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Gilg MR, Kerns EV, Gutierrez-Bayona NE, Kooyomjian C, Hinojosa NA. Dynamic Cohort Analysis Reveals Fluctuating Patterns of Selection Within a Hybrid Zone Between the Killifish Fundulus heteroclitus and F. grandis. Evol Biol 2021. [DOI: 10.1007/s11692-021-09553-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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McKenzie JL, Chung DJ, Healy TM, Brennan RS, Bryant HJ, Whitehead A, Schulte PM. Mitochondrial Ecophysiology: Assessing the Evolutionary Forces That Shape Mitochondrial Variation. Integr Comp Biol 2019; 59:925-937. [PMID: 31282925 DOI: 10.1093/icb/icz124] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The mitonuclear species concept hypothesizes that incompatibilities between interacting gene products of the nuclear and mitochondrial genomes are a major factor establishing and maintaining species boundaries. However, most of the data available to test this concept come from studies of genetic variation in mitochondrial DNA, and clines in the mitochondrial genome across contact zones can be produced by a variety of forces. Here, we show that using a combination of population genomic analyses of the nuclear and mitochondrial genomes and studies of mitochondrial function can provide insight into the relative roles of neutral processes, adaptive evolution, and mitonuclear incompatibility in establishing and maintaining mitochondrial clines, using Atlantic killifish (Fundulus heteroclitus) as a case study. There is strong evidence for a role of secondary contact following the last glaciation in shaping a steep mitochondrial cline across a contact zone between northern and southern subspecies of killifish, but there is also evidence for a role of adaptive evolution in driving differentiation between the subspecies in a variety of traits from the level of the whole organism to the level of mitochondrial function. In addition, studies are beginning to address the potential for mitonuclear incompatibilities in admixed populations. However, population genomic studies have failed to detect evidence for a strong and pervasive influence of mitonuclear incompatibilities, and we suggest that polygenic selection may be responsible for the complex patterns observed. This case study demonstrates that multiple forces can act together in shaping mitochondrial clines, and illustrates the challenge of disentangling their relative roles.
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Affiliation(s)
- Jessica L McKenzie
- Department of Zoology and Biodiversity Research Centre, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Dillon J Chung
- Department of Zoology and Biodiversity Research Centre, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Timothy M Healy
- Department of Zoology and Biodiversity Research Centre, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Reid S Brennan
- Department of Environmental Toxicology, University of California-Davis, 4138 Meyer Hall, 1 Shields Avenue, Davis, CA 95616, USA
| | - Heather J Bryant
- Department of Zoology and Biodiversity Research Centre, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Andrew Whitehead
- Department of Environmental Toxicology, University of California-Davis, 4138 Meyer Hall, 1 Shields Avenue, Davis, CA 95616, USA
| | - Patricia M Schulte
- Department of Zoology and Biodiversity Research Centre, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
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Chung DJ, Healy TM, McKenzie JL, Chicco AJ, Sparagna GC, Schulte PM. Mitochondria, Temperature, and the Pace of Life. Integr Comp Biol 2018; 58:578-590. [DOI: 10.1093/icb/icy013] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Affiliation(s)
- Dillon J Chung
- Department of Zoology and Biodiversity Research Centre, The University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4
| | - Timothy M Healy
- Department of Zoology and Biodiversity Research Centre, The University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California, San Diego, CA 92037, USA
| | - Jessica L McKenzie
- Department of Zoology and Biodiversity Research Centre, The University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4
| | - Adam J Chicco
- Department of Biomedical Sciences, Colorado State University, Fort Collins, CO 80523-1680, USA
| | - Genevieve C Sparagna
- Anschutz Medical Campus, Division of Cardiology, University of Colorado Denver, Aurora, CO 80045, USA
