Recent publications by faculty, students and post-doctoral fellows of the Murray State Biology Department
Murray State students, post-doctoral fellows and faculty are in bold. Current and former Murray State student authors are starred (*).
For more information on research areas in the Biology Department, click here.
Anderson, T. A*., C. L. Mott, B. A. Hartman*, and H. H. Whiteman. Biotic and abiotic predictors of larval salamander size and density. Copeia. In press.
Abstract. Both abiotic and biotic factors influence population and community structure. However, the simultaneous assessment of the relative importance of both types of factors is rarely performed for multiple traits of a population, such as body size and abundance. Comparisons among different demographic rates are necessary for teasing apart the importance of species interactions and/or environmental conditions on both population and community structure. We tested whether biotic (e.g., larval competition) or abiotic factors influenced larval salamander density and body size in natural populations of two known salamander competitors, Ambystoma talpoideum and A. maculatum. Over six years, we surveyed 33 ponds where these species co-occur in western Kentucky, USA. We found that larval densities between species were positively correlated, and that habitat features had contrasting, species-specific effects. Larval sizes for each species showed negative intra- and interspecific relationships with larval densities of each species, but larval A. maculatum generally exerted the stronger relative interspecific effect. Overall, our study highlights that different characteristics of a population (i.e. body size or abundance) may be differentially affected by abiotic and biotic factors, even for ecologically-similar, sympatric species. Understanding which traits are regulated by each component will advance our knowledge on how populations and communities are structured.
Canning, David R., N.R. Brelsford* & N.W. Lovett*. 2016. Chondroitin sulfate effects on neural stem cell differentiation. In Vitro Cell & Developmental Biology – Animal. Vol. 52, pp. 35-44. DOI: 10.1007/s11626-015-9941-8
Abstract. We have investigated the role chondroitin sulfate has on cell interactions during neural plate formation in the early chick embryo. Using tissue culture isolates from the prospective neural plate, we have measured neural gene expression profiles associated with neural stem cell differentiation. Removal of chondroitin sulfate from stage 4 neural plate tissue leads to altered associations of N-cadherin-positive neural progenitors and causes changes in the normal sequence of neural marker gene expression. Absence of chondroitin sulfate in the neural plate leads to reduced Sox2 expression and is accompanied by an increase in the expression of anterior markers of neural regionalization. Results obtained in this study suggest that the presence of chondroitin sulfate in the anterior chick embryo is instrumental in maintaining cells in the neural precursor state.
Parker, S.P, William B. Bowden, Michael B. Flinn. 2016. The effect of acid strength and postacidification reaction time on the determination of chlorophyll a in ethanol extracts of aquatic Periphyton. Limnology and Oceanography: Methods. In press.
Abstract. Quantification of chlorophyll a (Chl a) is essential to the study of aquatic ecosystems, yet differences in methodology may introduce significant errors to its determination in ethanol extracts. Insufficient acidification slows the conversion of Chl a to pheophytin a leading to an underestimate of Chl a concentration. Furthermore, slight differences in the postacidification reaction time can introduce greater errors in calculated Chl a and impede our ability to make cross-study comparisons. We used known concentrations of pure Chl a from the blue-green algae Anacystis nidulans dissolved in 95% ethanol to evaluate the effect of acid strength and postacidification reaction time on the spectrophotometric determination of Chl a. Increasing acid strength resulted in more rapid stabilization of calculated Chl a concentration. At reaction times less than 120 s estimates of Chl a deviated from known concentrations by as much as 84.8%. The magnitude of error in the calculated Chl a values were dependent on acid strength and reaction time, which allowed us to develop predictive equations to correct Chl a measurements that were insufficiently acidified or read prior to reaction completion. We validated our predictive equations using benthic periphyton samples from northern Alaska and northwestern Vermont, U.S.A. Our results indicate that under-acidified samples with known reaction times can be easily corrected so results from different methods can be standardized. For future analyses we recommend acidifying ethanol-extracted algal samples to 0.008 mol HCl L21 and allowing samples to react for 30–60 min to ensure accurate and consistent results.
