Congrats to Kira Delmore on the publication of her discovery of a genetic region underlying migratory orientation in Swainson’s Thrush. A massive accomplishment, involving migratory tracking, orientation experiments, and in-depth analysis of genomic variation.
The press release: Link
Articles: Audubon.org; IFLScience; Cosmos
CBC Radio’s interview of Kira Delmore
Global News’ television interview of Darren Irwin and Kira Delmore
Delmore, K.E., D.P.L. Toews, R.R. Germain, G.L. Owens, and D.E. Irwin. 2016. The genetics of seasonal migration and plumage color. Current Biology, corrected proof available online: http://dx.doi.org/10.1016/j.cub.2016.06.015. Link
• Variation in migratory route and plumage color is explained by genomic variation
• A region on chromosome 4 is strongly and additively associated with orientation
• This region includes circadian, nervous system, and cell signaling genes
• Recurrent selective sweeps have shaped variation in this region
Congrats to Dr. Seneviratne on a nice publication about two sapsucker hybrid zones:
Seneviratne, S.S., P. Davidson, K. Martin, and D.E. Irwin. 2016. Low levels of hybridization across two contact zones among three species of woodpeckers (Sphyrapicus sapsuckers). Journal of Avian Biology, online Early View: doi: 10.1111/jav.00946. Link
Abstract: Three species of closely related woodpeckers (sapsuckers; Sphyrapicus) hybridize where they come into contact, presenting a rare ‘λ-shape’ meeting of hybrid zones. Two of the three arms of this hybrid zone are located on either side of the Interior Plateau of British Columbia, Canada bordering the foothills of the Coast Mountains and the Rocky Mountains. The third arm is located in the eastern foothills of the Rocky Mountains. The zones of hybridization present high variability of phenotypes and alleles in relatively small areas and provide an opportunity to examine levels of reproductive isolation between the taxa involved. We examined phenotypes (morphometric traits and plumage) and genotypes of 175 live birds across the two hybrid zones. We used the Genotyping By Sequencing (GBS) method to identify 180 partially diagnostic single nucleotide polymorphisms (SNPs) to generate a genetic hybrid index (GHI) for each bird. Phenotypically diverged S. ruberand S. nuchalis are genetically closely related, while S. nuchalis and S. varius have similar plumage but are well separated at the genetic markers studied. The width of both hybrid zones is narrower than expected under neutrality, and analyses of both genotypes and phenotypes indicate that hybrids are rare in the hybrid zone. Rarity of hybrids indicates assortative mating and/or some form of fitness reduction in hybrids, which might maintain the species complex despite close genetic distance and introgression. These findings further support the treatment of the three taxa as distinct species.
Congrats to Saminda!
(Saminda Fernando is a PhD student at the University of Colombo who is advised by lab alumnus Dr. Sampath Seneviratne and co-advised by Darren Irwin)
Fernando, S.P., D.E. Irwin, and S.S. Seneviratne. 2016. Phenotypic and genetic analysis support distinct species status of the Red-backed Woodpecker (Lesser Sri Lanka Flameback: Dinopium psarodes) of Sri Lanka. The Auk: Ornithological Advances 133: 497-511. Link
Abstract: Hybridization has challenged taxonomy, since hybridizing forms could be stable evolutionary entities or ephemeral forms that are blending together. The island of Sri Lanka has 2 subspecies of the flameback woodpecker D. benghalense: D. b. jaffnense in the north and D. b. psarodes in the south. Red plumage separates the endemic phenotype D. b. psarodes from other subspecies of D. benghalense. Despite these differences, intermediate phenotypes in north-central Sri Lanka discouraged the elevation of D. b. psarodes into a full species. The recent HBW and BirdLife International checklist, however, has elevated D. b. psarodes to a full species (D. psarodes), primarily based on its plumage. To objectively evaluate whether this taxonomic elevation is warranted, we examined the phenotypic and genetic affinities of D. psarodes within the D. benghalense cluster. In doing that we provide the first quantitative phenotypic and genetic analysis across a hybrid zone for an Old World woodpecker group. We sampled woodpeckers along a line transect across the island and measured body shape/size, plumage, and genetic variation in a mitochondrial gene (Cytb). Plumage color ranged from red in the south to yellow in the north, with varying proportions of orange in north-central Sri Lanka (an area of ~66 km). Morphology (body shape/size) and plumage characters showed a clear separation. There are 2 mitochondrial haplotype groups, one in the north and one in the south. A mixture of north and south haplotypes were seen in north-central Sri Lanka. Width of the hybrid zone suggests that some form of selection limits the spread of hybrids into the range of parental forms. Morphological, plumage, and genetic traits are all indicative of limited hybridization in a narrow zone between the 2 taxa, supporting the treatment of D. psarodes as a distinct species. This study provides an illustrative example of extensive hybridization between stable taxonomic entities, discouraging the practice of merging hybridizing forms as single species.
