Evolution Commons^™

Does Shape Matter?: How Salamander Head Morphology Shifts Based On Environment, Caitlyn Pinaga, Naomi Ramirez, Sonia Cerrillo

Posters - 2026

Groundwater salamanders of the genus Eurycea represent a diverse group of amphibians inhabiting the aquifer systems of central Texas, where both surface-dwelling and fully subterranean species coexist. Subterranean habitats impose extreme selective pressures, including complete darkness, limited nutrient availability, and stable environmental conditions, which drive convergent morphological traits such as eye reduction or loss, decreased pigmentation, and elongation of appendages. A key evolutionary pattern seen in these systems is sensory compensation, in which the reduction of one sensory modality, in this case vision, is accompanied by the enhancement of others. In aquatic salamanders, this often involves expansion of the lateral …

Smell Over Sight: Determining Levels Of Olfactory Gene Expression Between Surface And Subterranean Eurycea Salamanders, Sonia Cerrillo, Iliana Melendez, Naomi Ramirez

Posters - 2026

In the karst aquifers of central Texas, including the Edwards and Trinity systems, organisms live in an environment defined by constant temperatures, total darkness, and scarce food resources. These conditions have driven the evolution of salamanders in the genus Eurycea, particularly those that have adapted to subterranean life. Cave-dwelling species like Eurycea rathbuni exhibit hallmark “blind salamander” traits, including educed eyes, loss of pigmentation, and flattened head morphology. In contrast, surface-dwelling relatives such as Eurycea nana and Eurycea sosorum retain fully developed eyes and pigmentation, while some species like Eurycea latitans display both surface and subterranean forms across different populations.

The Missing Lynx: Investigating Passive And Active Rewilding With The Eurasian Lynx, Isaiah Charles, Tatiana Flores, Isabella Lopez

Conservation Biology

The Eurasian Lynx (Lynx lynx) is a wild cat native to the boreal forests, mountains and grasslands of Europe and Asia (Bhattacharyya, 2025). The Eurasian lynx keep ungulate populations in check which allow for forests to recover from overgrazing, promoting biodiversity and ecological balance. However, the Eurasian lynx had become locally extinct across Europe by the 1900s due to habitat loss, hunting by farmers in retaliation for predation of livestock and the illegal fur trade. Conservation and ecological restoration efforts to rebuild the lynx population have been underway. Rewilding is a form of ecological restoration involving the reintroduction of a …

Analysis Of Mitochondrial Dna Haplotype Groups For South Texas Canids, Canis Rufus, After Past Hybridization Events, Isabella Lopez

Presentations - 2026

mtDNA: mitochondrial DNA; passed from maternal parent to offspring (Haplotype)

Haplotype:  a group of genes or genetic markers inherited together from a single parent (Haplotype)

Mitochondrial DNA haplotypes specific sequences of mtDNA that is passed exclusively from maternal parent to offspring (Giles et al. 1980)

Pro's:

It is passed unchanged from mother to offspring, meaning it is fairly stable (Giles et al. 1980)

Each cell has multiple mitochondria vs one nucleus , which means mtDNA it is more likely to be recoverable from degraded samples like scat (Templeton et al. 2013)

Mapping Sensory Landscapes: Distribution And Arrangement Of The Anterior Lateral Line System In Texas Catfish, Tatiana K. Flores, Ruben Tovar

Posters - 2026

Fish have a system of sensory organs known as the lateral line system. This system contains numerous mechanoreceptive neuromasts and electroreceptive ampullary organs (Northcutt et al, 2000). Neuromasts are small, hair-like structures located within canals in the lateral line system just under the fish’s skin and are open to the environment through small pores visible on its skin (Parker, 2025). Water flows into these canals through the pores which stimulates the sensitive hair cells, resulting in electrical signals sent to the fish’s brain. The brain interprets these signals and creates “images” of the fish’s surroundings, helping it to see even …

Does Habitat Predict Head Shape? A Comparative Geometric Morphometric Analysis Of Eurycea Spp., Sarah Flores-Garza, Alexa Miner, Gianna Montelongo

Posters - 2026

Subterranean environments impose strong selective pressures, including complete darkness and reliance on non-visual sensory systems. In Eurycea salamanders, these conditions are associated with traits such as reduced eyes and expanded head regions that improve sensory detection (Tovar et al., 2025). Subterranean species are often expected to share similar head shapes due to convergent evolution. However, not all species experience these pressures equally. Eurycea latitans is a polymorphic species that inhabits both surface and cave environments. Eurycea sp._NB is an obligate subterranean species, while Eurcyea sosorum is a surface species. This study tests whether habitat predicts head shape in Eurycea, or …

Teeth That Tell Time: Elemental Analysis From Shark Teeth, Gisele-Elizabeth Perez

Posters - 2026

Sharks (Chondrichthyes) have hunted in the oceans for over 400 million years, their teeth leaving history behind, constantly becoming a part of the fossilization process (Worm et al. 2013). Their survival throughout 5 major extinctions is due to their ability to adapt easily with slow metabolism, a wide range of diet, and an efficient physiology. Shark teeth are vital to the hunting and consumption of their prey, making it a point for scientists to study them. Their tooth minerals contain fluorapatite in their enameloid, and dentin in the “root” of the tooth, with extinct species containing dentin and hydroxyapatite in …

