In this study, I examined the effect of watershed urbanization on the invasion of alien woody species in riparian forests. This study was conducted in three major steps: 1) estimating the degree of watershed urbanization using impervious surface maps extracted from remote sensing images; 2) examining the effect of urbanization on hydrologic regime; and 3) investigating a relationship between watershed urbanization and ecosystem invasibility of a riparian forest. I studied twelve riparian forests along urban-rural gradients in Austin, Texas. Hydrologic regimes were quantified by transfer function (TF) models using four-year daily rainfall-streamflow data in two study periods (10/1988-09/1992 and 10/2004-09/2008) between which Austin had experienced rapid urbanization. For each study period, an impervious surface map was generated from Landsat TM image by a support vector machine (SVM) with pairwise coupling. SVM more accurately estimated impervious surface than other subpixel mapping methods. Ecosystem invasibilities were assessed by relative alien cover (RAC) of riparian woody species communities. The results showed that the effects of urbanization differ by hydrogeologic conditions. Of the study watersheds, seven located in a hillslope region experienced the diminishing peakflows between the two study periods, which are contrary to current urban hydrologic model. I attributed the decreased peakflows to land grading that transformed a hillslope into a stair-stepped landscape. In the rest of the watersheds, peakflow diminished between the two study periods perhaps due to the decrease in stormwater infiltration and groundwater pumpage that lowered groundwater level. In both types of watersheds, streamflow rising during a storm event more quickly receded as watershed became more urbanized. This study found a positive relationship between RAC and watershed impervious surface percentage. RAC was also significantly related to flow recession and canopy gap percentages, both of which are indicators of hydrologic disturbance. These results suggest that urbanization facilitated the invasion of alien species in riparian forests by intensifying hydrologic disturbance. The effects of urbanization on ecosystems are complex and vary by local hydrologeologic conditions. These results imply that protection of urban ecosystems should be based on a comprehensive and large-scale management plan.

Three protease inhibitor-like proteins (PILPs) identified from Bungarus multicinctus genome are structurally homologous with Kunitz-type proteinase inhibitor. The goal of the present study is to explore whether PILPs exhibit an inhibitory action on matrix metalloproteinase 2 (MMP-2) activity. Unlike PILP-1 and PILP-2, PILP-3 was found to inhibit MMP-2 activity as evidenced by specific substrate assay. Moreover, in vitro migration and invasion assays, and wound-healing assay showed that PILP-3 suppressed the migration and invasion of human neuroblastoma SK-N-SH cells. Pull-down assay and dot blotting-binding assay proved an interaction between PILP-3 and MMP-2. Nevertheless, PILP-3 did not affect either expression or secretion of MMP-2 in SK-N-SH cells. In terms of highly structural similarity between PILP-2 and PILP-3, two chimeric mutants in which amino acids at N-terminus and C-terminus of PILP-3 were substituted by those of PILP-2 were prepared. In contrast to N-terminus chimera, C-terminus mutant of PILP-3 was unable to inhibit MMP-2 activity and showed a reduction in binding with MMP-2. Taken together, our data suggest that PILP-3 may be a useful template for rational designing pharmaceutical agent in inhibiting MMP-2 activity.

Zugl.: Berlin, Humboldt-Univ., Diss., 2009

The invasive cactus moth, Cactoblastis cactorum, poses a threat to opunitoid cacti species of North America. The following work contains four separate studies investigating C. cactorum host plant preference and performance, predation and parastitism of C. cactorum, effects of C. cactorum on local Opuntia populations, and associational effects of host and non-host plants on C. cactorum and native Opuntia-feeding herbivores. We found that, among southwestern and Mexican opuntioid taxa, moths preferred O. engelmannii var. linguiformis and var. engelmannii for oviposition, while Consolea rubescens and O. streptacantha were superior larval hosts. Oviposition was best predicted by number of cladodes and degree of spininess; epidermal toughness was a significant predictor of most larval fitness parameters. In general, oviposition preference was not correlated with larval performance. A lack of co-evolutionary history between C. cactorum and North American opuntioid species may help explain this disconnect. We placed irradiated C. cactorum eggsticks and pupae on Opuntia plants in the field to test for predation. We found evidence of predation, most likely from ants, on ~16% of eggsticks and ~18% of pupae. Predation rates, ant abundance, and cladode growth were higher, and C. cactorum damage lower, on Opuntia located near the extrafloral nectar-producing legume Chamaecrista fasciculata. We attribute these associational effects to the ability of C. fasciculata to attract ants to its extrafloral nectar. Over the course of six years, ~78% of nearly 600 tagged Opuntia were attacked by C. cactorum at least once and ~76% of the plants survived. Two separate studies found that Opuntia stricta was more likely to be attacked by C. cactorum than O. humifusa; we also found that O. stricta was more likely to die following an attack. A plant's odds of survival decreased as C. cactorum attack frequency increased, but plants that did survive had positive growth rates, regardless of attack status. We did not find significant evidence of associational effects for O. humifusa and O. stricta, either for C. cactorum or native Opuntia-feeding herbivores. It could be that present herbivore densities are low enough, and host plants plentiful enough, to avoid mechanisms that usually lead to associational resistance or susceptibility. Overall, our results suggest that the presence and spread of C. cactorum should be taken seriously, especially for rare opuntioids and the Opuntia-rich deserts of North America. However, for more common opuntioid host species, there may be enough resistant or tolerant individuals, and sufficient top down control through ant predation, for populations to persist at current C. cactorum densities. We acknowledge that information on Opuntia reproduction and recruitment rates are needed to confirm this suggestion, and see this as an excellent opportunity for future research