| | - Patricia M Schulte
- Department of Zoology and Biodiversity Research Centre, The University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4
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Reid NM, Jackson CE, Gilbert D, Minx P, Montague MJ, Hampton TH, Helfrich LW, King BL, Nacci DE, Aluru N, Karchner SI, Colbourne JK, Hahn ME, Shaw JR, Oleksiak MF, Crawford DL, Warren WC, Whitehead A. The landscape of extreme genomic variation in the highly adaptable Atlantic killifish. Genome Biol Evol 2017; 9:659-676. [PMID: 28201664 PMCID: PMC5381573 DOI: 10.1093/gbe/evx023] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Revised: 01/30/2017] [Accepted: 02/04/2017] [Indexed: 12/22/2022] Open
Abstract
Understanding and predicting the fate of populations in changing environments require knowledge about the mechanisms that support phenotypic plasticity and the adaptive value and evolutionary fate of genetic variation within populations. Atlantic killifish (Fundulus heteroclitus) exhibit extensive phenotypic plasticity that supports large population sizes in highly fluctuating estuarine environments. Populations have also evolved diverse local adaptations. To yield insights into the genomic variation that supports their adaptability, we sequenced a reference genome and 48 additional whole genomes from a wild population. Evolution of genes associated with cell cycle regulation and apoptosis is accelerated along the killifish lineage, which is likely tied to adaptations for life in highly variable estuarine environments. Genome-wide standing genetic variation, including nucleotide diversity and copy number variation, is extremely high. The highest diversity genes are those associated with immune function and olfaction, whereas genes under greatest evolutionary constraint are those associated with neurological, developmental, and cytoskeletal functions. Reduced genetic variation is detected for tight junction proteins, which in killifish regulate paracellular permeability that supports their extreme physiological flexibility. Low-diversity genes engage in more regulatory interactions than high-diversity genes, consistent with the influence of pleiotropic constraint on molecular evolution. High genetic variation is crucial for continued persistence of species given the pace of contemporary environmental change. Killifish populations harbor among the highest levels of nucleotide diversity yet reported for a vertebrate species, and thus may serve as a useful model system for studying evolutionary potential in variable and changing environments.
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Affiliation(s)
- Noah M Reid
- Department of Environmental Toxicology, University of California, Davis, CA 95616
| | - Craig E Jackson
- School of Public and Environmental Affairs, Indiana University, Bloomington, IN 47405
| | - Don Gilbert
- Biology Department, Indiana University, Bloomington, IN 47405
| | - Patrick Minx
- McDonnell Genome Institute, Washington University School of Medicine, St Louis, MO 63108
| | - Michael J Montague
- McDonnell Genome Institute, Washington University School of Medicine, St Louis, MO 63108
| | - Thomas H Hampton
- Department of Microbiology and Immunology, Dartmouth College Geisel School of Medicine, Hanover, NH 03755
| | - Lily W Helfrich
- Biology Department, Woods Hole Oceanographic Institution, Woods Hole, MA 02543
| | - Benjamin L King
- Mount Desert Island Biological Laboratory, Salisbury Cove, ME 04672
| | - Diane E Nacci
- US Environmental Protection Agency, Office of Research and Development, Narragansett, RI, 02882
| | - Neel Aluru
- Biology Department, Woods Hole Oceanographic Institution, Woods Hole, MA 02543
| | - Sibel I Karchner
- Biology Department, Woods Hole Oceanographic Institution, Woods Hole, MA 02543
| | - John K Colbourne
- School of Biosciences, University of Birmingham, United Kingdom, B15 2TT
| | - Mark E Hahn
- Biology Department, Woods Hole Oceanographic Institution, Woods Hole, MA 02543
| | - Joseph R Shaw
- School of Public and Environmental Affairs, Indiana University, Bloomington, IN 47405
| | - Marjorie F Oleksiak
- Department of Marine Biology and Ecology, Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL 33149
| | - Douglas L Crawford
- Department of Marine Biology and Ecology, Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL 33149
| | - Wesley C Warren
