Digital Commons Network^™

Negative Plant–Soil Feedback Predicts Tree-Species Relative Abundance In A Tropical Forest, Scott A. Mangan, Stefan A. Schnitzer, Edward A. Herre, Keenan M.L. Mack, Mariana C. Valencia, Evelyn I. Sanchez, James D. Bever

Biological Sciences Faculty Research and Publications

The accumulation of species-specific enemies around adults is hypothesized to maintain plant diversity by limiting the recruitment of conspecific seedlings relative to heterospecific seedlings^1,2,3,4,5,6. Although previous studies in forested ecosystems have documented patterns consistent with the process of negative feedback^{7,8,9,10,11,12,13,14,15,16}, these studies are unable to address which classes of enemies (for example, pathogens, invertebrates, mammals) exhibit species-specific effects strong enough to generate negative feedback¹⁷, and whether …

Distinguishing Technology From Biology: A Critical Review Of The Use Of Gps Telemetry Data In Ecology, Mark Hebblewhite, Daniel T. Haydon

Biological Sciences Faculty Publications

In the past decade, ecologists have witnessed vast improvements in our ability to collect animal movement data through animal-borne technology, such as through GPS or ARGOS systems. However, more data does not necessarily yield greater knowledge in understanding animal ecology and conservation. In this paper, we provide a review of the major benefits, problems and potential misuses of GPS/Argos technology to animal ecology and conservation. Benefits are obvious, and include the ability to collect fine-scale spatio-temporal location data on many previously impossible to study animals, such as ocean-going fish, migratory songbirds and long-distance migratory mammals. These benefits come with significant …

Testing Hypotheses For Exotic Plant Success: Parallel Experiments In The Native And Introduced Ranges, Jennifer L. Williams, Harald Auge, John L. Maron

Biological Sciences Faculty Publications

A central question in ecology concerns how some exotic plants that occur at low densities in their native range are able to attain much higher densities where they are introduced. This question has remained unresolved in part due to a lack of experiments that assess factors that affect the population growth or abundance of plants in both ranges. We tested two hypotheses for exotic plant success: escape from specialist insect herbivores and a greater response to disturbance in the introduced range. Within three introduced populations in Montana, USA, and three native populations in Germany, we experimentally manipulated insect herbivore pressure …

From The Valleys To The Mountains: The Biographic History Of Antelope Squirrels, Bats, And Chipmunks In Western North America, Stacy James Mantooth

UNLV Theses, Dissertations, Professional Papers, and Capstones

Genetic differentiation within and between species often coincides with significant geological or climatic changes that have shaped the sizes and locations of their geographic ranges and altered the connectivity between populations over time. Across western North America, many endemic taxa experienced high levels of initial divergence associated with geological transformations of the Neogene, with subsequent diversification and geographic structuring of populations associated with climatic changes during the Quaternary. As such, we can use a combination of molecular markers and genetic analyses to effectively examine the evolutionary and biogeographic histories of populations, species, and regional biotas whose signatures of differentiation are …

Treefrog (Hyla Squirella) Responses To Rangeland And Management In Semi-Tropical Florida, Usa, Kathryn Windes

Electronic Theses and Dissertations

As urban areas expand, agricultural lands become increasingly important habitat for many species. Compared to some types of agricultural land-use, ranchlands provide vast expanses of minimally modified habitat that support many threatened and endangered species. Conservation biologists can promote ecologically sound management approaches by quantifying the effects of agricultural practices on resident species. I examined the effects of pasture management, cattle grazing, and landscape characteristics on both adult and larval treefrogs in a ranchland in south-central Florida. I experimentally determined optimal deployment of artificial treefrog shelters constructed of polyvinylchloride (PVC) pipe to efficiently sample adult treefrogs (Chapter 1). Seventy-two shelters …

Loss Of Foundation Species Increases Population Growth Of Exotic Forbs In Sagebrush Steppe, J S. Prevey, M J. Germino, Nancy J. Huntly

Biology Faculty Publications

The invasion and spread of exotic plants following land disturbance threatens semiarid ecosystems. In sagebrush steppe, soil water is scarce and is partitioned between deeprooted perennial shrubs and shallower-rooted native forbs and grasses. Disturbances commonly remove shrubs, leaving grass-dominated communities, and may allow for the exploitation of water resources by the many species of invasive, tap-rooted forbs that are increasingly successful in this habitat. We hypothesized that exotic forb populations would benefit from increased soil water made available by removal of sagebrush, a foundation species capable of deep-rooting, in semiarid shrub-steppe ecosystems. To test this hypothesis, we used periodic matrix …

