<p> Land use change to meet economic and societal demands has negatively impacted the current state of our world's ecosystems and biodiversity. The alarming rate of landscape change and degradation has prompted ecologists to conserve intact areas and restore historical habitats in the hopes of mitigating the potential damage. As a result, restoration ecology was developed and has grown dramatically within the past couple decades. Historically, the Mississippi Alluvial Valley, provided services such as water enhancement and nutrient cycling, and the characteristic bottomland hardwood forests dominated the land cover and were suitable habitat for many organisms, especially neotropical migrants. As the Upper Mississippi Alluvial Valley was converted into agricultural fields and locks and dams were installed, many neotropical migrants had steady population declines. More recent surveys have noted that approximately two-thirds of the neotropical migrants have been declining for the past half-century. For the past two decades, the U.S. Army Corp of Engineers (USACE) has been responsible for the restoration of bottomland hardwood forests in the Upper Mississippi Valley. Using birds as model organisms, this project assessed the restoration success of this site by (1) comparing avian richness, diversity, and density among a chronosequence of forest restoration age classes to determine any significant differences in species assemblage in the chronosequence and (2) creating a predictive habitat model that assists in the formulation of appropriate recommendations for restoration planning and management in the future. I hypothesize that species richness and diversity is highest at intermediate sites since they will have habitat characteristics of both grasslands and forests and that my habitat models identifies structural variables, such vegetation height, and tree height and ground cover as significant determinants of avian presence. Our study included a chronosequence of nine restoration sites and two references in which bird surveys and vegetation surveys were completed. Avian surveys consisted of 25-m fixed radius point counts at five plots per site. Sites were visited three times for the spring and fall data collections. Spring data will continue May 2014 due to unusual flooding conditions. Within the 25-m radius, a 17.84-m radius vegetation plot was created. Tree species, tree health variables, diameter at breast height (DBH), and abundance were recorded, and the tree was tagged. Shrub stem count data was recorded in four belts within each vegetation plot, with the condition that a shrub is at least 1-m in height. The plot was divided into four belts, and five quadrats of 0.5 m2 were formed along each belt to record forb and grass cover and litter depth. Species richness, Antilog Shannon-Weiner's Diversity Index, and Simpson's Diversity Index was calculated, and the vegetation data was used in the predictive habitat modeling. I recorded 52 bird species during the spring and 79 bird species during that fall that were within the 25-m radius. Bird species richness and diversity differed among the sites, and richness and diversity generally increased as the age of the site increased. Grassland and shrubland birds did not have any significant trends for vegetation parameters. However, most open woodland birds had a significant association with DBH, and a majority of forest birds had significant associations with tree height and crown size. The observed richness and diversity values contradict several studies but may be attributed to the productivity rate of the sites chosen. Density estimates can also be enhanced through new surveying methods which would address detectability issues for naturally skittish birds. Future restoration efforts should include the planting of fast-growing trees and shrubs in order to increase structural diversity at faster rates. In addition, more sites should be acquired and restored in order to create close patches for neotropical migrants to facilitate travel. Continuing efforts in restoration and appropriate management should emphasize the causes of declines for land birds and identify them early enough to develop an appropriate management plan.</p>

<p> I investigated the determinants of distributional patterns in the mussel <i> Mytilus californianus</i> in the Strait of Juan de Fuca in Washington State. A three pronged approach including evolutionary, geomorphological, and population ecology research methods elucidated processes determining the density and distribution of the species as well as forces impacting its future trajectory. Primary conclusions include: 1. Changes in aerial temperatures in Washington State in the near future are unlikely to dramatically influence the abundance and distribution of <i>Mytilus californianus.</i> 2. The interaction of sea level rise with the geomorphological features of rocky coasts has the potential to dramatically change the distribution and abundance of shallow water depth restricted species like <i>Mytilus californianus.</i> 3. Distributional patterns of <i> Mytilus californianus</i> occurring at multiple spatial scales are a result of the integration of population vital rates as determined by environmental gradients, and variation in vital rates are sometimes scale dependent (growth and recruitment rates) and sometimes not (survival rates). 4. Mussel populations were most sensitive to variation in growth rates, least sensitive to variation in recruitment rates, and intermediately sensitive to variation in survival. 5. <i>Mytilus californianus</i> density is unlikely to be primarily controlled by variation in growth rate or recruitment rate.</p>

Thesis (Ph.D.)--Lehigh University, 2008. / Adviser: Murray Itzkowitz.

