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Ryan K, Greenway R, Landers J, Arias-Rodriguez L, Tobler M, Kelley JL. Selection on standing genetic variation mediates convergent evolution in extremophile fish. Mol Ecol 2023; 32:5042-5054. [PMID: 37548336 DOI: 10.1111/mec.17081] [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: 04/10/2023] [Revised: 06/23/2023] [Accepted: 07/11/2023] [Indexed: 08/08/2023]
Abstract
Hydrogen sulfide is a toxic gas that disrupts numerous biological processes, including energy production in the mitochondria, yet fish in the Poecilia mexicana species complex have independently evolved sulfide tolerance several times. Despite clear evidence for convergence at the phenotypic level in these fishes, it is unclear if the repeated evolution of hydrogen sulfide tolerance is the result of similar genomic changes. To address this gap, we used a targeted capture approach to sequence genes associated with sulfide processes and toxicity from five sulfidic and five nonsulfidic populations in the species complex. By comparing sequence variation in candidate genes to a reference set, we identified similar population structure and differentiation, suggesting that patterns of variation in most genes associated with sulfide processes and toxicity are due to demographic history and not selection. But the presence of tree discordance for a subset of genes suggests that several loci are evolving divergently between ecotypes. We identified two differentiation outlier genes that are associated with sulfide detoxification in the mitochondria that have signatures of selection in all five sulfidic populations. Further investigation into these regions identified long, shared haplotypes among sulfidic populations. Together, these results reveal that selection on standing genetic variation in putatively adaptive genes may be driving phenotypic convergence in this species complex.
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Affiliation(s)
- Kara Ryan
- School of Biological Sciences, Washington State University, Pullman, Washington, USA
| | - Ryan Greenway
- Zoology and Evolutionary Biology, Department of Biology, University of Konstanz, Constance, Germany
- Division of Biology, Kansas State University, Manhattan, Kansas, USA
| | - Jake Landers
- School of Biological Sciences, Washington State University, Pullman, Washington, USA
| | - Lenin Arias-Rodriguez
- División Académica de Ciencias Biológicas, Universidad Juárez Autónoma de Tabasco (UJAT), Villahermosa, Mexico
| | - Michael Tobler
- Division of Biology, Kansas State University, Manhattan, Kansas, USA
| | - Joanna L Kelley
- School of Biological Sciences, Washington State University, Pullman, Washington, USA
- Department of Ecology and Evolutionary Biology, University of California Santa Cruz, Santa Cruz, California, USA
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2
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Lazado CC, Voldvik V, Timmerhaus G, Andersen Ø. Fast and slow releasing sulphide donors engender distinct transcriptomic alterations in Atlantic salmon hepatocytes. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2023; 260:106574. [PMID: 37244121 DOI: 10.1016/j.aquatox.2023.106574] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2022] [Revised: 05/08/2023] [Accepted: 05/11/2023] [Indexed: 05/29/2023]
Abstract
Hydrogen sulphide (H2S) is a naturally occurring compound generated either endogenously or exogenously and serves both as a gaseous signalling molecule and an environmental toxicant. Though it has been extensively investigated in mammalian systems, the biological function of H2S in teleost fish is poorly identified. Here we demonstrate how exogenous H2S regulates cellular and molecular processes in Atlantic salmon (Salmo salar) using a primary hepatocyte culture as a model. We employed two forms of sulphide donors: the fast-releasing salt form, sodium hydrosulphide (NaHS) and the slow-releasing organic analogue, morpholin-4-ium 4-methoxyphenyl(morpholino) phosphinodithioate (GYY4137). Hepatocytes were exposed to either a low (LD, 20 µg/L) or high (HD, 100 µg/L) dose of the sulphide donors for 24 hrs, and the expression of key sulphide detoxification and antioxidant defence genes were quantified by qPCR. The key sulphide detoxification genes sulfite oxidase 1 (soux) and the sulfide: quinone oxidoreductase 1 and 2 (sqor) paralogs in salmon showed pronounced expression in the liver and likewise responsive to the sulphide donors in the hepatocyte culture. These genes were ubiquitously expressed in different organs of salmon as well. HD-GYY4137 upregulated the expression of antioxidant defence genes, particularly glutathione peroxidase, glutathione reductase and catalase, in the hepatocyte culture. To explore the influence of exposure duration, hepatocytes were exposed to the sulphide donors (i.e., LD versus HD) either transient (1h) or prolonged (24h). Prolonged but not transient exposure significantly reduced hepatocyte viability, and the effects were not dependent on concentration or form. The proliferative potential of the hepatocytes was only affected by prolonged NaHS exposure, and the impact was not concentration dependent. Microarray analysis revealed that GYY4137 caused more substantial transcriptomic changes than NaHS. Moreover, transcriptomic alterations were more marked following prolonged exposure. Genes involved in mitochondrial metabolism were downregulated by the sulphide donors, primarily in NaHS-exposed cells. Both sulphide donors influenced the immune functions of hepatocytes: genes involved in lymphocyte-mediated response were affected by NaHS, whereas inflammatory response was targeted by GYY4137. In summary, the two sulphide donors impacted the cellular and molecular processes of teleost hepatocytes, offering new insights into the mechanisms underlying H2S interactions in fish.