<p>Basement membranes are a dense, sheet-like form of extracellular matrix that underlie epithelia and endothelia, and surround muscle, fat and Schwann cells. Basement membranes separate tissues and protect them from mechanical stresses. Although traditionally thought of as a static support structure, a growing body of evidence suggests that dynamic basement membrane deposition and modification instruct cell behavior and morphogenetic processes. In this thesis, I discuss how changes to basement membrane affect anchor cell (AC) invasion during C. elegans uterine vulval attachment. During AC invasion, the uterine AC breaches two juxtaposed basement membranes to contact the underlying vulval epithelium. Using live-cell imaging, genetics, molecular biology and electron microscopy I identify three modifications to the BM that affect AC invasion. In Chapter 2, I describe a system for linking juxtaposed basement membranes to stably align or connect adjacent tissues. This adhesion system promotes rapid AC invasion and also regulates a more long-term connection between the uterine tissue and the hypodermal seam cell in the adult worm. Chapter 3 elucidates how the BM component SPARC promotes cell invasion. As SPARC overexpression is correlated with cancer metastasis, this aims to understand how SPARC overexpression promote invasion in a pathological situation. In Chapter 4, I discuss preliminary data showing that the AC actively secretes laminin into the basement membrane targeted for invasion. I outline how future studies could elucidate the mechanism by which AC-derived laminin might promote cell invasion. Finally, Chapter 5 discusses conclusions and future directions for these studies.</p> / Dissertation

The formation of a continuous tubular network in the mammalian urinary system requires the interconnection of two epithelial populations with distinct cellular origins. The proximal component of the renal network is the nephron--a complex tubule responsible for much of the physiological action of the kidney. Nephrons connect to a collecting duct network to transport urine from the kidney to the bladder, via the ureter. I have used high-resolution image analysis of genetically labeled nephron and collecting duct networks together with apical and luminal markers to characterize the epithelial interconnection process in the developing kidney. Morphological protrusions at the distal end of the nephron precursor, adjacent to the tip of the collecting duct epithelium, precede luminal interconnection at the S-shaped body stage. Distal cells in the nephron precursor do not display clear epithelial junction complexes and show upregulation of phospho-myosin light chain, suggestive of a quasi-mesenchymal cell behavior. The close apposition of this group of cells with the collecting duct epithelium is facilitated by the absence on an intervening basal lamina. Live imaging of explanted kidneys suggests that distal cells break through into the lumen of the collecting duct epithelium and undergo cell death. No interconnection is observed upon Notch-mediated proximalization of distal cell fates. Furthermore, distal factor bone morphogenetic protein 2 (Bmp2) expression is lost in proximalized nephron precursor derivatives. Finally, I demonstrate that mice with specific loss of Bmp2 in nephron precursors and their derivatives results in a fraction of disconnected mature nephrons that later results in nephron atrophy and compromised renal function at juvenile stage compared to control mice. These data support a model in which the establishment of distal identity in nephron precursor cells closest to the nascent collecting duct epithelium leads to an active cell invasion that establishes a patent tubular interconnection between the nephron and collecting duct.

