Research interests

In our research we seek to deepen our understanding of the evolutionary origins of novelty, by gathering critical genetic data from a variety of plant, animal, and microbial taxa in field and laboratory settings, by developing and applying novel statistical analyses to genetic data, and through the development of theoretical models.

One goal of our research is to understand the genetic architecture of boundaries between species. Geographic contact between previously isolated lineages can lead to their coalescence through gene flow, or to the maintenance of derived characteristics in divergent lineages. Part of our work involves identifying the genetic conditions that favor either outcome. Decay of
  genetic differentiation between populations over time.

A second and related goal of our research is to contribute to our growing understanding of the genetics of adaptation. We develop statistical genetic methods for population genomics and for detecting the effects of selection on the genome.

Below is a description of some of the research projects that Alex Buerkle participates in or leads. Some additional projects are described on the webpages of individual members of the lab.

Genetic architecture of species boundaries

Barriers to gene flow allow discrete groups of organisms, such as species, to persist. In many cases reproductive barriers between taxa are incomplete and hybridization occurs in zones of geographic contact. A central focus of our research is to understand how different genetic architectures influence the fate of hybridizing taxa, and includes studies of the origin of diploid species through hybridization.

Schematic of introgression and clines at loci scattered
      across the genome.

Examples of research projects include:

  1. We have worked on statistical models for estimating ancestry and studying introgression (Gompert and Buerkle 2011,2012,2013; Gompert et al. 2012, 2014; Shastry et al. in review). Our work includes analyses of Populus, Lexer et al. 2007, 2010; Lindtke et al. 2012, 2014), sunflowers, (Buerkle and Rieseberg 2001, Scascitelli et al. 2010, sculpins (Nolte et al. 2009) and suckers (Mandeville et al. 2015, 2017), mice (Teeter et al. 2010), manakins (Parchman et al. 2013), butterflies (Gompert et al. 2012, 2014), spruce (Haselhorst et al. 2019), and other species.

    We have developed software that implements our analyses of hybrids (bgc, Gompert and Buerkle 2012; and introgress, Gompert and Buerkle 2010, hindex, Buerkle 2005). Most recently we have released the entropy software for the inference of genotype and ancestry in mixed-ploidy individuals and populations (Shastry et al. in review).

  2. Chromosomal blocks of parental in a hybrid species of
	sunflowers..

    We have modelled the efficacy of different genetic architectures in the maintenance of species barriers and found that alternative architectures have large effects on isolation (Gompert et al. 2012, Lindtke and Buerkle 2015).

    I have modeled the ecological and genetic conditions that affect the origin of species through hybridization, and specifically hybrid species that have arisen without an increase in ploidy (Buerkle et al. 2000). We also modeled the risk of extinction through hybridization (Buerkle et al. 2003).

    In a related study, we used genetic maps from three hybrid species of sunflowers and junction theory to infer the rate of genome stabilization that followed diploid hybrid speciation (Buerkle and Rieseberg 2008). More recently we have been studying multiple instances of diploid hybrid speciation in butterflies (Nice et al. 2013) and how the genetic composition of contemporary hybrids recapitulates the composition of older hybrid lineages (Chaturvedi et al. 2020).

Genetics of adaptation

Penstemon
	haydenii

DNA sequence variation makes it possible to study how specific genomic regions contribute to the expression of quantitative traits and allows an analysis of the genetic basis of adaptation and speciation.

For example, shifts to feeding on novel host plants are a key component of the origin of biodiversity in many insects. We are working on the repeatability and predictability of evolution associated with the shift to feeding on an introduced plant (alfalfa) by a butterfly in the Western U.S. (Gompert et al. 2015, Forister et al. 2020, and in press). We have also collaborated on the genomics of adaptation related to host shifts in Timema walking sticks (Nosil et al. 2013, Gompert et al. 2014, Soria-Carrasco et al. 2014. With collaborators, we have mapped traits in naturally occuring, recombinant, hybrid individuals (e.g., Bresadola et al. 2019)

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