Competition and Invasion in a Microcosmic Setting

Transcription

1 University f Tennessee, Knxville Trace: Tennessee Research and Creative Exchange University f Tennessee Hnrs Thesis Prjects University f Tennessee Hnrs Prgram Cmpetitin and Invasin in a Micrcsmic Setting Austin Ryce Faulkner University f Tennessee - Knxville Fllw this and additinal wrks at: Recmmended Citatin Faulkner, Austin Ryce, "Cmpetitin and Invasin in a Micrcsmic Setting" (2004). University f Tennessee Hnrs Thesis Prjects. This is brught t yu fr free and pen access by the University f Tennessee Hnrs Prgram at Trace: Tennessee Research and Creative Exchange. It has been accepted fr inclusin in University f Tennessee Hnrs Thesis Prjects by an authrized administratr f Trace: Tennessee Research and Creative Exchange. Fr mre infrmatin, please cntact trace@utk.edu.

2 UNIVERSITY HONORS PROGR~'1 SENIOR PROJECT - APPROVAL Name: _c.a.u.u'd"s.li-bl..!.!'.f\'-l..-...!.h...!:::'\l.:u:",,:,\ k:-f\:...::u=-- Cllege: Arts j SC;~c..e Ei3 Depamnent: Faculty Mentr: _-=0:..:..(.:: !i"J~Q.:.:.k:...;...;...:.. W_e..~,-h.. ~ 1"' I have reviewed this cmpleted senir hnrs thesis with this student Jnd certify that it is a prje:;~ ~mmensur:lte whh hnrs level undergraduate research in this tield. SIgned: ~ --3./<.( F.,-</hi,. Faculty Mentr Dace: LL~(?X Cmments (Optina!):

3 Austin Faulkner Senir Hnrs Prject: Cmpetitin and Invasin in a Micrcsmic Setting Spring 2004

4 Abstract Students: Austin Faulkner, Bill Hlmes, Jacb Kendrick, Jeff Lwder, Elizabeth Martin, and Alex Perkins Faculty Spnsrs: Suzanne Lenhart, Luis Grss, Jake Weltzin, and Jim Drake Abstract: Single species experiments with tw species frm genera Clpidium and Paramecium, and analysis f data were cmpleted t estimate grwth rates and carrying capacities. The underlying mdel fr each species is a differential equatin with lgistic grwth. Experimental data was used t estimate carrying capacity (K) and grwth rate (r) f the tw species. Next, the tw species were grwn in cmpetitin; that data was used t determine cmpetitin cefficients fr the tw species. This data will be used in the next phase f the experiment, which is t include a spatial cmpnent. We are currently in the prcess f determining migratin rates f the tw species; nce the rates have been determined experimentally we will begin the next phase. We hpe t prve that prpagule pressure will affect invasibility f a system that includes migratin.

5 Intrductin: Fr the past year I have been invlved in an undergraduate research experience. The gal f the research experience has been the study and creatin f Spatial Distributin Mdels f Invasive species; the research is paid fr thrugh a grant prvided by the NSF. The abstract abve, alng with the PwerPint presentatin, details the early stages f ne phase f the research: cmpetitin n a micrcsmic scale. In rder t understand hw invasin affects a system, it is imprtant t understand the effects f cmpetitin between the integrated species. With that in mind, a series f experiments were designed t study cmpetitin between tw micrrganisms: Clpidium striatum and Paramecium Aurelia. I was invlved in the design, creatin, data cllectin, and analysis stages f the experiments. Methds: Clpidium striatum and Paramecium aurelia were chsen as the tw initial species because they have similar life spans, prey slely n bacteria (they will nt eat themselves r each ther), and are easily identifiable. Prject One: The first phase f the experiment invlved independent grwth f the tw species t determine grwth rate (r) and carrying capacity (K) fr each. A multiple replicate system f three densities (ne, five and ten individuals per milliliter in 100 ml jars) and three replicates each was used t reduce errr in the final rates. 0.2 ml samples were taken each day and the individuals present in that sample cunted. Nutrient slutin was used t replace the sample remved frm each jar. Final numbers f each replicate were averaged tgether and used t cmpute (r) and (K) fr the tw species (fr