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Affiliation(s)
- Carlo C Lazado
- Nofima, The Norwegian Institute of Food, Fisheries and Aquaculture Research, Ås 1433, Norway.
| | - Vibeke Voldvik
- Nofima, The Norwegian Institute of Food, Fisheries and Aquaculture Research, Ås 1433, Norway
| | - Gerrit Timmerhaus
- Nofima, The Norwegian Institute of Food, Fisheries and Aquaculture Research, Ås 1433, Norway
| | - Øivind Andersen
- Nofima, The Norwegian Institute of Food, Fisheries and Aquaculture Research, Ås 1433, Norway
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3
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Akbarzadeh A, Selbie DT, Pon LB, Miller KM. Endangered Cultus Lake sockeye salmon exhibit genomic evidence of hypoxic and thermal stresses while rearing in degrading freshwater lacustrine critical habitat. CONSERVATION PHYSIOLOGY 2021; 9:coab089. [PMID: 34858597 PMCID: PMC8633632 DOI: 10.1093/conphys/coab089] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Revised: 10/25/2021] [Accepted: 11/01/2021] [Indexed: 06/13/2023]
Abstract
Water quality degradation due to lake eutrophication and climate change contributes to the risk of extirpation for the endangered Cultus Lake sockeye salmon. Sockeye salmon juveniles experience both low-oxygen water in profundal lake habitats and elevated temperatures above the thermocline during diel vertical migrations in summer and fall when the lake is thermally stratified. We used a transcriptomic tool (Salmon Fit-Chip) to determine whether salmon were experiencing thermal and/or hypoxic stress during this period. The results showed that over one-third of the fish were responding to either hypoxic (35.5%) or thermal stress (40.9%) during periods when these environmental stressors were pronounced within the lake, but not during periods when profundal dissolved oxygen was elevated and the water column was isothermal and cool. The most consistent signs of hypoxic stress occurred during July (52.2%) and September (44.4%). A total of 25.7% of individual fish sampled during months when both stressors were occurring (July, September, October) showed signatures of both stressors. When a combination of hypoxic and thermal stress biomarkers was applied, 92% of fish showed evidence of one or both stressors; hence, for at least several months of the year, most sockeye salmon juveniles in Cultus Lake are experiencing anthropogenically environmentally induced stress. We also detected the presence of pathogenic ciliate Ichthyoptherius multifiliis in the gill tissue of juveniles, with a higher infection signal in Cultus Lake compared to juveniles from nearby Chilliwack Lake. These data provide powerful new evidence that Cultus Lake sockeye salmon, which experience relatively lower juvenile survival than Chilliwack sockeye salmon, are more compromised by stress and carry a higher level of infection of at least one pathogenic agent. Thus, we hypothesize that the cumulative or synergistic interplay between stressors and diseases, clearly documented to be occurring within Cultus Lake, are contributing to increased mortality of endangered sockeye salmon.