Mapping Sensory Landscapes: Distribution And Arrangement Of The Anterior Lateral Line System In Texas Catfish, Tatiana Flores, Ruben Tovar

Research Papers

Fish have a system of sensory organs known as the lateral line system. This system contains numerous mechanoreceptive neuromasts and electroreceptive ampullary organs (Northcutt et al, 2000). Neuromasts are small, hair-like structures located within canals in the lateral line system just under the fish’s skin and are open to the environment through small pores visible on its skin (Parker, 2025). Water flows into these canals through the pores which stimulates the sensitive hair cells, resulting in electrical signals sent to the fish’s brain. The brain interprets these signals and creates “images” of the fish’s surroundings, helping it to see even …

Comparing Head Shape Of Polymorphic Subterranean E. Latitans And Subterranean E. Sp. 4, Brandon Chapa, Jordan Cosgrove, Lizzeth Holguin

Posters - 2026

Eurycea latitans (E. latitans) from Honey Creek Cave and unnamed Eurycea species from New Braunfels, Texas (E. sp. 4) are two paedomorphic subterranean species. E. latitans is polymorphic, meaning it also exists as a surface species. Similarities in morphology of subterranean salamander species may be due to convergent evolution as a result of living in similar environments. These similarities include having flatter, wider heads, and wider mouths than surface species (Tovar et al. 2025). Variation may also exist among different subterranean salamander species. Texas Eurycea salamanders display “complex patterns of morphological divergence”, suggesting that isolation and local environmental pressures can …

Comparing Gngt1 Expression In Eye Tissue Of Polymorphic Salamander Species Through Development, Fiona Coulbourne, Camila Cardozo, Macarena Machado, Ruben Tovar

Posters - 2026

The effect of the environment on organisms and their adaptations is widely studied. When exposed to different environmental niches, phenotypic adaptation is observed even within species. Animals that live in dark cave environments show a loss of their eyesight, since this sense is no longer useful to keep. Previous research has studied salamanders of the clade Eurycea and compared gene expression to subterranean and surface phenotypes1. E.pterophila is observed to express these two phenotypes depending on its environment, either Preserve Cave (subterranean) or Comal Springs (surface). Subterranean variant shows reduced eye volume and assumes to have decreased eyesight. Utilizing RNASeq …

Evolution Of Antibiotic Responses During Chronic P. Aeruginosa Infections In The Human Lung, David Frank Ritz

Dartmouth College Ph.D Dissertations

Typical antibiotic susceptibility testing (AST) of microbial samples is performed in homogeneous cultures in batch environments, which does not account for the highly heterogeneous and dynamic nature of antibiotic responses. The most common mutation found in P. aeruginosa lineages evolved during chronic cystic fibrosis infections in the human lung, a loss of function of repressor MexZ, increases basal levels of multidrug efflux MexXY, but does not increase resistance by traditional minimal inhibitory concentration (MIC) assays. Here, we use single cell microfluidics to show that P. aeruginosa’s response to aminoglycosides is highly heterogeneous, with only a subpopulation of cells surviving exposure. …

The Evolution Of Self-Awareness In Conscious Organisms, Robert A. Dielenberg

Journal of Conscious Evolution

Self-awareness in conscious organisms remains an enduring puzzle for philosophers and neuroscientists. This paper proposes a tripartite evolutionary model tracing its emergence through three sequential types: the sensory self (primitive egocentric, valence-tagged awareness of sensory states), the bodily self (external objectification of the body as a distinct entity, evidenced by mirror self-recognition in select species), and the cognitive self (internal objectification of the mind enabling recursive self-transformation). Adopting a monist framework, the model treats consciousness as the biological substrate of delayed neural apperception (the “Delayed Present”), within which selves emerge as increasingly sophisticated models. It distinguishes non-human metacognition—implicit, online regulation—from …

No Effect In Plasma Corticosterone Levels After Observation Of Diseased Conspecifics, B. M. Hardy, M. Chang, S. Mccallum, S. Santangelo, Patricia C. Lopes

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Organisms commonly respond to stressors in their environment by increasing the secretion of corticosterone (CORT). While increased CORT is acknowledged as a response to predation risk by organisms inhabiting a landscape of fear, new research raises the potential for changes in CORT as a response to the risk of infection by organisms in their environment. An increase in CORT of a healthy, uninfected individual in response to their perception of the risk of infection in their environment could change their susceptibility to infection, highlighting a significant role for CORT to alter host–pathogen dynamics. To investigate the effects of infection risk …

A Revision Of The Psammophilic Genus Liobuthus Birula, 1898 (Scorpiones: Buthidae), With A Description Of Four New Species From Central Asia, Victor Fet, František Kovařík, Graeme Lowe, Matthew R. Graham