6 results, see table 1). Mdels, assuming basic lgistic grwth, were made using the data. This infrmatin was used fr the next set f experiments, cmpetitin. Prject 2: During this stage f experimentatin a fur replicate system was used in rder t further reduce errr. Cultures f Clpidium striatum and Paramecium aurelia were grwn in mnculture (as a cntrl) and cmpetitin with three starting densities: 9:1,5:5 and 1:9 ratis (in individuals per ml) f Clpidium t Paramecium. The bject f this set f experiments was t determine simple cmpetitin cefficients, as well as t determine if prpagule pressure had an effect n species viability. Bth rganisms were grwn and sampled n a daily basis, at apprximately the same time each day. The data was then used t create rdinary differential equatins (ODEs), which were slved and pltted alng a timeline. Results: Analysis f the graphs led t the cnclusin that Clpidium is a better cmpetitr than Paramecium. The cmpetitin cefficients we assigned t the tw rganisms were 1.0 fr Clpidium and 0.5 fr Paramecium, meaning that Clpidium striatum has twice the cmpetitive effects n Paramecium aurelia than it has n itself. In ther wrds, each Clpidium is twice as effective at using resurces, s everyne present in a micrcsm "cunts" as tw Paramecium as far as the Paramecium are cncerned, and tw Paramecium are necessary t give the equivalent effect f ne Clpidium. Due t this fact, Clpidium was always able t ut-cmpete Paramecium, despite the fact that they have a lwer grwth rate and take lnger t reach carrying capacity (See Graphs 1, 2 and 3).

7 Cntrary t ur hypthesis, prpagule pressure did nt seem t change the final utcme f the cmpetitin; Clpidium always beat Paramecium eventually, with the frmer always driving the latter t extinctin. Alternating the initial densities f the tw species nly seemed t delay the utcme, but was unable t change it. It is pssible that extreme differences in initial density (i.e. ratis f 1000:1 Paramecium t Clpidium) culd change the eventual utcme, but accrding t the specifics f this experiment it seems as if the nly utcme f cmpetitin between these tw species is extinctin f Paramecium aurelia. Table 1: Clpidium 0.02 Paramecium 0.05 Grwth Rate (r) Carrying Capacity (K) 300 individuals per ml 250 individuals per ml Graph 1: 1:9 rati f Clpidium t Paramecium Estimated r (Paramecium): 0.05 Estimated K (Paramecium): 250 Estimated r (Clpidium): 0.02 Estimated K (Clpidium): Red = Paramecium Black = COlpidium Time in tii:us

8 Graph 2: 5:5 rati f Clpidium t Paramecium Estimated r (Paramecium): 0.05 Estimated K (Paramecium): 250 Estimated r (Clpidium): 0.02 Estimated K (Clpidium): 300 Red = Paramecium Black = COlpidium 300 II f bdivimals Time in I-kus 500 Graph 3: 9: 1 rati f Clpidium t Paramecium Estimated r (Paramecium): Estimated K (Paramecium): 250 Estimated r (Clpidium): 0.02 Estimated K (Clpidium): 300 Red = Paramecium Black = Clpidium 200 #I 01 Dilliduals Time in HIr.i

9 Discussin: The initial questin f the experiment was: Hw des prpagule pressure effect invasin? During the curse f the secnd cmpetitin experiment the questin was answered, at least t sme extent: even with ratis f 9: 1, the inferir cmpetitr (Paramecium) is unable t ut-cmpete, r even cexist, with the superir cmpetitr (Clpidium). Whether r nt this situatin wuld hld true with drastically different initial densities has yet t be determined, but future experiments in that directin may still be perfrmed. Thus far my invlvement with this research has given me the pprtunity t d persnal research in a lab setting, and ver the summer I will be able t intrduce a field cmpnent t my research. I will als be attending a natinal cnference spnsred by the Eclgical Sciety f America (ESA) in Prtland, Oregn. Wrking with students in the mathematical field has increased my understanding f mathematical appraches t bilgical prblems as well. I feel that wrking n this prject has helped me t learn mre abut my field f expertise while allwing me t interact with, and cme t better understand, ther appraches.