Derting, Terry L., D. Ebert-May, T. P. Henkel, J. Middlemis Maher, B. Arnold, and H. A. Passmore. 2016. Assessing faculty professional development in STEM higher education: Sustainability of outcomes. Science Advances 2:e1501422. http://dx.doi.org/10.1126/sciadv.1501422
Abstract. We tested the effectiveness of Faculty Institutes for Reforming Science Teaching (FIRST IV), a professional development program for postdoctoral scholars, by conducting a study of program alumni. Faculty professional development programs are critical components of efforts to improve teaching and learning in the STEM (Science, Technology, Engineering, and Mathematics) disciplines, but reliable evidence of sustained impacts of these programs is lacking. We used a paired design in which we matched a FIRST alumnus employed in a tenure-track position with a non-FIRST faculty member at the same institution. The members of a pair taught courses that were of similar size and level. To determine whether teaching practices of FIRST participants were more learner-centered compared with those of non-FIRST faculty, we compared faculty perceptions of their teaching strategies, perceptions of environmental factors that influence teaching, and actual teaching practice. Non-FIRST and FIRST faculty reported similar perceptions about their teaching strategies and teaching environment. FIRST faculty reported using active learning and interactive engagement in lecture courses more frequently compared with non-FIRST faculty. Ratings from external reviewers also documented that FIRST faculty taught class sessions that were learner-centered, contrasting with the teacher-centered class sessions of most non-FIRST faculty. Despite marked differences in teaching practice, FIRST and non-FIRST participants used assessments that targeted lower-level cognitive skills. Our study demonstrated the effectiveness of the FIRST program and the empirical utility of comparison groups, where groups are well-matched and controlled for contextual variables (e.g. departments), for evaluating the effectiveness of professional development on subsequent teaching practices.
He, X., K. S. He, J. Hyvönen 2016. Will bryophytes survive in a warming world? Perspectives in Plant Ecology, Evolution and Systematics 19, 49-60.
Abstract. Understanding how plant species respond to climate change is one of the great challenges in biodiversity conservation and sustainable ecosystem planning. Current studies of the impact of climate change on plants are biased to tracheophytes, i.e. vascular-plants. Only a few studies have been carried out on bryophytes despite the fact that they are ecologically equally important groups of embryophytes with their origins predating contemporary vascular-plants. Bryophytes fundamentally differ from vascular-plants in their small size and utilization of a poikilohydric strategy for water and nutrients; their survival and reproduction are highly dependent on their external environment. Thus, the results from studies of tracheophytes cannot be generalized on bryophytes. In this review, we synthesize information about the influence of environmental factors on bryophytes to understand their relation to climate, especially to temperature on a global scale. We discuss a range of critical topics, including the responses of photosynthetic activities to temperature changes, and the consequences of temperature change on the interactions between bryophytes and vascular-plants, as well as on peatland ecosystems. As many species thrive in relatively low temperatures, with a low potential for short-term thermal acclimation to higher temperature in a hydrated state, elevated temperatures may shorten the time of metabolic activity, and increase desiccation intensity. This can bring significant physiological pressure on the survival of poikilohydric bryophytes. As a consequence of global warming, significant losses in bryophyte diversity can be expected, particularly in areas harbouring large number of species such as boreal forests of higher latitudes, alpine biomes and higher altitudes on tropical mountains. Furthermore, the decline of bryophyte diversity will ultimately lead to an alteration of ecosystem structure and function, nutrient cycling, and carbon balance. Further exploration of bryophyte ecophysiology in the changing environment, particularly the acclimation potential of photosynthesis and its biochemical and enzyme level basis to predicted changes in temperature will provide new knowledge that will assist bryophyte conservation.
Lucas, C.M., Sheikh, P., Gagnon, P.R., and McGrath, D.G. 2016. How livestock and flooding mediate the ecological integrity of working forests in Amazon River floodplains. Ecological Applications 26(1): 190-202.
Moore, M. P.* and H. H. Whiteman. 2016. Natal philopatry increases with larval body condition in male, but not female, salamanders. Behavioral Ecology and Sociobiology 70: 1247-1255.