Formation damage is a common problem in petroleum reservoirs and happens in different stages of reservoir development from drilling to production. The causes of formation damage include particle invasion, formation fines migration, chemical precipitation, and pore deformation or collapse. Formation damage adversely affects productivity of wells by reducing the permeability of near wellbore region. Furthermore, formation damage also affects well logging results. Therefore, understanding the mechanism of formation damage is vital to predict the extent and severity of formation damage and to control it. This thesis is focused on the study of formation damage caused by external particle invasion. A simplified numerical method based on a commercial code PFC (Particle Flow Code) is proposed to simulate the particle invasion process. The fluid-particle interaction is simplified as hydrodynamic drag forces acted on particles by fluids; the particle-grain interaction is modeled as two rigid balls on contact. Furthermore, an pore network flow model is developed in this study to estimate permeability of damaged formations, which contain two well-separated particle sizes. The effects of the particle size and the initial formation porosity on formation damage are studied in detail. Our study shows that big particles tend to occupy the formation face, while small particles invade deep into the formation. Moreover, particles which are smaller than pore throats (entrances) impair permeability more than those bigger than pore throats. Our study also indicates that a higher initial formation porosity results in more particle invasion and permeability impairment. It is suggested that, in order to reduce formation damage, mud particle size distributions should be carefully selected according to given formation properties. Although our model has some limitations, it may serve as a tool to predict formation damage according to given parameters, and to understand the mechanism of formation damage from a micro-scopic point of view. / text

This dissertation presents four microbial microcosm-based experimental studies addressing questions related to the causes and consequences of biodiversity. All four studies adopted an approach that integrates ecology and evolutionary biology. Two studies explored the utility of knowledge on species phylogenetic relationships for understanding community assembly (chapter 1) and invasibility (chapter 3). The other two studies investigated the impacts of important ecological factors, including competition (chapter 2) and temporal niches (chapter 4), on adaptive radiation, using the rapidly diversifying bacterium Pseudomonas fluorescens SBW25 as the model organism. The first study, described in Chapter 1, examined how phylogenetic relatedness between competing species affected the strength of priority effects and ecosystem functioning during community assembly. Strong priority effects emerged only when competing bacterial species were phylogenetically most closely related, resulting in multiple community states associated with different assembly histories. In addition, the phylogenetic diversity of bacterial communities effectively predicted bacterial production and decomposition. The second study, described in Chapter 2, explored the role of competition in the adaptive radiation of P. fluorescens. The adaptive radiation was generally suppressed by competition, but its effect was strongly modulated by the phylogenetic relatedness between the diversifying and competing species and their immigration history. The inhibitive effect of competition on adaptive radiation was strongest when phylogenetic relatedness was high and when competitors were introduced earlier. The third study, described in Chapter 3, evaluated the relative importance of phylogenetic relatedness between resident and invading species and phylogenetic diversity of resident communities for invasibility. Laboratory bacterial communities containing a constant number of resident species with varying phylogenetic diversity and relatedness to invaders were challenged by nonresident bacterial species. Whereas invader abundance decreased as phylogenetic relatedness increased as predicted by Darwin's naturalization hypothesis, it was unaffected by phylogenetic diversity. The final study, described in Chapter 4, presented the first experimental demonstration of the maintenance of biodiversity that emerged from adaptive radiation in the presence of temporal niches. Only when provided with temporal niche opportunities were multiple derived phenotypes of P. fluorescens able to coexist as a result of negative frequency-dependent selection. When temporal niche was absent, the specialized phenotypes either did not emerge or were predominated by one superior phenotype.

No description available.