Phylogeographic And Phylogenetic Exploration Of Plethodon (Plethodontidae, Caudata) Salamanders In The Pacific Northwest, Tara Anne Pelletier

Dissertations and Theses

Genetic studies of amphibians often reveal substantial population structure due to either historical demographics from changing climate and geographic features over varying timeframes. Eight species of terrestrial salamanders (Family: Plethodontidae, Genus: Plethodon) reside in forests of the Pacific Northwest (PNW). Plethodon vehiculum is the most widespread and abundant terrestrial salamander in the PNW yet evolutionary studies are lacking. Using mitochondrial DNA (mtDNA) sequence data (D-loop and cytb) questions regarding the phylogeography of P. vehiculum and phylogenetics of western Plethodons are explored. Two major clades were defined in P. vehiculum, a southern clade in the Klamath-Siskiyou region and a …

Seasonal Variation In Diet Of A Marginal Population Of The Hispid Cotton Rat, Sigmodon Hispidus, Lynn A. Walker, Robert K. Rose

Virginia Journal of Science

Cotton rats live in oldfields, habitats with a variety of mostly herbaceous plants. Based on other studies, the hispid cotton rat, Sigmodon hispidus, eats many kinds of herbaceous plants but grasses predominate. In contrast, our population of cotton rats ate many monocots but mostly they were not grasses. Our study sought to determine the diet of the cotton rat in eastern Virginia, near the northern limit of distribution on the Atlantic Coast. Fecal samples, collected each month during an on-going capture-mark-release demographic study of the rodent community, were analyzed using a standard method. A greater variety of foods (including …

Landcover Change And Population Dynamics Of Florida Scrub-Jays And Florida Grasshopper Sparrows, David Breininger

Electronic Theses and Dissertations

I confronted empirical habitat data (1994-2004) and population data (1988-2005) with ecological theory on habitat dynamics, recruitment, survival, and dispersal to develop predictive relationships between landcover variation and population dynamics. I focus on Florida Scrub-Jays, although one chapter presents a model for the potential influence of habitat restoration on viability of the Florida Grasshopper Sparrow. Both species are unique to Florida landscapes that are dominated by shrubs and grasses and maintained by frequent fires. Both species are declining, even in protected areas, despite their protected status. I mapped habitat for both species using grid polygon cells to quantify population potential …

Population Genetics Of Island Endemics: Neutral And Major Histocompatibility Loci, Jennifer Lynn Bollmer

Dissertations

Island archipelagoes are ideal for the study of microevolutionary forces due to their multiple, closely related but geographically disjunct populations. I used both neutral and major histocompatibility complex (MHC) loci to determine the population genetic structures of bird species endemic to the Galapagos Islands. MHC molecules recognize foreign pathogens in the body, and these loci are known for their high degree of genetic variability maintained by natural selection. Small island populations are predicted to have reduced genetic variability due to the effects of genetic drift; however, selection may be strong enough to prevent the loss of variability at MHC loci. …

The Reproductive And Conservation Biology Of The Spotted Towhee In Urban Forest Fragments, Sarah Bartos Smith

Dissertations and Theses

I studied the demography, reproductive biology, and mating behavior of Spotted Towhees (Pipilo maculatus) in four urban parks in relation to park area, the presence of recreational trails, and the effects of habitat edges. Despite high towhee abundance in the parks, two of the four are population sinks with levels of yearly reproductive productivity that do not offset adult survival. The other two parks have sufficient reproduction to adequately result in stable or growing population sizes. Park area and the proportion of habitat edge had no influence on population growth rate, reproductive productivity, or survival. However, trail density …

Performance Of Dionaea Muscipula As Influenced By Developing Vegetation, James O. Luken

Biology

Demography, growth, and flowering of Dionaea muscipula (Venus' fly trap) were studied during three years (2003–2005) following prescribed fire. Data were collected in permanent quadrats where the developing vegetation was either repeatedly clipped or allowed to grow. Clipping increased light availability at the soil surface. Over the study period, seedling establishment and flowering declined with increasing time since the last prescribed burn. Seedling densities did not differ between clipped and control quadrats, although greater numbers of seedlings grew to adult size in control quadrats and this significantly influenced population size-class structure. Clipping had no effect on leaf number or senescence, …

