Genetics and Genomics Commons^™

Genome-Scale Data Reveal Deep Lineage Divergence And A Complex Demographic History In The Texas Horned Lizard (Phrynosoma Cornutum) Throughout The Southwestern And Central Us, Nicholas Finger, Keaka Farleigh, Jason T. Bracken, Adam D. Leaché, Olivier François, Ziheng Yang, Tomas Flouri, Tristan Charran, Tereza Jezkova, Dean A. Williams, Christopher Blair

Publications and Research

The southwestern and central US serve as an ideal region to test alternative hypotheses regarding biotic diversification. Genomic data can now be combined with sophisticated computational models to quantify the impacts of paleoclimate change, geographic features, and habitat heterogeneity on spatial patterns of genetic diversity. In this study we combine thousands of genotyping-by-sequencing (GBS) loci with mtDNA sequences (ND1) from the Texas Horned Lizard (Phrynosoma cornutum) to quantify relative support for different catalysts of diversification. Phylogenetic and clustering analyses of the GBS data indicate support for at least three primary populations. The spatial distribution of populations appears concordant …

Dynamics Of Hybrid Zones At A Continental Scale, Bradley T. Martin

Graduate Theses and Dissertations

Hybridization has traditionally been viewed as a happenstance that negatively impacts populations, but is now recognized as an important evolutionary mechanism that can substantially impact the evolutionary trajectories of gene pools, influence adaptive capacity, and contravene or reinforce divergence. Physiographic processes are important drivers of dispersal, alternately funneling populations into isolation, promoting divergence, or facilitating secondary contact of diverged populations, increasing the potential for hybridization. In North America, glacial-interglacial cycles and geomorphological changes have provided a dynamic backdrop over the last two million years that promoted such oscillations of population contraction and expansion. These biogeographic processes have resulted in regional …

Genetic Basis Of Hybrid Sterility Between Drosophila Pseudoobscura And D. Persimilis, Alannah J.P. Mattice

Electronic Thesis and Dissertation Repository

Speciation is the underlying process that leads to formation of new species, and therefore is the basis of biodiversity. Genes involved in each stage of speciation, such as those involved in interspecies sterility, remain elusive. Male hybrid sterility and postzygotic isolation between Drosophila pseudoobscura and D. persimilis was examined in this study through backcrossing of female hybrids into each parental line (introgression), selecting for a sterile sperm phenotype, needle-eye sperm. Sperm phenotypes did not separate through backcrossing; instead, males presented with multiple sperm phenotypes. A relationship between the phenotypes observed and the potential genes involved was examined through whole genome …

Genomic Adaptations To Salinity Resist Gene Flow In The Evolution Of Floridian Watersnakes, Rhett M. Rautsaw, Tristan D. Schramer, Rachel Acuña, Lindsay N. Arick, Mark Dimeo, Kathryn P. Mercier, Michael Schrum, Andrew J. Mason, Mark J. Margres, Jason L. Strickland, Christopher L. Parkinson

Publications and Research

The migration-selection balance often governs the evolution of lineages, and speciation with gene flow is now considered common across the tree of life. Ecological speciation is a process that can facilitate divergence despite gene flow due to strong selective pressures caused by ecological differences; however, the exact traits under selection are often unknown. The transition from freshwater to saltwater habitats provides strong selection targeting traits with osmoregulatory function. Several lineages of North American watersnakes (Nerodia spp.) are known to occur in saltwater habitat and represent a useful system for studying speciation by providing an opportunity to investigate gene flow …

Genomic Insights Into Speciation History And Local Adaptation Of An Alpine Aspen In The Qinghai–Tibet Plateau And Adjacent Highlands, Jia-Lang Li, Lin-Ling Zhong, Jing Wang, Tao Ma, Kang-Shan Mao, Lei Zhang

Aspen Bibliography

Natural selection serves as an important agent to drive and maintain interspecific divergence. Populus rotundifolia Griff. is an alpine aspen species that mainly occurs in the Qinghai–Tibet Plateau (QTP) and adjacent highlands, whereas its sister species, P. davidiana Dode, is distributed across southwest and central to northeast China in much lower altitude regions. In this study, we collected genome resequencing data of 53 P. rotundifolia and 42 P. davidiana individuals across their natural distribution regions. Our population genomic data suggest that the two species are well delimitated in the allopatric regions, but with hybrid zones in their adjacent region in …