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Affiliation(s)
- Arash Akbarzadeh
- Fisheries and Oceans Canada, Pacific Biological Station, 3190 Hammond Bay Road, Nanaimo, British Columbia, V9T 6N7, Canada
- Department of Fisheries, Faculty of Marine Science and Technology, University of Hormozgan, 9th km of Minab Road, Bandar Abbas, 79161 93145, Iran
| | - Daniel T Selbie
- Fisheries and Oceans Canada, Science Branch, Pacific Region, Cultus Lake Salmon Research Laboratory, 4222 Columbia Valley Hwy, Cultus Lake, British Columbia, V2R 5B6, Canada
| | - Lucas B Pon
- Fisheries and Oceans Canada, Science Branch, Pacific Region, Cultus Lake Salmon Research Laboratory, 4222 Columbia Valley Hwy, Cultus Lake, British Columbia, V2R 5B6, Canada
| | - Kristina M Miller
- Department of Fisheries, Faculty of Marine Science and Technology, University of Hormozgan, 9th km of Minab Road, Bandar Abbas, 79161 93145, Iran
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4
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Epigenetic inheritance of DNA methylation changes in fish living in hydrogen sulfide-rich springs. Proc Natl Acad Sci U S A 2021; 118:2014929118. [PMID: 34185679 PMCID: PMC8255783 DOI: 10.1073/pnas.2014929118] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Environmental factors can promote phenotypic variation through alterations in the epigenome and facilitate adaptation of an organism to the environment. Although hydrogen sulfide is toxic to most organisms, the fish Poecilia mexicana has adapted to survive in environments with high levels that exceed toxicity thresholds by orders of magnitude. Epigenetic changes in response to this environmental stressor were examined by assessing DNA methylation alterations in red blood cells, which are nucleated in fish. Males and females were sampled from sulfidic and nonsulfidic natural environments; individuals were also propagated for two generations in a nonsulfidic laboratory environment. We compared epimutations between the sexes as well as field and laboratory populations. For both the wild-caught (F0) and the laboratory-reared (F2) fish, comparing the sulfidic and nonsulfidic populations revealed evidence for significant differential DNA methylation regions (DMRs). More importantly, there was over 80% overlap in DMRs across generations, suggesting that the DMRs have stable generational inheritance in the absence of the sulfidic environment. This is an example of epigenetic generational stability after the removal of an environmental stressor. The DMR-associated genes were related to sulfur toxicity and metabolic processes. These findings suggest that adaptation of P. mexicana to sulfidic environments in southern Mexico may, in part, be promoted through epigenetic DNA methylation alterations that become stable and are inherited by subsequent generations independent of the environment.
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5
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Lau GY, Barts N, Hartley RC, Tobler M, Richards JG, Murphy MP, Arndt S. Detection of changes in mitochondrial hydrogen sulfide i n vivo in the fish model Poecilia mexicana (Poeciliidae). Biol Open 2019; 8:8/5/bio041467. [PMID: 31072908 PMCID: PMC6550084 DOI: 10.1242/bio.041467] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
In this paper, we outline the use of a mitochondria-targeted ratiometric mass spectrometry probe, MitoA, to detect in vivo changes in mitochondrial hydrogen sulfide (H2S) in Poecilia mexicana (family Poeciliidae). MitoA is introduced via intraperitoneal injection into the animal and is taken up by mitochondria, where it reacts with H2S to form the product MitoN. The MitoN/MitoA ratio can be used to assess relative changes in the amounts of mitochondrial H2S produced over time. We describe the use of MitoA in the fish species P. mexicana to illustrate the steps for adopting the use of MitoA in a new organism, including extraction and purification of MitoA and MitoN from tissues followed by tandem mass spectrometry. In this proof-of-concept study we exposed H2S tolerant P. mexicana to 59 µM free H2S for 5 h, which resulted in increased MitoN/MitoA in brain and gills, but not in liver or muscle, demonstrating increased mitochondrial H2S levels in select tissues following whole-animal H2S exposure. This is the first time that accumulation of H2S has been observed in vivo during whole-animal exposure to free H2S using MitoA. This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Gigi Y. Lau
- Department of Zoology, University of British Columbia, 6270 University Boulevard, Vancouver, BC V6T 1Z4, Canada,Authors for correspondence (, )
| | - Nicholas Barts
- Division of Biology, Kansas State University, 116 Ackert Hall, Manhattan, KS 66506, USA
| | - Richard C. Hartley
- WestCHEM School of Chemistry, University of Glasgow, Glasgow G12 8QQ, UK
| | - Michael Tobler
- Division of Biology, Kansas State University, 116 Ackert Hall, Manhattan, KS 66506, USA
| | - Jeffrey G. Richards
- Department of Zoology, University of British Columbia, 6270 University Boulevard, Vancouver, BC V6T 1Z4, Canada
| | - Michael P. Murphy
- MRC Mitochondrial Biology Unit, University of Cambridge, Hills Road, Cambridge CB2 0XY, UK
| | - Sabine Arndt
- MRC Mitochondrial Biology Unit, University of Cambridge, Hills Road, Cambridge CB2 0XY, UK .,Institute for Immunology, University Medical Center of the Johannes Gutenberg University Mainz, Langenbeckstr. 1, Mainz 55131, Germany
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6
