About Darren Irwin

I am a Professor in the Department of Zoology, and the Biodiversity Research Centre, at the University of British Columbia.

Lab snowshoeing trip

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On February 10th, we had a great time snowshoeing at Cypress Mountain. As a very experienced snowshoer, Silu led the way. Rashika in particular had fun, as it was her first time experiencing snow. And Maddie was enthusiastic, sort of a pre-celebration of her upcoming and now very successful MSc defence. Libby, Kenny, Ellen and I all had fun too.

Congrats to Madelyn Ore, M.Sc.!

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Congrats to Madelyn (“Maddie”) Ore for her excellent M.Sc. defence! Maddie’s thesis is titled “Geographic variation in song and genetics in the Townsend’s Warbler (Setophaga townsendi).” Maddie defended her thesis on March 1, and will be entering the Ph.D. program at Cornell University in September 2019.

Armando interviewed by CBC Radio about Haida Gwaii goshawks

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Dr. Geraldes did a great job with interviews on two CBC Radio stations, both on January 21st. You can listen here:

CBC Radio Victoria
CBC Radio Kelowna

These are both about our recent paper (open access!) on genomic variation in Northern Goshawks:

Geraldes, A.*, K. Askelson*, E. Nikelski, F.I. Doyle, W.L. Harrower, K. Winker, and D.E. Irwin. 2018. Population genomic analyses reveal a highly differentiated and endangered genetic cluster of northern goshawks (Accipiter gentilis laingi) in Haida Gwaii. Evolutionary Applications, online Early View: https://doi.org/10.1111/eva.12754. (*Shared first authorship)

For more about this paper, see: https://www.zoology.ubc.ca/~irwin/irwinlab/published-genomic-differentiation-of-goshawks/

Published: genomic differentiation of goshawks

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This week, our paper on genomic differentiation of Northern Goshawks was published. Sylvia Heredia of UBC Biology produced this wonderful graphic that summarizes the paper:

The Abstract:

Accurate knowledge of geographic ranges and genetic relationships among populations is important when managing a species or population of conservation concern. Along the western coast of Canada, a subspecies of the northern goshawk (Accipiter gentilis laingi) is legally designated as Threatened. The range and distinctness of this form, in comparison with the broadly distributed North American subspecies (Accipiter gentilis atricapillus), is unclear. Given this morphological uncertainty, we analyzed genomic relationships in thousands of single nucleotide polymorphisms identified using genotyping‐by‐sequencing of high‐quality genetic samples. Results revealed a genetically distinct population of northern goshawks on the archipelago of Haida Gwaii and subtle structuring among other North American sampling regions. We then developed genotyping assays for ten loci that are highly differentiated between the two main genetic clusters, allowing inclusion of hundreds of low‐quality samples and confirming that the distinct genetic cluster is restricted to Haida Gwaii. As the laingi form was originally described as being based on Haida Gwaii (where the type specimen is from), further morphological analysis may result in this name being restricted to the Haida Gwaii genetic cluster. Regardless of taxonomic treatment, the distinct Haida Gwaii genetic cluster along with the small and declining population size of the Haida Gwaii population suggests a high risk of extinction of an ecologically and genetically distinct form of northern goshawk. Outside of Haida Gwaii, sampling regions along the coast of BC and southeast Alaska (often considered regions inhabited by laingi) show some subtle differentiation from other North American regions. These results will increase the effectiveness of conservation management of northern goshawks in northwestern North America. More broadly, other conservation‐related studies of genetic variation may benefit from the two‐step approach we employed that first surveys genomic variation using high‐quality samples and then genotypes low‐quality samples at particularly informative loci.

The citation and link:

Geraldes, A.*, K. Askelson*, E. Nikelski, F.I. Doyle, W.L. Harrower, K. Winker, and D.E. Irwin. 2018. Population genomic analyses reveal a highly differentiated and endangered genetic cluster of northern goshawks (Accipiter gentilis laingi) in Haida Gwaii. Evolutionary Applications, online Early View: https://doi.org/10.1111/eva.12754. (*Shared first authorship)

The UBC press release: https://science.ubc.ca/news/haida-gwaiis-northern-goshawks-highly-distinct-and-risk

Media coverage:
CBC Radio interviews
CBC article by The Canadian Press

We thank the many sample contributors for their contributions to this study (see the Acknowledgements section of the paper).