Abstract. An individual’s physiological condition early in ontogeny often regulates natal dispersal and philopatry decisions, however increased condition promotes dispersal in some organisms, and philopatry in others. These disparate findings likely arise from interactions among an individual’s early life stage physiological condition, its likelihood of surviving a dispersal event (i.e. dispersal ability), and its motivation to leave its natal site (i.e. dispersal propensity). Due to the broad importance of reproductive site selection to population structure and dynamics, studies disentangling these various phenotype-dependent effects are critical. We evaluated the relationships between two aspects of larval physiological condition and natal philopatry in Arizona tiger salamanders (Ambystoma tigrinum nebulosum) in an isolated pond system. In this population, geographic distance between ponds is small, adult survivorship is very high, and thus the likelihood of a successful breeding event should mediate reproductive site selection as opposed to the likelihood of surviving the dispersal event. We found that natal philopatry increased with an estimate of long-term body condition in males, but there was no relationship in females. However, natal philopatry decreased with an estimate of short-term body condition. We also found that an individual’s natal pond had effects on philopatry that influenced both sexes, and were independent of the pond’s direct effects on body condition. Together, these findings strongly support the importance of an individual’s early developmental experience in the natal environment to its reproductive behaviors across its lifespan, and further highlight the value of considering how phenotype-dependent dispersal mechanisms may vary between the sexes.
Rocchini, D., Boyd, D. S., Féret, J.-B., Foody, G. M., He, K. S., Lausch, A., Nagendra, H., Wegmann, M., Pettorelli, N. (2016), Satellite remote sensing to monitor species diversity: potential and pitfalls. Remote Sensing in Ecology and Conservation, 2: 25–36. doi: 10.1002/rse2.9
Abstract. Assessing the level of diversity in plant communities from field-based data is difficult for a number of practical reasons: (1) establishing the number of sampling units to be investigated can be difficult; (2) the choice of sample design can impact on results; and (3) defining the population of concern can be challenging. Satellite remote sensing (SRS) is one of the most cost-effective approaches to identify biodiversity hotspots and predict changes in species composition. This is because, in contrast to field-based methods, it allows for complete spatial coverages of the Earth's surface under study over a short period of time. Furthermore, SRS provides repeated measures, thus making it possible to study temporal changes in biodiversity. Here, we provide a concise review of the potential of satellites to help track changes in plant species diversity, and provide, for the first time, an overview of the potential pitfalls associated with the misuse of satellite imagery to predict species diversity. Our work shows that, while the assessment of alpha-diversity is relatively straightforward, calculation of beta-diversity (variation in species composition between adjacent locations) is challenging, making it difficult to reliably estimate gamma-diversity (total diversity at the landscape or regional level). We conclude that an increased collaboration between the remote sensing and biodiversity communities is needed in order to properly address future challenges and developments.
Zheng J.*, Gao M, Huynh N.*, Tindell S.J.*, Vo H.D.L.*, McDonald W.H. and Arkov A.L. In vivo mapping of a dynamic ribonucleoprotein granule interactome in early Drosophila embryos. FEBS Open Bio, 6: 1248–1256 (2016).
Abstract. Macromolecular complexes and organelles play crucial roles within cells, but their native architectures are often unknown. Here, we use an evolutionarily conserved germline organelle, the germ granule, as a paradigm. In Drosophila embryos, we map one of its interactomes using a novel in vivo crosslinking approach that employs two interacting granule proteins and determines their common neighbor molecules. We identified an in vivo granule assembly of Tudor, Aubergine, motor and metabolic proteins, and RNA helicases, and provide evidence for direct interactions within this assembly using purified components. Our study indicates that germ granules contain efficient biochemical reactors involved in post-transcriptional gene regulation.
Anderson, T.L. * and H.H. Whiteman. 2015. Non-additive effects of intra- and interspecific competition between two larval salamanders. Journal of Animal Ecology 84: 765–772.
- Assessment of the relative strengths of intra- and interspecific competition has increased in recent years and is critical to understanding the importance of competition. Yet, whether intra- and interspecific competition can have non-additive effects has rarely been tested. The resulting fitness consequences of such non-additive interactions are important to provide the context necessary to advance our understanding of competition theory.
- We compared the strength of additive and non-additive intra- and interspecific competition by manipulating densities of a pair of larval salamanders (Ambystoma talpoideum and A. maculatum) in experimental mesocosms within a response surface design.
- Intraspecific density had the strongest effect on the strength of competition for both species, and few observed comparisons indicated interspecific competition was an important factor in predicting body size, growth or larval period length of either species.
- Non-additive effects of intra- and interspecific competition influenced some response variables, including size and mass at metamorphosis in A. maculatum, but at a reduced strength compared to intraspecific effects alone.
