Other Ecology and Evolutionary Biology Commons^™

Ectomycorrhizal Fungi Associated With Pinus Species Of California's Northwestern Coast, Monika Audrey Richardson

Cal Poly Humboldt theses and projects

Ectomycorrhizal (ECM) fungi are vital for increasing host plant uptake of nutrients and stress tolerance within ECM forest ecosystems. The species assemblage of ECM fungi can vary locally in response to numerous biotic and abiotic environmental factors. In California’s northwestern coast the occurrence of three Pinus species, along with a disjunction between populations of Pinus muricata in Mendocino and Humboldt Counties, offer a unique opportunity to investigate the spatial and host effects on pine-associated ECM fungi. Ectomycorrhizal fungal community structure was quantified from host tree roots and sequenced sporocarps occurring at the same sites to create a project specific ITS …

Postfire Habitat Use And Density Of Pacific Martens (Martes Caurina) In Lassen National Forest, California, Deirdre L. Replinger

Cal Poly Humboldt theses and projects

Increasing frequency, size, and severity of wildfires in western North America threatens forest-dependent wildlife species. The Pacific marten (Martes caurina) has historically been associated with mature, structurally complex forest throughout most of its range. Recently, martens have been detected in forests burned at high severity by the 2021 Dixie Fire—the largest recorded single fire in California state history. I used non-invasive remote camera traps and hair snares (n = 166 sites) to assess marten habitat use and density using spatial occupancy and spatial capture-recapture models. I detected martens across the burn severity gradient (unburned to high-severity) at …

Multiple Burn And Forest Characteristics Affect Gray Fox (Urocyon Cinereoargenteus) Occurrence Following A California Megafire, Amida Zohar Verhey

Cal Poly Humboldt theses and projects

In western North American forests, predator communities are faced with changing fire regimes and increased fire severity and size, particularly with megafires (>10,000 ha). As some wildlife communities may restructure following the loss of apex consumers, understanding post-fire space use of mid-trophic carnivores may inform species composition in these forests. I compared gray fox (Urocyon cinereoargenteus) occupancy in and around the 2021 Dixie Fire, the largest single-ignition fire in California state history, to examine which spatially variable burn and forest characteristics affected the space use of a widespread generalist mesopredator. Using 210 camera traps placed in 2023, …

Examining The Effects Of Songbird Nest Boxes And Habitat On Avian And Arthropod Communities In A Vineyard Ecosystem, Eleanor Macdonald

Cal Poly Humboldt theses and projects

Agricultural expansion threatens biodiversity, but integrating insectivorous birds into vineyard ecosystems may support both conservation and ecosystem services. We tested how nest boxes and habitat composition influence avian and arthropod communities in Napa Valley vineyards using a before-after, control-impact experiment across 20 sites. During the 2023-2024 breeding seasons we conducted avian point counts, sampled key pest and beneficial arthropods, and collected fecal samples from adult and nestling tree swallows (Tachycineta bicolor) and western bluebirds (Sialia mexicana) to detect vineyard pest DNA. Nest boxes significantly increased swallow and bluebird abundance within one year; swallow responses were strongest …

Investigating Fish Communities As Part Of The Food Web In Artificial Tidal Wetland Ponds Of Humboldt Bay, Ca, Lily M. Olmo

Cal Poly Humboldt theses and projects

In the face of global wetland loss, artificially created wetlands have the potential to restore ecosystem services for humans while also providing habitat for fish and wildlife. This study explored fish communities in three understudied artificial wetland ponds that are connected to Humboldt Bay in northern California and known to be important wildlife foraging areas. The objectives of this research were to 1) Characterize the environmental conditions of each pond, 2) Calculate the relative catch, richness, diversity, and biomass of fish in each pond, 3) Describe the movement of fish into and out of the ponds with the tides, and …

Roosting Habits Of Male Silver-Haired Bats In The Willard Creek Drainage Of Northeastern California, Alexander Christopher Lewis

