Research Description

Acclimation and Evolution

How an individual perceives environmental stress (e.g. social, physiological, nutritional, toxins) and responds at the molecular level (genetic and cellular changes), can affect how that individual behaves, its ability to reproduce, and its lifespan. My research integrates environmental variation, molecular networks, and life history to investigate how organisms respond to their environment at the individual level (plasticity and acclimation) and how this response can evolve across populations and across species. I am currently working on projects that address the following questions: 1) How do gene networks that link physiological stress and life-history traits evolve? 2) What is the persistence (transient, lifetime, or transgenerational) of epigenetic modification to the genome in response to physiological stress in ectotherms, and do these modifications play a role in adaptive acclimation within and across generations.




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Research Topics

How quickly an animal grows, how much they reproduce, and how quickly they age are traits that are regulated by both genetics and the environment. A considerable amount of scientific evidence indicates that these traits are interrelated and that in some circumstances there are trade-offs between them. A classic example is fast- versus slow-lifestyles where some animals grow fast, reproduce a lot and die "young" relative to others that grow slow, spread out their reproduction and live longer. We are fascinated with the molecular mechanisms that may drive these trade-offs. A major goal of our lab is to understand the molecular mechanisms regulating these traits and tradeoffs. We are especially interested in mitochondrial function and the insulin and insulin-like signaling network.

Previous research on garter snake populations characterized as slow-living and fast-living has demonstrated differences in how they respond to stressors at the molecular level, differences in the function of their mitochondria, and in their mitochondrial genomes. Work in Daphnia have demonstrated how food and temperature in an ectotherm can shift investment in reproduction and lifespan.

Photo credit: Dan Warner

Current research directions ongoing in the lab:

  • Further developing reptiles as models of aging at the organismal, physiological, and cellular level. We are developing reptile cell lines to help with this. (Amanda Clark)

  • Testing how investment in early life growth and reproduction may alter the rate of aging. And further, if this works differently in males versus females. (see link to the Aging Anoles Project).

  • Testing for trade-offs in regeneration and reproduction in lizards (Abby Beatty

  • The mitochondrial function and costs associated with asexuality in whiptail lizards (Randy Klabacka)

Key references associated with our lab:

  • Gangloff, E*, TS Schwartz,* R Klabacka(GS), A-Y Liu, N Huebschman(UO), AB Bronikowski. In Press. Mitochondria as the central character in a complex narrative: Linking genomics, energetics, and pace-of-life in natural populations of garter snakes. Experimental Gerontology.

  • Hoekstra, L, TS Schwartz, A Sparkman, D Miller, A Bronikowski. 2020. The untapped potential of reptile biodiversity for understanding how and why animals age. Functional Ecology. In Press.

  • Passow, CN, AM Bronikowski, H Blackmon, S Parsai, TS Schwartz, SE McGaugh. 2019 Contrasting patterns of rapid molecular evolution within the p53-network across mammal and reptile lineages. Genome Biology and Evolution. 11(3): 629-643.

  • Schwartz, TS, P Pearson(UO), J Dawson,  DB Allison, JM Gohlke. 2016. Effects of fluctuating temperature and food availability on reproduction and lifespan. Experimental Gerontology. 86: 62-72.   doi: 10.1016/j.exger.2016.06.010

  • Schwartz, TS, Z Arendsee(U*), AM Bronikowski. 2015. Mitochondrial divergence between slow- and fast-aging garter snakes. Experimental Gerontology. 71:135-146.  doi: 10.1016/j.exger.2015.09.004

  • Schwartz, TS, and AM Bronikowski. 2013. Dissecting molecular stress networks: identifying nodes of divergence between life-history phenotypes. Molecular Ecology. 22(3): 739-756 DOI: 10.1111/j.1365-294X.2012.05750.x

We study multiple molecular networks but one of our favorites is the Insulin and Insulin-like Signaling (IIS) network. The IIS network is a collection of hormones, receptors, and intracellular signaling proteins that regulates many aspects of life-history — reproduction, growth, stress response and aging — that vary across natural population of animals and across species.

Previous research on this network found it was more evolving rapidly in reptiles relative to mammals (McGaugh et al 2015). With this study, we exposed vast variation in the IIS network within and among amniotes. This provides a critical step to unlocking information that this signaling network may contain about vertebrate patterns of genetic regulation of metabolism, modes of reproduction, and rates of aging. Beyond this there is relatively little understanding of how the IIS network functions in reptiles (Schwartz and Bronikowski 2016). Current research in the lab is studying this network from different angles at the organismal, physiological, and molecular levels.

Protein structures of IGF1 hormone and IGF1 Cellular Receptor. Expanded atoms are amino acids that are quickly evolving in reptiles

Current research directions ongoing in the lab:

  • When, where, and how of IGF hormone and receptors expression. (Abby)

  • The Functional Consequences of Divergent Selection. We are exploring this sequence diversity of the hormones and the receptors through sequencing of the genes within and across anolis lizard species. To understand the functional consequences of the amino acid changes we are using recombinant (lizard) hormones for comparative experiments in a captive colony of wild-caught lizards and in their cell cultures to determine the functional roles of the observed amino acid substitutions in binding the receptors and the consequences on cellular and organismal growth. (Amanda)

Key references associated with our lab:

  • Schwartz, TS, AM Bronikowski. 2016. Evolution and Function of the Insulin and Insulin-like Signaling Network in Ectothermic Reptiles: Some Answers and More Questions? Integrative and Comparative Biology. 56(2): 171-184.

