Ecology and Evolutionary Biology Commons^™

Evaluating Current And Future Range Limits Of An Endangered, Keystone Rodent (Dipodomys Ingens), Ivy V. Widick

Cal Poly Humboldt theses and projects

Climate is often considered the single most important factor limiting species’ ranges. Other factors, such as biotic interactions, are often assumed to be included via abiotic proxies. However, differential responses to climate change may decouple these relationships or lead to adaptation to novel environments. Accounting for competition and local adaptation should more accurately describe environmental factors influencing current distributions and increase the predictive accuracy of future distributions. Modeling the endangered giant kangaroo rat (Dipodomys ingens) is an excellent application of these model improvements, as the species range consists of geographically and genetically isolated populations experiencing disparate climatic change. …

The Effects Of Forest Degradation On Dna Methylation In Central African Songbirds, Andrew K. Wiegardt

Cal Poly Humboldt theses and projects

Environmentally-induced stress can initiate a molecular response through DNA methylation, which can alter gene expression, thereby serving as a mechanism allowing individuals to acclimate to a changing environment within their lifetime. In addition to DNA methylation, the production and release of corticosterone is a physiological mechanism by which birds can cope with acute environmental stressors. To assess how environmental stress impacted DNA methylation and corticosterone, I collected blood and feather samples from three understory avian species (Alethe castanea, Bleda notatus and Pseudalethe poliocephala), along a disturbance gradient in the lowland Guinean rainforest adjacent to the village of …

A Comparison Of Community Structure In Regulated And Unregulated Reaches In The Upper Eel River, California, Lara Stephanie Jansen

Cal Poly Humboldt theses and projects

Flow regulation of rivers by impoundments and diversions can reduce hydrological variability. As a result, densities of algae and benthic macroinvertebrates often increase, but many sensitive taxa are lost, causing shifts across the food web. In Northern California, dams that reduce winter peak floods can result in the primary consumer community becoming dominated by grazers that are relatively invulnerable to predation, which can reduce the amount of energy transferred up the trophic levels. The steeper slope of the spring hydrograph recession limb downstream of a dam can also greatly impact instream diversity of periphyton, invertebrates and fish. The dam and …

Effects Of Manual And Mechanical Ammophila Arenaria Removal Techniques On Coastal Dune Plant Communities And Dune Morphology, Monique R. Silva Crossman

Cal Poly Humboldt theses and projects

The removal of invasive species as part of the restoration process can allow natives organisms to rebound. An ecosystem that incurs damages from invasive species is coastal sand dunes, which are dynamic systems. Some coastal sand dunes on the west coast of the United States have been invaded by Ammophila arenaria. The invasive grass, A. arenaria, is thought to alter and stabilize foredune morphology and reduce populations of native species. The objectives of my research are to examine the effects that manual and mechanical A. arenaria removal techniques have on coastal sand dune morphology and vegetative cover over time. …

Jeweled Spider Flies (Eulonchus Tristis) Are Important Pollinators Of Iris Bracteata, A Rare Siskiyou Mountain Endemic, Jean-Paul E. Ponte

Cal Poly Humboldt theses and projects

Little is known about the pollination biology of the Pacific Coast Irises (Iris: series Californicae, hereafter PCI), especially who visits and pollinates their flowers. In general, Iris flowers are considered bee-pollinated, however, flies in the genus Eulonchus (Acroceridae) are known to visit some PCI members. Therefore, I assessed the relative importance of Eulonchus and other insect visitors to the pollination of a rare PCI species native to the Siskiyou Mountains, I. bracteata.

Methods. I quantified pollinator importance for all flower visitors at sites in northern California and southern Oregon as the product of average visit rate and …

Hunting Habitat Use And Selection Patterns Of Barn Owl (Tyto Alba) In The Urban-Agricultural Setting Of A Prominent Wine Grape Growing Region Of California, Xeronimo A. Castaneda

Cal Poly Humboldt theses and projects

Large scale conversion of uncultivated land to agriculture threatens wildlife and can diminish ecosystem services provided by nature. Understanding how wildlife provision ecosystem services may incentivize wildlife conservation in agricultural landscapes. Attracting barn owls (Tyto alba) to nest on farms for pest management has been documented worldwide, but has not been thoroughly evaluated in vineyard agroecosystems. Napa Valley, California is a renowned winegrape growing region, and viticulturists encourage barn owl occupancy to help minimize plant damage from pocket gophers (Thomomys bottae) and voles (Microtus spp.). This study aimed to establish a basis for revealing the …

In The Face Of Drought: Do Fuel Treatments Promote Resistance To Multi-Year Drought In A Mixed-Conifer Forest Of Northern California?, Michael Vernon

Cal Poly Humboldt theses and projects

Climate change is predicted to increase the frequency, duration, and severity of drought events across many bioregions. Forest managers have two active management techniques to promote resistance and resilience to drought: prescribed fire and mechanical thinning. Generally applied to reduce fuels and fire hazard, treated areas may also reduce competition for resources that may improve tree-growth during drought and reduce mortality. The recent severe and prolonged drought in California allowed me to investigate the effects of climate stress and fuel treatments on tree growth responses in a dry mixed-conifer forest ecosystem.