Cal Poly Humboldt theses and projects

Silver-haired bats (Lasionycteris noctivagans) are one of the most widely distributed forest bats in North America. Although wildfires have been increasing across their range, how they respond to wildfire is understudied. Previous studies on silver-haired bats and fire focused on roosting behavior in low-severity controlled burns or used acoustics to understand activity levels post-wildfire. Quantifying how silver-haired bats use the physical structures created by high-severity wildfires and the landscape features in which they occur is critical in the face of rapidly shifting fire regimes. During the summer of 2023 and 2024 I radio-tracked male silver-haired bats to 37 roosts …

Bird Predation On Coho Salmon (Oncorhynchus Kisutch) In Humboldt Bay, Colton J. Dixon

Cal Poly Humboldt theses and projects

Coho Salmon (Oncorhynchus kisutch) populations along the west coast of the United States are declining. In Humboldt County, located in northwestern California, Coho Salmon have been in decline since their federal listing as threatened in 1997, primarily due to habitat loss from logging, agriculture, and urban development. Although these anthropogenic factors caused salmon populations to decline, bird predation may also be hindering population recovery, as evidenced by the recovery of Passive Integrated Transponder (PIT) tags, originally implanted in Coho Salmon, from bird colonies in Humboldt Bay. This study examines predation by Double-crested Cormorants (Phalacrocorax auritus), Caspian …

Fire Severity Mediates Marten And Fisher Occurrence: Impacts Of The Dixie Fire On A Carnivore Community, Christopher James Collier

Cal Poly Humboldt theses and projects

The consumption of an astounding one million acres resulted from California’s largest single fire to date, the 2021 Dixie Fire. The social and economic losses associated with the fire were immediately apparent, but the effects on wildlife remained unknown. While previous research has suggested mixed or low severity fire may be beneficial to certain wildlife species, the responses to megafires are poorly understood for many carnivores. To better understand these responses to severe fire, I used a random sampling design stratified by burn severity to survey in and around the Dixie Fire footprint using baited camera stations. This allowed me …

The Effects Of Native Perennial Cover On Physiological Indicators Of Habitat Quality For Sparrows In California Coastal Prairie Rangelands, Madeleine A. Ybarra

Cal Poly Humboldt theses and projects

Prescribed grazing management can have myriad effects on wildlife, with low to moderate grazing being associated with an increased abundance of some grassland birds. Specifically, Grasshopper Sparrow (Ammodramus savannarum) and Savannah Sparrow (Passerculus sandwichensis) abundance have been shown to be positively associated with both grazing and a higher percentage of native plant cover. However, measures of abundance provide an incomplete assessment of habitat quality for birds. Physiological and morphological measurements can help indicate environmental stress in individual birds, which reveals more information about habitat quality. We measured body condition and heterophil:lymphocyte ratios to gauge avian stress …

Scale And Habitat Effects On Measurement Of Streptomyces Biogeography And Biodiversity, Terilyn A. Stoflet

Cal Poly Humboldt theses and projects

Bacteria in the genus Streptomyces are detected in most soils around the world, as well as on and in seeds, plants, animals, insects and the wind. Currently, more than 700 valid species of Streptomyces have been identified worldwide. Streptomyces produce the majority of antibiotics, antivirals and antifungals, as well as important agricultural bioactive molecules due to their unique genetic capabilities. Their distinct genetic abilities allow them to produce an unlimited amount of biosynthetic gene clusters, or BGC’s. Although many compounds come from Streptomyces, scientists have not discovered the biogeographic patterns of this genus. The biogeography of Streptomyces is a …

Comparing Mexican Spotted Owl Habitat Suitability In Two Different Habitat Types Using A Multi-Scale Ensemble Learning Framework, Danial Nayeri

