A Comparative Study of Isolation in Headwater Fishes

Headwater resident fishes may be prone to a high rate of population fragmentation within river networks because large streams have habitat conditions outside of their preferred ecological niche and may limit gene flow in the dendritic ecological network. To investigate patterns of population structure, asymmetrical gene flow, and influences on genetic distance and isolation from connecting habitat pathways, species specific ecological traits, and basin scale characteristics, a multi-species, multi-regional study was performed. Six headwater species of fish from four taxonomic groupings were sampled for genetic material in three regions of paired neighbor drainages and then genotyped for eight microsatellite loci. All species were found to have a nested hierarchical population structure relating to regional and geographical structure of drainages. There were also differences in rates of fragmentation across the species and regions studied, with Fundulus olivaceus and the Lower Mississippi River having the lowest rates. Most of the headwater species were found to have patterns with the majority of drainages supporting asymmetrical upstream gene flow along the main stem of the networks. Five of the species were found to have significant Isolation by Distance, and four of the species were found to have significant Isolation by Resistance due to large streams. The reservoir in the Pearl River was found to not significantly increase genetic distance, while the reservoir in the Little Red River significantly increased genetic distance. Headwater specialization and a combination of opportunistic strategy and periodic strategy life history traits were found to increase isolation rates across species. The amount of available habitat within drainages and the shape of the drainage were found to have the most influence on genetic distance patterns at large scales. This study shows that natural fragmentation of populations within networks is common across different species of headwater fishes, and is related to specific ecological characteristics of those species and regional characteristics of the drainage network. This project contributes to the understanding of how habitat preference within dendritic networks influences genetic population structure and provides a background rate of fragmentation in common headwater species that can be used for comparison with threatened or endangered species

Caveat Fiduciarius: Unions, Pension Fund Investments, and the Capital-Pre-Recognition Agreement Exchange

John H. Fanning Labor Law Writing Competition Winner, 200

FIELD INSTRUCTION: IS THE HEART OF SOCIAL WORK EDUCATION STILL BEATING IN THE EASTERN CAPE?

This paper presents part of the findings that emerged from a recent research project entitled “A qualitative evaluation of social work field instruction being offered by universities in the Eastern Cape, South Africa.” Field instruction is the heart of social work training. This key component of social work training has been placed under increasing pressure in the Eastern Cape. The findings presented in this paper highlight the strengths and weaknesses of field instruction programmes as well as the constraints facing universities in the Eastern Cape. In conclusion, it was found that the heart of social work education is, indeed, still beating strongly in the Eastern Cape

Magneto-optical study of electron occupation and hole wave functions in stacked self-assembled InP quantum dots

We have studied the magnetophotoluminescence of doubly stacked layers of self-assembled InP quantum dots in a GaInP matrix. 4.0±0.1 monolayers of InP were deposited in the lower layer of each sample, whereas in the upper layer 3.9, 3.4, and 3.0 monolayers were used. Low-temperature photoluminescence measurements in zero magnetic field are used to show that, in each case, only one layer of dots is occupied by an electron, and imply that when the amount of InP in both layers is the same, the dots in the upper layer are larger. High-field photoluminescence data reveal that the position and extent of the hole wave function are strongly dependent on the amount of InP in the stack. ©2001 American Institute of Physics

Problems and Current Trends in Rock Magnetism and Paleomagnetism

Continental drift, seafloor spreading, plate tectonics: These terms conjure up a picture of the whole of Earth\u27s lithospheric plates in motion, a picture that truly represents a revolution in the earth sciences that took place in the 1960s and permanently changed our view of a more static world. If someone were to ask which subdiscipline of the geosciences has provided the crucial quantitative evidence about the past locations of discrete parts of continental and oceanic plates, the answer would be geomagnetism and paleomagnetism. Polarity stratigraphy, based on radiometrically dated 180° reversals of the dipolar geomagnetic field, informs us about the locations of parts of the seafloor in the past, and paleomagnetically determined paleolatitudes of continental rocks provide similar information about past locations of continental plates