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Brown AP, Arias-Rodriguez L, Yee MC, Tobler M, Kelley JL. Concordant Changes in Gene Expression and Nucleotides Underlie Independent Adaptation to Hydrogen-Sulfide-Rich Environments. Genome Biol Evol 2018; 10:2867-2881. [PMID: 30215710 PMCID: PMC6225894 DOI: 10.1093/gbe/evy198] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/11/2018] [Indexed: 12/23/2022] Open
Abstract
The colonization of novel environments often involves changes in gene expression, protein coding sequence, or both. Studies of how populations adapt to novel conditions, however, often focus on only one of these two processes, potentially missing out on the relative importance of different parts of the evolutionary process. In this study, our objectives were 1) to better understand the qualitative concordance between conclusions drawn from analyses of differential expression and changes in genic sequence and 2) to quantitatively test whether differentially expressed genes were enriched for sites putatively under positive selection within gene regions. To achieve this, we compared populations of fish (Poecilia mexicana) that have independently adapted to hydrogen-sulfide-rich environments in southern Mexico to adjacent populations residing in nonsulfidic waters. Specifically, we used RNA-sequencing data to compare both gene expression and DNA sequence differences between populations. Analyzing these two different data types led to similar conclusions about which biochemical pathways (sulfide detoxification and cellular respiration) were involved in adaptation to sulfidic environments. Additionally, we found a greater overlap between genes putatively under selection and differentially expressed genes than expected by chance. We conclude that considering both differential expression and changes in DNA sequence led to a more comprehensive understanding of how these populations adapted to extreme environmental conditions. Our results imply that changes in both gene expression and DNA sequence-sometimes at the same loci-may be involved in adaptation.
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Affiliation(s)
- Anthony P Brown
- School of Biological Sciences, Washington State University, 100 Dairy Road, Pullman, WA 99164
| | - Lenin Arias-Rodriguez
- División Académica de Ciencias Biológicas, Universidad Juárez Autónoma de Tabasco (UJAT), C.P. 86150, Villahermosa, Tabasco, México
| | - Muh-Ching Yee
- Stanford Functional Genomics Facility, CCSR 0120, Stanford, CA 94305
| | - Michael Tobler
- Division of Biology, Kansas State University, 116 Ackert Hall, Manhattan, KS 66506
| | - Joanna L Kelley
- School of Biological Sciences, Washington State University, 100 Dairy Road, Pullman, WA 99164
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7
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Zimmer C, Riesch R, Jourdan J, Bierbach D, Arias-Rodriguez L, Plath M. Female Choice Undermines the Emergence of Strong Sexual Isolation between Locally Adapted Populations of Atlantic Mollies ( Poecilia mexicana). Genes (Basel) 2018; 9:E232. [PMID: 29724050 PMCID: PMC5977172 DOI: 10.3390/genes9050232] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Revised: 04/23/2018] [Accepted: 04/25/2018] [Indexed: 11/16/2022] Open
Abstract
Divergent selection between ecologically dissimilar habitats promotes local adaptation, which can lead to reproductive isolation (RI). Populations in the Poecilia mexicana species complex have independently adapted to toxic hydrogen sulfide and show varying degrees of RI. Here, we examined the variation in the mate choice component of prezygotic RI. Mate choice tests across drainages (with stimulus males from another drainage) suggest that specific features of the males coupled with a general female preference for yellow color patterns explain the observed variation. Analyses of male body coloration identified the intensity of yellow fin coloration as a strong candidate to explain this pattern, and common-garden rearing suggested heritable population differences. Male sexual ornamentation apparently evolved differently across sulfide-adapted populations, for example because of differences in natural counterselection via predation. The ubiquitous preference for yellow color ornaments in poeciliid females likely undermines the emergence of strong RI, as female discrimination in favor of own males becomes weaker when yellow fin coloration in the respective sulfide ecotype increases. Our study illustrates the complexity of the (partly non-parallel) pathways to divergence among replicated ecological gradients. We suggest that future work should identify the genomic loci involved in the pattern reported here, making use of the increasing genomic and transcriptomic datasets available for our study system.
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Affiliation(s)
- Claudia Zimmer
- College of Animal Science & Technology, Northwest A&F University, Yangling 712100, China.
- Department of Ecology and Evolution, Goethe University of Frankfurt, Max-von-Laue-Straße 13, D-60438 Frankfurt am Main, Germany.
| | - Rüdiger Riesch
- Centre for Ecology, Evolution and Behaviour, School of Biological Sciences, Royal Holloway University of London, Egham, Surrey TW20 0EX, UK.
| | - Jonas Jourdan
- Department of River Ecology and Conservation, Senckenberg Research Institute and Natural History Museum Frankfurt, D-63571 Gelnhausen, Germany.
| | - David Bierbach
- Department of Biology and Ecology of Fishes, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Müggelseedamm 310, D-12587 Berlin, Germany.
| | - Lenin Arias-Rodriguez
- División Académica de Ciencias Biológicas, Universidad Juárez Autónoma de Tabasco (UJAT), 86150 Villahermosa, Tabasco, Mexico.
| | - Martin Plath
- College of Animal Science & Technology, Northwest A&F University, Yangling 712100, China.