- Intraspecific competition was thus the dominant biotic interaction, but non-additive effects also impact the outcome of competition in these species, validating the importance of testing for and incorporating non-additive density effects into competition models.
Anderson, T.L.* and H.H. Whiteman. 2015. Asymmetric effects of intra- and interspecific competition on a pond-breeding salamander. Ecology 96:1681-1690.
Abstract. A fundamental goal of evolutionary ecology is to understand how asymmetric competition influences phenotype expression, yet few studies have quantified the relative effects of intra- and interspecific competition on phenotypes. We examined the effects of intra- and interspecific larval competition on both discrete and continuous phenotype expression of the facultatively paedomorphic mole salamander (Ambystoma talpoideum). We manipulated the density and frequency of larval A. talpoideum and a common competitor, the spotted salamander (A. maculatum), in experimental mesocosms within a response surface design. The production of discrete ontogenetic morphs (metamorphs, paedomorphs, and overwintering larvae) was affected more by intraspecific than interspecific competition, but the effect varied between morphs. Paedomorph and metamorph production were more strongly affected by intraspecific than interspecific competition, while the production of overwintering larvae was affected by each type of competition approximately equally. Paedomorphs largely occurred only at low conspecific densities, overwintering larvae primarily occurred at high overall densities, and metamorph production peaked at intermediate densities of con- and heterospecifics. Density-dependent intraspecific competition had stronger effects on body size and growth rates than interspecific competition for both metamorphs and overwintering larvae, whereas interspecific competition more strongly affected paedomorph size. Overall, these results support the hypothesis that intraspecific competition influences both continuous and discrete phenotypic expression more strongly than interspecific competition. Fluctuating strengths of each type of competition can affect variation in life history strategies by influencing discrete ontogenetic pathways via individual body sizes, leading to differential morph production and fitness within and among morphs.
Oliver M. Beckers, Wendy Anderson, and Armin P. Moczek. 2015. A combination of developmental plasticity, parental effects, and genetic differentiation mediates divergences in life history traits between dung beetle populations. Evolution and Development 17(2): 148-159.
Abstract. The dung beetle, Onthophagus taurus, was introduced < 50 years ago from its native Mediterranean range into Western Australia (WA) and the Eastern United States (EUS). The intensity of intra- and interspecific competition for dung as a breeding resource is substantially higher in WA. First, we tested whether differential resource competition in the two exotic ranges is associated with divergences in life history traits, which impact on resource use. We predicted that high levels of resource competition in WA should favor females that produce brood balls more efficiently and of altered size, and produce offspring more readily when a breeding opportunity arises. Furthermore, we predicted that larvae from WA populations may have evolved more efficient development and thus exhibit higher eclosion success, shorter development time, and altered body size under standardized conditions. Second, we examined the likely developmental mechanisms underlying these divergences, i.e., genetic differentiation, developmental plasticity, or parental effects in a common garden experiment. Field-collected EUS and WA populations significantly differed, as predicted, in most of the traits examined. However, these differences are facilitated by a complex combination of proximate mechanisms. Developmental plasticity and (grand) parental effects mediated differences related to reproductive performance, whereas genetic differentiation mediated differences in the duration of larval development. Our study highlights that population divergences can be the product of a patchwork of proximate mechanisms, with each mechanism adjusting different traits in a way that the resulting composite phenotype may be better suited to its competitive environment.
Chesika Crump* and Terry L. Derting. 2015. Effects of pet therapy on the psychological and physiological stress levels of first-year female undergraduates. North American Journal of Psychology 17:575-590.
Abstract. Our research objective was to determine if animal-assisted activities (AAA) reduce the physiological and psychological stress levels of first-year female undergraduates. In study I, 27 first-year college women and 9 privately-owned registered therapy dogs were recruited. Blood pressure (BP), heart rate (HR), and psychological stress and arousal level were measured and analyzed. In study II, we recruited 61 first-year female students (34 experimental and 28 control) who interacted with 7 registered pet therapy dogs. Salivary cortisol level and psychological stress and arousal level were measured and analyzed for a dog-therapy group and a control group. Animal-assisted activities were associated with a significant decrease in psychological stress and increase in psychological arousal in both studies. There were no significant effects of AAA on diastolic BP, HR, or salivary cortisol level. Our findings indicated that AAA could provide an inexpensive approach to alleviating psychological stress in students and, potentially, other populations of young adults.