- McDonnell Genome Institute, Washington University School of Medicine, St Louis, MO 63108
| | - Andrew Whitehead
- Department of Environmental Toxicology, University of California, Davis, CA 95616
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Oziolor EM, Bigorgne E, Aguilar L, Usenko S, Matson CW. Evolved resistance to PCB- and PAH-induced cardiac teratogenesis, and reduced CYP1A activity in Gulf killifish (Fundulus grandis) populations from the Houston Ship Channel, Texas. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2014; 150:210-9. [PMID: 24699180 DOI: 10.1016/j.aquatox.2014.03.012] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2013] [Revised: 03/07/2014] [Accepted: 03/11/2014] [Indexed: 05/06/2023]
Abstract
The Houston Ship Channel (HSC), connecting Houston, Texas to Galveston Bay and ultimately the Gulf of Mexico, is heavily industrialized and includes several areas that have historically been identified as containing significant levels of mercury, dioxins, furans, polychlorinated biphenyls (PCBs), and polycyclic aromatic hydrocarbons (PAHs). Gulf killifish, Fundulus grandis, inhabit this entire estuarine system, including the most contaminated areas. F. grandis is the sister species of the well-established estuarine model organism Fundulus heteroclitus, for which heritable resistance to both PCB and PAH toxicity has been documented in several populations. F. grandis collected from two Superfund sites on the HSC and from a reference population were used to establish breeding colonies. F1 embryos from HSC populations were approximately 1000-fold more resistant to PCB126- and 2-5-fold more resistant to coal tar-induced cardiovascular teratogenesis, relative to embryos from the reference population. Reciprocal crosses between reference and contaminated populations exhibit an intermediate level of resistance, confirming that observed protection is genetic and biparentally inherited. Ethoxyresorufin-O-deethylase (EROD) data confirm a reduction in basal and induced cytochrome P4501A (CYP1A) activity in resistant populations of F. grandis. This result is consistent with responses previously described for resistant populations of F. heteroclitus, specifically a recalcitrant aryl hydrocarbon receptor (AHR) pathway. The decreased levels of cardiovascular teratogenesis, and decrease in CYP1A inducibility in response to PCB126 and a PAH mixture, suggest that HSC F. grandis populations have adapted to chronic contaminants exposures via a mechanism similar to that previously described for F. heteroclitus. To the best of our knowledge, this is the first documentation of evolved pollution resistance in F. grandis. Additionally, the mechanistic similarities between the population adaptation observed in this study and previous work in F. heteroclitus suggest that genetic variation predating the evolutionary divergence of these two species may best explain the apparent rapid parallel evolution of pollution resistance in genetically and geographically distinct species and populations.
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Affiliation(s)
- Elias M Oziolor
- Department of Environmental Science and the Center for Reservoir and Aquatic Systems Research (CRASR), Baylor University, Waco, TX 76798, United States; Institute for Biomedical Studies, Baylor University, Waco, TX 76798, United States
| | - Emilie Bigorgne
- Department of Environmental Science and the Center for Reservoir and Aquatic Systems Research (CRASR), Baylor University, Waco, TX 76798, United States
| | - Lissette Aguilar
- Department of Environmental Science and the Center for Reservoir and Aquatic Systems Research (CRASR), Baylor University, Waco, TX 76798, United States; The Institute for Ecological, Earth, Environmental Sciences, Baylor University, Waco, TX 76798, United States
| | - Sascha Usenko
- Department of Environmental Science and the Center for Reservoir and Aquatic Systems Research (CRASR), Baylor University, Waco, TX 76798, United States; The Institute for Ecological, Earth, Environmental Sciences, Baylor University, Waco, TX 76798, United States
| | - Cole W Matson
- Department of Environmental Science and the Center for Reservoir and Aquatic Systems Research (CRASR), Baylor University, Waco, TX 76798, United States; Institute for Biomedical Studies, Baylor University, Waco, TX 76798, United States; The Institute for Ecological, Earth, Environmental Sciences, Baylor University, Waco, TX 76798, United States.
