Open Access. Powered by Scholars. Published by Universities.®

Systems Biology Commons

Open Access. Powered by Scholars. Published by Universities.®

Articles 151 - 158 of 158

Full-Text Articles in Systems Biology

Regional Variation In Recruitment Of Hemlock Seedlings And Saplings In The Upper Great Lakes, Usa, Thomas P. Rooney, Ronald J. Mccormick, Stephen L. Solheim, Donald M. Waller Aug 2000

Regional Variation In Recruitment Of Hemlock Seedlings And Saplings In The Upper Great Lakes, Usa, Thomas P. Rooney, Ronald J. Mccormick, Stephen L. Solheim, Donald M. Waller

Biological Sciences Faculty Publications

Mature eastern hemlock–northern hardwood forest cover decreased drastically in the upper Midwest following European settlement and has yet to rebound substantially. Previous studies show that stands retaining substantial hemlock canopy coverage have low hemlock seedling and sapling densities. Results from various geographically restricted studies suggest several possible mechanisms that could cause low seedling or sapling density. We examined the relative importance of these proposed mechanisms in the Southern Superior Uplands Section of the Laurentian Forest Province. We surveyed 294- m2 plots in 100 hemlock stands in northern Wisconsin and western upper Michigan to assess how these proposed mechanisms affect the …


Periphyton Production On Wood And Sediment: Substratum-Specific Response To Laboratory And Whole-Lake Nutrient Manipulations, Yvonne Vadeboncoeur, David M. Lodge Mar 2000

Periphyton Production On Wood And Sediment: Substratum-Specific Response To Laboratory And Whole-Lake Nutrient Manipulations, Yvonne Vadeboncoeur, David M. Lodge

Biological Sciences Faculty Publications

Substratum heterogeneity is a large source of variability in periphyton production, but the influence of substratum on periphyton response to experimental manipulations is rarely measured. Using laboratory and whole-lake experiments, we compared area-specific primary production of periphyton on wood (epixylon) and sediment (epipelon), and tested whether periphyton on the 2 substrata responded differently to water-column fertilization. In the laboratory, natural periphyton assemblages on wood or sediment were exposed to 1 of 6 treatments in a fully factorial (light [250, 70, or 10 μmol m−2 s−1] × nutrient [control or + N and P]) experiment. We measured 14 …


Exploring Cost Constraints On Stem Elongation In Plants Using Phenotypic Manipulation, Don Cipollini, Jack C. Schultz Feb 1999

Exploring Cost Constraints On Stem Elongation In Plants Using Phenotypic Manipulation, Don Cipollini, Jack C. Schultz

Biological Sciences Faculty Publications

Negative associations between individual life‐history traits of an organism are referred to as life‐history trade‐offs (Stearns 1992; Zera et al. 1998). The existence of costly trade‐offs is thought to have favored the evolution of phenotypic plasticity as a mechanism through which organisms can account for environmental heterogeneity while modulating costs and benefits incurred by fixed allocation to competing functions (Bradshaw 1965; Stearns 1992; Sultan 1995; Dudley and Schmitt 1996; Pigliucci 1996). In plants, the ability to modify stem elongation in response to environmental cues appears to be a classic form of adaptive phenotypic plasticity (Sultan 1995; Gedroc et al. 1996). …


Top-Down Cascade From A Bitrophic Predator In An Old-Field Community, Matthew D. Moran, Thomas P. Rooney, L. E. Hurd Jan 1996

Top-Down Cascade From A Bitrophic Predator In An Old-Field Community, Matthew D. Moran, Thomas P. Rooney, L. E. Hurd

Biological Sciences Faculty Publications

We tested the hypothesis that a bitrophic (third and fourth level) arthropod predator can exert a cascading, top-down influence on other arthropods and plants in an early successional old field. First-stadium mantids, Tenodera sinensis, were added to replicated open-field plots in numbers corresponding to naturally occurring egg hatch density and allowed to remain for ≈ 2 mo. Sticky-trap dispersal barriers around both control and mantid-addition plots allowed us to monitor emigration of arthropods continuously during the experiment. Biomass of herbivores, carnivores, and plants, and abundances of arthropod taxa within plots were determined at the beginning, middle, and end of …