To assess tree-growth responses to fuel treatments during severe …

A Comparison Of Benthic Macroinvertebrate Assemblages Between Perennial And Intermittent Headwater Streams Of The Mattole River In Northern California, Usa, Mason S. London

Cal Poly Humboldt theses and projects

Intermittent streams are common throughout the world and comprise 60% or more of total river lengths in the conterminous United States. Despite their prevalence, intermittent streams are understudied, particularly first-order headwater streams, which are vital for maintaining the function, health and biotic diversity of river networks. In June 2016, I sampled five intermittent and five perennial headwater streams in the Mattole River watershed in northwestern coastal California, USA, to compare benthic macroinvertebrate (BMI) assemblages between intermittent and perennial streams. BMI samples were collected using a 500µm mesh D-net at eight randomly located riffles along a 150-m reach, and then composited, …

The Influence Of Canopy Cover And Climate On Early Life-Stage Vital Rates For Northern Red-Legged Frogs (Rana Aurora), And The Implications For Population Growth Rates, Kecly Mcharry

Cal Poly Humboldt theses and projects

Many amphibian species are in decline due to habitat loss and changing climates. Understanding how habitat characteristics and climate influence vital rates, and if they act in concert or in opposition can inform management decisions. This study investigated the potential interaction of canopy cover and climate on early stage vital rates of northern red-legged frogs. Demographic data were collected from sample populations in experimental canopy cover treatments across a latitudinal distribution. Rearing cages were used to estimate hatch success, and mark-recapture surveys to estimate tadpole survival. Ambient air temperature was used as an index of climate because it is easily …

Habitat Use And Movement Patterns Of Two Redwood Forest Salamanders, Aneides Vagrans And Ensatina Eschscholtzii, With An Examination Of The Efficacy Of Pit Tags For Marking Small Plethodontids, Christian Brown

Cal Poly Humboldt theses and projects

The habitat use and movements of small, secretive salamanders are generally poorly understood, in part due to the difficulty associated with marking and recapturing such animals. This study was designed to test the efficacy, both in the laboratory and in the field, of using passive integrated transponder (PIT) tags to mark and track two small-bodied plethodontid salamander species native to coastal northwestern California, Aneides vagrans, the Wandering Salamander, and Ensatina eschscholtzii, the Ensatina Salamander.

Aneides vagrans inhabits tree crowns. Using cover objects and visual encounter surveys, I searched for A. vagrans in the angiosperm understory canopy at least twice …

Movement, Habitat, And Home Range Of Introduced Bullfrogs (Lithobates Catesbeianus) On Mad River Gravel Ponds (Humboldt Co., Ca, Usa), With Implications For Hydro-Modification As A Method Of Management, Madeline C. Cooper

Cal Poly Humboldt theses and projects

American Bullfrogs are a non-native, invasive species in California (USA), where they are known to have deleterious effects on many native species. Carnivorous adults prey on native amphibians and fish, while herbivorous tadpoles outcompete native tadpoles for algal food resources. Bullfrogs have been successful at colonizing old tailing ponds and other pools left over from mining activities, and these relict pools are common on many rivers in California. Information on the dispersal capabilities of Bullfrogs could help predict range expansions and inform management decisions. Unfortunately, this information is lacking from both their native and invaded range. From May to August …

Modeling The Spread Of Sudden Oak Death Across A Heterogeneous Landscape In Redwood National Park Using A Spatially-Explicit Epidemiological Model, Laura A. Morgan

Cal Poly Humboldt theses and projects

The pathogen Phytophthora ramorum, the causal agent of Sudden Oak Death (SOD), is responsible for the deaths of millions of oak (Quercus spp.) and tanoak (Notholithocarpus densiflorus) trees in California and Oregon (USA). A recent infection in Redwood National Park (RNP) in California (USA) provided an opportunity to adapt an existing SOD model to assess the efficacy of current and proposed management strategies. A common method of SOD treatment includes killing both infected and uninfected hosts in the area of infection, as well as the area surrounding the infection to create buffers to account for undetected …

Darlingtonia Californica Phytotelma Organisms: Spatial Relations Within The Metacommunity, Stefani Marie Brandt

