Understanding patterns of competition and admixture between spotted and barred owls

Campus: UCSF

PI(s): Wall (UCSF), Dumbacher (California Academy of Sciences)

Background: Spotted owls (Strix occidentalis) are large, charismatic birds found in old- growth forests in western North America. Over the past century, spotted owl populations have suffered a precipitous decline, due to loss of habitat from logging and competition from the invasive barred owl (Strix varia). Barred owls are native to Eastern North America, but have recently expanded their range westward through Canada and then south along the West coast. While barred owls are known to out-compete spotted owls in regions where they are coincident, it is not known to what extent the two owls have interbred in the wild. Some California populations of barred owls show phenotypes that are intermediate between Eastern barred owls and spotted owls, suggesting either recent admixture or recent adaptation to new environments. The goal of this project is to (1) determine the timing and extent of admixture between the two species, and (2) identify genes or regions subject to recent adaptation (and/or adaptive introgression) in the invading barred owl populations.

Approach: Our plan is to use low-coverage whole-genome sequence data from a wide range of samples, as well as novel methods for quantifying admixture and selection, to address these questions.

Resources: We have already generated a draft de novo genome assembly of the spotted owl (scaffold N50 ~3 Mb), using Illumina sequencing of paired-end and mate- pair libraries with insert sizes ranging from 170 bp to 10 Kb. We also have 20X WGS data from one Eastern barred owl and 0.02 – 2X WGS data from 52 additional owl samples, including spotted owls, barred owls and putative hybrids (most have <0.5X coverage).