Life Sciences Commons^™

(Non)Parallel Developmental Mechanisms In Vertebrate Appendage Reduction And Loss, Samantha Swank, Thomas Sanger, Yoel E. Stuart

Biology: Faculty Publications and Other Works

Appendages have been reduced or lost hundreds of times during vertebrate evolution. This phenotypic convergence may be underlain by shared or different molecular mechanisms in distantly related vertebrate clades. To investigate, we reviewed the developmental and evolutionary literature of appendage reduction and loss in more than a dozen vertebrate genera from fish to mammals. We found that appendage reduction and loss was nearly always driven by modified gene expression as opposed to changes in coding sequences. Moreover, expression of the same genes was repeatedly modified across vertebrate taxa. However, the specific mechanisms by which expression was modified were rarely shared. …

Developmental Nonlinearity Drives Phenotypic Robustness, Rebecca M. Green, Jennifer L. Fish, Nathan M. Young, Francis J. Smith, Benjamin Roberts, Katie Dolan, Irene Choi, Courtney L. Leach, Paul Gordon, James M. Cheverud, Charles C. Roseman, Trevor J. Williams, Ralph S. Marcucio, Benedikt Hallgrímsson

Biology: Faculty Publications and Other Works

Robustness to perturbation is a fundamental feature of complex organisms. Mutations are the raw material for evolution, yet robustness to their effects is required for species survival. The mechanisms that produce robustness are poorly understood. Nonlinearities are a ubiquitous feature of development that may link variation in development to phenotypic robustness. Here, we manipulate the gene dosage of a signaling molecule, Fgf8, a critical regulator of vertebrate development. We demonstrate that variation in Fgf8 expression has a nonlinear relationship to phenotypic variation, predicting levels of robustness among genotypes. Differences in robustness are not due to gene expression variance or …

Experimental Evolution Of Specialism In A Wild Virus, Alexander Kula

Master's Theses

A pathogen's ability to successfully replicate and persist within a new host population is fraught with obstacles. While an expanded host-range allows for a greater chance at successful replication, such generalists are typically outcompeted by species which have specialized and adapted host-specific features. Although the most ubiquitous species on earth, very few bacteria-infecting viral species (bacteriophages) with truly broad host-ranges have been identified; this is partially due to the fact that only a small fraction of bacteria (and thus likely hosts) are amenable to laboratory conditions. Nevertheless, the processes of expanding as well as narrowing host-range are not well understood …

Characterizing The Evolutionary Path(S) To Early Homo, Lauren Schroeder, Charles C. Roseman, James M. Cheverud, Rebecca R. Ackermann

Biology: Faculty Publications and Other Works

Numerous studies suggest that the transition from Australopithecus to Homo was characterized by evolutionary innovation, resulting in the emergence and coexistence of a diversity of forms. However, the evolutionary processes necessary to drive such a transition have not been examined. Here, we apply statistical tests developed from quantitative evolutionary theory to assess whether morphological differences among late australopith and early Homo species in Africa have been shaped by natural selection. Where selection is demonstrated, we identify aspects of morphology that were most likely under selective pressure, and determine the nature (type, rate) of that selection. Results demonstrate that selection must …

Comparative Phyloclimatic Analysis And Evolution Of Ecological Niches In The Scimitar Babblers (Aves: Timaliidae: Pomatorhinus), Arpad S. Nyari, Sushma Reddy

Biology: Faculty Publications and Other Works

We present the first extensive and integrative analysis of niche evolution based on climatic variables and a dated molecular phylogeny of a heterogeneous avian group of Southeast Asian scimitar babblers of the genus Pomatorhinus. The four main clades of scimitar babblers have species that co-occur in similar areas across southern Asia but some have diverged at different timeframes, with the most recently evolved clade harboring the highest number of species. Ecological niche models and analysis of contributing variables within a phylogenetic framework indicate instances of convergent evolution of members of different clades onto similar ecological parameter space, as well …

Adaptive Evolution And Inherent Tolerance To Extreme Thermal Environments, Jennifer Cox, Alyxandria Schubert, Michael Travisano, Catherine Putonti

Bioinformatics Faculty Publications

Background

When introduced to novel environments, the ability for a species to survive and rapidly proliferate corresponds with its adaptive potential. Of the many factors that can yield an environment inhospitable to foreign species, phenotypic response to variation in the thermal climate has been observed within a wide variety of species. Experimental evolution studies using bacteriophage model systems have been able to elucidate mutations, which may correspond with the ability of phage to survive modest increases/decreases in the temperature of their environment.

Results

Phage ΦX174 was subjected to both elevated (50°C) and extreme (70°C+) temperatures for anywhere from a few …

Diaspora, A Large Family Of Ty3-Gypsy Retrotransposons In Glycine Max, Is An Envelope-Less Member Of An Endogenous Plant Retrovirus Lineage, Sho T. Yano, Bahman Panbehi, Arpita Das, Howard M. Laten

Biology: Faculty Publications and Other Works

Background

The chromosomes of higher plants are littered with retrotransposons that, in many cases, constitute as much as 80% of plant genomes. Long terminal repeat retrotransposons have been especially successful colonizers of the chromosomes of higher plants and examinations of their function, evolution, and dispersal are essential to understanding the evolution of eukaryotic genomes. In soybean, several families of retrotransposons have been identified, including at least two that, by virtue of the presence of an envelope-like gene, may constitute endogenous retroviruses. However, most elements are highly degenerate and are often sequestered in regions of the genome that sequencing projects initially …