Earl, J. E.*, and H. H. Whiteman. 2015. Are commonly used fitness predictors accurate? A meta-analysis of amphibian size and age at metamorphosis. Copeia 103:297-309. Awarded Best Paper in Herpetology (2015) by the ASIH.
Abstract. Reaching developmental milestones younger and at larger sizes is commonly claimed to reflect increased fitness. However, the amount of fitness gained from being larger and younger at a milestone may vary with several attributes, particularly evolutionary history, life history and environmental characteristics. We used a meta-analysis to investigate whether these attributes affected the utility of developmental milestones to be used as predictors of future fitness. We chose amphibian size at and time to metamorphosis (SAM and TTM, respectively) as model developmental milestones, because studies have examined SAM and TTM’s efficacy for fitness prediction (via post-metamorphic fitness proxies) and they are commonly used in a variety of studies testing ecological and evolutionary theory and more applied research on the effects of anthropogenic stressors. We found variation in the predictive power of SAM and TTM for post-metamorphic performance. SAM was a more consistent predictor of post-metamorphic performance than TTM, but also had a higher sample size. Life history and study design (i.e. laboratory vs. field studies), but not evolutionary history, were important for explaining variation in predictive power for post-metamorphic performance. The correlation between SAM and performance increased with the proportion of time to maturity reached at metamorphosis, suggesting that species can compensate for initial fitness reductions through ontogeny. Because numerous researchers use size and age at developmental milestones to indicate fitness, we urge caution in interpreting their results due to the species- and system-specific nature of fitness surrogates
Paul R. Gagnon, Heather A. Passmore, Matthew Slocum, Jonathan A. Myers, Kyle E. Harms, William J. Platt and C. E. Timothy Paine. 2015. Fuels and fires influence vegetation via above- and belowground pathways in a high-diversity plant community. Journal of Ecology 103: 1009-1019.
- Fire strongly influences plant populations and communities around the world, making it an important agent of plant evolution. Fire influences vegetation through multiple pathways, both above- and belowground. Few studies have yet attempted to tie these pathways together in a mechanistic way through soil heating even though the importance of soil heating for plants in fire-prone ecosystems is increasingly recognized.
- Here we combine an experimental approach with structural equation modelling (SEM) to simultaneously examine multiple pathways through which fire might influence herbaceous vegetation. In a high-diversity longleaf pine groundcover community in Louisiana, USA, we manipulated fine-fuel biomass and monitored the resulting fires with high-resolution thermocouples placed in vertical profile above- and belowground.
- We predicted that vegetation response to burning would be inversely related to fuel load owing to relationships among fuels, fire temperature, duration and soil heating.
- We found that fuel manipulations altered fire properties and vegetation responses, of which soil heating proved to be a highly accurate predictor. Fire duration acting through soil heating was important for vegetation response in our SEMs, whereas fire temperature was not.
- Our results indicate that in this herbaceous plant community, fire duration is a good predictor of soil heating and therefore of vegetation response to fire. Soil heating may be the key determinant of vegetation response to fire in ecosystems wherein plants persist by re-sprouting or reseeding from soil-stored propagules.
- Synthesis. Our SEMs demonstrate how the complex pathways through which fires influence plant community structure and dynamics can be examined simultaneously. Comparative studies of these pathways across different communities will provide important insights into the ecology, evolution and conservation of fire-prone ecosystems.
Ebert-May, D. T. L. Derting, T. P. Henkel, J. Middlemis Maher, J. L. Momsen, B. Arnold, and H.A. Passmore. 2015. Breaking the cycle: Future faculty begin teaching with learner-centered strategies after professional development. CBE – Life Sciences Education 14:1-12.
Abstract. The availability of reliable evidence for teaching practice after professional development is limited across STEM disciplines, making the identification of professional development “best practices” and effective models for change difficult. We aimed to determine the extent to which postdoctoral fellows (i.e., future biology faculty) believed in and implemented evidence-based pedagogies after completion of a two-year professional development program, Faculty Institutes for Reforming Science Teaching (FIRST IV). Postdocs (PDs) attended a two-year training program during which they completed self-report assessments of their beliefs about teaching and gains in pedagogical knowledge and experience, and provided copies of class assessments and video recordings of their teaching. The PDs reported greater use of learner-centered compared with teacher-centered strategies. These data were consistent with the results of expert reviews of teaching videos. The majority of PDs (86%) received video ratings that documented active engagement of students and implementation of learner-centered classrooms. Despite practice of higher-level cognition in class sessions, the items used by the PDs on their assessments of learning focused on lower-level cognitive skills. We attributed the high success of the FIRST IV program to our focus on inexperienced teachers, an iterative process of teaching practice and reflection, and development of and teaching a full course.