This research was funded by grants from Genome British Columbia; British Columbia Ministry of Forests, Lands and Natural Resource Operations; Coast Forest Products Association; Western Forest Products; and the Natural Sciences and Engineering Research Council of Canada.

Published: Genomic islands of differentiation across 3 warbler species pairs

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Today, published in Molecular Ecology: our paper comparing patterns of genomic differentiation across three hybridizing species pairs of warblers. This paper is the culmination of many years of work by a great group of 10 collaborators.

The citation:

Irwin, D.E., B. Milá, D.P.L. Toews, A. Brelsford, H.L. Kenyon, A.N. Porter, C. Grossen, K.E. Delmore, M. Alcaide, and J.H. Irwin. 2018. A comparison of genomic islands of differentiation across three young avian species pairs. Molecular Ecology, online Early View: https://doi.org/10.1111/mec.14858

The Abstract:

Detailed evaluations of genomic variation between sister species often reveal distinct chromosomal regions of high relative differentiation (i.e., “islands of differentiation” in FST), but there is much debate regarding the causes of this pattern. We briefly review the prominent models of genomic islands of differentiation and compare patterns of genomic differentiation in three closely related pairs of New World warblers with the goal of evaluating support for the four models. Each pair (MacGillivray’s/mourning warblers; Townsend’s/black‐throated green warblers; and Audubon’s/myrtle warblers) consists of forms that were likely separated in western and eastern North American refugia during cycles of Pleistocene glaciations and have now come into contact in western Canada, where each forms a narrow hybrid zone. We show strong differences between pairs in their patterns of genomic heterogeneity in FST, suggesting differing selective forces and/or differing genomic responses to similar selective forces among the three pairs. Across most of the genome, levels of within‐group nucleotide diversity (πWithin) are almost as large as levels of between‐group nucleotide distance (πBetween) within each pair, suggesting recent common ancestry and/or gene flow. In two pairs, a pattern of the FSTpeaks having low πBetween suggests that selective sweeps spread between geographically differentiated groups, followed by local differentiation. This “sweep‐before‐differentiation” model is consistent with signatures of gene flow within the yellow‐rumped warbler species complex. These findings add to our growing understanding of speciation as a complex process that can involve phases of adaptive introgression among partially differentiated populations.

New publication: ZW sex chromosomes and speciation

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Darren has published a review of sex chromosomes evolution and speciation in birds and other ZW systems. This is an invited submission for a special issue of Molecular Ecology, on “Sex Chromosomes and Speciation.”

Here’s the citation and link:

Irwin, D.E. 2018. Sex chromosomes and speciation in birds and other ZW systems. Molecular Ecology, online Early View: https://doi.org/10.1111/mec.14537

Brelsford, Toews & Irwin: Proceedings B paper on genomic basis of colour

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Congrats to Alan Brelsford and David Toews, co-first authors on our new paper on the loci underlying colour pattern differences across the Audubon’s / myrtle warbler hybrid zone.

The paper:
Brelsford, A.*, D.P.L. Toews*, and D.E. Irwin. 2017. Admixture mapping in a hybrid zone reveals loci associated with avian feather coloration. Proceedings B 284: 20171106. *Shared first authorship.  Link

The UBC Science press releaseLink

The key figure from the paper, showing the result of a genome-wide association study of colour differences between the two forms:

The Abstract:
Identifying the genetic bases for colour patterns has provided important insights into the control and expression of pigmentation and how these characteristics influence fitness. However, much more is known about the genetic bases for traits based on melanin pigments than for traits based on another major class of pigments, carotenoids. Here, we use natural admixture in a hybrid zone between Audubon’s and myrtle warblers (Setophaga coronata auduboni/S. c. coronata) to identify genomic regions associated with both types of pigmentation. Warblers are known for rapid speciation and dramatic differences in plumage. For each of five plumage coloration traits, we found highly significant associations with multiple single-nucleotide polymorphisms (SNPs) across the genome and these were clustered in discrete regions. Regions near significantly associated SNPs were enriched for genes associated with keratin filaments, fibrils that make up feathers. A carotenoid-based trait that differs between the taxa—throat colour—had more than a dozen genomic regions of association. One cluster of SNPs for this trait overlaps the Scavenger Receptor Class F Member 2 (SCARF2) gene. Other scavenger receptors are presumed to be expressed at target tissues and involved in the selective movement of carotenoids into the target cells, making SCARF2 a plausible new candidate for carotenoid processing. In addition, two melanin-based plumage traits—colours of the eye line and eye spot—show very strong associations with a single genomic region mapping to chromosome 20 in the zebra finch. These findings indicate that only a subset of the genomic regions differentiated between these two warblers are associated with the plumage differences between them and demonstrate the utility of reduced-representation genomic scans in hybrid zones.

 

Toews, Heavyside & Irwin publish paper on migration of myrtle warblers

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Congrats to co-authors David Toews and Julian Heavyside on our publication showing that the Myrtle Warblers (a form of Yellow-rumped Warbler) migrating down the Pacific Coast of North America are primarily breeding in Alaska, the Yukon, and northern BC, rather than further east.

The UBC Science press release: Isotope fingerprints in feathers reveal songbirds’ secret breeding grounds

The citation:

Toews, D.P.L., J. Heavyside, and D.E. Irwin. 2017. Linking the wintering and breeding grounds of warblers along the Pacific Flyway. Ecology and Evolution, online Early View.  DOI: 10.1002/ece3.3222   Link (open access!)

The Abstract:
Long-distance migration is a behavior that is exhibited by many animal groups. The evolution of novel migration routes can play an important role in range expansions, ecological interactions, and speciation. New migration routes may evolve in response to selection in favor of reducing distance between breeding and wintering areas, or avoiding navigational barriers. Many migratory changes are likely to evolve gradually and are therefore difficult to study. Here, we attempt to connect breeding and wintering populations of myrtle warblers (Setophaga coronata coronata) to better understand the possible evolution of distinct migration routes within this species. Myrtle warblers, unlike most other warblers with breeding ranges primarily in eastern North America, have two disjunct overwintering concentrations—one in the southeastern USA and one along the Pacific Coast—and presumably distinct routes to-and-from these locations. We studied both myrtle and Audubon’s warblers (S. c. auduboni) captured during their spring migration along the Pacific Coast, south of the narrow region where these two taxa hybridize. Using stable hydrogen isotopes and biometric data, we show that those myrtle warblers wintering along the southern Pacific Coast of North America are likely to breed at high latitudes in Alaska and the Yukon rather than in Alberta or further east. Our interpretation is that the evolution of this wintering range and migration route along the Pacific Coast may have facilitated the breeding expansion of myrtle warblers into northwestern North America. Moreover, these data suggest that there may be a migratory divide within genetically similar populations of myrtle warblers.


Myrtle warbler (copyright: Darren Irwin)

 

Ildiko Szabo et al.: First House Swift in Americas

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Congrats to lead author Ildiko Szabo and coauthors Kimberly Walters and James Rourke on our publication documenting the first specimen of House Swift in the Americas:

Szabo, I., K. Walters, J. Rourke, and D.E. Irwin. 2017. First record of House Swift (Apus nipalensis) in the Americas. Wilson Journal of Ornithology 129: 411-416.  Link

The Abstract:
A carcass of a House Swift (Apus nipalensis) found in Ladner, British Columbia on 18 May 2012 appears to be the first documented record of this species in the Americas. Identification is based on DNA sequencing and morphometric characters. University of British Columbia Beaty Biodiversity Museum Cowan Tetrapod Collection catalogue number B017056 has been assigned to this specimen (round study skin, spread wing, partial skeleton, and tissue samples).

Feel free to email me for a PDF of the full publication.