Does Habitat Affect Clonal Demography? An Experiment With Polygonella Myriophylla In Roadside And Florida Scrub, Kristina Dianne Horn

Electronic Theses and Dissertations

Polygonella myriophylla (Polygonaceae) is a clonal shrub listed as endangered and narrowly endemic to pyrogenic scrub ecosystems in central Florida. It is almost restricted to gaps within the matrix of shrubs in the scrub but also occurs along adjacent road-side habitats. I hypothesize that persistent disturbed microhabitats and more dynamic sand accretion in roadsides will increase rooting probabilities compared to more stable scrub habitats, affecting survival, growth and reproduction. In April 2004- March 2006, I compared plant (genet) and basal branch (ramet) performance between experimentally manipulated plants in native scrub and roadside habitats at two locations within the Lake Wales …

Demographic Consequences Of Managing For Florida Scrub-Jays (Aphelocoma Coerulescens) On An Isolated Preserve., Casey Lyon

Electronic Theses and Dissertations

Many species naturally occupy discrete habitat patches within a mosaic of habitats that vary in quality. The Florida scrub-jay (Aphelocoma coerulescens) is endemic to Florida scrub, a habitat that is naturally patchy and greatly reduced in area over recent decades owing to development and urbanization. Because of this habitat loss, future management of Florida scrub-jays will focus on smaller, fragmented tracts of land. My study examines such a tract, Lyonia Preserve, southwest Volusia County, FL. This preserve was unoccupied by scrub-jays prior to habitat restoration. The preserve is now frequently managed exclusively for scrub-jays as a habitat island surrounded by …

Models Of Density‐Dependent Genic Selection And A New Rock‐Paper‐Scissors Social System, Barry Sinervo, Benoit Heulin, Yann Surget-Groba, Jean Clobert, Donald B. Miles, Ammon Corl, Alexis Chaine, Alison Davis

Biology Faculty Publications

We describe new ESS models of density regulation driven by genic selection to explain the cyclical dynamics of a social system that exhibits a rock-paper-scissors (RPS) set of three alternative strategies. We tracked changes in morph frequency and fitness of Lacerta vivipara and found conspicuous RPS cycles. Morphs of Uta and Lacerta exhibited parallel survival-performance trade-offs. Frequency cycles in both species of lizards are driven by genic selection. In Lacerta, frequency of each allele in adult cohorts had significant impacts on juvenile recruitment, similar to mutualistic, altruistic, and antagonistic relations of RPS alleles in Uta. We constructed evolutionarily stable strategy …

Consumers Limit The Abundance And Dynamics Of A Perennial Shrub With A Seed Bank, Matthew J. Kauffman, John L. Maron

Biological Sciences Faculty Publications

For nearly 30 years, ecologists have argued that predators of seeds and seedlings seldom have population-level effects on plants with persistent seed banks and density-dependent seedling survival. We parameterized stage-based population models that incorporated density dependence and seed dormancy with data from a 5.5-year experiment that quantified how granivorous mice and herbivorous voles influence bush lupine (Lupinus arboreus) demography. We asked how seed dormancy and density-dependent seedling survival mediate the impacts of these consumers in dune and grassland habitats. In dune habitat, mice reduced analytical lambda (the intrinsic rate of population growth) by 39%, the equilibrium number of above-ground plants …

Human Activity Mediates A Trophic Cascade Caused By Wolves, Mark Hebblewhite, Clifford A. White, Clifford G. Nietvelt, John A. Mckenzie, Tomas E. Hurd, John M. Fryxell, Suzanne E. Bayley, Paul C. Paquet

Biological Sciences Faculty Publications

Experimental evidence of trophic cascades initiated by large vertebrate predators is rare in terrestrial ecosystems. A serendipitous natural experiment provided an opportunity to test the trophic cascade hypothesis for wolves (Canis lupus) in Banff National Park, Canada. The first wolf pack recolonized the Bow Valley of Banff National Park in 1986. High human activity partially excluded wolves from one area of the Bow Valley (low-wolf area), whereas wolves made full use of an adjacent area (high-wolf area). We investigated the effects of differential wolf predation between these two areas on elk (Cervus elaphus) population density, adult …

Demographic And Spatial Responses Of Coyotes To Changes In Food And Exploitation, Eric M. Gese