Gao, Ming, T.C. Thomson, T.M. Creed*, S. Tu, S.N. Loganathan, C.A. Jackson, P. McCluskey*, Y. Lin, S.E. Collier, Z. Weng, P. Lasko, M.D. Ohi, A.L. Arkov, 2015. Glycolytic enzymes localize to ribonucleoprotein granules in Drosophila germ cells, bind Tudor and protect from transposable elements, EMBO Reports 16: 379-386.
Abstract. Germ cells give rise to all cell lineages in the next-generation and are responsible for the continuity of life. In a variety of organisms, germ cells and stem cells contain large ribonucleoprotein granules. Although these particles were discovered more than 100 years ago, their assembly and functions are not well understood. Here we report that glycolytic enzymes are components of these granules in Drosophila germ cells and both their mRNAs and the enzymes themselves are enriched in germ cells. We show that these enzymes are specifically required for germ cell development and that they protect their genomes from transposable elements, providing the first link between metabolism and transposon silencing. We further demonstrate that in the granules, glycolytic enzymes associate with the evolutionarily conserved Tudor protein. Our biochemical and single-particle EM structural analyses of purified Tudor show a flexible molecule and suggest a mechanism for the recruitment of glycolytic enzymes to the granules. Our data indicate that germ cells, similarly to stem cells and tumor cells, might prefer to produce energy through the glycolytic pathway, thus linking a particular metabolism to pluripotency.
He, Kate. S., Bradley, B. A., Cord, A. F., Rocchini, D., Tuanmu, M.-N., Schmidtlein, S., Turner, W., Wegmann, M., Pettorelli, N. (2015), Will remote sensing shape the next generation of species distribution models?. Remote Sensing in Ecology and Conservation, 1: 4–18. doi: 10.1002/rse2.7
Abstract. Two prominent limitations of species distribution models (SDMs) are spatial biases in existing occurrence data and a lack of spatially explicit predictor variables to fully capture habitat characteristics of species. Can existing and emerging remote sensing technologies meet these challenges and improve future SDMs? We believe so. Novel products derived from multispectral and hyperspectral sensors, as well as future Light Detection and Ranging (LiDAR) and RADAR missions, may play a key role in improving model performance. In this perspective piece, we demonstrate how modern sensors onboard satellites, planes and unmanned aerial vehicles are revolutionizing the way we can detect and monitor both plant and animal species in terrestrial and aquatic ecosystems as well as allowing the emergence of novel predictor variables appropriate for species distribution modeling. We hope this interdisciplinary perspective will motivate ecologists, remote sensing experts and modelers to work together for developing a more refined SDM framework in the near future.
Macagno, Anna L.M., Oliver M. Beckers, Armin P. Moczek. 2015. Differentiation of ovarian development and the evolution of fecundity in rapidly diverging exotic beetle populations. Journal of Experimental Biology A: Ecological Genetics and Physiology (online) DOI: 10.1002/jez.1959
Abstract. Fecundity is a fundamental determinant of fitness, yet the proximate developmental and physiological mechanisms that enable its often rapid evolution in natural populations are poorly understood. Here, we investigated populations derived from two exotic ranges the dung beetle Onthophagus taurus established in the early 1970's. These populations are subject to drastically different levels of resource competition in the field and have diverged dramatically in female fecundity. Specifically, Western Australian O. taurus experience high levels of resource competition, and exhibit greatly elevated reproductive output compared to beetles from the Eastern US, where resource competition is minimal and female fecundity is low. We compared patterns of ovarian maturation, relative investment into and timing of egg production, and potential trade-offs between ovarian investment and the duration of larval development and adult body size between populations representative of both exotic ranges. We found that the rapid divergence in fecundity between exotic populations is associated with striking differences in several aspects of ovarian development: (1) Western Australian females exhibit accelerated ovarian development, (2) produce more eggs, (3) bigger eggs, and (4) start laying eggs earlier compared to their Eastern US counterparts. At the same time, divergence in ovarian maturation patterns occurred alongside changes in (5) larval developmental time, and (6) adult body size and (7) mass. Western Australian females take longer to complete larval development and, surprisingly, emerge into smaller yet heavier adults than size-matched Eastern US females. We discuss our results in the context of the evolutionary developmental biology of fecundity in exotic populations.
