Temperature alone does not explain patterns of Batrachochytrium dendrobatidis infections in the green frog Lithobates clamitans.
Korfel, CA, Hetherington, TE. Diseases of Aquatic Organisms. 2014. 109(3):177-185. DOI: 10.3354/dao02749
Batrachochytrium dendrobatidis (Bd) is an invasive, waterborne fungal pathogen that has caused significant declines and extinctions of amphibian species worldwide. Temperature is a major factor impacting the growth and spread of Bd, but little is known regarding the associated patterns in natural habitats. This study analyzed the temperature-associated trends, as correlated with season and microhabitat, of Bd prevalence and infection intensity in green frogs Lithobates clamitans in a temperate environment (central Ohio, USA). Bd was widely distributed at the study sites and found in more than half of the frogs sampled. Bd prevalence was significantly higher in the spring and in forested stream habitats compared to emergent wetland habitats. In contrast, Bd infection intensities tended to be higher in summer. Given the known temperature sensitivity of Bd as demonstrated in laboratory studies, these findings suggest that temperature may be an important factor determining Bd prevalence in green frogs at our study sites, but that factors other than temperature are more important in determining infection intensity. Our findings suggest that future monitoring of Bd among vulnerable species in regions experiencing seasonal temperature variation should study a range of environmental variables to better understand the dynamic relationship between Bd and its amphibian hosts.
Insights from the DNA databases: Approaches to the phylogenetic structure of Acanthamoeba
Paul A. Fuerst. 2014. Experimental Parasitology. DOI: 10.1016/j.exppara.2014.06.020
Species of Acanthamoeba have been traditionally described using morphology (primarily cyst structure), or cytology of nuclear division (used by Pussard and Pons, 1977). Twenty-plus putative species were proposed based on such criteria. Morphology, however, is often plastic, dependent upon culture conditions. DNA sequences of the nuclear small subunit (18S) rRNA that can be used for the study of the phylogeny of Acanthamoeba have increased from a single sequence in 1986 to more than 1800 in 2013. Some of the patterns of the sequence data for Acanthamoeba are reviewed, and some of the insights that this data illuminates are illustrated. In particular, the data suggest the existence of 20 or more genotypic types, a number not dissimilar to the number of named species of Acanthamoeba. However, molecular studies make clear that the relationship between phylogenetic relatedness and species names as we know them for Acanthamoeba is tenuous at best.
Identification of a putative antifreeze protein gene that is highly expressed during preparation for winter in the sunn pest, Eurygaster maura
Nurper Guz , Umut Toprak, Asli Dageri, M. Oktay Gurkan, David L. Denlinger. Journal of Insect Physiology. Volume 68, September 2014, Pages 30–35. DOI: 10.1016/j.jinsphys.2014.06.021
A cDNA library generated from the fat body of field-collected, diapausing adults of the sunn pest, Eurygaster maura revealed the presence of a transcript that encodes a protein that shares the distinct physiochemical and structural features of an insect antifreeze protein. The transcript, which is most abundant in the midgut, accumulates in adults as they leave the fields in late summer and migrate to surrounding mountainous areas to overwinter. Transcript abundance again declines when adults return to the fields the following spring. This winter pattern of abundance suggests that this protein may be critical for winter survival in the cold regions where the bug enters its obligatory diapause.
Sequence-Related Amplified Polymorphism (SRAP) Markers: A Potential Resource for Studies in Plant Molecular Biology
Daniel W. H. Robarts and Andrea D. Wolfe. Applications in Plant Sciences 2(7):1400017. 2014. doi: http://dx.doi.org/10.3732/apps.1400017
In the past few decades, many investigations in the field of plant biology have employed selectively neutral, multilocus, dominant markers such as inter-simple sequence repeat (ISSR), random-amplified polymorphic DNA (RAPD), and amplified fragment length polymorphism (AFLP) to address hypotheses at lower taxonomic levels. More recently, sequence-related amplified polymorphism (SRAP) markers have been developed, which are used to amplify coding regions of DNA with primers targeting open reading frames. These markers have proven to be robust and highly variable, on par with AFLP, and are attained through a significantly less technically demanding process. SRAP markers have been used primarily for agronomic and horticultural purposes, developing quantitative trait loci in advanced hybrids and assessing genetic diversity of large germplasm collections. Here, we suggest that SRAP markers should be employed for research addressing hypotheses in plant systematics, biogeography, conservation, ecology, and beyond. We provide an overview of the SRAP literature to date, review descriptive statistics of SRAP markers in a subset of 171 publications, and present relevant case studies to demonstrate the applicability of SRAP markers to the diverse field of plant biology. Results of these selected works indicate that SRAP markers have the potential to enhance the current suite of molecular tools in a diversity of fields by providing an easy-to-use. highly variable marker with inherent biological significance.
