Evolution Commons^™

Limb Development In Salamanders: An Evolutionary Perspective To The Tetrapod Limb, Sruthi Purushothaman

Theses and Dissertations--Biology

Vertebrate limb is an ideal model to study growth, patterning and morphogenesis and the interplay between these processes. The developing limb bud is a three-dimensional structure and its outgrowth depends on the interaction between 2 important signaling centers: the Apical Ectodermal Ridge (AER) at the junction of the dorsal and ventral halves of the limb bud and the Zone of Polarizing activity (ZPA) in the posterior mesenchyme. These centers produce their respective key molecules and the close interplay between them specifies structures along the anterior-posterior (thumb to pinky), proximal-distal (shoulder to fingertips) and dorsal-ventral (knuckle to palm) axes.

Developmental biologists …

A Tale Of Winglets: Evolution Of Flight Morphology In Stick Insects, Yu Zeng, Connor O'Malley, Sonal Singhal, Faszly Rahim, Sehoon Park, Xin Chen, Robert Dudley

Publications and Research

The evolutionary transition between winglessness and a full-winged morphology requires selective advantage for intermediate forms. Conversely, repeated secondary wing reductions among the pterygotes indicates relaxation of such selection. However, evolutionary trajectories of such transitions are not well-characterized. The stick insects (Phasmatodea) exhibit diverse wing sizes at both interspecific and intersexual levels, and thus provide a system for examining how selection on flight capability, along with other selective forces, drives the evolution of flight-related morphology. Here, we examine variation in relevant morphology for stick insects using data from 1,100+ individuals representing 765 species. Although wing size varies along a continuous spectrum, …

Identification Of Odorant Receptor Genes In The Antennal Transcriptome Of The Common Eastern Fireflies, Photinus Pyralis, Hanh Tran

Honors Theses

The insect odorant receptor, OR, gene family has been hypothesized to play a critical role in reproduction. Odorant receptor proteins, located on the olfactory sensory neuronal dendrites, detect odorant chemicals such as pheromones and then mediate key behaviors such as mate choice. Although olfaction is known to play a predominant role in sexual communication, there are still large numbers of olfactory genes that have not been studied in many insect species including fireflies. In this study, I investigated the sequencing data of one of the common eastern fireflies, Photinus pyralis (Coleoptera: Lampyridae). This firefly species is well known for their …

Appealing To Human Intuitions To Reduce Animal Abuse, Yzar S. Wehbe, Todd K. Shackelford

Animal Sentience

Social scientists may be able to find ways to positively affect people’s evolved moral compasses, thereby doing the planet and its inhabitants a great kindness. They could help to shape a constituency that is increasingly opposed to animal abuse in its largest-scale manifestations, factory farming and wet markets. This would, in turn, motivate people to elect ethical leaders who view inaction with regard to animal abuse as a serious moral and medical mistake, if only indirectly due to factory farming’s exacerbation of the threats zoonoses pose to humans.

The Host Gatekeeper: Using The Flagellar Pathway To Understand Symbiont Host Adaptation, Adam R. Pollio

Graduate Theses, Dissertations, and Problem Reports (ETD)

The acquisition of microbial partners is a strategy used by a diverse group of arthropods to overcome ecological barriers that might normally make certain niches uninhabitable. The unique phylogenetic opportunities attainable from the natural experiment of the Sodalis-allied clade allow for better understanding of how molecular structures evolve through time. Here, we focus on the evolution of the flagellar synthesis pathway, due to its complexity and ability to diverge in response to ecological pressures. We used this molecular pathway and natural experiment to show that normal evolutionary outcomes associated with symbiosis (i.e., genome reduction) do not explain the predicted conservation …

Trees, Fungi, Insects: How Host Plant Genetics Builds A Community, Sandra Jeanne Simon

Graduate Theses, Dissertations, and Problem Reports (ETD)

Organisms, such as fungi and insects, can cause millions of acres of agricultural and forest damage, while others provide billions of dollars in ecological services such as education, aesthetic enjoyment, pollination, and gardening. Plant breeding and biotechnology can potentially help establish a balance between the proliferation of detrimental pests and attraction of beneficial insects. Variation in plant physiological and morphological characteristics are extremely important in the ability of host tissues to support many different types of organisms. When that variation is genetically heritable in a plant population, shifts in the underlying genes can have predictable consequences in structuring entire ecosystems. …

Developmental Mechanisms For The Diversification Of Polyphenic Morphs In The Head Horn Of Onthophagine Beetles (Coleoptera: Scarabaeidae Onthophagus Taurus): Plasticity Through Nutrition, Logan Paul Zeigler

Graduate Theses, Dissertations, and Problem Reports (ETD)