Cal Poly Humboldt theses and projects

Habitat fragmentation and loss are major threats to species conservation worldwide. Studying species-habitat relationships is a crucial first step toward understanding species habitat requirements, which is necessary for conservation and management planning. However, some species inhabit a range of habitat types, potentially making the use of range-wide habitat models inappropriate due to non-stationarity. The Mexican spotted owl (Strix occidentalis lucida) (MSO) is a species that inhabits both forests and rocky canyonlands, two habitats with large differences in environmental conditions. It is unclear whether the species uses habitat differently in these two habitat types or if previously builthabitat models …

Carnivore And Ungulate Occurrence In A Fire-Prone Region, Sara J. Moriarty-Graves

Cal Poly Humboldt theses and projects

Increasing fire size and severity in the western United States causes changes to ecosystems, species’ habitat use, and interspecific interactions. Wide-ranging carnivore and ungulate mammalian species and their interactions may be influenced by an increase in fire activity in northern California. Depending on the fire characteristics, ungulates may benefit from burned habitat due to an increase in forage availability, while carnivore species may be differentially impacted, but ultimately driven by bottom-up processes from a shift in prey availability. I used a three-step approach to estimate the single-species occupancy of four large mammal species: mountain lion (Puma concolor), coyote …

Effects Of Ph, Eelgrass, And Settlement Substrate On The Growth Of Juvenile Magallana (Crassostrea) Gigas, A Commercially Important Oyster Species, Johnny S. Roche

Cal Poly Humboldt theses and projects

Worsening ocean acidification (OA), resulting from ongoing absorption of atmospheric carbon dioxide (CO₂) by the oceans, threatens marine life globally. Calcifying organisms, especially their early life stages, are particularly vulnerable; this includes the economically important Pacific oyster, Magallana (Crassostrea) gigas. Uptake of dissolved CO₂ through photosynthesis by seagrasses, like eelgrass (Zostera marina), may benefit calcifying organisms by increasing pH and carbonate availability. I conducted laboratory and field experiments to quantify carbonate chemistry modification by eelgrass and potential mitigation of OA impacts on growth in juvenile Pacific oysters. In the laboratory experiment, daytime …

Polymorphism Of Melanin-Based Pigments In Barn Owls In Winegrape Vineyards In Napa Valley, California, Laura Mariana Echávez Montenegro

Cal Poly Humboldt theses and projects

Many raptor species exhibit plumage polymorphism. Through the expression of a particular phenotype, polymorphism allows individuals to exploit alternative spatial or temporal environments and food resources most successfully. Barn Owls display within-species variation in their plumage, ranging from reddish to whitish and from heavily spotted to having no spots at all. In heterogeneous landscapes in Europe and the Middle East, reddish Common Barn Owls (Tyto alba) inhabit territories with proportionally more arable fields and consume proportionally more voles than mice in contrast to their whiter counterparts; a phenomenon known as habitat matching choice. This study sought to quantify …

Effects Of Oyster Aquaculture On Elasmobranch Abundance And Habitat Use In Humboldt Bay, Ca, Rose Harman

Cal Poly Humboldt theses and projects

Habitat modification from aquaculture can have large effects on natural communities, with the habitat complexity provided by aquaculture structure positively influencing benthic invertebrates and small fish abundance. However, the effects of aquaculture on larger predatory fish like elasmobranchs (i.e., sharks and rays), which use nearshore habitat to forage and provide top-down control of these ecosystems, is largely unknown. Over two years, I deployed baited remote underwater video systems (BRUVS) to examine the effects of oyster aquaculture and environmental variables such as habitat (mudflat or eelgrass), salinity (ppt), turbidity (m), temperature (°C), pH (mV), dissolved oxygen (mg · L^-1), …

Phylogenetic And Geographic Relationships Of Cheilostome Bryozoans In The Eastern Pacific, Hannah E. Lee