- Shaanxi Key Laboratory of Molecular Biology for Agriculture, Northwest A&F University, Yangling 712100, China.
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8
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Barts N, Greenway R, Passow CN, Arias-Rodriguez L, Kelley JL, Tobler M. Molecular evolution and expression of oxygen transport genes in livebearing fishes (Poeciliidae) from hydrogen sulfide rich springs. Genome 2018; 61:273-286. [DOI: 10.1139/gen-2017-0051] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Hydrogen sulfide (H2S) is a natural toxicant in some aquatic environments that has diverse molecular targets. It binds to oxygen transport proteins, rendering them non-functional by reducing oxygen-binding affinity. Hence, organisms permanently inhabiting H2S-rich environments are predicted to exhibit adaptive modifications to compensate for the reduced capacity to transport oxygen. We investigated 10 lineages of fish of the family Poeciliidae that have colonized freshwater springs rich in H2S—along with related lineages from non-sulfidic environments—to test hypotheses about the expression and evolution of oxygen transport genes in a phylogenetic context. We predicted shifts in the expression of and signatures of positive selection on oxygen transport genes upon colonization of H2S-rich habitats. Our analyses indicated significant shifts in gene expression for multiple hemoglobin genes in lineages that have colonized H2S-rich environments, and three hemoglobin genes exhibited relaxed selection in sulfidic compared to non-sulfidic lineages. However, neither changes in gene expression nor signatures of selection were consistent among all lineages in H2S-rich environments. Oxygen transport genes may consequently be predictable targets of selection during adaptation to sulfidic environments, but changes in gene expression and molecular evolution of oxygen transport genes in H2S-rich environments are not necessarily repeatable across replicated lineages.
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Affiliation(s)
- Nicholas Barts
- Division of Biology, Kansas State University, 116 Ackert Hall, Manhattan, KS 66506, USA
| | - Ryan Greenway
- Division of Biology, Kansas State University, 116 Ackert Hall, Manhattan, KS 66506, USA
| | - Courtney N. Passow
- Ecology, Evolution and Behavior, University of Minnesota St. Paul, 205 Cargill Building, St. Paul, MN 55108, USA
| | - Lenin Arias-Rodriguez
- División Académica de Ciencias Biológicas, Universidad Juárez Autónoma de Tabasco (UJAT), C.P. 86150, Villahermosa, Tabasco, México
| | - Joanna L. Kelley
- Department of Biological Sciences, Washington State University, 431 Heald Hall, Pullman, WA 99164, USA
| | - Michael Tobler
- Division of Biology, Kansas State University, 116 Ackert Hall, Manhattan, KS 66506, USA
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9
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Bierbach D, Arias-Rodriguez L, Plath M. Intrasexual competition enhances reproductive isolation between locally adapted populations. Curr Zool 2017; 64:125-133. [PMID: 29492045 PMCID: PMC5809038 DOI: 10.1093/cz/zox071] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Accepted: 11/22/2017] [Indexed: 02/07/2023] Open
Abstract
During adaptation to different habitat types, both morphological and behavioral traits can undergo divergent selection. Males often fight for status in dominance hierarchies and rank positions predict reproductive success. Ecotypes with reduced fighting abilities should have low reproductive success when migrating into habitats that harbor ecotypes with superior fighting abilities. Livebearing fishes in the Poecilia mexicana-species complex inhabit not only regular freshwater environments, but also independently colonized sulfidic (H2S-containing) habitats in three river drainages. In the current study, we found fighting intensities in staged contests to be considerably lower in some but not all sulfidic surface ecotypes and the sulfidic cave ecotype compared with populations from non-sulfidic surface sites. This is perhaps due to selection imposed by H2S, which hampers oxygen uptake and transport, as well as cellular respiration. Furthermore, migrants from sulfidic habitats may lose fights even if they do not show overall reduced aggressiveness, as physiological performance is likely to be challenged in the non-sulfidic environment to which they are not adapted. To test this hypothesis, we simulated migration of H2S-adapted males into H2S-free waters, as well as H2S-adapted cave-dwelling males into sulfidic surface waters. We found that intruders established dominance less often than resident males, independent of whether or not they showed reduced aggressiveness overall. Our study shows that divergent evolution of male aggressive behavior may also contribute to the maintenance of genetic differentiation in this system and we call for more careful evaluation of male fighting abilities in studies on ecological speciation.
