Ethan Linck

Postdoc @ U. Tennessee

My research uses population genetics to understand how ecological processes influence speciation and shape genomic variation in nonmodel organisms. I collect empirical data from wild populations of birds and insects and validate models using evolutionary simulations and theory.

Selection, gene flow, and complexity in speciation

After decades of imprecise verbal models and a general sense that Darwin misnamed his famous book, a resurgence of theory and the onset of high throughput DNA sequencing has reinvigorated the study of speciation. We’re now faced with reconciling biological intuition and evidence from species distributions (that suggest geographic isolation is crucial to most speciation events) with new theory and genomic evidence (which suggest that gene flow and selection are rampant throughout the evolutionary history of diverging lineages). The central chapter of my dissertation used young sister species segregating across a strong environmental gradient to understand the the relative importance of these forces using phenotypic data and whole genome sequencing. Based partly on these results, my collaborator CJ Battey and I are finish up a manuscript that on establishes the relative ease of a model of speciation with periodic gene flow pulses, likely a common historical scenario.

The genomic landscape of divergence in Syma kingfishers

Molecular ecology and population genomics

The toolkit of population genetics is a powerful aid in studying dispersal, migration, reproductive behavior, niche dynamics, and other ecological processes in nonmodel organisms. I have used genome-wide DNA sequence data to study migratory divides in an iconic songbird, investigate drift / migration balance in highly vagile “supertramp” species, and test predictions of Dan Janzen’s classic paper on why mountain passes are “higher” in the tropics (an ongoing collaboration with my current postdoc advisor Kimberly Sheldon). Because these methods are incredibly complex and can be prone to analytical biases, I have also worked to validate laboratory methods for collecting population genomic data from degraded DNA sources and understand how coalescent theory can explain why bioinformatic filtering steps can alter inferred patterns of population genetic structure.

Mutational age and minor allele frequencies across a coalescent tree

Tropical natural history

Basic natural history observations are the raw material of biological hypotheses. The sheer overwhelming grandeur of tropical montane biodiversity has played a significant role in determining my interests as a biologist, but for many species (the vast majority?) we lack detailed information on distributions, life history, dispersal behavior, reproduction, and other basic biological parameters. I am committed to the slow but invaluable work of contributing these fundamental data, and have written notes on high alpine bird communities, nesting biology in a widespread swallow, and a longer paper on using specimen records and the emerging biodiversity informatics infrastructure to infer migratory behavior. I am particularly interested in natural history of the rainforests of New Guinea and Solomon Islands, where I have spent significant time and reported on community conservation initiatives as a photojournalist.

A high elevation Wattled Brushturkey (megapode) egg from 1800m on Mt. Wilhelm, Papua New Guinea