Cal Poly Humboldt theses and projects

The phylum Bryozoa is an incredibly diverse group of marine invertebrates with a widespread global distribution that is well suited for evolutionary studies but whose phylogenetic relationships are still poorly understood. Although recent studies on bryozoan taxonomies and phylogenies have increased, there is still a lack of assessment of species found at shallow water (<1 m) to intertidal depths. In this study, I aimed to expand the taxonomic sampling and assessment of the phylogenetic diversity of cheilostome bryozoans along the California coastline by utilizing mitochondrial DNA as well as inferring potential correlations between species presence and dispersal range both within and between rocky outer coast and sheltered harbor habitats. Illumina high-throughput sequencing was used to produce mitogenomes for cheilostome bryozoan samples collected off rocks from two rocky intertidal sites and off settlement panels from two harbor sites. Phylogenetic analyses generated evolutionary hypotheses of species relationships alongside geographic mapping of their distribution. This study identified 15 distinct species that represent 10 different families to form the first comprehensive phylogeny for multiple bryozoan families in California across a total range of approximately 973 km of coastline. Three genetically distinct species were found at multiple sites that are separated by a combination of rocky shores and sandy beaches, which indicates that the dispersal range of these species are not limited by geographic barriers along the coast of California. These results provide a future opportunity for further integration of this data with the phylogenies generated in this study to examine more robust evolutionary hypotheses for the phylogenetic and geographic relationships of Californian bryozoan species.

Activity Patterns Of The Del Norte Salamander (Plethodon Elongatus): Monitoring Plethodontid Behavior Using Pit Tag Surveys, Sabrina Horrack

Cal Poly Humboldt theses and projects

Semi-fossorial plethodontid salamanders exhibit behavioral plasticity to avoid desiccation, retreating underground to shelter from adverse conditions such as low precipitation and high temperatures. In this study, I used passive integrated transponder (PIT) tag surveys to monitor this behavior in the Del Norte salamander (Plethodon elongatus), a small plethodontid native to northwestern California and southwestern Oregon. Within its range, a climatic gradient exists in which coastal areas experience milder temperatures and high precipitation, while inland areas tend to have colder winters, hotter summers, and lower precipitation. By monitoring the activity patterns of this species in inland and coastal areas, …

Use Of Redwood Basal Hollows By Bats: A Focus On The Townsend's Big-Eared Bat On The North Coast Of California, Amon Jotesh Armstrong

Cal Poly Humboldt theses and projects

Loss of roosting resources, either through disturbance or removal, negatively affects bats. For sensitive species, such as the Townsend’s big-eared bat (Corynorhinus townsendii), determining roost requirements is a critical component in conserving their habitat. Such cavity roosting bats on the North Coast of California may use hollows in large redwood trees. In this study, I examined the factors determining the use of basal tree hollows by different bat species at eight redwood forest sites in Del Norte, Humboldt, and Mendocino Counties, California. Bat guano was collected from 179 basal hollow roosts from 2017 to 2018, and guano mass …

Do Beaver Dam Analogues Act As Passage Barriers To Juvenile Coho Salmon And Juvenile Steelhead Trout?, Christopher G. O'Keefe

Cal Poly Humboldt theses and projects

In the Pacific Northwest, the human-caused reduction of quality and quantity of freshwater rearing habitat is a limiting factor for Pacific Salmon populations. Beaver dam analogues (BDAs) increase suitable rearing habitat for juvenile salmonids and promote the restoration of critical stream processes. Installing BDAs is an increasingly popular alternative to more intensive restoration techniques, due to the relatively low cost and effort required to install BDA structures. However, widespread installation of BDAs has been slowed by regulatory agencies’ concerns that BDAs may impede fish passage. Few studies have empirically assessed the extent to which BDAs impede fish passage, and no …

Phylogenetic And Population Genetic Analysis Of The Humboldt's Flying Squirrel Using High-Throughput Sequencing Data, Stella Chi Yuan

