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Porter CK, Romero FG, Adams DC, Bowie RCK, Riddell EA. Adaptive and non-adaptive convergent evolution in feather reflectance of California Channel Islands songbirds. Proc Biol Sci 2023; 290:20231914. [PMID: 37964520 PMCID: PMC10646447 DOI: 10.1098/rspb.2023.1914] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2023] [Accepted: 10/23/2023] [Indexed: 11/16/2023] Open
Abstract
Convergent evolution is widely regarded as a signature of adaptation. However, testing the adaptive consequences of convergent phenotypes is challenging, making it difficult to exclude non-adaptive explanations for convergence. Here, we combined feather reflectance spectra and phenotypic trajectory analyses with visual and thermoregulatory modelling to test the adaptive significance of dark plumage in songbirds of the California Channel Islands. By evolving dark dorsal plumage, island birds are generally less conspicuous to visual-hunting raptors in the island environment than mainland birds. Dark dorsal plumage also reduces the energetic demands associated with maintaining homeothermy in the cool island climate. We also found an unexpected pattern of convergence, wherein the most divergent island populations evolved greater reflectance of near-infrared radiation. However, our heat flux models indicate that elevated near-infrared reflectance is not adaptive. Analysis of feather microstructure suggests that mainland-island differences are related to coloration of feather barbs and barbules rather than their structure. Our results indicate that adaptive and non-adaptive mechanisms interact to drive plumage evolution in this system. This study sheds light on the mechanisms driving the association between dark colour and wet, cold environments across the tree of life, especially in island birds.
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Affiliation(s)
- Cody K. Porter
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, IA 50011, USA
| | - Faye G. Romero
- Department of Biology, University of Rochester, Rochester, NY 14620, USA
| | - Dean C. Adams
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, IA 50011, USA
| | - Rauri C. K. Bowie
- Museum of Vertebrate Zoology and Department of Integrative Biology, University of California Berkeley, Berkeley, CA 94720, USA
| | - Eric A. Riddell
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, IA 50011, USA
- Department of Biology, University of North Carolina – Chapel Hill, Chapel Hill, NC 27599, USA
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Myers BM, Burns KJ, Clark CJ, Brelsford A. Sampling affects population genetic inference: A case study of the Allen's (Selasphorus sasin) and rufous hummingbird (Selasphorus rufus). J Hered 2023; 114:625-636. [PMID: 37455658 DOI: 10.1093/jhered/esad044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2022] [Accepted: 07/12/2023] [Indexed: 07/18/2023] Open
Abstract
Gene flow can affect evolutionary inference when species are undersampled. Here, we evaluate the effects of gene flow and geographic sampling on demographic inference of 2 hummingbirds that hybridize, Allen's hummingbird (Selasphorus sasin) and rufous hummingbird (Selasphorus rufus). Using whole-genome data and extensive geographic sampling, we find widespread connectivity, with introgression far beyond the Allen's × rufous hybrid zone, although the Z chromosome resists introgression beyond the hybrid zone. We test alternative hypotheses of speciation history of Allen's, rufous, and Calliope (S. calliope) hummingbird and find that rufous hummingbird is the sister taxon to Allen's hummingbird, and Calliope hummingbird is the outgroup. A model treating the 2 subspecies of Allen's hummingbird as a single panmictic population fit observed genetic data better than models treating the subspecies as distinct populations, in contrast to morphological and behavioral differences and analyses of spatial population structure. With additional sampling, our study builds upon recent studies that came to conflicting conclusions regarding the evolutionary histories of these 2 species. Our results stress the importance of thorough geographic sampling when assessing demographic history in the presence of gene flow.
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Affiliation(s)
- Brian M Myers
- Department of Biological Sciences, San Diego State University, San Diego, CA, United States
| | - Kevin J Burns
- Department of Biological Sciences, San Diego State University, San Diego, CA, United States
| | - Christopher J Clark
- Department of Evolution, Ecology, and Organismal Biology, Speith Hall, University of California, Riverside, CA, United States
| | - Alan Brelsford
- Department of Evolution, Ecology, and Organismal Biology, Speith Hall, University of California, Riverside, CA, United States
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Gamboa MP, Ghalambor CK, Scott Sillett T, Morrison SA, Chris Funk W. Adaptive divergence in bill morphology and other thermoregulatory traits is facilitated by restricted gene flow in song sparrows on the California Channel Islands. Mol Ecol 2021; 31:603-619. [PMID: 34704295 DOI: 10.1111/mec.16253] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Revised: 09/20/2021] [Accepted: 09/27/2021] [Indexed: 02/06/2023]
Abstract
Disentangling the effects of neutral and adaptive processes in maintaining phenotypic variation across environmental gradients is challenging in natural populations. Song sparrows (Melospiza melodia) on the California Channel Islands occupy a pronounced east-west climate gradient within a small spatial scale, providing a unique opportunity to examine the interaction of genetic isolation (reduced gene flow) and the environment (selection) in driving variation. We used reduced representation genomic libraries to infer the role of neutral processes (drift and restricted gene flow) and divergent selection in driving variation in thermoregulatory traits with an emphasis on the mechanisms that maintain bill divergence among islands. Analyses of 22,029 neutral SNPs confirm distinct population structure by island with restricted gene flow and relatively large effective population sizes, suggesting bill differences are probably not a product of genetic drift. Instead, we found strong support for local adaptation using 3294 SNPs in differentiation-based and environmental association analyses coupled with genome-wide association tests. Specifically, we identified several putatively adaptive and candidate loci in or near genes involved in bill development pathways (e.g., BMP, CaM, Wnt), confirming the highly complex and polygenic architecture underlying bill morphology. Furthermore, we found divergence in genes associated with other thermoregulatory traits (i.e., feather structure, plumage colour, and physiology). Collectively, these results suggest strong divergent selection across an island archipelago results in genomic changes in a suite of traits associated with climate adaptation over small spatial scales. Future research should move beyond studying univariate traits to better understand multidimensional responses to complex environmental conditions.