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Whitehead A. Evolutionary Genomics of Environmental Pollution. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2014; 781:321-37. [DOI: 10.1007/978-94-007-7347-9_16] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
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Whitehead A, Roach JL, Zhang S, Galvez F. Salinity- and population-dependent genome regulatory response during osmotic acclimation in the killifish (Fundulus heteroclitus) gill. ACTA ACUST UNITED AC 2012; 215:1293-305. [PMID: 22442367 DOI: 10.1242/jeb.062075] [Citation(s) in RCA: 77] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The killifish Fundulus heteroclitus is abundant in osmotically dynamic estuaries and it can quickly adjust to extremes in environmental salinity. We performed a comparative osmotic challenge experiment to track the transcriptomic and physiological responses to two salinities throughout a time course of acclimation, and to explore the genome regulatory mechanisms that enable extreme osmotic acclimation. One southern and one northern coastal population, known to differ in their tolerance to hypo-osmotic exposure, were used as our comparative model. Both populations could maintain osmotic homeostasis when transferred from 32 to 0.4 p.p.t., but diverged in their compensatory abilities when challenged down to 0.1 p.p.t., in parallel with divergent transformation of gill morphology. Genes involved in cell volume regulation, nucleosome maintenance, ion transport, energetics, mitochondrion function, transcriptional regulation and apoptosis showed population- and salinity-dependent patterns of expression during acclimation. Network analysis confirmed the role of cytokine and kinase signaling pathways in coordinating the genome regulatory response to osmotic challenge, and also posited the importance of signaling coordinated through the transcription factor HNF-4α. These genome responses support hypotheses of which regulatory mechanisms are particularly relevant for enabling extreme physiological flexibility.
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Affiliation(s)
- Andrew Whitehead
- University of California, Davis, Environmental Toxicology Department, Davis, CA 95616, USA.
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Whitehead A, Pilcher W, Champlin D, Nacci D. Common mechanism underlies repeated evolution of extreme pollution tolerance. Proc Biol Sci 2011; 279:427-33. [PMID: 21733895 DOI: 10.1098/rspb.2011.0847] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Human alterations to the environment can exert strong evolutionary pressures, yet contemporary adaptation to human-mediated stressors is rarely documented in wildlife populations. A common-garden experimental design was coupled with comparative transcriptomics to discover evolved mechanisms enabling three populations of killifish resident in urban estuaries to survive normally lethal pollution exposure during development, and to test whether mechanisms are unique or common across populations. We show that killifish populations from these polluted sites have independently converged on a common adaptive mechanism, despite variation in contaminant profiles among sites. These populations are united by a similarly profound desensitization of aryl-hydrocarbon receptor-mediated transcriptional activation, which is associated with extreme tolerance to the lethal effects of toxic dioxin-like pollutants. The rapid, repeated, heritable and convergent nature of evolved tolerance suggests that ancestral killifish populations harboured genotypes that enabled adaptation to twentieth-century industrial pollutants.
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Affiliation(s)
- Andrew Whitehead
- Department of Biological Sciences, Louisiana State University, 202 Life Sciences Building, Baton Rouge, LA 70803, USA.