Demonstrating Mate Choice Copying In Spiders Requires Further Research, R. Tucker Gilman, Kasey Fowler-Finn, Eileen A. Hebets

Eileen Hebets Publications

Mate choice copying—when individuals learn to prefer mates or mate types that have been chosen by others—can influence trait evo-lution and speciation (Varela et al. 2018; Dion et al. 2019). Most examples of mate choice copying are from fish, birds, and mammals including humans (Varela et al. 2018). However, 2 invertebrate examples—fruit flies and wolf spiders—have been used to argue that the phenomenon may be phylogenetically widespread, and perhaps the rule rather than the exception in nature (Varela et al. 2018). Here, we revisit the evidence for mate choice copying in wolf spiders (Fowler-Finn et al. 2015) in light of …

Probability, Populations, Phylogenetics And Hominin Speciation, Niccolo Caldararo

Human Biology Open Access Pre-Prints

A number of recent articles have appeared on the hominin Denisova fossil remains. Many of them focus on attempts to produce DNA sequences from the extracted samples. Often these project mtDNA sequences from the fossil remains of a number of Neandertal fossils and the Denisovans in an attempt to understand the evolution of Mid Pleistocene human ancestors. These papers, introduce a number of problems in the interpretation of speciation in hominins. One concerns the degradation of the ancient DNA and its interpretation as authentic genetic information. Another concerns the idea of “species” versus that of “population” and the use of …

The Fruitless Gene Influences Female Mate Preference In Drosophila, Tabashir A. Chowdhury

Electronic Thesis and Dissertation Repository

Species can arise as a result of reproductive barriers that prevent gene flow between diverging populations that force them to remain isolated from one another. Behavioural isolation is one of the earliest acting reproductive barriers determined by the evolution of mating preferences that prevent inter-specific matings. Several traits have been identified that contribute to behavioural isolation, but the genetic basis of interspecific female preference is yet to be determined. I used genetic mapping techniques to identify and confirm that the fruitless gene is affecting species-specific female rejection of interspecies males, contributing to the behavioural isolation between Drosophila melanogaster and D. …

Contemporary Sexual Selection Does Not Explain Variation In Male Display Traits Among Populations, J. Colton Watts, Allissa Flynn, Brigitte Tenhumberg, Eileen Hebets

Brigitte Tenhumberg Papers

Sexual selection is widely hypothesized to facilitate the evolution of reproductive isolation through divergence in sexual traits and sexual trait preferences among populations. However, direct evidence of divergent sexual selection causing intraspecific trait divergence remains limited. Using the wolf spider Schizocosa crassipes, we characterized patterns of female mate choice within and among geographic locations and related those patterns to geographic variation in male display traits to test whether divergent sexual selection caused by mate choice explains intraspecific trait variation. We found evidence of phenotypic selection on male behavior arising from female mate choice, but no evidence that selection varied …

Cryptic Diversity And Discordance In Single‐Locus Species Delimitation Methods Within Horned Lizards (Phrynosomatidae: Phrynosoma), Christopher Blair, Robert W. Bryson Jr.

Publications and Research

Biodiversity reduction and loss continues to progress at an alarming rate, and thus there is widespread interest in utilizing rapid and efficient methods for quantifying and delimiting taxonomic diversity. Single-locus species-delimitation methods have become popular, in part due to the adoption of the DNA barcoding paradigm. These techniques can be broadly classified into tree-based and distance-based methods depending on whether species are delimited based on a constructed genealogy. Although the relative performance of these methods has been tested repeatedly with simulations, additional studies are needed to assess congruence with empirical data. We compiled a large data set of mitochondrial ND4 …

Cellular/Molecular Analysis Of Interspecies Sterile Male Hybrids In Drosophila, Rachelle L. Kanippayoor