Cal Poly Humboldt theses and projects

The intraspecific genetic variation and diversity within the Humboldt’s flying squirrel (Glaucomys oregonensis) has not yet been characterized despite its elevation to full species in 2017. The San Bernardino flying squirrel (G. o. californicus) is thought to be the southernmost population of G. oregonensis and is restricted to the San Bernardino and San Jacinto Mountains in California, but recent surveys indicate they have been extirpated from the latter locality. In order to provide baseline genetic data across the geographic range of G. oregonensis, I had the following objectives: 1) investigate the intraspecific molecular variation in …

The Effect Of Shade Tree Species On Bird Communities In Central Kenyan Coffee Farms, Deven Kammerichs-Berke

Cal Poly Humboldt theses and projects

Shade coffee has been recognized as a well-studied example of a land-sharing management strategy that both creates habitat for tropical birds while also maintaining agricultural yield. Despite the general consensus that shade coffee is more “bird-friendly” than a sun coffee monoculture, little work has been done to investigate the effects of specific shade tree species on bird diversity and their capacity to help deliver ecosystem services. Previous studies in temperate regions have demonstrated that due to shared evolutionary histories, native plant species are better at promoting native arthropod numbers, which in turn support a greater number of birds. This study …

The Effects Of Woody Vegetation Encroachment And Removal Within A Coastal Fen, Joseph Saler

Cal Poly Humboldt theses and projects

Early successional wetland habitat is being lost in temperate regions worldwide as a result of changes in disturbance regimes that allow for the establishment and dominance of woody species. In particular, this phenomenon is pronounced in fens, which harbor high numbers of rare herbaceous species that require early successional habitat. I investigated the relationship between woody vegetation encroachment and herbaceous species diversity within a Northern California coastal fen that has been undergoing encroachment by woody vegetation for ca. 80 years by recording species richness and cover data from 338 permanent plots throughout the fen. I also investigated the effect of …

Impacts Of Ocean Acidification On Intertidal Macroalgae And Algivore Preference, Andrea Michelle Fieber

Cal Poly Humboldt theses and projects

Ocean acidification, a facet of global climate change, has the potential to induce changes in marine macroalgae that modify their existing interactions with algivorous invertebrates. In this study, I examined the effects of elevated carbon dioxide (pCO₂) on several species of intertidal macroalgae (Phaeophyta, Rhodophyta) and evaluated the present-day and predicted future preferences of algivores (Pugettia producta and Tegula funebralis) by assessing grazing rates on untreated algal tissue and on algae exposed to high-pCO₂ seawater. Both red and brown algae grew faster in elevated pCO₂ than in ambient seawater, …

Multivariate Habitat-Based Predictive Modeling Of Three Demersal Rockfish Species In Central California, Georgia R. Martel

Cal Poly Humboldt theses and projects

Accurate, spatially explicit models of rockfish abundance are critical in implementing ecosystem-based management strategies and designating essential fish habitats and marine protected areas. Multibeam bathymetry methods and visual, non-extractive submersible transect surveys were combined to collect environmental variables and fish abundance data at three distinct sites within the study region. Zero-adjusted models were developed using habitat classification analyses of high-resolution (5 m) digital elevation models. Model accuracies were assessed by using a reserved subset of the original datasets. To demonstrate that a model’s predictive power was linked to its spatial origins, Mean Absolute Error and coefficient of determination values were …

Spatiotemporal Variability Of Rockfish Recruitment On California's North Coast In Relation To Habitat Availability, Carolyn Belak

Cal Poly Humboldt theses and projects

Characterizing primary drivers of temporal and spatial variability in recruitment is imperative to understanding the role of pre- and post-settlement processes influencing marine population dynamics. On benthic reefs, the quality and quantity of suitable settlement habitat can alter post-settlement density-dependent mortality rates and increase chances of survival. The north coast of California has experienced highly unusual oceanographic conditions in recent years, leading to severe loss of highly productive kelp forests and potentially deleterious ecosystem consequences. In the present thesis, I aimed to determine the effects of canopy-forming bull kelp (Nereocystis) and alternative complex habitats on the recruitment of …