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Eberhardt AL, Burdick DM, Dionne M. The Effects of Road Culverts on Nekton in New England Salt Marshes: Implications for Tidal Restoration. Restor Ecol 2010. [DOI: 10.1111/j.1526-100x.2010.00721.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Bozinovic G, Oleksiak MF. Embryonic gene expression among pollutant resistant and sensitive Fundulus heteroclitus populations. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2010; 98:221-229. [PMID: 20363516 PMCID: PMC3225961 DOI: 10.1016/j.aquatox.2010.02.022] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2009] [Revised: 02/08/2010] [Accepted: 02/16/2010] [Indexed: 05/22/2023]
Abstract
Changes in gene expression, coupled with biochemical, physiological, and behavioral alterations, play a critical role in adaptation to environmental stress. Our goal was to explore ways natural populations may have adapted to local, polluted environments. We took advantage of natural populations of Fundulus heteroclitus, one of the few studied fish species in North America that has established resistant populations in highly contaminated urban estuaries. We analyzed morphology, physiology, and gene expression of developing F. heteroclitus embryos during late organogenesis (stage 31); these embryos were from both resistant and sensitive populations and were raised in a common, unpolluted environment. While cardiac heart rates show significant differences between embryos of parents from clean and heavily contaminated Superfund sites, time-to-stage, embryo morphology, and gene expression profile analyses do not differ significantly between untreated embryos from resistant and sensitive populations. Further evaluation that includes tissue-specific approaches in gene expression analysis and larger sample sizes may be necessary to highlight important phenotypes associated with mechanisms of sensitivity and resistance among natural F. heteroclitus embryo populations. Alternatively, population differences may be masked by developmental canalization, and biologically important differences between sensitive and resistant embryos may only manifest with exposure (e.g., be dependent on gene by environment interactions).
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Affiliation(s)
- Goran Bozinovic
- Department of Environmental and Molecular Toxicology, Box 7633, North, Carolina State University, Raleigh, NC 27695-7633, United States.
| | - Marjorie F Oleksiak
- Rosenstiel School of Marine and Atmospheric Sciences, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149, United States.
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11
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Duvernell DD, Lindmeier JB, Faust KE, Whitehead A. Relative influences of historical and contemporary forces shaping the distribution of genetic variation in the Atlantic killifish, Fundulus heteroclitus. Mol Ecol 2008; 17:1344-60. [PMID: 18302693 DOI: 10.1111/j.1365-294x.2007.03648.x] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A major goal of population genetics research is to identify the relative influences of historical and contemporary processes that serve to structure genetic variation. Most population genetic models assume that populations exist in a state of migration-drift equilibrium. However, in the past this assumption has rarely been verified, and is likely rarely achieved in natural populations. We assessed the equilibrium status at both local and regional scales of the Atlantic killifish, Fundulus heteroclitus. This species is a model organism for the study of adaptive clinal variation, but has also experienced a complicated history of range expansion and secondary contact following allopatric divergence, potentially obscuring the influence of contemporary evolutionary processes. Presumptively neutral genetic markers (microsatellites) demonstrated zones of secondary intergradation among coastal populations centred around northern New Jersey and the Chesapeake Bay region. Analysis of genetic variation indicated isolation by distance among some populations and provided supporting evidence that the Delaware Bay, but not the Chesapeake Bay, has acted as a barrier to dispersal among coastal populations. Bayesian estimates indicated large effective population sizes and low migration rates, and were in good agreement with empirically derived estimates of population and neighbourhood size from mark-recapture studies. These data indicate that populations are not in migration-drift equilibrium at a regional scale, and suggest that contributing factors include large population size combined with relatively low migration rates. These conditions should be considered when interpreting the evolutionary significance of the distribution of genetic variation among F. heteroclitus populations.
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Affiliation(s)
- David D Duvernell
- Department of Biological Sciences, Southern Illinois University Edwardsville, Edwardsville, IL 62026, USA.
