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Johnson SB, Winnikoff JR, Schultz DT, Christianson LM, Patry WL, Mills CE, Haddock SHD. Speciation of pelagic zooplankton: Invisible boundaries can drive isolation of oceanic ctenophores. Front Genet 2022; 13:970314. [PMID: 36276958 PMCID: PMC9585324 DOI: 10.3389/fgene.2022.970314] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Accepted: 09/12/2022] [Indexed: 11/13/2022] Open
Abstract
The study of evolution and speciation in non-model systems provides us with an opportunity to expand our understanding of biodiversity in nature. Connectivity studies generally focus on species with obvious boundaries to gene flow, but in open-ocean environments, such boundaries are difficult to identify. Due to the lack of obvious boundaries, speciation and population subdivision in the pelagic environment remain largely unexplained. Comb jellies (Phylum Ctenophora) are mostly planktonic gelatinous invertebrates, many of which are considered to have freely interbreeding distributions worldwide. It is thought that the lobate ctenophore Bolinopsis infundibulum is distributed throughout cooler northern latitudes and B. vitrea warmer. Here, we examined the global population structure for species of Bolinopsis with genetic and morphological data. We found distinct evolutionary patterns within the genus, where B. infundibulum had a broad distribution from northern Pacific to Atlantic waters despite many physical barriers, while other species were geographically segregated despite few barriers. Divergent patterns of speciation within the genus suggest that oceanic currents, sea-level, and geological changes over time can act as either barriers or aids to dispersal in the pelagic environment. Further, we used population genomic data to examine evolution in the open ocean of a distinct lineage of Bolinopsis ctenophores from the North Eastern Pacific. Genetic information and morphological observations validated this as a separate species, Bolinopsis microptera, which was previously described but has recently been called B. infundibulum. We found that populations of B. microptera from California were in cytonuclear discordance, which indicates a secondary contact zone for previously isolated populations. Discordance at this scale is rare, especially in a continuous setting.
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Affiliation(s)
- Shannon B. Johnson
- Monterey Bay Aquarium Research Institute, Moss Landing, CA, United States
- *Correspondence: Shannon B. Johnson, ; Steven H. D. Haddock,
| | - Jacob R. Winnikoff
- Monterey Bay Aquarium Research Institute, Moss Landing, CA, United States
- Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, Santa Cruz, CA, United States
| | - Darrin T. Schultz
- Monterey Bay Aquarium Research Institute, Moss Landing, CA, United States
- Department of Neurosciences and Developmental Biology, University of Vienna, Vienna, Austria
- Department of Biomolecular Engineering and Bioinformatics, University of California, Santa Cruz, Santa Cruz, CA, United States
| | | | - Wyatt L. Patry
- Animal Care Division, Monterey Bay Aquarium, Monterey, CA, United States
| | - Claudia E. Mills
- Friday Harbor Laboratories and the Department of Biology, University of Washington, Friday Harbor, WA, United States
| | - Steven H. D. Haddock
- Monterey Bay Aquarium Research Institute, Moss Landing, CA, United States
- *Correspondence: Shannon B. Johnson, ; Steven H. D. Haddock,
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Çilingir FG, Hansen D, Bunbury N, Postma E, Baxter R, Turnbull L, Ozgul A, Grossen C. Low‐coverage reduced representation sequencing reveals subtle within‐island genetic structure in Aldabra giant tortoises. Ecol Evol 2022; 12:e8739. [PMID: 35342600 PMCID: PMC8931707 DOI: 10.1002/ece3.8739] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2021] [Revised: 02/28/2022] [Accepted: 03/01/2022] [Indexed: 02/01/2023] Open
Affiliation(s)
- F. Gözde Çilingir
- Department of Evolutionary Biology and Environmental Studies University of Zurich Zurich Switzerland
| | - Dennis Hansen
- Zoological Museum University of Zurich Zurich Switzerland
- Indian Ocean Tortoise Alliance Victoria Seychelles
| | - Nancy Bunbury
- Seychelles Islands Foundation Victoria Seychelles
- Centre for Ecology and Conservation College of Life and Environmental Sciences University of Exeter Penryn UK
| | - Erik Postma