<p> Communication facilitates almost every social interaction between organisms and this communication is especially important for mate acquisition. Anuran amphibians are an excellent model system to study mate choice behaviors and sexual selection. In this work I recorded male calls of the spring peeper, <i> Pseudacris crucifer</i>, between two populations (Maryland and Louisiana) and analyzed call parameters such as frequency, duration, and rise and fall time. I found differences in the frequency and the frequency sweep of the calls. I conducted choice experiments to test female mating preferences in the Louisiana population and found a preference for longer calls over short calls. Females did not express a preference for frequency, frequency sweep, or local (LA) versus foreign (MD) calls. I also conducted multimodal signaling experiments on the t&uacute;ngara frog, <i>Physalaemus pustulosus</i>. I used natural calls and a robotic t&uacute;ngara frog to determine how females assess different signal modalities (auditory versus visual). I tested previously established attractive calls against unattractive calls, paired with the robo-frog and inflating vocal sac, to see if the visual stimulus would modulate the attractiveness of the call. The presence of the vocal sac did not make the unattractive call more attractive. The vocal sac may have important implications for localization in a more complex environment but here, it did not act as a mate attracting signal. This study provides the ground work necessary for multimodal signaling in spring peepers and for complex sensory environment choice tests in the t&uacute;ngara frog.</p>

<p> Invasive tamarisk has many impacts in freshwater systems including increasing soil salinity, decreasing water content, and causing a shift in food web structure. Tamarisk species originally introduced to the US have hybridized and have been documented invading salt marsh systems in San Diego County, California. The main goals of this study were to determine the impacts of tamarisk within a salt marsh and among genetic types of tamarisk. Amplified Fragment Length Polymorphism was used to determine genetic identity of each individual salt-marsh invading tamarisk. Abiotic impacts depended on microhabitat, as did tamarisk tree morphology, and infauna community composition. Tamarisk altered abiotic factors in the upland and upstream microhabitats and altered infauna community composition in the marsh microhabitat. 17.8% of trees were hybrids of <i> T. ramosissima</i> x <i>T. chinensis.</i> The remainder were pure <i>T. chinensis.</i> Tamarisk genetic identity did not influence abiotic factors, although invertebrate diversity was lower beneath pure <i> T. chinensis</i> than the hybrid. The tamarisk invasion was not an <i> in-situ</i> hybridization and had the most pervasive impact on the infauna in the marsh microhabitat.</p>

<p> Bur oak (Quercus macrocarpa Michx.) savannas of the Great Plains have long been reported to be disappearing and/or progressing to other vegetative schemes. These losses are directly relatable to the arrival of European settlers and their subsequent suppression in natural prairie fires, along with the introduction of domestic livestock. A preliminary investigation of the floristic composition within remaining oak savannas of Custer County, Nebraska was conducted as a base means of documenting plant diversity within the remaining savannas of central Nebraska. The point-centered quarter method was used to determine species, density, relative density, frequency, relative frequency, dominance, relative dominance, and importance values (IV). The Swedish-increment boring method was applied to woody vegetation to document tree ages and compositional change in the savanna over time. Exclusion cages on oak seedlings, vegetative and soil sampling were also utilized. Results indicated a bleak future for the remaining savannas of Nebraska. Bur oak averaged an importance value of 159.10 out of 300.00, leaving a substantial portion of the importance values divided among several fire-sensitive species. The majority of bur oaks sampled were distributed among the higher size classes, indicating a low rate of recruitment. Age class distributions further support this conclusion with a minuscule number of oaks younger than 25 years of age and the majority of the species recorded over 100 years of age. Seedling survivability tests during summer months produced low survivorship (3.13%) due to drought and large/small mammal herbivory. Winter testing displayed similar results. Vegetation sampling indicated high percentages of exposed till and weedy plant species, indicating a long history of abuse. Soil tests resulted in significant differences in phosphorus and zinc concentrations. As oak recruitment failings continue on a near global scale, more research should be conducted to assist in the conservation and management of these vital ecosystems.</p>