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Affiliation(s)
- David Bierbach
- Department of Biology and Ecology of Fishes, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Müggelseedamm 310, 12587 Berlin, Germany
| | - Lenin Arias-Rodriguez
- División Académica de Ciencias Biológicas, Universidad Juárez Autónoma de Tabasco (UJAT), 86150 Villahermosa, Tabasco, México
| | - Martin Plath
- College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi 712100, China
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10
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Passow CN, Henpita C, Shaw JH, Quackenbush CR, Warren WC, Schartl M, Arias-Rodriguez L, Kelley JL, Tobler M. The roles of plasticity and evolutionary change in shaping gene expression variation in natural populations of extremophile fish. Mol Ecol 2017; 26:6384-6399. [PMID: 28926156 DOI: 10.1111/mec.14360] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Revised: 09/06/2017] [Accepted: 09/07/2017] [Indexed: 12/22/2022]
Abstract
The notorious plasticity of gene expression responses and the complexity of environmental gradients complicate the identification of adaptive differences in gene regulation among populations. We combined transcriptome analyses in nature with common-garden and exposure experiments to establish cause-effect relationships between the presence of a physiochemical stressor and expression differences, as well as to test how evolutionary change and plasticity interact to shape gene expression variation in natural systems. We studied two evolutionarily independent population pairs of an extremophile fish (Poecilia mexicana) living in toxic, hydrogen sulphide (H2 S)-rich springs and adjacent nontoxic habitats and assessed genomewide expression patterns of wild-caught and common-garden-raised individuals exposed to different concentrations of H2 S. We found that 7.7% of genes that were differentially expressed between sulphidic and nonsulphidic ecotypes remained differentially expressed in the laboratory, indicating that sources of selection other than H2 S-or plastic responses to other environmental factors-contribute substantially to gene expression patterns observed in the wild. Concordantly differentially expressed genes in the wild and the laboratory were primarily associated with H2 S detoxification, sulphur processing and metabolic physiology. While shared, ancestral plasticity played a minor role in shaping gene expression variation observed in nature, we documented evidence for evolved population differences in the constitutive expression as well as the H2 S inducibility of candidate genes. Mechanisms underlying gene expression variation also varied substantially across the two ecotype pairs. These results provide a springboard for studying evolutionary modifications of gene regulatory mechanisms that underlie expression variation in locally adapted populations.
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Affiliation(s)
| | - Chathurika Henpita
- Department of Integrative Biology, Oklahoma State University, Stillwater, OK, USA
| | - Jennifer H Shaw
- Department of Integrative Biology, Oklahoma State University, Stillwater, OK, USA
| | - Corey R Quackenbush
- School of Biological Sciences, Washington State University, Pullman, WA, USA
| | - Wesley C Warren
- McDonnell Genome Institute, Washington University, St. Louis, MO, USA
| | - Manfred Schartl
- Physiological Chemistry, University of Würzburg, Würzburg, Germany.,Comprehensive Cancer Center Mainfranken, University Clinic Würzburg, Würzburg, Germany.,Hagler Institute for Advanced Studies and Department of Biology, Texas A&M University, College Station, TX, USA
| | - Lenin Arias-Rodriguez
- División Académica de Ciencias Biológicas, Universidad Juárez Autónoma de Tabasco, Villahermosa, México
| | - Joanna L Kelley
- School of Biological Sciences, Washington State University, Pullman, WA, USA
| | - Michael Tobler
- Division of Biology, Kansas State University, Manhattan, KS, USA
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11
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Sommer-Trembo C, Bierbach D, Arias-Rodriguez L, Verel Y, Jourdan J, Zimmer C, Riesch R, Streit B, Plath M. Does personality affect premating isolation between locally-adapted populations? BMC Evol Biol 2016; 16:138. [PMID: 27338278 PMCID: PMC4918032 DOI: 10.1186/s12862-016-0712-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2016] [Accepted: 06/13/2016] [Indexed: 12/11/2022] Open
Abstract
