Ecological and evolutionary effects of dispersal on freshwater zooplankton

A recent focus on contemporary evolution and the connections between communities has sought to more closely integrate the fields of ecology and evolutionary biology. Studies of coevolutionary dynamics, life history evolution, and rapid local adaptation demonstrate that ecological circumstances can dictate evolutionary trajectories. Thus, variation in species identity, trait distributions, and genetic composition may be maintained among ecologically divergent habitats. New theories and hypotheses (e.g., metacommunity theory and the Monopolization hypothesis) have been developed to understand better the processes occurring in spatially structured environments and how the movement of individuals among habitats contributes to ecology and evolution at broader scales. As few empirical studies of these theories exist, this work seeks to further test these concepts. Spatial and temporal dispersal are the mechanisms that connect habitats to one another. Both processes allow organisms to leave conditions that are suboptimal or unfavorable, and enable colonization and invasion, species range expansion, and gene flow among populations. Freshwater zooplankton are aquatic crustaceans that typically develop resting stages as part of their life cycle. Their dormant propagules allow organisms to disperse both temporally and among habitats. Additionally, because a number of species are cyclically parthenogenetic, they make excellent model organisms for studying evolutionary questions in a controlled environment. Here, I use freshwater zooplankton communities as model systems to explore the mechanisms and consequences of dispersal and to test these nascent theories on the influence of spatial structure in natural systems. In Chapter one, I use field experiments and mathematical models to determine the range of adult zooplankton dispersal over land and what vectors are moving zooplankton. Chapter two focuses on prolonged dormancy of one aquatic zooplankter, Daphnia pulex. Using statistical models with field and mesocosm experiments, I show that variation in Daphnia dormant egg hatching is substantial among populations in nature, and some of that variation can be attributed to genetic differences among the populations. Chapters three and four explore the consequences of dispersal at multiple levels of biological organization. Chapter three seeks to understand the population level consequences of dispersal over evolutionary time on current patterns of population genetic differentiation. Nearby populations of D. pulex often exhibit high population genetic differentiation characteristic of very low dispersal. I explore two alternative hypotheses that seek to explain this pattern. Finally, chapter four is a case study of how dispersal has influenced patterns of variation at the community, trait and genetic levels of biodiversity in a lake metacommunity.

Expected rates of return to education / BEBR No. 832

Bibliography: p. 23-25.

Integral Piezoactuator System with Optimum Placement of Functionally Graded Material - A Topology Optimization Paradigm

Piezoactuators consist of compliant mechanisms actuated by two or more piezoceramic devices. During the assembling process, such flexible structures are usually bonded to the piezoceramics. The thin bonding layer(s) between the compliant mechanism and the piezoceramic may induce undesirable behavior, including unusual interfacial nonlinearities. This constitutes a drawback of piezoelectric actuators and, in some applications, such as those associated to vibration control and structural health monitoring (e. g., aircraft industry), their use may become either unfeasible or at least limited. A possible solution to this standing problem can be achieved through the functionally graded material concept and consists of developing `integral piezoactuators`, that is those with no bonding layer(s) and whose performance can be improved by tailoring their structural topology and material gradation. Thus, a topology optimization formulation is developed, which allows simultaneous distribution of void and functionally graded piezoelectric materials (including both piezo and non-piezoelectric materials) in the design domain in order to achieve certain specified actuation movements. Two concurrent design problems are considered, that is the optimum design of the piezoceramic property gradation, and the design of the functionally graded structural topology. Two-dimensional piezoactuator designs are investigated because the applications of interest consist of planar devices. Moreover, material gradation is considered in only one direction in order to account for manufacturability issues. To broaden the range of such devices in the field of smart structures, the design of integral Moonie-type functionally graded piezoactuators is provided according to specified performance requirements.

Contributions to the flora of South America: Studies on Andean Compositae, I. Studies in South American plants, II.

v.27:no.1(1950)

Contributions to the flora of South America: Studies on Andean Compositae, II. Studies in South American plants, III.

v.27:no.2(1951)

Arctoid genetic characters as related to the genus Parictis / [by] John Clark -- and Thomas E. Guensburg, University of Illinois. [Patricia M. Williams -- editor.]

v.26:no.1(1972)

Special Investigation of Certain Grants Administered by The Department of Curriculum and Instruction, College of Education, Iowa State University of Science and Technology, For the Period September 1, 1999 through November 30, 2003

State University Audit Report - Special Investigation

Special Investigation of Certain Grants Administered by The Department of Curriculum and Instruction, College of Education, Iowa State University of Science and Technology, For the Period September 1, 1999 through November 30, 2003

State University Audit Report - Special Investigation

University of Iowa Graduate College news. Fall 2004.

Newsletter on the activities of the University of Iowa Graduate College.

University of Iowa Graduate College news. Spring 2005.

Newsletter on the activities of the University of Iowa Graduate College.

University of Iowa Graduate College news. Fall 2005.

Newsletter on the activities of the University of Iowa Graduate College.

University of Iowa Graduate College news. Spring 2006.

Newsletter on the activities of the University of Iowa Graduate College.

University of Iowa Graduate College news. Fall 2006.

Newsletter on the activities of the University of Iowa Graduate College.

University of Iowa Graduate College news. Spring 2007.

Newsletter on the activities of the University of Iowa Graduate College.