Alexis Mychajliw

investigating the past, present, and future of island mammals. and ones with wiggly noses, too.

Research

Genomes, bones, and sediments hold clues to how species have responded to challenges in the past. I apply a diverse methodological toolkit to understand how ecological interactions have changed over the past 25,000 years into today.

My research has two main foci:

1. Identifying mechanisms & traits underlying species survival or extinction in the Late Quaternary

2. Reconstructing species responses to anthropogenic/climatic changes to inform conservation baselines and our understanding of fundamental ecological/evolutionary processes


Does Dietary Generalism Promote Resilience in a Relictual Insectivore?

The solenodon persists today in fragmented populations across Hispaniola despite the island’s ~85% extinction rate for native nonvolant mammals in the Late Holocene. Entering the Anthropocene, deforestation for agricultural expansion, the spread of alien species, and illegal charcoal production are radically altering the solenodon’s native habitats.

I assess whether dietary flexibility is the mechanism promoting the survival of a relictual insectivore, the Hispaniolan solenodon, across a continuum of natural and agricultural landscapes. I combine DNA metabarcoding techniques with stable isotope analysis for a holistic understanding of prey diversity and trophic position.

I collected samples with Dominican conservationists Pedro Martinez, Yimell Corona, Nicolas Corona, and Gerson Feliz. Working with Kristine Bohmann and Martin Nielsen at the Centre for GeoGenetics, I used DNA metabarcoding techniques to elucidate the dietary diversity held within each fecal sample. At Stanford’s Stable Isotope Biogeochemistry Lab I am analyzing δC and δN.

This project is funded by the Stanford Center for Computational, Evolutionary, and Human Genomics and the American Society of Mammalogists.


Testing Ecological Hypotheses Using 15,000 Years of Species Extinctions & Invasions

Working with Siobhan Cooke of Johns Hopkins University, Juan Almonte of the Museo Nacional de Historia Natural, Gerson Feliz of Grupo Jargua, and Craig Koenigs of UC Santa Barbara, we excavated a fossiliferous cave deposit in Parque Nacional Jaragua, Dominican Republic. Using radiocarbon dating, I am establishing a secure chronology for our stratigraphic levels – providing a platform to evaluate community structure across key environmental perturbations.

Our stratigraphic levels span the extinction of native species and the arrival of invasive species, providing ecological snapshots to address hypotheses of niche contraction, competitive release, and whether invasive species have wider niche breadths than natives. Stable isotopes provide the quantitative basis for addressing these ecological hypotheses.

Conservation paleobiology

We apply these findings to conservation efforts in the national park, and make connections to the modern “stratigraphic level” using transect studies of vegetation and camera-trapping by undergraduate honors student Lauren Gibson.

This project is funded by an NSF Doctoral Dissertation Improvement Grant, the Stanford Center for Latin American Studies, and the Lewis & Clark Fund for Exploration & Research.


Population Responses to Pleistocene-Anthropocene Environmental Change

Genetics, distributions, morphology

Using DNA from museum skins and excavated subfossils, I am working to catalogue solenodon genetic diversity at important time points to contextualize their modern distribution and confirm subspecies designations. Undergraduate honors student Lauren Gibson is using ancient, historic, and modern occurrence points to provide distribution models that complement our genetic data.

I am working with additional undergraduate students to use geometric morphometrics in assessing how populations of a Caribbean insectivore, Nesophontes, partitioned resources and what traits/mechanisms contributed to their extinction.


Extinction Chronology of Island Mammals – Caribbean & Worldwide

A size-biased extinction pattern has been well documented across the Late Quaternary for megafaunal mammals on continents. However, far less is known how the unique evolutionary histories and historical cultural contingencies have shaped extinction patterns on islands. I have worked to holistically address extinction drivers using archaeological, colonial/historical, and paleoecological records.

Using the published literature and my own excavations, I have 1) reconstructed the mammal communities of Late Quaternary, historical, and modern island systems; 2) developed body-size continuums for these communities using morphological measures; and 3) collaborated to understand the role of life history in shaping extinction patterns.


Reconstructing Late Quaternary Extinction Drivers in South America

As part of a diverse group of paleontologists, archaeologists, and ecologists from North and South America led by Tony Barnosky, Emily Lindsey, and Natalia Villavicencio of UC Berkeley, I am working to understand the anthropogenic and climatic drivers of megafaunal mammal extinctions. I use this as a 1) continental comparison for my islands studies, and 2) an opportunity to learn quantitative approaches to reconstructing the human and ecological dimensions of extinction.

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Density of archaeological sites through time. From Goldberg et al 2016

Prehistoric human demography: setting the stage for megafauna extinctions

With fellow Stanford graduate student Amy Goldberg, I developed the largest published dataset of radiocarbon dates for South America. We show humans act like invasive species until a secondary growth period linked to sedentism.

 Paleoecological drivers of human demographic change

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Photo by Amy Goldberg

Using pollen cores and oxygen isotope records, I am working to bring a macroecological perspective to South American archaeology. My reconstructions of regional vegetation and climatic changes contextualize changes in human demography as well as megafaunal abundance declines.

This NSF-funded working group is entitled: “South American Megafauna Extinction: A Test of Synergistic Effects of Climate Change and Human Population Growth in Magnifying Extinction Intensity

 

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