Background One aspect of premating isolation between diverging, locally-adapted population pairs is female mate choice for resident over alien male phenotypes. Mating preferences often show considerable individual variation, and whether or not certain individuals are more likely to contribute to population interbreeding remains to be studied. In the Poecilia mexicana-species complex different ecotypes have adapted to hydrogen sulfide (H2S)-toxic springs, and females from adjacent non-sulfidic habitats prefer resident over sulfide-adapted males. We asked if consistent individual differences in behavioral tendencies (animal personality) predict the strength and direction of the mate choice component of premating isolation in this system. Results We characterized focal females for their personality and found behavioral measures of ‘novel object exploration’, ‘boldness’ and ‘activity in an unknown area’ to be highly repeatable. Furthermore, the interaction term between our measures of exploration and boldness affected focal females’ strength of preference (SOP) for the resident male phenotype in dichotomous association preference tests. High exploration tendencies were coupled with stronger SOPs for resident over alien mating partners in bold, but not shy, females. Shy and/or little explorative females had an increased likelihood of preferring the non-resident phenotype and thus, are more likely to contribute to rare population hybridization. When we offered large vs. small conspecific stimulus males instead, less explorative females showed stronger preferences for large male body size. However, this effect disappeared when the size difference between the stimulus males was small. Conclusions Our results suggest that personality affects female mate choice in a very nuanced fashion. Hence, population differences in the distribution of personality types could be facilitating or impeding reproductive isolation between diverging populations depending on the study system and the male trait(s) upon which females base their mating decisions, respectively. Electronic supplementary material The online version of this article (doi:10.1186/s12862-016-0712-2) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Carolin Sommer-Trembo
- College of Animal Science and Technology, Northwest A&F University, Yangling, 712100, People's Republic of China. .,Department of Ecology and Evolution, J.W. Goethe University Frankfurt, Max-von-Laue-Straße 13, 60438, Frankfurt am Main, Germany.
| | - David Bierbach
- Department of Biology and Ecology of Fishes, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Müggelseedamm 310, 12587, Berlin, Germany
| | - Lenin Arias-Rodriguez
- División Académica de Ciencias Biológicas, Universidad Juárez Autónoma de Tabasco, Villahermosa, Tabasco, CP. 86150, Mexico
| | - Yesim Verel
- Department of Ecology and Evolution, J.W. Goethe University Frankfurt, Max-von-Laue-Straße 13, 60438, Frankfurt am Main, Germany
| | - Jonas Jourdan
- Department of Ecology and Evolution, J.W. Goethe University Frankfurt, Max-von-Laue-Straße 13, 60438, Frankfurt am Main, Germany.,Biodiversity and Climate Research Centre (BiK-F), Senckenberganlage 25, 60325, Frankfurt am Main, Germany
| | - Claudia Zimmer
- College of Animal Science and Technology, Northwest A&F University, Yangling, 712100, People's Republic of China.,Department of Ecology and Evolution, J.W. Goethe University Frankfurt, Max-von-Laue-Straße 13, 60438, Frankfurt am Main, Germany
| | - Rüdiger Riesch
- School of Biological Sciences, Royal Holloway, University of London, Egham Hill, Egham, TW20 0EX, UK
| | - Bruno Streit
- Department of Ecology and Evolution, J.W. Goethe University Frankfurt, Max-von-Laue-Straße 13, 60438, Frankfurt am Main, Germany
| | - Martin Plath
- College of Animal Science and Technology, Northwest A&F University, Yangling, 712100, People's Republic of China
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12
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Schulz‐Mirbach T, Eifert C, Riesch R, Farnworth MS, Zimmer C, Bierbach D, Klaus S, Tobler M, Streit B, Indy JR, Arias‐Rodriguez L, Plath M. Toxic hydrogen sulphide shapes brain anatomy: a comparative study of sulphide‐adapted ecotypes in the
Poecilia mexicana
complex. J Zool (1987) 2016. [DOI: 10.1111/jzo.12366] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Affiliation(s)
- T. Schulz‐Mirbach
- Department Biology II Ludwig‐Maximilians‐University Munich Planegg‐Martinsried Germany
| | - C. Eifert
- Ecology and Evolution J. W. Goethe University Frankfurt Frankfurt am Main Germany
| | - R. Riesch
- School of Biological Sciences Royal Holloway University of London Egham UK
| | - M. S. Farnworth
- Göttingen Center for Molecular Biosciences Georg‐August‐University Göttingen Göttingen Germany
| | - C. Zimmer
- Ecology and Evolution J. W. Goethe University Frankfurt Frankfurt am Main Germany
| | - D. Bierbach
- Department of Biology and Ecology of Fishes Leibniz‐Institute of Freshwater Ecology and Inland Fisheries Berlin Germany
| | - S. Klaus
- Ecology and Evolution J. W. Goethe University Frankfurt Frankfurt am Main Germany
| | - M. Tobler