- Centre for Ecology and Conservation College of Life and Environmental Sciences University of Exeter Penryn UK
| | | | | | - Arpat Ozgul
- Department of Evolutionary Biology and Environmental Studies University of Zurich Zurich Switzerland
| | - Christine Grossen
- Department of Evolutionary Biology and Environmental Studies University of Zurich Zurich Switzerland
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Perez M, Breusing C, Angers B, Beinart RA, Won YJ, Young CR. Divergent paths in the evolutionary history of maternally transmitted clam symbionts. Proc Biol Sci 2022; 289:20212137. [PMID: 35259985 PMCID: PMC8905170 DOI: 10.1098/rspb.2021.2137] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Vertical transmission of bacterial endosymbionts is accompanied by virtually irreversible gene loss that results in a progressive reduction in genome size. While the evolutionary processes of genome reduction have been well described in some terrestrial symbioses, they are less understood in marine systems where vertical transmission is rarely observed. The association between deep-sea vesicomyid clams and chemosynthetic Gammaproteobacteria is one example of maternally inherited symbioses in the ocean. Here, we assessed the contributions of drift, recombination and selection to genome evolution in two extant vesicomyid symbiont clades by comparing 15 representative symbiont genomes (1.017-1.586 Mb) to those of closely related bacteria and the hosts' mitochondria. Our analyses suggest that drift is a significant force driving genome evolution in vesicomyid symbionts, though selection and interspecific recombination appear to be critical for maintaining symbiont functional integrity and creating divergent patterns of gene conservation. Notably, the two symbiont clades possess putative functional differences in sulfide physiology, anaerobic respiration and dependency on environmental vitamin B12, which probably reflect adaptations to different ecological habitats available to each symbiont group. Overall, these results contribute to our understanding of the eco-evolutionary processes shaping reductive genome evolution in vertically transmitted symbioses.
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Affiliation(s)
- Maëva Perez
- Department of Biological Sciences, Université de Montréal, Montreal, Canada
| | - Corinna Breusing
- Graduate School of Oceanography, University of Rhode Island, Narragansett, RI, USA
| | - Bernard Angers
- Department of Biological Sciences, Université de Montréal, Montreal, Canada
| | - Roxanne A Beinart
- Graduate School of Oceanography, University of Rhode Island, Narragansett, RI, USA
| | - Yong-Jin Won
- Division of EcoScience, Ewha Womans University, Seoul, South Korea
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Breusing C, Johnson SB, Tunnicliffe V, Clague DA, Vrijenhoek RC, Beinart RA. Allopatric and Sympatric Drivers of Speciation in Alviniconcha Hydrothermal Vent Snails. Mol Biol Evol 2020; 37:3469-3484. [PMID: 32658967 PMCID: PMC7743903 DOI: 10.1093/molbev/msaa177] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Despite significant advances in our understanding of speciation in the marine environment, the mechanisms underlying evolutionary diversification in deep-sea habitats remain poorly investigated. Here, we used multigene molecular clocks and population genetic inferences to examine processes that led to the emergence of the six extant lineages of Alviniconcha snails, a key taxon inhabiting deep-sea hydrothermal vents in the Indo-Pacific Ocean. We show that both allopatric divergence through historical vicariance and ecological isolation due to niche segregation contributed to speciation in this genus. The split between the two major Alviniconcha clades (separating A. boucheti and A. marisindica from A. kojimai, A. hessleri, and A. strummeri) probably resulted from tectonic processes leading to geographic separation, whereas the splits between co-occurring species might have been influenced by ecological factors, such as the availability of specific chemosynthetic symbionts. Phylogenetic origin of the sixth species, Alviniconcha adamantis, remains uncertain, although its sister position to other extant Alviniconcha lineages indicates a possible ancestral relationship. This study lays a foundation for future genomic studies aimed at deciphering the roles of local adaptation, reproductive biology, and host–symbiont compatibility in speciation of these vent-restricted snails.