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Affiliation(s)
- Maybellene P Gamboa
- Department of Organismal Biology and Ecology, Colorado College, Colorado Springs, Colorado, USA
| | - Cameron K Ghalambor
- Department of Biology, Graduate Degree Program in Ecology, Colorado State University, Fort Collins, Colorado, USA.,Department of Biology, Centre for Biodiversity Dynamics (CBD), Norwegian University of Science and Technology (NTNU), Trondheim, Norway
| | - T Scott Sillett
- Migratory Bird Center, Smithsonian Conservation Biology Institute, National Zoological Park, Washington, District of Columbia, USA
| | | | - W Chris Funk
- Department of Biology, Graduate Degree Program in Ecology, Colorado State University, Fort Collins, Colorado, USA
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Myers BM, Burns KJ, Clark CJ, Brelsford A. The population genetics of nonmigratory Allen's Hummingbird ( Selasphorus sasin sedentarius) following a recent mainland colonization. Ecol Evol 2021; 11:1850-1865. [PMID: 33614008 PMCID: PMC7882939 DOI: 10.1002/ece3.7174] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Revised: 12/10/2020] [Accepted: 12/17/2020] [Indexed: 02/01/2023] Open
Abstract
Allen's Hummingbird comprises two subspecies, one migratory (Selasphorus sasin sasin) and one nonmigratory (S. s. sedentarius). The nonmigratory subspecies, previously endemic to the California Channel Islands, apparently colonized the California mainland on the Palos Verdes Peninsula some time before 1970 and now breeds throughout coastal southern California. We sequenced and compared populations of mainland nonmigratory Allen's Hummingbird to Channel Island populations from Santa Catalina, San Clemente, and Santa Cruz Island. We found no evidence of founder effects on the mainland population. Values of nucleotide diversity on the mainland were higher than on the Channel Islands. There were low levels of divergence between the Channel Islands and the mainland, and Santa Cruz Island was the most genetically distinct. Ecological niche models showed that rainfall and temperature variables on the Channel Islands are similar in the Los Angeles basin and predicted continued expansion of nonmigratory Allen's Hummingbird north along the coast and inland. We also reviewed previous genetic studies of vertebrate species found on the Channel Islands and mainland and showed that broad conclusions regarding island-mainland patterns remain elusive. Challenges include the idiosyncratic nature of colonization itself as well as the lack of a comprehensive approach that incorporates similar markers and sampling strategies across taxa, which, within the context of a comparative study of island-mainland relationships, may lead to inconsistent results.
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Affiliation(s)
- Brian M. Myers
- Department of BiologySan Diego State UniversitySan DiegoCAUSA
| | - Kevin J. Burns
- Department of BiologySan Diego State UniversitySan DiegoCAUSA
| | - Christopher J. Clark
- Department of Evolution, Ecology, and Organismal BiologySpeith HallUniversity of CaliforniaRiversideCAUSA
| | - Alan Brelsford
- Department of Evolution, Ecology, and Organismal BiologySpeith HallUniversity of CaliforniaRiversideCAUSA
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Mcglaughlin ME, Riley L, Helenurm K, Wallace LE. Does Channel Island Acmispon (Fabaceae) form cohesive evolutionary groups? WEST N AM NATURALIST 2018. [DOI: 10.3398/064.078.0414] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
| | - Lynn Riley
- Department of Biology, University of South Dakota, Vermillion, SD 57069
| | - Kaius Helenurm
- Department of Biology, University of South Dakota, Vermillion, SD 57069
| | - Lisa E. Wallace
- Department of Biological Sciences, Old Dominion University, Norfolk, VA 23529
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Karin BR, Cicero C, Koo MS, Bowie RCK. The role of history and ecology as drivers of song divergence in Bell’s and Sagebrush sparrows (Artemisiospiza, Aves: Passerellidae). Biol J Linn Soc Lond 2018. [DOI: 10.1093/biolinnean/bly090] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Benjamin R Karin
- Museum of Vertebrate Zoology, Valley Life Sciences Building, University of California, Berkeley, CA, USA
- Department of Integrative Biology, Valley Life Sciences Building, University of California, Berkeley, CA, USA
| | - Carla Cicero
- Museum of Vertebrate Zoology, Valley Life Sciences Building, University of California, Berkeley, CA, USA
| | - Michelle S Koo
- Museum of Vertebrate Zoology, Valley Life Sciences Building, University of California, Berkeley, CA, USA
| | - Rauri C K Bowie
- Museum of Vertebrate Zoology, Valley Life Sciences Building, University of California, Berkeley, CA, USA
- Department of Integrative Biology, Valley Life Sciences Building, University of California, Berkeley, CA, USA
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The Mouse-colored Tyrannulet (Phaeomyias murina) is a species complex that includes the Cocos Flycatcher (Nesotriccus ridgwayi), an island form that underwent a population bottleneck. Mol Phylogenet Evol 2016; 101:294-302. [DOI: 10.1016/j.ympev.2016.04.031] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Revised: 04/19/2016] [Accepted: 04/24/2016] [Indexed: 11/22/2022]
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