H + O2 reaction at this collision energy proceeds via two competing mechanisms: reaction involving a long-lived complex and direct reaction

Gene array profiling of large hypothalamic CNS regions in lactating and randomly cycling virgin mice

A dramatic example of neuronal and physiological plasticity in adult mammals occurs during the transition from a non-maternal to a maternal, lactating state. In this study we compared gene expression within a large continuous region of the CNS involved in maternal behaviors (hypothalamus, preoptic regions, and nucleus accumbens) between lactating (L) (postpartum Day 7) and randomly cycling virgin (V) outbred mice. Using high density oligonucleotide arrays representing 11,904 genes, two statistical algorithms were used to identify significant differences in gene expression: robust multi array (p \u3c 0.001) (n = 92 genes) and significance analysis of microarrays using a 10% false discover rate (n = 114 genes). 27 common genes were identified as significant using both techniques. A subset of genes (n = 5) were selected and examined by real-time PCR. Our findings were consistent with previous published work. For example, neuropeptide Y (NPY) and proenkephalin were elevated in L mice, whereas POMC was decreased. Increased levels of NPY Y2 receptor and polo-like kinase and decreased levels of endothelin receptor type b in L mice are examples of novel gene expression changes not previously identified. Expression differences occurred in broad classes. Together, our findings provide possible new material on gene expression changes that may support maternal behaviors. The advantages and drawbacks of sampling large CNS regions using arrays are discussed