Cal Poly Humboldt theses and projects

The California pitcher plant, Darlingtonia californica, provides a unique setting to research community ecology because it harbors small ponds of water, or phytotelmata, in its modified leaves. Each phytotelma hosts a unique community of various invertebrates who live among carcasses of drowned plant prey. These pitchers and their inquiline communities are relatively small yet abundant in the wild, resulting in an ideal natural setup for community composition comparisons. There have been no previous studies that research D. californica inquiline communities across multiple geographic regions concurrently. This study sought to survey phytotelma communities throughout the range of D. californica at …

An Estimation Of Potential Salmonid Habitat Capacity In The Upper Mainstem Eel River, California, Emily J. Cooper

Cal Poly Humboldt theses and projects

In Northern California’s Eel River watershed, the two dams that make up the Potter Valley Project (PVP) restrict the distribution and production of anadromous salmonids, and current populations of Chinook Salmon (Oncorhynchus tshawytscha) and steelhead trout (O. mykiss) in the upper mainstem Eel River are in need of recovery. In anticipation of the upcoming FERC relicensing of the PVP, this project provides an estimation of the extent of potential salmonid habitat and its capacity for steelhead trout and Chinook Salmon in the upper mainstem Eel River watershed above the impassable Scott Dam. Using three fish passage …

Molt In Individuals: A Description Of Prealternate Molt Phenology In A Population Of Snowy Plovers In Humboldt County, California, Alexa Dejoannis

Cal Poly Humboldt theses and projects

Molt in birds is an essential physiological process. Intrinsic and extrinsic conditions, such as age, sex, location, or food stress, may cause individual variation in molt phenology. This study describes the timing of prealternate molt in western snowy plovers (Charadrius nivosus nivosus) wintering in Humboldt County, California, USA. Between July 2014 and April 2015, I photographed uniquely marked plovers twice a month and assigned dates of initiation and completion. I modeled sex, age, hatch date, and breeding location as predictors of molt phenology. I observed prealternate molt from October to April, which is earlier than previously described. Males …

Evaluating Brandt’S Cormorant (Phalacrocorax Penicillatus) Reproductive Success: Effects Of Parental Care Behaviors And Estimating Individual Chick Survival, Shannon Murphy

Cal Poly Humboldt theses and projects

Variation in reproductive success is widely measured in seabird biology in an effort to indicate changes in the marine environment, or understand basic questions about ecology or conservation of seabirds. When variation in seabird reproductive success is suggested to indicate changes in the marine environment without identifying the proximate causes of such variation, inference is limited to association, and the proximate causes themselves could prove more effective as indicators. My study informs this problem by examining and quantifying proximate causes of variation in reproductive success, at the level of nests and individual chicks.

I used video of Brandt’s Cormorant ( …

Genetic Structure And Connectivity Of The Endangered Giant Kangaroo Rat (Dipodomys Ingens) In A Heterogeneous Environment, Nathan Alexander

Cal Poly Humboldt theses and projects

Movement ecology and dispersal are important aspects of species’ life histories that can inform conservation and management. Dispersal is often cryptic and difficult to detect, but recent advances genetic technology and applications have provided new approaches to identifying and describing dispersal patterns. Giant kangaroo rats (Dipodomys ingens) are an endangered heteromyid that appear to persist in small subpopulations in a heterogeneous environment of their northern range, the Ciervo-Panoche Natural Area, California. Previous work suggested high levels of genetic diversity between populations with genetic distances not being correlated to geographic distances. Here, I identified landscape population structure through clustering …

Early Seral Mixed-Conifer Forest Structure And Composition Following A Wildfire Reburn In The Sierra Nevada, Erin Alvey

Cal Poly Humboldt theses and projects

Before the era of modern fire suppression, California’s northern Sierra Nevada mixed-conifer and yellow pine forests were self-regulating; recurring short-interval, low-mixed severity wildfires maintained forest structure and composition, which in turn exerted bottom-up controls on subsequent wildfires. As a result of fire suppression, and coupled with the effects of climate warming and other anthropogenic disturbances, the fundamental structure of mixed-conifer and yellow pine forests has shifted. Wildfires may now be increasing in size, severity, and frequency across western North America. However, little is known about the post-fire impacts of repeat wildfire on a forest after a long era of suppression. …

Juvenile Survival And Adult Return As A Function Of Freshwater Rearing Life History For Coho Salmon In The Klamath River Basin, Molly Gorman

Cal Poly Humboldt theses and projects

The Scott and Shasta rivers, Klamath River tributaries, experience spatial disparity in habitat quality in spring and summer as a result of historical and current land-use. Juvenile Coho Salmon (Oncorhynchus kisutch) born in the upper tributary reaches often rear in natal streams before migrating to sea. However, those born in the lower reaches often encounter unsuitable habitat and emigrate during their first spring to seek non-natal rearing habitats. It is assumed that these early outmigrants are population losses. This study evaluated first-summer survival, and contribution to the adult population, of non-natal rearing juveniles in the Klamath River Basin. …