Der Anteil an nicht-einheimischen Pflanzenarten (Neophyten), die durch menschlichen Einfluss in neue Gebiete eingebracht worden sind, hat in den letzten zwei Jahrhunderten deutlich zugenommen. Weltweit gefährdet die Invasion von Neophyten beträchtlich die einheimische Biodiversität und Ökosystemfunktionen. Verschiedene biologische Eigenschaften (z.B. hohe Zuwachsrate und schnelle Vermehrung) führen zu einer besseren Konkurrenzfähigkeit von invasiven Arten und verursachen Veränderungen in der natürlichen Artzusammensetzung. Eine genauere Erfassung der Eigenschaften, die Neophyten zu starken Konkurrenten machen, könnte dabei helfen pflanzliche Invasionen besser zu verstehen und zukünftig effektiver zu steuern. Topfversuche ermöglichen die Untersuchung von Pflanzeninteraktionen unter kontrollierten Bedingungen ohne den schwer kalkulierbaren Einfluss heterogener Umweltfaktoren. Allerdings führen die Langlebigkeit und die größeren Dimensionen von Baumindividuen zu mehr Problemen in Topfversuchen im Vergleich zur Untersuchung krautiger Pflanzen. Aus diesem Grund wurde im Rahmen eines Reviews Literatur ausgewertet, um einen Überblick über die praktische Durchführung von Topfversuchen, die sich ausschließlich mit Baumarten beschäftigen, zu geben. Es ist offensichtlich, dass der Vorteil von Topfversuchen zugleich auch einen Nachteil darstellt: Aufgrund der kontrollierten Bedingungen sind Topfversuche in ihrer Eignung natürliche Gegebenheiten zu imitieren immer eingeschränkt. Die Zuverlässigkeit von Topfversuchen bei der Vorhersage des Baumwachstums unter natürlichen Bedingungen ist daher problematisch. Eine Möglichkeit um die Übertragbarkeit von Topfversuchen zu verbessern, könnte die Durchführung zusätzlicher Felduntersuchungen sein. In einem Topfversuch wurden die, durch Unterschiede in der Wuchsrate, Biomasseproduktion und Biomasseverteilung bedingten, Konkurrenzmechanismen von zwei einheimischen (Quercus robur L., Carpinus betulus L.) und zwei nicht-einheimischen Baumarten untersucht (Prunus serotina Ehrh., Robinia pseudoacacia L.). Einjährige Jungpflanzen wurden verschiedenen intra- und interspezifischen Konkurrenzbedingungen ausgesetzt, mit oder ohne den Einfluss von Wurzelkonkurrenz. Um die Konkurrenzmechanismen genauer zu bestimmen, wurde zwischen Wurzel- und Sprosskonkurrenz unterschieden, indem entweder ober- oder unterirdische Plastiktrennwände in die Töpfe integriert wurden. Es wurde angenommen, dass die Gesamtbiomasseproduktion der Neophyten im Vergleich zur Biomasseproduktion der einheimischen Baumarten signifikant höher ist und dies zu einer Verringerung der Biomasse von Q. robur und C. betulus führt. Des Weiteren wurde der Einfluss der unterirdischen Konkurrenz auf das Wachstum und die Biomasseverteilung der einheimischen Arten gemäß der ‚balanced-growth hypothesis‘ untersucht. Unsere Ergebnisse bestätigen die Annahmen, dass die Biomasseproduktion der beiden Neophyten P. serotina und R. pseudoacacia signifikant höher ist und dies zu einem großen Konkurrenzvorteil und zu einer Biomassereduktion der beigemischten konkurrenzschwächeren einheimischen Arten führt. Der Konkurrenzdruck auf Q. robur und C. betulus wurde vor allem durch die Wurzelkonkurrenz der nicht-einheimischen Arten verursacht. Die Ausschaltung von unterirdischen Pflanzeninteraktionen durch Trennwände führte somit zu einem Anstieg der Biomasseproduktion der beiden einheimischen Arten. Demzufolge scheint sogar ein begrenztes Wurzelvolumen bessere Wachstumsbedingungen zu bieten als direkter Wurzelkontakt mit invasiven Konkurrenten. In Übereinstimmung mit der ‚balanced-growth hypothesis‘ reagieren Q. robur und C. betulus auf die starke unterirdische Konkurrenz durch die Neophyten, indem sie mehr Biomasse in Richtung der Wurzeln transportieren. Die verstärkte Investition der Pflanzen in die Wurzeln geht vor allem zu Lasten von Blatt- und Astbiomasse. Außerdem hat sich gezeigt, dass Artenmischungen aus einheimischen und nicht-einheimischen Bäumen mehr Biomasse produzieren, als man anhand des Wachstums dieser Arten in Monokulturen erwartet hätte. Im Vergleich zu Monokulturen oder Mischungen beider Neophyten war der Konkurrenzdruck für P. serotina und R. pseudoacacia in Mischungen mit den weniger produktiven einheimischen Baumarten geringer. Bei Betrachtung der beiden nicht-einheimischen Arten wird deutlich, dass P. serotina signifikant mehr Biomasse produziert. Trotzdem hat R. pseudoacacia aufgrund der starken Wurzelkonkurrenz einen negativen Einfluss auf die Biomasseproduktion von P. serotina. Wachsen die beiden konkurrenzstarken Neophyten zusammen in einem Topf, produzieren sie weniger Biomasse als in den entsprechenden Monokulturen. Es gibt Anzeichen dafür, dass die starke Konkurrenzfähigkeit der invasiven Neophyten oftmals zu Lasten ihrer Stresstoleranz geht. Damit einhergehend zeigten die beiden nicht-einheimischen Arten im Topfversuch eine höhere Mortalitätsrate: Vor allem P. serotina scheint zudem empfindlich gegenüber Schatten, Trockenheit und Überflutung zu sein. Möglicherweise könnte diese Schwachstelle der Neophyten genutzt werden, um eine weitere Ausbreitung einzudämmen.