left: USGS/photo by John Felis
Novel molecular approach demonstrates that turbid river plumes reduce predation mortality on larval fish
Lucia B. Carreon-Martinez, Kyle W. Wellband, Timothy B. Johnson, Stuart A. Ludsin and Daniel D. Heath. 2014. Molecular Ecology 23.21: 5366–5377. DOI: 10.1111/mec.12927
Turbidity associated with river plumes is known to affect the search ability of visual predators and thus can drive ‘top-down’ impacts on prey populations in complex ecosystems; however, traditional quantification of predator–prey relationships (i.e. stomach content analysis) often fails with larval fish due to rapid digestion rates. Herein, we use novel molecular genetic methods to quantify larval yellow perch (YP) in predator stomachs in western Lake Erie to test the hypothesis that turbidity drives variation in larval predation. We characterize predator stomach content DNA to first identify YP DNA (single nucleotide polymorphism) and then quantify larval YP predation (microsatellite allele counting) in two river plumes differing in turbidity. Our results showed elevated larval YP predation in the less turbid river plume, consistent with a top-down impact of turbidity on larval survival. Our analyses highlight novel ecological hypothesis testing using the power of innovative molecular genetic approaches.
Phylogenetic relationships and character evolution in Heuchera (Saxifragaceae) on the basis of multiple nuclear loci
Ryan A. Folk, John V. Freudenstein. Am. J. Bot. September 2014. doi: 10.3732/ajb.1400290
Premise of the study: The use of multiple genetic regions from the nuclear genome, including low-copy markers, has long been recognized as essential to robust phylogenetic construction, addressing gene tree incongruence, and allowing increased resolution to test current taxonomy and resolve basic hypotheses about character evolution, biogeography, and other organismal traits of interest to biologists. Heuchera, the largest genus of Saxifragaceae endemic to North America, has presented an unusually difficult case for systematists with limited sampling in previous molecular studies. We used morphological and multilocus molecular phylogenetic data to test the monophyly of Heuchera, better resolve hypotheses of relationships, and test hypotheses of character evolution, biogeography, and diversification rates.
Disproportionate Awards for Women in Disciplinary Societies Advances in Gender Research
Erin L. Cadwalader, Joan M. Herbers, Alice B. Popejoy. Series ISSN: 1529-2126, DOI: 10.1108/S1529-212620140000019011
Multiple factors contribute to the attrition of women from STEM (science, technology, engineering, and mathematics). A lack of recognition for scholarly contributions is one piece of the puzzle. Awards are crucial not only for recognizing achievement but also for making individuals feel that their contributions are valued. Additionally, awards for research are important for promotion to various levels within the academic hierarchy, including tenure and promotion. With a grant from the National Science Foundation (NSF), the Association for Women in Science (AWIS) has been examining the ways in which women are recognized for their achievements by professional disciplinary societies.
Phylogenetic Analysis and the Evolution of the 18S rRNA Gene Typing System of Acanthamoeba
Paul A. Fuerst, Gregory C. Booton, Monica Crary. 2014. Journal of Eukaryotic Microbiology. DOI: 10.1111/jeu.12186
Species of Acanthamoeba were first described using morphological characters including cyst structure and cytology of nuclear division. More than twenty nominal species were proposed using these methods. Morphology, especially cyst shape and size, has proven to be plastic and dependent upon culture conditions. The DNA sequence of the nuclear small subunit (18S) rRNA, the Rns gene, has become the most widely accepted method for rapid diagnosis and classification of Acanthamoeba. The Byers-Fuerst lab first proposed an Rns typing system in 1996. Subsequent refinements, with an increasing DNA database and analysis of diagnostic fragments within the gene, have become widely accepted by the Acanthamoeba research community. The development of the typing system, including its current state of implementation is illustrated by three cases: (i) the division between sequence types T13 and T16; (ii) the diversity within sequence supertype T2/T6, and (iii) verification of a new sequence type, designated T20. Molecular studies make clear the disconnection between phylogenetic relatedness and species names, as applied for the genus Acanthamoeba. Future reconciliation of genetic types with species names must become a priority, but the possible shortcomings of the use of a single gene when reconstructing the evolutionary history of the acanthamoebidae must also be resolved.