Cellular metabolic rates from primary dermal fibroblast cells isolated from birds of different body masses
Ana Gabriela Jimenez, Joseph B. Williams. Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
Volume 176, October 2014, Pages 41–48. DOI: 10.1016/j.cbpa.2014.07.009.
The rate of metabolism is the speed at which organisms use energy, an integration of energy transformations within the body; it governs biological processes that influence rates of growth and reproduction. Progress at understanding functional linkages between whole organism metabolic rate and underlying mechanisms that influence its magnitude has been slow despite the central role this issue plays in evolutionary and physiological ecology. Previous studies that have attempted to relate how cellular processes translate into whole-organism physiology have done so over a range of body masses of subjects. However, the data still remains controversial when observing metabolic rates at the cellular level. To bridge the gap between these ideas, we examined cellular metabolic rate of primary dermal fibroblasts isolated from 49 species of birds representing a 32,000-fold range in body masses to test the hypothesis that metabolic rate of cultured cells scales with body size. We used a Seahorse XF-96 Extracellular flux analyzer to measure cellular respiration in fibroblasts. Additionally, we measured fibroblast size and mitochondrial content. We found no significant correlation between cellular metabolic rate, cell size, or mitochondrial content and body mass. Additionally, there was a significant relationship between cellular basal metabolic rate and proton leak in these cells. We conclude that metabolic rate of cells isolated in culture does not scale with body mass, but cellular metabolic rate is correlated to growth rate in birds.
Climate refugia: joint inference from fossil records, species distribution models and phylogeography
Gavin, D. G., Fitzpatrick, M. C., Gugger, P. F., Heath, K. D., Rodríguez-Sánchez, F., Dobrowski, S. Z., Hampe, A., Hu, F. S., Ashcroft, M. B., Bartlein, P. J., Blois, J. L., Carstens, B. C., Davis, E. B., de Lafontaine, G., Edwards, M. E., Fernandez, M., Henne, P. D., Herring, E. M., Holden, Z. A., Kong, W.-s., Liu, J., Magri, D., Matzke, N. J., McGlone, M. S., Saltré, F., Stigall, A. L., Tsai, Y.-H. E. and Williams, J. W. Climate refugia: joint inference from fossil records, species distribution models and phylogeography. New Phytologist. 2014. doi: 10.1111/nph.12929
Climate refugia, locations where taxa survive periods of regionally adverse climate, are thought to be critical for maintaining biodiversity through the glacial–interglacial climate changes of the Quaternary. A critical research need is to better integrate and reconcile the three major lines of evidence used to infer the existence of past refugia – fossil records, species distribution models and phylogeographic surveys – in order to characterize the complex spatiotemporal trajectories of species and populations in and out of refugia. Here we review the complementary strengths, limitations and new advances for these three approaches. We provide case studies to illustrate their combined application, and point the way towards new opportunities for synthesizing these disparate lines of evidence. Case studies with European beech, Qinghai spruce and Douglas-fir illustrate how the combination of these three approaches successfully resolves complex species histories not attainable from any one approach. Promising new statistical techniques can capitalize on the strengths of each method and provide a robust quantitative reconstruction of species history. Studying past refugia can help identify contemporary refugia and clarify their conservation significance, in particular by elucidating the fine-scale processes and the particular geographic locations that buffer species against rapidly changing climate.
Changes in soil nitrogen cycling in a northern temperate forest ecosystem during succession
L. E. Nave, J. P. Sparks, J. Le Moine, B. S. Hardiman, K. J. Nadelhoffer, J. M. Tallant, C. S. Vogel, B. D. Strahm, P. S. Curtis. Biogeochemistry. 2014.
Nitrogen (N) transformations in forest soils are fundamentally important to plant and microbial N nutrition and the N balance of forest ecosystems, but changes in the patterns and rates of N transformations during forest succession are poorly understood. In order to better understand how soil N cycling changes during ecosystem succession, we analyzed four years of soil N cycling measurements in a 90-year-old secondary forest undergoing dieback of early-successional, dominant canopy trees. We expected that tree mortality would decrease root biomass, leading to increased soil NH4 + availability, and that these changes would prompt fundamental shifts in the N cycle such as the initiation of significant nitrification and increased cycling of oxidized N compounds in gas phase and soil solution. As expected, indices of soil NH4 + and NO3 − availability increased with successional stage (defined as the proportion of dead trees), and were negatively correlated with the amount of fine root biomass. However, the standing amount of fine root biomass was not affected by tree mortality; increased soil NH4 + and NO3 − availability therefore more likely resulted from successional increases in N-mineralization than decreases in root N uptake. Nitrification (as indicated by NO efflux as a proxy) increased due to elevated substrate (NH4 +) availability, and the soil solution NO3 − concentration increased as a result. Soil N2O efflux was not affected by succession, nor was it related to other N cycling parameters. Collectively, these results indicate that recent successional advancement has accelerated soil N cycling and shifted the N economy of this ecosystem towards greater importance of NO3 −.