Electronic Thesis and Dissertation Repository

Over time, genetic differences can accumulate between populations that are geographically separated. This genetic divergence can lead to the evolution of reproductive isolating mechanisms that reduce gene flow between the populations and, upon secondary contact, result in distinct species. The process of speciation is, thus, what accounts for the multitude of species that contribute to the rich biodiversity on Earth. Interspecies hybrid sterility is a postzygotic isolating mechanism that affects the development of hybrids, rendering them sterile. A notable trend, known as Haldane's Rule, describes that heterogametic individual (e.g. males in Drosophila) are more susceptible to sterility than homogametic …

Genetics Of Female Interspecific Mate Rejection In Species Of Drosophila, Ryan Calhoun

Electronic Thesis and Dissertation Repository

Speciation can occur when accumulated differences in mating behavior force diverging species to remain reproductively isolated from one another. A key determinant of behavioural isolation is the evolution of female mating preferences that prevent interspecific males from mating. However, no individual genes involved in species-specific preferences of females have yet been identified. Using various genetic mapping techniques available for studying strains and species of Drosophila, I identify candidate genes involved in D. simulans female discrimination against D. melanogaster males. One candidate gene in particular, Katanin-60, was selected for further characterization. Katanin-60 is a gene encoding a microtubule severing …

Patterns Of Morphological And Molecular Evolution In The Antillean Tree Bat, Ardops Nichollsi (Chiroptera: Phyllostomidae), Roxanne J. Larsen, Peter A. Larsen, Caleb D. Phillips, Hugh H. Genoways, Gary G. Kwiecinski, Scott C. Pedersen, Carleton J. Phillips, Robert J. Baker

University of Nebraska State Museum: Mammalogy Papers

Species endemic to oceanic islands offer unique insights into the mechanisms underlying evolution and have served as model systems for decades. Often these species show phenotypic variation that is correlated with the ecosystems in which they occur and such correlations may be a product of genetic drift, natural selection, and/or environmental factors. We explore the morphologic and genetic variation within Ardops nichollsi, a species of phyllostomid bat endemic to the Lesser Antillean islands. Ardops nichollsi is an ideal taxon to investigate the tempo of evolution in Chiroptera, as it: is a recently derived genus in the family Phyllostomidae; contains …

Genomic Plasticity And Rapid Host Switching Can Promote The Evolution Of Generalism: A Case Study In The Zoonotic Pathogen Campylobacter, Dan J. Woodcock, Peter Krusche, Norval J. C. Strachan, Ken J. Forbes, Frederick M. Cohan, Guillaume Meric, Samuel K. Sheppard

Frederick M. Cohan

The Maintenance Of Phenotypic Divergence Through Sexual Selection: An Experimental Study In Barn Swallows Hirundo Rustica, Rebecca Safran, Yoni Vortman, Brittany R. Jenkins, Joanna K. Hubbard, Matt Wilkins, Rachel J. Bradley, Arnon Lotem

School of Biological Sciences: Faculty Publications

Previous studies have shown that sexual signals can rapidly diverge among closely related species. However, we lack experimental studies to demonstrate that differences in trait-associated reproductive performance maintain sexual trait differences between closely related populations, in support for a role of sexual selection in speciation. Populations of Northern Hemisphere distributed barn swallows Hirundo rustica are closely related, yet differ in two plumage-based traits: ventral color and length of the outermost tail feathers (streamers). Here we provide experimental evidence that manipulations of these traits result in different reproductive consequences in two subspecies of barn swallow: (H. r. erythrogaster in North …

The Complexities Of Female Mate Choice And Male Polymorphisms: Elucidating The Role Of Genetics, Age, And Mate-Choice Copying, Kasey D. Fowler-Finn, Laura Sullivan-Beckers, Amy M. Runck, Eileen A. Hebets

Eileen Hebets Publications

Genetic, life history, and environmental factors dictate patterns of variation in sexual traits within and across populations, and thus the action and outcome of sexual selection. This study explores patterns of inheritance, diet, age, and mate-choice copying on the expression of male sexual signals and associated female mate choice in a phenotypically diverse group of Schizocosa wolf spiders. Focal spiders exhibit one of two male phenotypes: ‘ornamented’ males possess large black brushes on their forelegs, and ‘non-ornamented’ males possess no brushes. Using a quantitative genetics breeding design in a mixed population of ornamented/non-ornamented males, we found a strong genetic basis …