Moore, Michael P.*, Tobias Landberg, and Howard H. Whiteman. 2015. Maternal investment mediates offspring life history variation with context-dependent fitness consequences. Ecology 96:2499-2509.
Abstract. Maternal effects, such as per capita maternal investment, often interact with environmental conditions to strongly affect traits expressed early in ontogeny. However, their impact on adult life history traits and fitness components is relatively unknown. Theory predicts that lower per capita maternal investment will have strong fitness costs when the offspring develop in unfavorable conditions, yet few studies have experimentally manipulated per capita maternal investment and followed offspring through adulthood. We used a surgical embryonic yolk removal technique to investigate how per capita maternal investment interacted with an important ecological factor, larval density, to mediate offspring life history traits through reproductive maturity in an amphibian, Ambystoma talpoideum. We predicted that increased larval density would reinforce the life history variation induced by differences in per capita investment (i.e., Controls vs. Reduced Yolk), with Reduced larvae ultimately expressing traits associated with lower fitness than Controls when raised at high densities. We found that Reduced individuals were initially smaller and more developed, caught up in size to Controls within the first month of the larval stage, but were smaller at the end of the larval stage in low densities. Reduced individuals also were more likely to undergo metamorphosis at high densities and mature females invested in more eggs for their body sizes than Controls. Together, our results do not support our hypothesis, but instead indicate that Reduced individuals express traits associated with higher fitness when they develop in high-density environments, but lower fitness in low-density environments. The observed life history and fitness patterns are consistent with the ‘‘maternal match’’ hypothesis, which predicts that when the maternal environment (e.g., high density) results in phenotypic variation that is transmitted to the offspring (e.g., reduced per capita yolk investment), and offspring face that same environment (e.g., high larval density), the fitness of both mother and offspring is maximized.
Ruegg. J., Dodds, W. K., Daniels, M. D., Sheehan, K. R., Baker, C. L., Bowden, W. B., Farrell, K. J., Flinn, M., Harms, T. K., Jones, J. J., Koenig, L. E. (2015). BASEFLOW PATTERNS OF GEOMORPHIC HETEROGENEITY IN STREAM NETWORKS ACROSS BIOMES. Landscape Ecology. Springer, 31:119-136. DOI: DOI 10.1007/s10980-015-0289-y
Abstract. Context Spatial scaling of ecological processes is facilitated by quantifying underlying habitat attributes. Physical and ecological patterns are often measured at disparate spatial scales limiting our ability to quantify ecological processes at broader spatial scales using physical attributes. Objective We characterized variation of physical stream attributes during periods of high biological activity (i.e., baseflow) to match physical and ecological measurements and to identify the spatial scales exhibiting and predicting heterogeneity. Methods We measured canopy cover, wetted width, water depth, and sediment size along transects of 1st–5th order reaches in five stream networks located in biomes from tropical forest to arctic tundra. We used hierarchical analysis of variance with three nested scales (watersheds, stream orders, reaches) to identify scales exhibiting significant heterogeneity in attributes and regression analyses to characterize gradients within and across stream networks. Results Heterogeneity was evident at one or multiple spatial scales: canopy cover and water depth varied significantly at all three spatial scales while wetted width varied at two scales (stream order and reach) and sediment size remained largely unexplained. Similarly, prediction by drainage area depended on the attribute considered: depending on the watershed, increases in wetted width and water depth with drainage area were best fit with a linear, logarithmic, or power function. Variation in sediment size was independent of drainage area. Conclusions The scaling of ecologically relevant baseflow physical characteristics will require study beyond the traditional bankfull geomorphology since predictions of baseflow physical attributes by drainage area were not always best explained by geomorphic power laws.
