Who

Elevational Generalism

Most Andean birds inhabit narrow elevational ranges thought to be set by a combination of biological and environmental factors. Very few species inhabit more than 3,000 meters in elevation. Those that do must compensate for large shifts in temperture, UV exposure, and the partial pressure of oxygen. Are these exceptional species physiologically adapting in the face of gene flow or are plastic and behavioral responses allowing them to persist across diverse environmental conditions and preventing them from specializing on narrower elevation zones?

In Gadek et al. 2017 I found that elevational generalists are either in the process of diversifying, expanding across the gradient, or undertaking seasonal or resource-pulse driven elevational migration, and that elevational generalism is an unstable and ephemeral condition.

Conceptual figure illustrating the three main mechanisms at play in the maintenence or erosion of elevational generalist's wide ranges.

Evolution of Elevational Ranges

The evolutionary history of neotropical birds has undoubtedly been influenced by Andean uplift, leaving us with current patterns of high diversity and endemism in and around the Andes. I ask: How did modern elevational ranges form and change over time? How rapidly have they shifted? Are upward and downward shifts symmetrically distributed across the elevation gradient? and how do patterns of range evolution differ among clades? This work is being done in collaboration with Eli Stone and Selina Bauernfeind.

Figure illustrating historical dynamics of upper elevation limits. Shows rates of shift in contour crossings/10 Ma for expansions of the upper limit in green and contractions of the upper limit in purple.

Plasticity and Adaptation During Extreme Elevational Transitions

Plastic responses to acute changes in elevation are well documented and shared across many vertebrates. Similarly, genetic adaptation to high elevation environments often acts on predictable physiological pathways. But how do these processes interact, and how do they transition between one another?

To ask these questions, we sampled the entire Peruvian range of two co-distributed marsh birds ( Phleocryptes melanops & Tachuris rubrigastra). These birds have disjunct elevational ranges, inhabiting coastal marshes at sea level and high elevation marshes above 4000 meters. Are the high elevation populations adapted(ing) to the dramatically lower oxygen availability? Or has gene flow and/or recent colonization failed to suppress short term acclimatization responses? This work is in collaboration with Jessie Williamson.

Photograph of Many-colored Rush Tyrant (Tachuris rubrigastra) from Puerto Viejo, Peru in 2016.

Malaria in Sky Islands

Avian malaria is a widspread chronic disease of birds caused by multiple Apicomplexan organisms. To understand how host and pathogen communities vary across the landscape we surveyed birds and parasite communities among Southwestern sky islands and simulated null communities to compare against empirical data.

We found that parasite communities differed between sky islands relative to null community models, suggesting idiosyncratic colonization and extirpation dynamics. This work is in collaboration with Dr. Christopher Witt, Lisa Barrow, Jessie Williamson, Selina Bauernfeind, and Rosario Marroquin-Flores.

Figure modified from Barrow et al. 2021 showing observed (dashed lines) and expected Jaccard Index values. Expected values obtained from 10,000 randomly simulated communities. Illustrates how observed communities in two "sky islands" differ from expectations.

Tracheal Evolution in Sandhill Cranes

The sandhill crane (Grus canadensis ) is among the few bird species that exhibit tracheal elongation. Within this species there is substantial size dimorphism between subspecies. Jones & Witt 2014 found that the smaller subspecies that undertake longer distance migrations had proportionally longer trachea hypothesized to make smaller birds sound bigger. I am interested in assessing the symmetry and strength of sexual dimorphism within sandhill cranes.

Posterior distributions of sexual dimorphism index for tracheal length by subspecies. Black circles, thick, and thin bars indicate the posterior median, 50, and 90 % credible intervals respectively

Evolutionary and ecological drivers of microbe-host associations in the lung mycobiomes of birds

Microbiomes are being published at a rapid pace. Yet wild bird microbiomes and specifically their fungal components (mycobiomes) are largely undescribed. Furthermore, how microbiomes are structured by phylogenetic, geographic, and life history traits remains understudied. Baseline knowledge of the makeup of these communities and factors that affect their assembly and maintenance hold important implications for disease ecology, public health, and large scale coevolutionary processes.

We are describing the first lung mycobiomes of birds and modeling the associations of phylogeny, morphology, and ecology with lung fungal communities. This project is in collaboration with Paris Hamm & Michael Mann utilizing samples collected and stored in the Museum of Southwestern Biology.

Global and subsampled generalized dissimilarity models showing geographic, morphological, and phylogenetic predictors of fungal community dissimilarity. Figure shows (height of dashed lines) that phylogenetic distance and maximum latitude of bird hosts explains the most dissimilarity among lung fungal communities