Developmental plasticity is the phenotypic variation between organisms that is caused by environmental interactions affecting the developmental systems of organisms. The research focused primarily on nutrition-responsive developmental plasticity. In this research we used the nutritionally determined head horn development of Onthophagus taurus to better understand the developmental mechanisms and genetic underpinnings of nutrition-responsive trait development. We focused specifically on altering the availability of specific nutrition-related primary metabolites, cholesterol and palmitic acid, identified in the activity of The Hedgehog pathway, a critical pathway in head horn development. By altering diet composition using cholesterol, reducing transcript expression of an acyltransferase gene, rasp …

The Effects Of Internal Physiology On Polyphenic Horn Development In The Dung Beetle Onthophagus Taurus, Naomi Garrett Williamson

Graduate Theses, Dissertations, and Problem Reports (ETD)

An organism’s phenotype can be affected in development by alterations to gene expression based on environmental inputs. Nutrition is one such environmental input and the central regulator of development of large horn or small horn phenotypes in the dung beetle species, Onthophagus taurus. However, little is known about the nature of chemical compounds that are critical to this plastic horn development. To better understand these compounds, we are utilizing an untargeted metabolomic approach as well as a targeted gene approach. Through the metabolomic approach, it was uncovered that environmental conditions tend to have a greater impact on metabolomic composition …

The Evolution Of Dragons, Laura J. Mayfield

Undergraduate Theses, Professional Papers, and Capstone Artifacts

Dragons have been depicted in human art as early as 4500 BCE. For centuries, these fantasy creatures have inspired countless folk and fantasy tales, as well as appearing in the art of different cultures around the world. Now there are thousands of different depictions of these huge, flying, fire-breathing lizards, but are any of them possible? In this study, I reference peer-reviewed scientific articles, phylogenetic analysis, and paleoart studies to create biologically-sound dragons. Basing the dragon lineage on a real branch of webbed-winged scansoriopterygids—an extinct family of climbing and gliding maniraptoran dinosaurs—I explored the possible wing-structure, fire-breathing abilities, and effects …

From Organisms To Ecosystems: Impacts Of Limb Loss And Regeneration On Crayfish Behavior, Luc Arnaud Dunoyer

Theses and Dissertations--Biology

The ability of some organisms to regenerate tissues and organs has fascinated naturalists since antiquity, dating back to the earliest accounts of scientific inquiry with Aristotle in Ancient Greece. Then, Darwin’s theory invigorated some scientists’ dream of stimulating (or reactivating) regenerative capacities in human beings by showing that we are related to highly regenerative organisms. More recently, a renewed interest in discovering the molecular and genetic basis for organ and tissue regeneration has led biologists to focus more specifically on a restrictive set of model organisms.

Although the process of limb regeneration is different between invertebrate and vertebrate organisms, it …

From Genes To Species: Ecological Speciation With Gene Flow In Neodiprion Pinetum And N. Lecontei, Emily E. Bendall

Theses and Dissertations--Biology

My dissertation focuses on how differences accumulate across the genome during ecological speciation with geneflow. To do this I used two species of Neodiprionpine sawflies, which are plant-feeding hymenopterans with high host specificity. I used experimental crosses to measure both intrinsic and extrinsic postzygotic isolation and to understand the contribution of specific traits to reproductive isolation. Despite substantial genetic divergence and haploid males in which all recessive incompatibilities should be expressed, I found surprisingly little evidence of intrinsic postzygotic isolation. Recombination in hybrid males may reconstitute viable genotypes and counteract the effects of haploidy in males. Nevertheless, hybrids have …

Extreme Offspring Ornamentation In American Coots Is Favored By Selection Within Families, Not Benefits To Conspecific Brood Parasites, Bruce E. Lyon, Daizaburo Shizuka

School of Biological Sciences: Faculty Publications

Offspring ornamentation typically occurs in taxa with parental care, suggesting that selection arising from social interactions between parents and offspring may underlie signal evolution. American coot babies are among the most ornamented offspring found in nature, sporting vividly orange-red natal plumage, a bright red beak, and other red parts around the face and pate. Previous plumage manipulation experiments showed that ornamented plumage is favored by strong parental choice for chicks with more extreme ornamentation but left unresolved the question as to why parents show the preference. Here we explore natural patterns of variation in coot chick plumage color, both within …

The Influence Of Breeding Density On Female Aggression, Parental Care, And Ornamentation In A Secondary-Cavity Nesting Warbler, Elsa B. Chen

Theses and Dissertations

Tradeoffs between individual survival and reproductive success associated with aggressive behaviors are a driving force of evolution, but these tradeoffs are often overlooked for aggressive conspecific interactions between females. For avian males, it is well documented that more aggressive individuals tend to provide less parental care. In the few studies that address this in females, the tradeoffs seem to be more context-dependent, varying due to factors such as predation pressure and habitat quality. The relationship between female ornamentation and aggression is similarly understudied, but evidence suggests that both aggression and ornamentation are important traits involved in social selection – the …