How Body Size and Food Availability Influence First-Winter Growth and Survival of a Stocked Piscivore
Jahn L. Kallis, Elizabeth A. Marschall. 2014. Transactions of the American Fisheries Society. 143.6:1434-1444. DOI: 10.1080/00028487.2014.945660
The first winter of life can play an important role in the success of age-0 fishes. First-winter survival is often size dependent, with larger fish exhibiting higher survival than small fish. Cohorts of age-0 saugeye female Walleye Sander vitreus × male Sauger S. canadensis stocked into Ohio reservoirs exhibit overwinter shifts toward larger body sizes; however, it is unclear whether growth, size-dependent mortality, or size-dependent emigration underlie this phenomenon. Saugeye may experience low prey availability during the overwinter period, making them especially vulnerable to starvation. Furthermore, survivors emerging from winter in poor energetic condition may experience reduced spring foraging success and growth. We used a combination of overwinter PIT tag studies in the field and overwinter outdoor pool experiments to understand these direct and indirect effects of winter on survival and size distributions of cohorts of saugeye. Using PIT tags to allow us to track growth of individuals in reservoirs, we found that saugeye of all sizes increased in length over winter, there was no evidence of size-dependent overwinter mortality, and rates of emigration out of the reservoir were greater for large saugeye than small saugeye. Thus, only growth rate, and not mortality or emigration biased toward small fish, can explain the observed overwinter shift in size distributions. In pool experiments, we found no direct effects of winter on survival, even in the complete absence of food, and no negative consequences of starvation over the winter on the ability of saugeye to resume feeding in the spring. Our results suggest that shifts in size distributions of first-year cohorts over winter are driven by growth rather than mortality. Neither direct effects of first winter on survival nor indirect effects mediated through effects of starvation on future foraging ability are important in recruitment success of saugeye in Ohio reservoirs.
Aquatic Ecology Laboratory
“Professional societies and gender equity in STEM.” Women in STEM Careers: International Perspectives on Increasing Workforce Participation, Advancement and Leadership
Erin Cadwalader, Joan M. Herbers, and Alice B. Popejoy. Ed.Diana Bilimoria, Ed.Linley Lord. Edward Elgar Publishing, 2014. 288 pages.
Google book available.
Rapid changes in cell physiology as a result of acute thermal stress House sparrows, Passer domesticus.
Ana G. Jimenez, , Joseph B. Williams. Journal of Thermal Biology. 46. 31–39. 2014. DOI: 10.1016/j.jtherbio.2014.10.001
Given that our climate is rapidly changing, Physiological Ecologists have the critical task of identifying characteristics of species that make them either resilient or susceptible to changes in their natural air temperature regime. Because climate change models suggest that heat events will become more common, and in some places more extreme, it is important to consider how extreme heat events might affect the physiology of a species. The implications of more frequent heat wave events for birds have only recently begun to be addressed, however, the impact of these events on the cellular physiology of a species is difficult to assess. We have developed a novel approach using dermal fibroblasts to explore how short-term thermal stress at the whole animal level might affect cellular rates of metabolism. House sparrows, Passer domesticus were separated into a “control group” and a “heat shocked” group, the latter acclimated to 43 °C for 24 h. We determined the plasticity of cellular thermal responses by assigning a “recovery group” that was heat shocked as above, but then returned to room temperature for 24 h. Primary dermal fibroblasts were grown from skin of all treatment groups and the pectoralis muscle was collected. We found that glycolysis (ECAR) and oxygen consumption rates (OCR), measured using a Seahorse XF 96 analyzer, were significantly higher in the fibroblasts from the heat shocked group of House sparrows compared with their control counterparts. Additionally, muscle fiber diameters decreased and, in turn, Na+–K+-ATPase maximal activity in the muscle significantly increased in heat shocked sparrows compared with birds in the control group. All of these physiological alterations due to short-term heat exposure were reversible within 24 h of recovery at room temperature. These results show that acute exposure to heat stress significantly alters the cellular physiology of sparrows, but that this species is plastic enough to recover from such a thermal insult within 24 h.
Part-Time on the Tenure Track
Herbers, Joan M. 2014. ASHE Higher Education Report. 40.5:1-161. DOI: 10.1002/aehe.20017