  • Reding, DM, EA Addis, MG Palacios, TS Schwartz, AM Bronikowski. 2016. Environmental and genetic effects on insulin-like signaling and postnatal growth in garter snakes with divergent life histories. General and Comparative Endocrinology. 233: 88-99. doi: 10.1016/j.ygcen.2016.05.018

  • McGaugh SE, AM Bronikowski, C-H Kuo, DM Reding, EA Addis, LE Flagel, FJ Janzen, TS Schwartz. 2015. Rapid molecular evolution across amniotes of the IIS/TOR network. PNAS. 112(22): 7055-7060.   doi: 10.1073/pnas.1419659112​

The "Island Rule" is a worldwide phenomenon of rapid body size evolution on islands where smaller taxa show a tendency towards dwarfism, and larger taxa show a tendency towards gigantism. On the Channel Islands off the coast of California three species of reptiles have evolved to be dwarf relative to the mainland populations. We are using the repeated evolution of dwarfism to understand  how molecular networks (genes, hormone regulation, etc) underlying complex traits, such as body size, can evolve. These molecular data are integrated with estimates of reproductive output obtained through advanced field-portable ultrasound technology which can inform us about the life history evolution of these species as well that allows us to extend our understanding of the process of convergent evolution on correlated life-history traits.

Current research directions ongoing in the lab:

  • Development of draft genomes for gopher snake and southern alligator lizard.

  • Whole Genome Population Sequencing of the gopher snake across mainland and island populations to understand demographic history and to identify genes under selection.

  • Development of alligator lizard cell lines from mainland and island populations so we can study cell physiology in the lab.

Key references associated with our lab:

  • Sparkman, AM, AD Clark, LJ Brummett(UO), KR Chism(UO), LL Combrink(UO), NM Kabey(UO), TS Schwartz. 2018. Convergence in reduced body size, head size, and blood glucose in three island reptiles. Ecology and Evolution. 8(12):6169-6182. doi: 10.1002/ece3.4171

Santa Cruz Island snakes, gopher snake (brown) and yellow-bellied racer (gray). These populations have body size that is 30 - 14% smaller than mainland populations.

Stress Response and Stress Resilience

Within and across Generations

Photo credit: Rory Telemeco

In natural environments, individuals experience multiple stressors throughout their lives. Stressors can come in the form of temperature (heat/cold), social interactions, habitat destruction/degradation, food availability, predation, and even intense periods of growth and reproduction. How individuals respond to these stressors, and interactions among these stressors, will determine their capacity to survive and reproduce, and ultimately if the population will persist.

Current research directions ongoing in the lab:

  • Understanding the effects of multiple stressors (fire ants and heat stress) in fence lizards at physiological and gene expression levels. (Dasia)

  • The effects of heat stress on damage and resilience within and across generations using zebra finches through collaboration with Dr. Haruka Wada (see Link to Project page for Stress Resilience).

Key references associated with our lab:

  •  Telemeco, RS(PS), D Simpson(GS), C Tylan, T Langkilde, TS Schwartz. 2019. Contrasting cellular and endocrine responses of lizards to divergent ecological stressors. Integrative and Comparative Biology.

  • Nelson, JRG, TS Schwartz, JM Gohlke. 2018. Influence of maternal age on the effects of seleno-L-methionine in the model organism Daphnia pulex under standard and heat stress conditions. Reproductive Toxicology. 75:1-9. doi: 10.1016/j.reprotox.2017.11.001

  • Schwartz, TS, and AM Bronikowski. 2013. Dissecting molecular stress networks: identifying nodes of divergence between life-history phenotypes. Molecular Ecology. 22(3): 739-756 DOI: 10.1111/j.1365-294X.2012.05750.x

It has been well established that habitat loss is associated with emerging infectious diseases. Most hypotheses to explain this association focus on ecological drivers and community structure; however, none have been developed to consider coevolutionary selective pressures across a fragmented landscape. We developed the ‘coevolution effect’  hypothesis that proposes within habitat fragments, shifts in population structure among hosts, obligate parasites, and pathogens function in parallel and act as ‘coevolutionary engines’, accelerating pathogen diversification, and therefore increasing pathogen diversity across a degraded landscape. When combined with bridge vectors (e.g., mosquitoes and ticks) this increases the probability that pathogens with zoonotic potential may spill over into human communities.

Current research directions ongoing in the lab:

  • Population genomics of lemurs lice and their viruses to begin to test the hypothosis

Key references associated with our lab:

Current research directions ongoing in the lab:

  • High Quality Chromosome-level genome assembly for the fence lizard.

  • Draft genome for the Southern Alligator Lizard

  • Draft genomes for two strains of Daphnia pulicaria.

Key references associated with our lab:

  • Waits, D, D Simpson(REU), A Sparkman, AM Bronikowski, TS Schwartz. 2020. Utility of reptile blood transcriptomes in molecular ecology. Molecular Ecology Resources. 20(1) 

  • McGaugh SE, AM Bronikowski, C-H Kuo, DM Reding, EA Addis, LE Flagel, FJ Janzen, TS Schwartz. 2015. Rapid molecular evolution across amniotes of the IIS/TOR network. PNAS. 112(22): 7055-7060.   doi: 10.1073/pnas.1419659112​

  • Schwartz, TS*, H Tae*, Y Yang, K Mockaitis, JL Van Hemert, SR Proulx, J-H Choi, and AM Bronikowski. 2010. A garter snake transcriptome: pyrosequencing, de novo assembly, and sex-specific differences. BMC Genomics. 11: 694-715.