Chapter 11 eco case studies (2).docx

4 Pages
51 Views

Department
Biological Sciences
Course Code
BIOC50H3
Professor
Marc Cadotte

This preview shows page 1. Sign up to view the full 4 pages of the document.
Description
BIOB50: Ecology – Marc Cadotte Chapter 11: Competition - Case Studies Tilman = laboratory experiment: - Examined competition of silica (SiO ) in 2resh water diatoms = single-celled algae - Diatoms use silica to construct cell walls - Tilman grew 2 diatom species = Synedra ulna and Asterionella formosa - Grew S. ulna and A. Formosa both separately and then in completion w/ each other = measures how diatom pop densities and silica concentrations in water changed over time - When grown alone, each species reduced resource = silica to a low, constant concentration – each species reached stable pop size - S. ulna had a lower stable pop size than A. formosa and also reduced silica levels lower than A. formosa - When 2 species competed w/ each other, S. ulna drove A. Formosa to extinction b/c it reduced silica levels so low that A. formosa couldn’t survive Scott Wilson & David Tilman = transplant experiment: - Used Schizachyrium scoparium = perennial grass species native to Minnesota - 5x5 plats of natural vegetation growing in low-nitrogen, sandy soils - For 3 years, treated half of the plots w/ high-nitrogen fertilizer/year - After 3 years, the planted S. scoparium in the plots – some to high-nitrogen and some to low-nitrogen plots - Had 3 treatments: o 1) w/ neighbours left intact o 2) w/ neighbour roots left intact but neighbour’s shoots tied back o 3) w/ neighbour roots and shoots both removed - treatment 1 = had both below-ground and above-ground competition (nitrogen in soil and light from sun) - treatment 3 = no competition - treatment 2 = only below-ground competition - Wilson and Tilman found that while the total competition (sum of below-ground and above-ground competition) didn’t differ between low and high nitrogen plots, below-ground competition was more intense in low-nitrogen plots - *intensity of competition can increase when the resource being competed for becomes scarce* Schoener - Examined results of 164 published studies on competition and found that of 390 species studied, 76% showed effects of competition under some circumstances, and 57% showed effects of competition under all circumstances tested Connell - Examined results of 72 studies and found that competition was important for 50% of 215 species Gurevitch BIOB50: Ecology – Marc Cadotte - Analyzed magnitude of competitive effects found for 93 species in 46 studies published 1980-89 - Showed that competition had significant (and variable) effects on wide range of organisms (carnivores, herbivores, producers/plants) Acorn Barnacle = interference competition - As it grows, acorn barnacle = Semibalanus balanoides often crushes/smothers nearby individuals of another barnacle species = Chthamalus stellatus - Therefore, Semibalanus directly prevents Chthamalus from living in most portions of rocky intertidal zone Spotted knapweed = allelopathy - Aka Centaurea maculosa = native to Eurasia, accidently introduced to North America in 1800s - A contaminant in crop seeds – rapidly spread across US and Canada causing ~42 million $ annual losses - Has ability to spread so rapidly because: o Cattle avoid eating it, therefore more likely to survive than native grasses that cattle do eat o Spotted knapweed releases toxin = catechin into surrounding soils  Catechin reduces germination and growth of native grasses  Exposure to catechin activates 100s of genes in native grasses that compete w/ spotted knapweed – some genes cause root cells of grasses to ‘commit suicide’ which kills the root and allows spotter knapweed to grow = potential competitive advantage Brown & Davidson - Experiments on rodents and ants = test whether competition also occurs between groups of distantly- related species o Thought the 2 species might compete because they both eat the seeds of desert plants and the sizes of the seeds they prefer overlap a lot - In Tucson, Arizona – used 3 years and 4 treatments: o 1) Plots where ¼-inch wire mesh fence excluded seed-eating rodents and rodents w/in the fence were removed by trapping o 2) plots where seed-eating ants were excluded by insecticides o 3) plats where both rodents and ants were excluded by fencing, trapping, and insecticides o 4) plot where rodents and ants were left undisturbed = control group - *found that ants and rodents compete for food* - # of ant colonies increased by 71% in plots where rodents were excluded (plot 1) - # of rodents increased by 18% and 24% in biomass in plots where ants were excluded (plot 2) - Plot 3 = both ants and rodents excluded – seed availability increased by 450% compared to all other plots o Plots 1, 2, and 4 all had somewhat same seed densities - Under natural conditions, each group ex
More Less
Unlock Document

Only page 1 are available for preview. Some parts have been intentionally blurred.

Unlock Document
You're Reading a Preview

Unlock to view full version

Unlock Document

Log In


OR

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


OR

By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.


Submit