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Affiliation(s)
- Corinna Breusing
- Graduate School of Oceanography, University of Rhode Island, Narragansett, RI
| | | | - Verena Tunnicliffe
- Department of Biology and School of Earth and Ocean Sciences, University of Victoria, Victoria, BC, Canada
| | - David A Clague
- Monterey Bay Aquarium Research Institute, Moss Landing, CA
| | | | - Roxanne A Beinart
- Graduate School of Oceanography, University of Rhode Island, Narragansett, RI
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Russell SL, Pepper-Tunick E, Svedberg J, Byrne A, Ruelas Castillo J, Vollmers C, Beinart RA, Corbett-Detig R. Horizontal transmission and recombination maintain forever young bacterial symbiont genomes. PLoS Genet 2020; 16:e1008935. [PMID: 32841233 PMCID: PMC7473567 DOI: 10.1371/journal.pgen.1008935] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2019] [Revised: 09/04/2020] [Accepted: 06/16/2020] [Indexed: 12/30/2022] Open
Abstract
Bacterial symbionts bring a wealth of functions to the associations they participate in, but by doing so, they endanger the genes and genomes underlying these abilities. When bacterial symbionts become obligately associated with their hosts, their genomes are thought to decay towards an organelle-like fate due to decreased homologous recombination and inefficient selection. However, numerous associations exist that counter these expectations, especially in marine environments, possibly due to ongoing horizontal gene flow. Despite extensive theoretical treatment, no empirical study thus far has connected these underlying population genetic processes with long-term evolutionary outcomes. By sampling marine chemosynthetic bacterial-bivalve endosymbioses that range from primarily vertical to strictly horizontal transmission, we tested this canonical theory. We found that transmission mode strongly predicts homologous recombination rates, and that exceedingly low recombination rates are associated with moderate genome degradation in the marine symbionts with nearly strict vertical transmission. Nonetheless, even the most degraded marine endosymbiont genomes are occasionally horizontally transmitted and are much larger than their terrestrial insect symbiont counterparts. Therefore, horizontal transmission and recombination enable efficient natural selection to maintain intermediate symbiont genome sizes and substantial functional genetic variation.
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Affiliation(s)
- Shelbi L. Russell
- Department of Molecular Cellular and Developmental Biology. University of California Santa Cruz, Santa Cruz, California, United States of America
- Department of Biomolecular Engineering. University of California Santa Cruz, Santa Cruz, California, United States of America
| | - Evan Pepper-Tunick
- Department of Biomolecular Engineering. University of California Santa Cruz, Santa Cruz, California, United States of America
- Genomics Institute, University of California, Santa Cruz, California, United States of America
| | - Jesper Svedberg
- Department of Biomolecular Engineering. University of California Santa Cruz, Santa Cruz, California, United States of America
- Genomics Institute, University of California, Santa Cruz, California, United States of America
| | - Ashley Byrne
- Department of Molecular Cellular and Developmental Biology. University of California Santa Cruz, Santa Cruz, California, United States of America
| | - Jennie Ruelas Castillo
- Department of Molecular Cellular and Developmental Biology. University of California Santa Cruz, Santa Cruz, California, United States of America
| | - Christopher Vollmers
- Department of Biomolecular Engineering. University of California Santa Cruz, Santa Cruz, California, United States of America
- Genomics Institute, University of California, Santa Cruz, California, United States of America
| | - Roxanne A. Beinart
- Graduate School of Oceanography. University of Rhode Island, Narragansett, Rhode Island, United States of America
| | - Russell Corbett-Detig
- Department of Biomolecular Engineering. University of California Santa Cruz, Santa Cruz, California, United States of America
- Genomics Institute, University of California, Santa Cruz, California, United States of America
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Rieseberg L, Geraldes A, Taberlet P. Editorial 2020. Mol Ecol 2020; 29:1-19. [DOI: 10.1111/mec.15328] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2019] [Accepted: 12/06/2019] [Indexed: 11/27/2022]