Euscorpius

The rare Central Asian psammophilic scorpion genus, Liobuthus Birula, 1898 (Scorpiones: Buthidae), is revised. Five species are delineated according to results from three species delimitation approaches using mitochondrial DNA. Results are supported by diagnostic morphology, including an assessment of the distinctive neobothriotaxy. The type species, L. kessleri Birula, 1898, is confirmed for Iran (northeast), Turkmenistan and Uzbekistan (south). Four new species are described: L. atamuradovi sp. n. (Turkmenistan),  L. danovi sp. n. (Kazakhstan, northern Turkmenistan, Uzbekistan), L. shukurovi sp. n. (southwestern Tajikistan), and L. vachoni sp. n. (southern Kazakhstan), The unique additive neobothriotaxy (on both pedipalp femur and patella) …

A Simple And Affordable Protocol To Assess Censer Seed Dispersal: First Confirmation Of The Mechanism In The Genus Solanum, Abigail J. Motter, Christopher T. Martine, Melody P. Sain

Faculty Journal Articles

The censer seed dispersal mechanism, whereby mature fruits are retained on plants and seeds dispersed by mechanical shaking, is among the most specialized wind-aided seed dispersal strategies employed by the flowering plants. An efficient, affordable, and easily repeatable protocol for determining whether a species uses this unusual mechanism of seed dispersal is lacking. Our focal species, Solanum tudununggae, is one of just two Solanum species (in a fleshy-fruited genus of ca. 1200 species) hypothesized to use this dispersal mechanism as a means to move seeds farther from parent plants than would gravity alone.

The Presence Of Predators Moderates Evolutionary Responses Of Trinidadian Killifish To A Novel Parasite, Anne E. Christian

Biology Dissertations

The Healthy Herds Hypothesis suggests the idea that prey populations derive a benefit from their predators: predators reduce the exposure of their prey to infectious disease, both by limiting prey population densities and by eliminating sick individuals. Much research has focused on the balancing effect that predators have on ecosystems. There is a current need for research into whether these effects cause evolutionary shifts in prey populations, where strong predation pressure prevents prey species from evolving physiological tolerance or resistance to infectious agents. Parasites especially often have rapid effects on host evolution, due to exploitative interactions.

I seek to address …

Stress And Reward Interactions In Substance Use Disorder: An Evolutionary Mismatch Framework, Nicholas L. Castrucci

Honors Theses and Capstones

Substance use disorder (SUD) is a major public health concern characterized by compulsive substance use despite adverse consequences. While contemporary models emphasize biological, psychological, and environmental contributors, stress- and reward-related systems are often examined in isolation. This review integrates these systems within an evolutionary mismatch framework to examine how chronic stress exposure and repeated substance use increase vulnerability to addiction. Stress and reward systems are evolutionarily conserved but may become chronically dysregulated under modern conditions characterized by persistent psychosocial stressors and highly potent rewarding stimuli. This is associated with converging neuroadaptations across stress and reward circuitry, resulting in altered affective …

The Impacts Of Wing-Flashing By Northern Mockingbirds On Foraging, Parental Care, And Reproductive Success, Anna R. Starman

Undergraduate Honors Theses

Foraging efficiency may be enhanced by flashing patches of white wing and tail feathers and has been documented in several avian species. Northern Mockingbirds (Mimus polyglottos, NOMO) exhibit this “wing-flashing” (WF) behavior while foraging, during displays, and in response to predators. In NOMOs, WF has been hypothesized to increase foraging success, but previous findings are inconclusive. To further investigate the biological role(s) of WF behavior in NOMOs, the ventral surface of white primary feathers of male NOMOs were artificially darkened, and the foraging and provisioning rates of undarkened (control) males and their mates were compared. While foraging, undarkened …

Equid Major Histocompatibility Complex (Mhc) Evolution & Genome Organization, Lauren C. Johnson

Theses and Dissertations--Veterinary Science

The evolution of modern horses has a well-documented fossil record and has long been of interest to the genetics community. Although non-caballine equids (e.g. zebras, donkeys, and asses) can hybridize with horses, the resulting offspring are typically infertile. Despite these reproductive barriers, genomic analyses reveal regions of high sequence similarity among equid species. This dissertation investigates the role of historical introgression in the evolution of modern Equus species. The first chapter re-evaluates earlier findings derived from a limited horse population and a single reference genome. The variants of the identified regions were pushed through Ensembl’s Variant Effect Predictor to assess …

Phylogeography, Fungal Host Specificity, And Fitness In The Corallorhiza Maculata Species Complex, Hana Thixton-Nolan

Graduate Theses, Dissertations, and Problem Reports (ETD)

Mycoheterotrophic plants exploit fungi for most or all nutritional needs, providing a compelling system to address the evolutionary consequences of genome reduction, population-level variation, and germination requirements. I am using the widespread Corallorhiza maculata species complex to address questions of genomic variation, fungal host specificity, morphological variation, and germination requirements across the broad geographic range from Mexico to northern North America. This complex contains C. bulbosa, C. macrantha, and C. mertensiana, the latter with three varieties (maculata, occidentalis, and mexicana). These taxa vary in flowering time, floral morphology, and fungal associations. However, the degree …