Tag: Matt Streisfeld

Characterizing Genetic Relationships Underlying Adaptive Flower Color Divergence in Mimulus aurantiacus

Presenter: Connor Benson

Mentors: Matt Streisfeld and Sean Stankowski, Biology

Poster: 4

Major: Biology

Understanding the genetic basis of adaptive traits lends insight into the mechanisms that generate biodiversity. Flower color has been implicated as an adaptive trait in numerous studies, and is thought to be a primary driver
of speciation in angiosperms due to selection by differential pollinator preference. Here I used molecular genetic techniques to examine the relationship between two regulatory genes involved in the production of red floral pigment, a trait thought to underlie the evolution of two new subspecies in Mimuls aurantiacus. I used genotype-phenotype comparisons in lab bred plants to characterize how MaMyb1, the less studied of these two genes, impacts the production of red floral pigment. I also utilized virus-induced gene silencing in an attempt to understand the functional role of MaMyb1 in producing red flowers. My results thus far suggest that MaMyb1 does not play a significant role in producing red flower pigment. This work aims to better our understanding of the genetic relationships underlying flower color divergence in an important model system for the study of speciation.

Genetic Architecture of Local Adaptation and Reproductive Isolation in Mimulus aurantiacus

Presenter: Hanna McIntosh

Faculty Mentor: Matt Streisfeld, Sean Stankowski

Presentation Type: Poster 76

Primary Research Area: Science

Major: Environmental Science

Funding Source: UROP Mini-Grant, University of Oregon, $1000

A major goal of speciation research is to understand the genetic architecture of isolating barriers. Theoretical studies predict that isolating barriers are most effective if they have a simple genetic basis and are controlled by loci in
the same genomic regions. To test this hypothesis, we used Quantitative Trait Locus (QTL) mapping to determine the genetic architecture of floral trait divergence between red and yellow ecotypes of the monkeyflower Mimulus aurantiacus. These ecotypes are closely related, but partially isolated due to preferences of different pollinators for contrasting floral traits. We phenotyped an F2 mapping population (n=226) and used RADseq to generate a high- density genetic map to investigate two floral traits—color and size—thought to underlie preference. Using a multi- QTL model, we identified 2 QTLs for flower color and 3 QTLs for flower size. For size, the total phenotypic variation explained by the 3 QTLs was 36%, indicating that this trait is controlled by many genes of small effect. In contrast, a single QTL explained over 65% of variation in flower color. While recent studies have shown that multiple isolating traits are controlled by the same genomic region, we observed no QTL overlap for color and size. In addition to revealing the genetic basis of adaptation in M. aurantiacus, our results show that complex, simple, and genetically- independent traits can contribute to reproductive isolation early in speciation.

Parallel Evolution of Floral Adaptation In Mimulus Aurantiacus

Presenter(s): Connor Lane − Biology

Faculty Mentor(s): Matt Streisfeld

Poster 86

Research Area: Science

It is common to find that the same traits have evolved independently across different species, a phenomenon referred to as parallel evolution. Diverse examples of parallelism exist across all domains of life, including the multiple appearances of wings in mammals, insects, and birds. Mimulus aurantiacus, the bush monkeyflower, is an excellent system for studying parallel evolution, because differences in the color, shape, and size of flowers are maintained due to natural selection by animal pollinators. However, flowers that are visually similar across two regions of southern California (San Diego and Orange Counties) are genetically distinct, suggesting that the same floral differences evolved independently in both regions. We hypothesize that these genetic differences exist due to an historical geographic barrier that prevented genetic exchange between the regions. We measured several traits such as the length, width, and color of flowers from plants in different populations native to the Camp Pendleton Marine Base, which lies in between San Diego and Orange Counties. My results show that flowers with intermediate characteristics are common in Camp Pendleton that are likely the product of hybridization between genetically distinct plants. Ongoing analyses that combine these data with genomic information test for the presence of a barrier to genetic exchange that previously isolated these populations. Understanding the mechanisms that drive parallel evolution of trait differences in San Diego and Orange Counties will yield insights into the role that natural selection plays in creating the amazing diversity of life on earth.

The Effect of Geography on Genome-Wide Patterns in Mimulus Aurantiacus

Presenter(s): Conner Lane

Faculty Mentor(s): Matt Streisfeld

Poster 58

Session: Sciences

Characterizing patterns of the genome for species spanning a large geographic space may influence the way we understand evolutionary differences between populations. For example, areas of the genome that are highly differentiated and are presumed to result from natural selection may instead arise from genome properties such as low diversity that exaggerate the differences between populations. As a first step towards making conclusions about natural selection in Mimulus aurantiacus, a phenotypically diverse plant occurring continuously across Southern California, we tested for correlations between genome statistics to characterize ways in which properties of the genome may be contributing to differences between populations. As an example, we expect high within-population diversity (π) to mask “real” differences between populations, leading to a lower differentiation score (FST), which we did observe. We also expected this negative relationship between π and FST to grow stronger with higher distance corresponding to more “real” differences to be masked by the within-population variation, which we only observed weak patterns of. This trend of correlations existing but only being weakly associated with geographic distance held true for all statistical comparisons. We conclude that M. aurantiacus does display specific genome properties that may act as confounding variables for processes we wish to examine such as natural selection. However, these patterns do not strongly correlate with greater isolation due to distance, indicating that genome properties may have less of an effect on distantly related populations than we might have otherwise assumed.

Genomic ancestry is explained by both geography and ecology in Mimulus aurantiacus

Presenter(s): Connor Lane—Biology

Faculty Mentor(s): Matt Streisfeld

Session 4: Preserving Mother Earth

One of the main goals of evolutionary biology and ecology is to understand the mechanisms by which the vast diversity in life on Earth is created . Integral to this process is speciation, where one species diverges into two . Recent work has shown that speciation can occur even if populations are not completely isolated with each other, which is known as speciation with gene flow . To understand this phenomenon, we perform a survey characterizing genetic admixture and genomic ancestry in Mimulus aurantiacus ssp . puniceus . From here, we test whether or not certain genome features thought to be indicative of local adaptation covary with geographic space and environmental differences . We hypothesize that due to local adaptation being well-characterized within ssp . puniceus, we will observe substantial genetic subdivision in our survey and find that important genome statistics covary with environment due to adaptation leading to genetic isolation . From our survey, we found both an extraordinary amount of genetic subdivision in ssp . puniceus, indicating that what we consider to be one subspecies has many distinct groups . In addition to this, we find that the most differentiated groups within puniceus have indistinguishable floral trait distributions, hinting at a deeper history of isolation rather than these groups being separated due to natural selection . Population genomic data reveals that variation in genome features signaling divergence is explained by variation in both geography and environment, implying that both neutral processes based on geographic isolation and positive selection due to local ecology are important for shaping the genome .