We wrote this review as an invited contribution to the Encyclopedia of Evolutionary Biology. The full citation:
Irwin, D.E., and D.B. Wake. 2016. Ring species. Vol. 3, Pages 467-475 in Encyclopedia of Evolutionary Biology, edited by R. M. Kliman. Oxford: Academic Press.
To read, you have three options (I recommend number 3):
- Purchase the article from Science Direct for $31.50: http://www.sciencedirect.com/science/article/pii/B9780128000496000779
- Purchase the Encyclopedia from Elsevier for only $1,260.00 😉 http://store.elsevier.com/product.jsp?isbn=9780128000496
- Email me a request to send you the PDF, and I will gladly do so.
A ring species is a ring of populations in which there is only a single species boundary. Two contacting forms behave as distinct species yet are connected by a long chain of populations through which there is gradual or stepwise change. Such situations provide an illustration of how the process of speciation, by which one species splits into two, can occur. Ring species are rare, but two cases provide good examples of how ring species can teach us about speciation: greenish warblers and Ensatina salamanders.
The award “recognizes the student whose record, in the opinion of the Faculty, is the best in the graduating class in the Doctoral Degree.”
Kira also won the Bill Milsom Prize, for the best Ph.D. dissertation in Zoology.
Congrats to Kira for earning these honours!
Congrats to Kira, Haley, and Ryan on a nice paper!
Delmore, K.E., L. Kenyon, R.R. Germain, and D.E. Irwin. 2015. Phenotypic divergence during speciation is inversely associated with differences in seasonal migration. Proceedings of the Royal Society of London B 282: 20151921. Link
Abstract: Differences in seasonal migration might promote reproductive isolation and differentiation by causing populations in migratory divides to arrive on the breeding grounds at different times and/or produce hybrids that take inferior migratory routes. We examined this question by quantifying divergence in song, colour, and morphology between sister pairs of North American migratory birds. We predicted that apparent rates of phenotypic differentiation would differ between pairs that do and do not form migratory divides. Consistent with this prediction, results from mixed effects models and Ornstein–Uhlenbeck models of evolution showed different rates of divergence between these groups; surprisingly, differentiation was greater among non-divide pairs. We interpret this finding as a result of variable rates of population blending and fusion between partially diverged forms. Ancient pairs of populations that subsequently fused are now observed as a single form, whereas those that did not fuse are observable as pairs and included in our study. We propose that fusion of two populations is more likely to occur when they have similar migratory routes and little other phenotypic differentiation that would cause reproductive isolation. By contrast, pairs with migratory divides are more likely to remain reproductively isolated, even when differing little in other phenotypic traits. These findings suggest that migratory differences may be one among several isolating barriers that prevent divergent populations from fusing and thereby increase the likelihood that they will continue differentiating as distinct species.
On July 21st, Kira Delmore expertly defended her Ph.D. dissertation, titled “Migratory Divides and the Genetic Basis of Reproductive Isolation.”
Dr. Delmore’s published dissertation chapters include the following:
Delmore, K.E., J.W. Fox, and D.E. Irwin. 2012. Dramatic intraspecific differences in migratory routes, stopover sites and wintering areas revealed using light-level geolocators. Proceedings of the Royal Society of London B 279: 4582-4589. Link; PDF
Delmore, K.E., and D.E. Irwin. 2014. Hybrid songbirds employ intermediate routes in a migratory divide. Ecology Letters 17: 1211-1218. Link
Delmore, K.E., S. Hübner, N.C. Kane, R. Schuster, R.L. Andrew, F. Câmara, R. Guigo, and D.E. Irwin. 2015. Genomic analysis of a migratory divide reveals candidate genes for migration and implicates selective sweeps in generating islands of differentiation. Molecular Ecology 24: 1873-1888. Link
With more on the way!
Some coverage in the media:
Discover Magazine blog
UBC press release
Read more about Kira’s work (including lots of links to media coverage) here.
Congrats Dr. Delmore!!
Alison did an excellent job presenting and defending her MSc thesis, titled “An analysis of ecological traits as reproductive barriers between the MacGillivray’s (Geothlypis tolmiei) and Mourning (G. philadelphia) warblers.”
Congrats to Julie!
Lee-Yaw, J.A., and D.E. Irwin. 2015. The importance (or lack thereof) of niche divergence to the maintenance of a northern species complex: the case of the long-toed salamander (Ambystoma macrodactylum Baird). Journal of Evolutionary Biology 28: 917-930. Link
My favourite tweet about this paper:
@phylobiogeo: alternative title… One niche to rule them all: the case of the long-toed salamander (Ambystoma macrodactylum)
Congrats to Kira and co-authors!
Delmore, K.E., S. Hübner, N.C. Kane, R. Schuster, R.L. Andrew, F. Câmara, R. Guigo, and D.E. Irwin. 2015. Genomic analysis of a migratory divide reveals candidate genes for migration and implicates selective sweeps in generating islands of differentiation. Molecular Ecology doi: 10.1111/mec.13150 Link