Wildlife Damage Management Conference

Lethal control for reducing carnivore populations is a contentious issue throughout the world. While computer simulations have been developed modeling the effects of population reduction on coyote (Canis latrans) population parameters, testing these hypotheses with empirical data from the field is lacking. We documented the demographic and spatial responses of coyotes to changes in the levels of food resources and human exploitation on the Piñon Canyon Maneuver Site, southeastern Colorado. We captured, radio-collared, and tracked 92 (53 M: 39 F) coyotes from March 1983 to April 1989. Of these, 74 animals were residents from 32 packs, plus 12 …

The Effect Of Wildfire On Populations Of The Jemez Mountains Salamander (Plethodon Neomexicanus) With Consideration To Arthropod Prey Availability Following The Cerro Grande Fire Of Northern New Mexico, Michelle R. Cummer

Biology

Fire regimes in North America, including the American Southwest, have undergone relatively dramatic shifts in the last century, resulting in novel stand-replacing fires that are changing landscapes in unprecedented ways. Some possible effects of these novel landscape changes on a terrestrial plethodontid salamander (Plethodon neomexicanus) were investigated. Microhabitat temperatures in four burn-severity types following recent fires were measured. Temperatures were significantly greater in high-severity and moderate-severity burn areas than in low-severity and unburned areas. Salamander presence/absence data from four burn-severity types that were documented as having salamanders prior to wildfire are considered. The proportions of presence and absence …

Effects Of Density On Timing Of Emergence And Its Consequences For Survival And Growth In Two Communities Of Annual Plants, Roy Turkington, Deborah E. Goldberg, Linda Olsvig-Whittaker, Andrew R. Dyer

Faculty Publications

We tested whether increasing seed density results in a change in the timing of emergence in two communities of sand dune annual plants in Israel. Specifically we tested (i) if emergence is accelerated or delayed due to high seed density. We also tested two predictions about the consequences of changes in the timing of emergence; (ii) seedlings emerging earlier will have higher survival and growth; (iii) the advantage of earlier emergence increases as seed density increases. We examined these predictions for both monocots and dicots growing under different irrigation regimes and using species from a desert and a semi-arid community …

Natal Dispersal Of Beavers In The Embarras River Watershed In Central Illinois, Erin A. Cleere

Masters Theses

Dispersal is an important mechanism influencing the dynamics, genetics, spatial distribution and size of wildlife populations (Gese and Mech 1991). Natal dispersal may afford individuals breeding opportunities and access to resources, while reducing inbreeding and competition with family members. However, dispersal also can be risky if mortality rates are high or if mates or suitable habitat are unavailable. When dispersal costs are high, subadults may be better off remaining in their natal territory.

Although a number of previous studies have investigated natal dispersal in beavers (Castor canadensis), conclusions regarding the percentage of subadults that disperse, timing of dispersal, evidence of …

Summer Activity Of Small Snakes In Four Habitats In Northwestern Missouri, L. D. Johnson, Geoffrey R. Smith, Jessica E. Rettig

Faculty Publications

No abstract provided.

Testing For Resistance Of Pelagic Marine Copepods To A Toxic Dinoflagellate, Sean Colin, Hans G. Dam

Arts & Sciences Faculty Publications

With few exceptions, the evolutionary consequences of harmful algae to grazers in aquatic systems remain unexplored. To examine both the ecological and evolutionary consequences of harmful algae on marine zooplankton, we used a two-fold approach. In the first approach, we examined the life history responses of two geographically separate Acartia hudsonica (Copepoda Calanoida) populations reared on diets containing the toxic dinoflagellate Alexandrium fundyense . One copepod population was from a region, Casco Bay, Maine, USA, that has experienced recurrent blooms of highly toxic Alexandrium spp. for decades; whereas the other population from Great Bay, New Jersey, USA, has never been …

Life-History Variation In The Sagebrush Lizard (Sceloporus Graciosus): Phenotypic Plasticity Or Local Adaptation?, Michael W. Sears

Publications

We performed a laboratory common-environment study to determine the genetic and environmental sources of variation in growth rates of the sagebrush lizard (Sceloporus graciosus). Hatchling lizards were reared from gravid females collected from three study populations along an elevational gradient in southern Utah, USA. Hatchlings were fed ad libidum and were maintained on a 14:10 light:dark cycle, with temperatures at 33°C and 21°C during photophase and scotophase, respectively. Each hatchling was randomly assigned to either a water-supplementation treatment or a control group receiving no supplemental water. Once every five days, the water-supplemented lizards were administered orally a quantity …