Rocchini, D., Andreo, V., Förster, M., Garzon-Lopez, C.X., Gutierrez, A.P., Gillespie ,T.W., Hauffe, H.C., He, K.S., Kleinschmit, B., Mairota, P., Marcantonio, M., Metz, M., Nagendra, H., Pareeth, S., Ponti, L., Ricotta, C., Rizzoli, A., Schaab, G., Zebisch, M., Zorer, R., Neteler, M. 2015. Potential of remote sensing to predict species invasions - a modeling perspective. Progress in Physical Geography 39: 283-309.
Abstract. Understanding the causes and effects of species invasions is a priority in ecology and conservation biology. One of the crucial steps in evaluating the impact of invasive species is to map changes in their actual and potential distribution and relative abundance across a wide region over an appropriate time span. While direct and indirect remote sensing approaches have long been used to assess the invasion of plant species, the distribution of invasive animals is mainly based on indirect methods that rely on environmental proxies of conditions suitable for colonization by a particular species. The aim of this article is to review recent efforts in the predictive modelling of the spread of both plant and animal invasive species using remote sensing, and to stimulate debate on the potential use of remote sensing in biological invasion monitoring and forecasting. Specifically, the challenges and drawbacks of remote sensing techniques are discussed in relation to: i) developing species distribution models, and ii) studying life cycle changes and phenological variations. Finally, the paper addresses the open challenges and pitfalls of remote sensing for biological invasion studies including sensor characteristics, upscaling and downscaling in species distribution models, and uncertainty of results.
Wilson, N.*, Flinn, M., West, B.*, Hereford, J. (2015). Identification of sound-producing Hydrophilid beetles in recordings using digital signal processing. The Coleopterists Bulletin (vol. 69, 2 ed., pp. 305-315).
Abstract. Hydrophone recordings from three aquatic beetle species within the family Hydrophilidae, Berosus pantherinus (LeConte), Tropisternus blatchleyi (d’Orchymont), and Tropisternus collaris (F.), were used to create an automated identification program. The identification program was designed using digital signal processing techniques and is capable of identifying which species is present from hydrophone recordings alone. Using features based on the frequency content of each beetle call and background sounds in reference recordings, half-second segments of audio recordings were classified as a specific beetle species call, a general beetle distress call, or as noise. Classification accuracy ranged from 87.5% for reference recordings. Training calls had accuracies of 98% and above between beetle species and noise. The majority of beetle recordings in a mesocosm environment were classified correctly. Often, T. blatchleyi was false-positively identified in recordings with non-beetle background noises, such as frogs or traffic, suggesting similar active frequencies in the T. blatchelyi features and these noises. The use of digital signal processing to identify aquatic invertebrates by sound is a new technique that has potential uses in taxonomy, surveys, and long-term biomonitoring of aquatic systems by providing a hands-free method of detection, and eventually identification, in the field.
Zhang Z, Pan X, Zhang Z, He K.S, Li B. 2015. Specialist Insect Herbivore and Light Availability Do Not Interact in the Evolution of an Invasive Plant. PLoS ONE 10(9) e0139234.doi:10.1371/journal.pone.0139234
Abstract. Release from specialist insect herbivores may allow invasive plants to evolve traits associated with decreased resistance and increased competitive ability. Given that there may be genetic trade-off between resistance and tolerance, invasive plants could also become more tolerant to herbivores. Although it is widely acknowledged that light availability affects tolerance to herbivores, little information is available for whether the effect of light availability on tolerance differ between the introduced and native populations. We conducted a com-mon garden experiment in the introduced range of Alternanthera philoxeroides using ten invasive US and ten native Argentinean populations at two levels of light availability and in the presence or absence of a specialist stem-boring insect Agasicles hygrophila. Plant bio-mass (total and storage root biomass), two allocation traits (root/shoot ratio and branch intensity, branches biomass/main stem biomass) and two functional traits (specific stem length and specific leaf area), which are potentially associated with herbivore resistance and light capture, were measured. Overall, we found that A .philoxeroides from introduced ranges had comparable biomass and tolerance to specialist herbivores, lower branch intensity, lower specific stem length and specific leaf area. Moreover, introduced populations displayed higher shade tolerance of storage root biomass and lower plastic response to shading in specific stem length. Finally, light availability had no significant effect on evolution of tolerance to specialist herbivores of A. philoxeroides. Our results suggest that post-introduction evolution might have occurred in A. philoxeroides. While light availability did not influence the evolution of tolerance to specialist herbivores, increased shade tolerance and release from specialist insects might have contributed to the successful invasion of A. philoxeroides.