<p> Amphidromous species migrate between fresh water and the sea for larval development. Many caridean shrimps, especially <i>Macrobrachium </i> spp., are amphidromous, and some populations are found far-upstream within continental river systems. This project tested the hypothesis that populations of <i>Macrobrachium ohione</i> from the Atchafalaya and Mississippi Rivers are amphidromous. </p><p> In the laboratory, I tested the hypothesis that upstream populations of <i>M. ohione</i> have freshwater larval development. My results indicated that saline habitats are essential for <i>M. ohione</i> development, and larval mortality increased after 3-4 days of freshwater drifting. This provides indirect evidence that upstream populations have extended marine larval development. </p><p> Due to their limited freshwater survival, <i>M. ohione</i> must deliver larvae to the sea. Spatial-temporal analysis in the Atchafalaya and Mississippi Rivers reported an influx of reproductive-sized shrimps and females with near-hatching broods into coastal sites. This suggests that females are migrating downstream to hatch larvae in downstream habitats. </p><p> Stable isotope analysis indicated that the upstream juvenile migration originates from saline habitats. Video surveillance revealed that juveniles migrate throughout the night at an average speed of &sim; 0.56 km hr^-1, and swimming speeds were related to the water velocity they swam against. From these results, I estimated that juveniles are capable of migrating to far-upstream habitats within their life span (1-2 years). </p><p> Lastly, I investigated how dams affect the juvenile migration, and tested juvenile migrant climbing abilities. This study reported greater densities of juveniles downstream of dams than upstream of dams, indicating the dams impede the juvenile migration downstream of Old River Control. Shrimp climbing studies revealed that at various inclinations and water velocities, ~ 52% of the shrimps were climbing the shrimp ramp and ~ 12% completed the climb. These results demonstrated juveniles can climb bypass structures with detectable water flows. </p><p> My findings suggest that <i>M. ohione</i> populations within the Mississippi River System are amphidromous, because they require marine larval development and long-distance migrations are conducted to and from the sea. This study may serve as a general model for migrations of amphidromous shrimps in comparable large rivers, and potentially contribute to freshwater shrimp conservation.</p>

<p> This study assessed the occurrence and impacts of maternal metal transfer in live-bearing fish. The occurrence was investigated in two different species (<i>Gambusia affinis</i>and <i>Heterandria formosa</i>), while the impacts were studied only in <i>G. affinis.</i> Occurrence and impacts were addressed by exposing gravid females for 10 days to 0.15 &mu;M of copper or cadmium, transferring the fish to clean water, monitoring their reproduction and collecting newborn offspring for further analyses of their health and reproductive success. </p><p> Maternal transfer of copper and cadmium occured in both study species. Metal levels decreased in subsequent broods and in broods born later after a female's exposure. Metal exposure impacted the reproductive success of exposed-females; effects included smaller broods and more broods were aborted broods or contained dead offspring. Many effects remained for second broods developing well after the exposure. </p><p> The maternal metal exposure also impacted the offspring's health. Newborn offspring were smaller at birth, had reduced calcium levels, had a lowered metal tolerance, and had cellular membrane damage. When these offspring grew up, they had an increased rate of malformations, a smaller size at sexual maturity, increased gestation time and fewer broods. In spite of the impacts on life history parameters found in the laboratory, effects on population dynamics were very limited for greenhouse mesocosm populations established with the offspring of exposed females. </p><p> Effects for the essential metal (copper) and the nonessential metal (cadmium) were generally similar. A few effects, like those on body size, were evident for copper but not for cadmium. However, several of the more severe impacts, like the increase in malformations and reductions in the number of broods, were greatest for the offspring of the cadmium-exposed females. </p><p> This is the first report demonstrating negative impacts resulting from a short-term maternal metal exposure in live-bearing fishes. Effects were evident not just for reproduction of exposed-females but also for their offspring's health and reproduction. The latter continued beyond the offspring that were developing during exposure. This study demonstrated that the internal development in live-bearing fish may not spare the developing young from impacts caused by a metal-contaminated environment.</p>