The prevalence of rickettsial and ehrlichial organisms in Amblyomma americanum ticks collected from Ohio and surrounding areas between 2000 and 2010
Robert R. Fitak, Daryl J. Kelly, Mary K. Daniels, Ju Jiang, Allen L. Richards, Paul A. Fuerst. Ticks and Tick-borne Diseases. 2014. DOI: 10.1016/j.ttbdis.2014.06.005
The lone star tick, Amblyomma americanum, feeds upon a variety of hosts and is a known vector of several human pathogens. In Ohio, populations of A. americanum have been expanding their range and increasing in abundance and distribution, thereby elevating the public health concerns regarding bites from this species. We used a set of PCR assays to detect the presence of ehrlichial and rickettsial species in A. americanum ticks submitted to the Ohio Department of Health Zoonotic Disease Program over an 11-year period (2000-2010). We did not detect the presence of known pathogens Rickettsia rickettsii or Ehrlichia chaffeensis, but we did identify the presence of two other bacterial species: ‘Candidatus Rickettsia amblyommii’, and Ehrlichia sp. Panola Mountain. ‘Candidatus R. amblyommii’ was the most common species identified (30.2%), whereas the ehrlichiae was quite rare (0.6%). With growing evidence implicating both ‘Candidatus Rickettsia amblyommii’ and Ehrlichia sp. Panola Mountain in mild to moderate human disease, our results support the importance of continued monitoring of A. americanum ticks for the presence of potential pathogens.
Genetic analysis among environmental strains of Balamuthia mandrillaris recovered from an artificial lagoon and from soil in Sonora, Mexico
Luis Fernando Lares-Jiménez, Gregory C. Booton, Fernando Lares-Villa, Carlos Arturo Velázquez-Contreras, Paul A. Fuerst. Experimental Parasitology. 2014. DOI: 10.1016/j.exppara.2014.07.007
Since the first report of Balamuthia mandrillaris as a causative agent of granulomatous amoebic encephalitis in humans, the environmental niche of this amoeba was assumed to be restricted to soil and dust. A single isolation from water was recently made independently by us from Northern Mexico. Now we report the isolation of 8 new strains of B. mandrillaris from Mexico. This continues the pattern of an excess of isolates from North America, compared to other parts of the world. All of the new isolates are environmental isolates, 7 from water samples and one from soil. The identity of each isolate was confirmed by PCR and by examining the sequences of the mitochondrial 16S-like rRNA gene. Success in amplification was determined using comparisons of amplifications of DNA from the strain CDC: V039 and the water strain (ITSON-BM1) as positive controls. The DNA sequences of the new isolates were compared to older strains from clinical cases using phylogenetic analysis, showing very high sequence similarity. The similarity among the new isolates and with previous clinical and environmental isolates of B. mandrillaris was also examined using biochemical and immunological studies. High homogeneity of total protein products, and similarity in antigenic moiety among the eight new isolates and two controls was found. Taken together, the molecular and biochemical studies indicate very low levels of genetic variation within B. mandrillaris.
Tutor choice and imitation accuracy during song learning in a wild population of the Puget Sound white-crowned sparrow
Douglas A. Nelson, Angelika Poesel. Behavioral Ecology and Sociobiology. August 2014
Songbirds learn to sing by modeling their songs on the songs of other males through a process of social learning. Models of social learning predict that animals should be selective in what and when they learn. In this study, we asked whether young males in a wild population of the Puget Sound white-crowned sparrow, Zonotrichia leucophrys pugetensis, were selective in their choice of tutor models and what factors influenced how accurately they imitated tutors’ songs. We first examined two strategies for tutor choice: whether pupils have a conformity bias and/or a preference for high-quality tutors. In keeping with a conformity bias, tutors that sang song types that were relatively common within a radius of about 500 m of their territory were more likely to be imitated than were tutors that sang rarer song types. Most potential tutors were not imitated by pupils. Aspects of tutor quality, such as age, pairing status, and survival to the next year had no effect on whether a tutor’s song was imitated. Secondly, we tested whether pupil repertoire size, pupil quality, and local abundance of tutor models affected the accuracy of song imitations. We found a trade-off between repertoire size and tutor imitation accuracy with males that sang two or more song types developing significantly poorer imitations than males that sang one type. We discuss possible functions of a conformity learning strategy and factors that could produce a trade-off between imitation accuracy and repertoire size.