Chromosomal Rearrangements Directly Cause Underdominant F1 Pollen Sterility In Mimulus Lewisii-M. Cardinalis Hybrids, Angela M. Stathos

Graduate Student Theses, Dissertations, & Professional Papers

Chromosomal rearrangements can contribute to the evolution of postzygotic reproductive isolation directly, by disrupting meiosis in F₁ hybrids, or indirectly, by suppressing recombination among genic incompatibilities. Because direct effects of rearrangements on fertility imply fitness costs during their spread, understanding the mechanism of F₁ hybrid sterility is integral to reconstructing the role(s) of rearrangements in speciation. In hybrids between monkeyflowers Mimulus cardinalis and M. lewisii, rearrangements contain all quantitative trait loci (QTLs) for both premating barriers and pollen sterility, suggesting that they may have facilitated speciation in this model system. I used artificial chromosome doubling and …

Postzygotic Isolation In Drosophila Simulans And D. Mauritiana, Christopher T. D. Dickman

Electronic Thesis and Dissertation Repository

The study of speciation requires examination of barriers that produce and maintain species separation. Using Drosophila simulans and D. mauritiana, this thesis focuses on post-zygotic isolating mechanisms, which occur after the formation of interspecies hybrids. This study aims to examine the genetic causes of male hybrid sterility and decreased hybrid female lifespan. Quantitative trait locus (QTL) mapping using flies with an attached-X chromosome, identified seven autosomal QTLs that contribute to hybrid sterility. Separately, reduction in hybrid female lifespan was noted for females bearing an attached-X chromosome and was more severe in individuals who were mated. This reduction is caused …

A Robust New Metric Of Phenotypic Distance To Estimate And Compare Multiple Trait Differences Among Populations, Rebecca Safran, Samuel Flaxman, Michael Kopp, Darren E. Irwin, Derek Briggs, Matthew R. Evans, W. Chris Funk, David A. Gray, Eileen A. Hebets, Nathalie Seddon, Elizabeth Scordato, Laurel B. Symes, Joseph A. Tobias, David P.L. Toews, J. Albert C. Uy

Eileen Hebets Publications

Whereas a rich literature exists for estimating population genetic divergence, metrics of phenotypic trait divergence are lacking, particularly for comparing multiple traits among three or more populations. Here, we review and analyze via simulation Hedges’ g, a widely used parametric estimate of effect size. Our analyses indicate that g is sensitive to a combination of unequal trait variances and unequal sample sizes among populations and to changes in the scale of measurement. We then go on to derive and explain a new, non-parametric distance measure, “Δp”, which is calculated based upon a joint cumulative distribution function (CDF) from all …

Successful Genotyping Of Microsatellites In The Woolly Mammoth, Yasuko Ishida, Alfred L. Roca, Stephen Fratpietro, Alex D. Greenwood

Biological Sciences Faculty Publications

Genetic analyses using ancient DNA from Pleistocene and early Holocene fossils have largely relied on mitochondrial DNA (mtDNA) sequences. Among woolly mammoths, Mammuthus primigenius, mtDNA analyses have identified 2 distinct clades (I and II) that diverged 1-2 Ma. Here, we establish that microsatellite markers can be effective on Pleistocene samples, successfully genotyping woolly mammoth specimens at 2 loci. Although significant differentiation at the 2 microsatellite loci was not detected between 16 clade I and 4 clade II woolly mammoths, our results demonstrate that the nuclear population structure of Pleistocene species can be examined using fast-evolving nuclear microsatellite markers.

Speciation In The Aedes Triseriatus Species Complex, David B. Taylor

David B Taylor

Interspecific hybridization was used to determine the genetic relationships between the four species of mosquitoes in the Triseriatus and Zoosophus groups of the aedine subgenus Protomacleaya (Diptera: Culicidae). Four factors were investigated: 1) fertility of intra- and interspecific crosses, 2) morphology of the interspecific hybrids and the genetic bases of morphological characters, 3) modes of postcopulatory reproductive isolation and 4) types of chromosomal changes occurring during and subsequent to the divergence of the species. Hybrid progeny were produced in 11 of the 12 possible crosses between the four species. Only the Aedes zoosophus female X A. brelandi male cross failed …