Population Structure

Population Genetics of Saltmarsh Sparrows: 

Past work has focused on investigating population structure of Saltmarsh Sparrows in the Northeastern United States at both a regional and local scale. Due to their exclusive reliance on a patchily distributed and fragmented habitat, coupled with evidence of high site fidelity, Saltmarsh Sparrows provide an interesting system for investigating genetic structure and metapopulation dynamics.

Saltmarsh Sparrow Populations in New England
Saltmarsh Sparrow Populations in New England

 

 

 

 

We are continuing this work with the addition sampling locations and genetic markers to better understand metapopulation dynamics in Saltmarsh Sparrows. We have also included patch level habitat characteristics as a means to identify marsh features that best predict the observed patterns of genetic variation.


Sharp-tailed Sparrow Subspecies Complex:

We have just completed some new research focused on delineating boundaries within the Saltmarsh-Nelson’s sparrow subspecies complex. The taxonomic history of the Saltmarsh and Nelson’s sparrow has long been a topic of ornithological debate. To address these questions, we used reduced representation sequencing to investigate patterns of differentiation across subspecies.

The patterns of genetic differentiation that we detected do not support the five currently recognized subspecies units. Our sampling of the sparrow complex revealed discordant patterns of genetic and morphological variation, with the observed genetic variation failing to mirror current subspecies delineations across this group. While we found intraspecific differences in morphology, differences in structural measurements fell along a continuous gradient, making it difficult to draw population boundaries based on phenotype alone. This contrasts with the observed genetic variation, which identifies three genetic clusters corresponding to both subspecies of A. caudacutus, freshwater A. nelsoni, and coastal A. nelsoni (N-SUB).

PCA plot of Saltmarsh and Nelson's sparrows for three morphological traits (A) and PCA plot of Saltmarsh and Nelson's sparrows for 1,929 SNPs (B). Colors represent subspecies groups
PCA plot of Saltmarsh and Nelson’s sparrows for three morphological traits (A) and PCA plot of Saltmarsh and Nelson’s sparrows for 1,929 SNPs (B). Colors represent subspecies groups