Ethanol: A Better Preservation Technique For Daphnia, A. Ross Black, Stanley I. Dodson

Biology Faculty Publications

A 4% formalin-40% sucrose solution has been used by limnologists for three decades as the preferred freshwater zooplankton preservative because it kills and fixes cladocera (Branchiopoda) with relatively little distortion. Because of the increasing evidence of health hazards related to formalin, we sought an alternative, safer preservative that satisfies the need for low distortion. Our results suggest the ethanol preservative methods (70% and 95% treatments) are as good or better as using 4% sugar formalin to fix and store samples. Our results indicate the best method is to fix samples in 95% EtOH followed by storage in 70% EtOH. This …

A Survey Of The Mammals Of The Archie Carr And Pelican Island National Wildlife Refuges, Joseph S. Weidlich

Retrospective Theses and Dissertations

ABSTRACT This summarizes a study conducted on the Archie Carr (ACNWR) and Pelican Island (PINWR) National Wildlife Refuges located on the barrier island complex of southern Brevard and northern Indian River counties, Florida. Major objectives of this study were designed to 1) survey the mammals of the ACNWR and PINWR, 2) perform a small mammal population demographic study in coastal scrub and maritime hammock habitats, and 3) document a population monitoring project of Peromyscus po/ionotus niveiventris in northern Indian River County at Treasure Shores Park, within ACNWR Segment 4. A total of7,279 trap nights was compiled during the survey portion …

Treefall Gaps And The Maintenance Of Species Diversity In A Tropical Forest, Stefan A. Schnitzer, Walter P. Carson

Biological Sciences Faculty Research and Publications

The maintenance of species diversity by treefall gaps is a long‐standing paradigm in forest ecology. Gaps are presumed to provide an environment in which tree species of differing competitive abilities partition heterogeneous resources. The empirical evidence to support this paradigm, however, remains scarce, and some recent studies even suggest that gaps do not maintain the diversity of shade‐tolerant species. Although there is evidence that gaps maintain the diversity of pioneer trees, most of this evidence comes from studies that did not make comparisons between gaps and intact forest sites (controls). Further, nearly all studies on the maintenance of diversity by …

Ecology And Sympatric Relations Of Crevice Salamanders In Randolph County, West Virginia, Jayme Linn Waldron

Theses, Dissertations and Capstones

By implementing a mark-recapture study, I investigated the ecology of three species of sympatric plethodontid salamanders (Aneides aeneus, Desmognathus ochrophaeus, and Plethodon glutinosus) on rock outcrops in the Westvaco Wildlife and Ecosystem Research Forest, Randolph County, West Virginia. By examining activity patterns, vertical stratification, and habitat preference for A. aeneus, D. ochrophaeus, and P. glutinosus, I attempted to offer some insight into how these sympatric species avoid competition on small, isolated rock outcrops. Twenty-one surveys, both nocturnal and diurnal, were performed between 11 May and 17 October, 1999. During this time, 89 salamanders, encompassing five species ( …

Insect Herbivory Above- And Belowground: Individual And Joint Effects On Plant Fitness, John L. Maron

Biological Sciences Faculty Publications

Understanding of the selective effects of insect herbivory on plants comes primarily from studies of herbivory aboveground. The impact of belowground herbivory, either in isolation or in concert with herbivory aboveground, on plant fitness is only beginning to be understood.

I reduced the densities of root-boring ghost moth (Hepialus californicus) larvae and/or flower- and seed-feeding insects of bush lupine (Lupinus arboreus), a woody shrub, and followed fecundity and survival of plants for three years. In year one, suppression of aboveground herbivores increased mean seed output by 31%, but suppression of belowground herbivores had no significant effect …

Secondary Reproductive Strategies Of The Eastern Kingbird (Tyrannus Tyrannus), Assessed By Dna Fingerprinting And Egg Physiognomy, Diane L. Rowe

Biology

Extra-pair fertilization, a secondary breeding strategy, was detected in the eastern kingbird (Tyrannus tyrannus) using multi-locus DNA fingerprinting. I assessed the genetic parentage of 20 broods in a population of kingbirds in central New York. Two DNA probes were used to test for exclusion of nestlings as true offspring of one or both social parents. Band-sharing coefficients and the number of novel bands were used to discern which parent was not a first-degree relative of the nestling in question. No cases of conspecific brood parasitism or quasi-parasitism were documented. However, extra-pair paternity was found to be very common, …