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12
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Schulte PM. Responses to environmental stressors in an estuarine fish: Interacting stressors and the impacts of local adaptation. J Therm Biol 2007. [DOI: 10.1016/j.jtherbio.2007.01.012] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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13
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McMillan AM, Bagley MJ, Jackson SA, Nacci DE. Genetic diversity and structure of an estuarine fish (Fundulus heteroclitus) indigenous to sites associated with a highly contaminated urban harbor. ECOTOXICOLOGY (LONDON, ENGLAND) 2006; 15:539-48. [PMID: 16988885 DOI: 10.1007/s10646-006-0090-4] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 06/23/2006] [Indexed: 05/04/2023]
Abstract
Intense selection on isolated populations can cause loss of genetic diversity, which if persistent, reduces adaptive potential and increases extinction probability. Phenotypic evidence of inherited tolerance suggests that polychlorinated biphenyls (PCBs), have acted as strong selective agents on populations of a non-migratory fish, Fundulus heteroclitus, indigenous to heavily contaminated sites. To evaluate population genetic structure and test for effects of intense, multi-generational PCB contamination on genetic diversity, we used AFLP analysis on fish collected from six sites along the east coast of North America that varied widely in PCB contamination. The sites included a heavily contaminated urban harbor (New Bedford, MA), an adjacent moderately contaminated sub-estuary (Buzzards Bay, MA), and an uncontaminated estuary 60 km away (Narragansett, RI). AFLP markers distinguished populations at moderate and small scales, suggesting genetic differentiation at distances of 2 km or less. Genetic diversity did not differ across the study sites. Genome-wide diversity may have been preserved because of large effective population sizes and/or because the mechanism for genetic adaptation to these contaminants affected only a small number of loci. Alternatively, loss in diversity may have been restored with moderate levels of migration and relatively short generation time for this species.
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Affiliation(s)
- Amy M McMillan
- Biology Department, State University of New York College at Buffalo, 1300 Elmwood Ave., Buffalo, NY 14222, USA.
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Adams SM, Lindmeier JB, Duvernell DD. Microsatellite analysis of the phylogeography, Pleistocene history and secondary contact hypotheses for the killifish, Fundulus heteroclitus. Mol Ecol 2006; 15:1109-23. [PMID: 16599970 DOI: 10.1111/j.1365-294x.2006.02859.x] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The mummichog, Fundulus heteroclitus, exhibits extensive latitudinal clinal variation in a number of physiological and biochemical traits, coupled with phylogeographical patterns at mitochondrial and nuclear DNA loci that suggest a complicated history of spatially variable selection and secondary intergradation. This species continues to serve as a model for understanding local and regional adaptation to variable environments. Resolving the influences of historical processes on the distribution of genetic variation within and among extant populations of F. heteroclitus is crucial to a better understanding of how populations evolve in the context of contemporary environments. In this study, we analysed geographical patterns of genetic variation at eight microsatellite loci among 15 populations of F. heteroclitus distributed throughout the North American range of the species from Nova Scotia to Georgia. Genetic variation in Northern populations was lower than in Southern populations and was strongly correlated with latitude throughout the species range. The most common Northern alleles at all eight loci exhibited concordant latitudinal clinal patterns, and the existence of an abrupt transition zone in allele frequencies between Northern and Southern populations was similar to that observed for mitochondrial DNA and allozyme loci. A significant pattern of isolation by distance was observed both within and between northern and southern regions. This pattern was unexpected, particularly for northern populations, given the recent colonization history of post-Pleistocene habitats, and was inconsistent with either a recent northward population expansion or a geographically restricted northern Pleistocene refugium. The data provided no evidence for recent population bottlenecks, and estimates of historical effective population sizes suggest that post-Pleistocene populations have been large throughout the species distribution. These results suggest that F. heteroclitus was broadly distributed throughout most of its current range during the last glacial event and that the abrupt transition in allele frequencies that separate Northern and Southern populations may reflect regional disequilibrium conditions associated with the post-Pleistocene colonization history of habitats in that region.
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Affiliation(s)
- Stephanie M Adams
- Department of Biological Sciences, Southern Illinois University Edwardsville, Edwardsville, Illinois 62026, USA
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15
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Ellis WL, Bell SS. Conditional use of mangrove habitats by fishes: Depth as a cue to avoid predators. ACTA ACUST UNITED AC 2004. [DOI: 10.1007/bf02803423] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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