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Cryptic and extensive hybridization between ancient lineages of American crows.
Mol Ecol. 2020 03; 29(5):956-969.ME

Abstract

Most species and therefore most hybrid zones have historically been defined using phenotypic characters. However, both speciation and hybridization can occur with negligible morphological differentiation. Recently developed genomic tools provide the means to better understand cryptic speciation and hybridization. The Northwestern Crow (Corvus caurinus) and American Crow (Corvus brachyrhynchos) are continuously distributed sister taxa that lack reliable traditional characters for identification. In this first population genomic study of Northwestern and American crows, we use genomic SNPs (nuDNA) and mtDNA to investigate the degree of genetic differentiation between these crows and the extent to which they may hybridize. Our results indicate that American and Northwestern crows have distinct evolutionary histories, supported by two nuDNA ancestry clusters and two 1.1%-divergent mtDNA clades dating to the late Pleistocene, when glacial advances may have isolated crow populations in separate refugia. We document extensive hybridization, with geographic overlap of mtDNA clades and admixture of nuDNA across >900 km of western Washington and western British Columbia. This broad hybrid zone consists of late-generation hybrids and backcrosses, but not recent (e.g., F1) hybrids. Nuclear DNA and mtDNA clines had concordant widths and were both centred in southwestern British Columbia, farther north than previously postulated. Overall, our results suggest a history of reticulate evolution in American and Northwestern crows, perhaps due to recurring neutral expansion(s) from Pleistocene glacial refugia followed by lineage fusion(s). However, we do not rule out a contributing role for more recent potential drivers of hybridization, such as expansion into human-modified habitats.

Authors+Show Affiliations

Department of Biology, University of Washington, Seattle, WA, USA. Burke Museum of Natural History and Culture, Seattle, WA, USA.Department of Biology, University of Washington, Seattle, WA, USA. Burke Museum of Natural History and Culture, Seattle, WA, USA.Department of Psychology, University of Washington, Seattle, WA, USA.Department of Biology, University of Washington, Seattle, WA, USA. Burke Museum of Natural History and Culture, Seattle, WA, USA.Burke Museum of Natural History and Culture, Seattle, WA, USA.US Geological Survey, Alaska Science Center, Anchorage, AK, USA.Department of Biology, University of Washington, Seattle, WA, USA. Burke Museum of Natural History and Culture, Seattle, WA, USA.

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

32034818

Citation

Slager, David L., et al. "Cryptic and Extensive Hybridization Between Ancient Lineages of American Crows." Molecular Ecology, vol. 29, no. 5, 2020, pp. 956-969.
Slager DL, Epperly KL, Ha RR, et al. Cryptic and extensive hybridization between ancient lineages of American crows. Mol Ecol. 2020;29(5):956-969.
Slager, D. L., Epperly, K. L., Ha, R. R., Rohwer, S., Wood, C., Van Hemert, C., & Klicka, J. (2020). Cryptic and extensive hybridization between ancient lineages of American crows. Molecular Ecology, 29(5), 956-969. https://doi.org/10.1111/mec.15377
Slager DL, et al. Cryptic and Extensive Hybridization Between Ancient Lineages of American Crows. Mol Ecol. 2020;29(5):956-969. PubMed PMID: 32034818.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Cryptic and extensive hybridization between ancient lineages of American crows. AU - Slager,David L, AU - Epperly,Kevin L, AU - Ha,Renee R, AU - Rohwer,Sievert, AU - Wood,Chris, AU - Van Hemert,Caroline, AU - Klicka,John, Y1 - 2020/03/01/ PY - 2018/12/11/received PY - 2019/12/30/revised PY - 2020/02/05/accepted PY - 2020/2/9/pubmed PY - 2020/2/9/medline PY - 2020/2/9/entrez KW - Pleistocene refugia KW - geographic cline KW - hybrid swarm KW - mitonuclear concordance KW - reticulate evolution SP - 956 EP - 969 JF - Molecular ecology JO - Mol. Ecol. VL - 29 IS - 5 N2 - Most species and therefore most hybrid zones have historically been defined using phenotypic characters. However, both speciation and hybridization can occur with negligible morphological differentiation. Recently developed genomic tools provide the means to better understand cryptic speciation and hybridization. The Northwestern Crow (Corvus caurinus) and American Crow (Corvus brachyrhynchos) are continuously distributed sister taxa that lack reliable traditional characters for identification. In this first population genomic study of Northwestern and American crows, we use genomic SNPs (nuDNA) and mtDNA to investigate the degree of genetic differentiation between these crows and the extent to which they may hybridize. Our results indicate that American and Northwestern crows have distinct evolutionary histories, supported by two nuDNA ancestry clusters and two 1.1%-divergent mtDNA clades dating to the late Pleistocene, when glacial advances may have isolated crow populations in separate refugia. We document extensive hybridization, with geographic overlap of mtDNA clades and admixture of nuDNA across >900 km of western Washington and western British Columbia. This broad hybrid zone consists of late-generation hybrids and backcrosses, but not recent (e.g., F1) hybrids. Nuclear DNA and mtDNA clines had concordant widths and were both centred in southwestern British Columbia, farther north than previously postulated. Overall, our results suggest a history of reticulate evolution in American and Northwestern crows, perhaps due to recurring neutral expansion(s) from Pleistocene glacial refugia followed by lineage fusion(s). However, we do not rule out a contributing role for more recent potential drivers of hybridization, such as expansion into human-modified habitats. SN - 1365-294X UR - https://www.unboundmedicine.com/medline/citation/32034818/Cryptic_and_extensive_hybridization_between_ancient_lineages_of_American_crows L2 - https://doi.org/10.1111/mec.15377 DB - PRIME DP - Unbound Medicine ER -
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