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Wilkins LGE. Can interspecies affairs in the dark lead to evolutionary innovation? Mol Ecol 2019; 28:4693-4696. [PMID: 31659841 DOI: 10.1111/mec.15262] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Revised: 10/01/2019] [Accepted: 10/03/2019] [Indexed: 11/28/2022]
Abstract
Evolutionary adaptation is the adjustment of species to a new or changing environment. Engaging in mutualistic microbial symbioses has been put forward as a key trait that promotes the differential, evolutionary success of many animal and plant lineages (McFall-Ngai, 2008). Microbial mutualists allow these organisms to occupy new ecological niches where they could not have persisted on their own or would have been constrained by competitors. Vertical transmission of beneficial microbial symbionts from parents to the offspring is expected to link the adaptive association between a given host and microbe, and it can lead to coevolution and sometimes even cospeciation (Fisher, Henry, Cornwallis, Kiers, & West, 2017). Vertical transmission also causes bottlenecks that strongly reduce the effective population size and genetic diversity of the symbiont population. Moreover, vertically transmitted symbionts are assumed to have fewer opportunities to exchange genes with relatives in the environment. In a "From the Cover" article in this issue of Molecular Ecology, Breusing, Johnson, Vrijenhoek, and Young (2019) investigated whether hybridization among different host species could lead to interspecies exchange of otherwise strictly vertically transmitted symbionts. Hybridization of divergent lineages can potentially cause intrinsic and extrinsic incompatibilities, swamp rare alleles, and lead to population extinctions. In some cases, however, it might also create novel trait combinations that lead to evolutionary innovation (Marques, Meier, & Seehausen, 2019). Breusing et al. (2019) linked the concept of hybridization to symbiont transmission, and their findings have significant implications for the study of evolution of vertically transmitted symbionts and their hosts.
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Affiliation(s)
- Laetitia G E Wilkins
- Genome and Biomedical Sciences Facility, University of California, Davis, Davis, CA, USA
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Breusing C, Johnson SB, Vrijenhoek RC, Young CR. Host hybridization as a potential mechanism of lateral symbiont transfer in deep-sea vesicomyid clams. Mol Ecol 2019; 28:4697-4708. [PMID: 31478269 PMCID: PMC7004080 DOI: 10.1111/mec.15224] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Revised: 08/01/2019] [Accepted: 08/06/2019] [Indexed: 12/16/2022]
Abstract
Deep-sea vesicomyid clams live in mutualistic symbiosis with chemosynthetic bacteria that are inherited through the maternal germ line. On evolutionary timescales, strictly vertical transmission should lead to cospeciation of host mitochondrial and symbiont lineages; nonetheless, examples of incongruent phylogenies have been reported, suggesting that symbionts are occasionally horizontally transmitted between host species. The current paradigm for vesicomyid clams holds that direct transfers cause host shifts or mixtures of symbionts. An alternative hypothesis suggests that hybridization between host species might explain symbiont transfers. Two clam species, Archivesica gigas and Phreagena soyoae, frequently co-occur at deep-sea hydrocarbon seeps in the eastern Pacific Ocean. Although the two species typically host gammaproteobacterial symbiont lineages marked by divergent 16S rRNA phylotypes, we identified a number of clams with the A. gigas mitotype that hosted symbionts with the P. soyoae phylotype. Demographic inference models based on genome-wide SNP data and three Sanger sequenced gene markers provided evidence that A. gigas and P. soyoae hybridized in the past, supporting the hypothesis that hybridization might be a viable mechanism of interspecific symbiont transfer. These findings provide new perspectives on the evolution of vertically transmitted symbionts and their hosts in deep-sea chemosynthetic environments.
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Affiliation(s)
- Corinna Breusing
- Monterey Bay Aquarium Research Institute, Moss Landing, CA, USA.,National Oceanography Centre, Southampton, UK
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