Benthic-Pelagic Links: Responses Of Benthos To Water-Column Nutrient Enrichment, S. C. Blumenshine, Yvonne Vadeboncoeur, D. M. Lodge, K. L. Cottingham, S. E. Knight Sep 1994

Benthic-Pelagic Links: Responses Of Benthos To Water-Column Nutrient Enrichment, S. C. Blumenshine, Yvonne Vadeboncoeur, D. M. Lodge, K. L. Cottingham, S. E. Knight

Biological Sciences Faculty Publications

Although the responses of pelagic algae and invertebrates to gradients of nutrient enrichment are well known, less is known about the responses of benthos to such gradients or how benthic and pelagic responses may interact. We performed a 9-wk experiment in 2000-L mesocosms in the field to test for the effect of water-column nutrient enrichment on phytoplankton, algae on sediments (epipelon) and hard surfaces (plastic strips), as well as pelagic and benthic primary consumers. The experimental design consisted of 4 nutrient enrichment rates (0, 0.5, 1.0 and 2.0 μg P L-1 d-1, together with N to yield …


Longitudinal Dynamics Of Seston Concentration And Composition In A Lake Outlet Stream, Yvonne Vadeboncoeur Jun 1994

Longitudinal Dynamics Of Seston Concentration And Composition In A Lake Outlet Stream, Yvonne Vadeboncoeur

Biological Sciences Faculty Publications

Concentrations of suspended particulate organic carbon (POC), dissolved organic carbon, bacteria, and chlorophyll a were measured in a lake outlet in western Montana, USA. Seven sites within the first 3 km downstream from the lake were sampled over 14 mo. Downstream change in concentration of each variable was tested for fit to a power function (C=aDb). Downstream changes in POC, bacteria, and chlorophyll a, sometimes fit a power function, and the value of the exponent b was positively correlated with discharge. At low discharge, a downstream decline in lake algae was accompanied by an increase in stream algae. …


Micronuclear Genome Organization In Euplotes Crassus: A Transposonlike Element Is Removed During Macronuclear Development, Scott Everet Baird, Gina M. Fino, Susan L. Tausta, Lawrence A. Klobutcher Sep 1989

Micronuclear Genome Organization In Euplotes Crassus: A Transposonlike Element Is Removed During Macronuclear Development, Scott Everet Baird, Gina M. Fino, Susan L. Tausta, Lawrence A. Klobutcher

Biological Sciences Faculty Publications

After mating, hypotrichous ciliated protozoa transform a set of their micronuclear chromosomes into thousands of short, linear DNA molecules that form the macronuclear genome. To examine micronuclear genome organization in the hypotrich Euplotes crassus, we have analyzed two cloned segments of micronuclear DNA as well as the macronuclear DNA molecules that are derived from them. E. crassus was found to display a number of features characteristic of other hypotrich genomes, including (i) clustering and close spacing of the precursors of macronuclear DNA molecules, (ii) the frequent occurrence of internal eliminated sequences within macronuclear precursors, (iii) overlapping macronuclear precursors, (iv) lack …


Characterization Of Chromosome Fragmentation In Two Protozoans And Identification Of A Candidate Fragmentation Sequence In Euplotes Crassus, Scott Everet Baird, Lawrence A. Klobutcher Jan 1989

Characterization Of Chromosome Fragmentation In Two Protozoans And Identification Of A Candidate Fragmentation Sequence In Euplotes Crassus, Scott Everet Baird, Lawrence A. Klobutcher

Biological Sciences Faculty Publications

Following the sexual cycle, hypotrichous ciliated protozoans fragment a set of their micronuclear chromosomes to generate the thousands of short, linear DNA molecules present in the transcriptionally active macronucleus. We have used a hybrid selection procedure to examine macronuclear DNA molecules for subtelomeric length heterogeneity to determine whether chromosome fragmentation occurs at unique or multiple sites. The results suggest that multiple, but closely spaced, chromosome fragmentation sites are used by Oxytricha nova. In contrast, Euplotes crassus uses unique chromosome fragmentation sites in a reproducible manner to generate the ends of macronuclear DNA molecules. Additional studies compared DNA sequences in …