Tree Squirrels And Fishers In Northern California: The Effects Of Masting Hardwoods On Stand Use, Andria M. Townsend

Cal Poly Humboldt theses and projects

In western North America, tree squirrels such as western gray (Sciurus griseus) and Douglas squirrels (Tamiasciurus douglasii) are potentially important prey for fishers (Pekania pennanti). Western gray squirrels in particular may be highly ranked due to their large body size. Masting trees including black oak (Quercus kelloggii) and tanoak (Notholithocarpus densiflorus) produce an important food source for tree squirrels; therefore, forest stands containing these trees may be useful to foraging fishers. I hypothesized that; 1) the abundance of western gray and Douglas squirrels in a stand is influenced by the …

Evidence For A New Search Behavior: Porcupines “Scout” For Winter Habitat During Summer In A Coastal Dune System, Pairsa N. Belamaric

Cal Poly Humboldt theses and projects

Species are often challenged by periodic changes in food availability and habitat quality. These environmental conditions may provide strong selective pressure for animals to strategically "scout" for important resources during periods of abundance, when exploratory movements are less costly. North American porcupines experience a drastic shift in forage quality from summer - a time of abundant, high quality forage - to winter, a nutritional bottleneck. I evaluated potential scouting behaviors of porcupines in Tolowa Dunes State Park, California using movement and habitat-use data. I compared summer and winter space use of porcupines using GPS data and monitored seasonal use of …

Evaluation Of Range-Wide Occupancy And Survey Methods For The Giant Kangaroo Rat (Dipodomys Ingens), Alyssa E. Semerdjian

Cal Poly Humboldt theses and projects

Though habitat suitability and occupancy are often correlated, they cannot always be inferred from each other. Therefore, a solid understanding of both is essential to effectively manage species. Recent studies have assessed range-wide habitat suitability for the giant kangaroo rat (Dipodomys ingens; GKR), but data regarding occupancy is lacking in parts of its distribution. Satellite and aerial imagery were used to identify GKR burrows across their known range, producing a range-wide occupancy map and non-invasive survey methods including track plates, manned flight, unmanned aerial vehicle, and sign surveys were conducted to determine effective methods for monitoring GKR occupancy. …

Ecological Consequences Of Sea Star Wasting Disease: Non-Consumptive Effects And Trait-Mediated Indirect Interactions From Pisaster Ochraceus, Timothy Ian Mcclure

Cal Poly Humboldt theses and projects

Consumptive effects (CEs) of predators are an important factor in structuring biological communities, but further work is needed to understand how the interaction between spatial and temporal differences in predator density affects non-consumptive effects (NCEs) on prey. NCEs can cause indirect effects on food resources, known as trait-mediated indirect interactions (TMIIs), and thus can also affect community structure. However, few studies have considered the relationships between spatial and temporal predator density variation and the strength of NCEs and TMIIs in the natural environment. The ochre star Pisaster ochraceus is common predator of the herbivorous black turban snail Tegula funebralis, imposing …

Life History Of The Coastal Tailed Frog (Ascaphus Truei) Across An Elevational Gradient, Adrian Daniel Macedo

Cal Poly Humboldt theses and projects

The life history of a species is described in terms of its growth, longevity, and reproduction. Unsurprisingly, life history traits are known to vary in many taxa across environmental gradients. In the case of amphibians, species at high elevations and latitudes tend to have shorter breeding seasons, shorter activity periods, longer larval periods, reach sexual maturity at older ages, and produce fewer and larger clutches per year.

The Coastal Tailed Frog (Ascaphus truei) is an ideal species for the study of geographic variation in life history because it ranges across most of the Pacific Northwest from northern California …