More Than Meets The Eye: A Taxonomic Revision Of The Nearctic Species In The Eye-Gnat Genus Amiota Loew (Diptera: Drosophilidae), Lance E. Jones

Dissertations and Theses

Thorough biotic inventories are still needed even in families as seemingly well-studied as fruit flies (Diptera: Drosophilidae). Drosophilidae have had an outsize effect on the history of biology because of their pivotal role in the study of genetics, development, and evolution. Even with more than a century of intensive study, large gaps remain in our understanding of diversity in this fly family, including well-studied areas such as North America. This thesis presents a taxonomic revision of the Nearctic species of the genus Amiota Loew. Twenty-three species are identified as being new to science for publication at a later date. This …

Evidence Of Local Adaptation To Climate In An Invasive Ectotherm: A Study On The Eurasian Gypsy Moth (Lymantria Dispar) In North America, Phillip M. Gibbs

Theses and Dissertations

Invasive species exist in nearly every ecosystem both terrestrial and aquatic. Improving our understanding of the mechanisms that shape the ability of these organisms to physiologically cope with their surroundings will be crucial to preparing for future impacts of climate change. The Gypsy Moth (Lymantria dispar) has been expanding its range across North America over the last 100+ years since its arrival in Medford, Massachusetts. This study quantifies upper thermal limits (UTL) across 8 different populations of L. dispar in North America and seeks to determine if signals of local adaptation to climate across a latitudinal gradient may …

Interspecific Gene Flow Potentiates Adaptive Evolution In A Hybrid Zone Formed Between Pinus Strobiformis And Pinus Flexilis, Mitra Menon

Theses and Dissertations

Species range margins are often characterised by high degrees of habitat fragmentation resulting in low genetic diversity and higher gene flow from populations at the core of the species range. Interspecific gene flow from a closely related species with abutting range margins can increase standing genetic diversity and generate novel allelic combinations thereby alleviating limits to adaptive evolution in range margin populations. Hybridization driven interspecific gene flow has played a key role in the demographic history of several conifer due to their life history characteristics such as weak crossability barriers and long generation times. Nevertheless, demonstrating whether introgression is adaptive …

Effects Of Insect Opportunists On A Four-Level Trophobiotic System Involving Nectar-Producing Galls Of The Cynipid Wasp Disholcaspis Quercusmamma (Hymenoptera: Cynipidae), Stephanie L. Smith

Masters Theses

The induction of plant galls is considered an adaptive life history trait found in many insect groups. The formation of galls provides several advantages to the gall maker, such as enhanced nutrition, favorable microclimate, and protection from natural enemies, including parasitoids, inquilines, and predators. Order Hymenoptera has many gall-making species, belonging to the gall wasp family Cynipidae. As an extended phenotype of the gall makers, some galls exhibit very sophisticated adaptive mechanisms involving multilevel species interactions. In particular, the oak galls of the Cynipid species Disholcaspis quercusmamma, found in much of Illinois, produce a palatable, sugary nectar-like secretion, attracting …

Spatial And Temporal Genetic Structure Of Winter-Run Steelhead (Oncorhynchus Mykiss) Returning To The Mad River, California, Steven R. Fong

Cal Poly Humboldt theses and projects

Distinct populations of steelhead in the wild are in decline. The propagation of steelhead in hatcheries has been used to boost population numbers for recreational fisheries and for use in conservation. However, hatchery breeding practices of steelhead can result in changes in genetic structure. I investigated the genetic structure of winter-run steelhead (Oncorhynchus mykiss) returning to the Mad River, California, where a hatchery has been used enhance production for recreational fisheries since 1971. Genetic variability in Mad River steelhead was evaluated using 96 single nucleotide polymorphisms (SNPs) among 4203 individuals, including the Mad River and nearby locations, and …

Compassionate Conservation And Elephant Personhood, Arian D. Wallach, Sujeewa Jasinghe, Sudarshani Fernando, Jessica Bell Rizzolo

Animal Sentience

Baker and Winkler (2020) advocate a rehabilitation program that would end the oppression of elephants — not by severing human-elephant relations, but by enabling human-bonded elephants to live a full life. We consider this program within a compassionate conservation framework, which recognises all sentient beings as persons. From this vantage point, we gaze further into the future to ask what direction just human-elephant relations could take: What could emerge from a human-elephant relation once elephants are no longer enslaved and requiring rescue? We envisage a future — beyond captivity and rewilding — of elephant sovereignty.

One Welfare, The Role Of Health Professionals, And Climate Change, Anne Fawcett

Animal Sentience

Wiebers & Feigin argue that the COVID-19 crisis is a call for humanity to rethink our relationships with animals and the environment. This One Welfare approach has implications for the role of health care professionals and demands that we address climate change.