- Division of Biology Kansas State University Manhattan KS USA
| | - B. Streit
- Ecology and Evolution J. W. Goethe University Frankfurt Frankfurt am Main Germany
| | - J. R. Indy
- División Académica de Ciencias Biológicas Universidad Juárez Autónoma de Tabasco (UJAT) Villahermosa Tabasco México
| | - L. Arias‐Rodriguez
- División Académica de Ciencias Biológicas Universidad Juárez Autónoma de Tabasco (UJAT) Villahermosa Tabasco México
| | - M. Plath
- College of Animal Science and Technology Northwest A&F University Yangling China
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13
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Korshunov S, Imlay KRC, Imlay JA. The cytochrome bd oxidase of Escherichia coli prevents respiratory inhibition by endogenous and exogenous hydrogen sulfide. Mol Microbiol 2016; 101:62-77. [PMID: 26991114 DOI: 10.1111/mmi.13372] [Citation(s) in RCA: 68] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/12/2016] [Indexed: 12/31/2022]
Abstract
When sulfur compounds are scarce or difficult to process, Escherichia coli adapts by inducing the high-level expression of sulfur-compound importers. If cystine then becomes available, the cystine is rapidly overimported and reduced, leading to a burgeoning pool of intracellular cysteine. Most of the excess cysteine is exported, but some is adventitiously degraded, with the consequent release of sulfide. Sulfide is a potent ligand of copper and heme moieties, raising the prospect that it interferes with enzymes. We observed that when cystine was provided and sulfide levels rose, E. coli became strictly dependent upon cytochrome bd oxidase for continued respiration. Inspection revealed that low-micromolar levels of sulfide inhibited the proton-pumping cytochrome bo oxidase that is regarded as the primary respiratory oxidase. In the absence of the back-up cytochrome bd oxidase, growth failed. Exogenous sulfide elicited the same effect. The potency of sulfide was enhanced when oxygen concentrations were low. Natural oxic-anoxic interfaces are often sulfidic, including the intestinal environment where E. coli dwells. We propose that the sulfide resistance of the cytochrome bd oxidase is a key trait that permits respiration in such habitats.
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Affiliation(s)
- Sergey Korshunov
- Department of Microbiology, University of Illinois, Urbana, IL, 61801, USA
| | - Karin R C Imlay
- Department of Microbiology, University of Illinois, Urbana, IL, 61801, USA
| | - James A Imlay
- Department of Microbiology, University of Illinois, Urbana, IL, 61801, USA
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14
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Pfenninger M, Patel S, Arias-Rodriguez L, Feldmeyer B, Riesch R, Plath M. Unique evolutionary trajectories in repeated adaptation to hydrogen sulphide-toxic habitats of a neotropical fish (Poecilia mexicana). Mol Ecol 2016; 24:5446-59. [PMID: 26405850 DOI: 10.1111/mec.13397] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2015] [Revised: 09/05/2015] [Accepted: 09/22/2015] [Indexed: 12/20/2022]
Abstract
Replicated ecological gradients are prime systems to study processes of molecular evolution underlying ecological divergence. Here, we investigated the repeated adaptation of the neotropical fish Poecilia mexicana to habitats containing toxic hydrogen sulphide (H2 S) and compared two population pairs of sulphide-adapted and ancestral fish by sequencing population pools of >200 individuals (Pool-Seq). We inferred the evolutionary processes shaping divergence and tested the hypothesis of increase of parallelism from SNPs to molecular pathways. Coalescence analyses showed that the divergence occurred in the face of substantial bidirectional gene flow. Population divergence involved many short, widely dispersed regions across the genome. Analyses of allele frequency spectra suggest that differentiation at most loci was driven by divergent selection, followed by a selection-mediated reduction of gene flow. Reconstructing allelic state changes suggested that selection acted mainly upon de novo mutations in the sulphide-adapted populations. Using a corrected Jaccard index to quantify parallel evolution, we found a negligible proportion of statistically significant parallel evolution of Jcorr = 0.0032 at the level of SNPs, divergent genome regions (Jcorr = 0.0061) and genes therein (Jcorr = 0.0091). At the level of metabolic pathways, the overlap was Jcorr = 0.2545, indicating increasing parallelism with increasing level of biological integration. The majority of pathways contained positively selected genes in both sulphide populations. Hence, adaptation to sulphidic habitats necessitated adjustments throughout the genome. The largely unique evolutionary trajectories may be explained by a high proportion of de novo mutations driving the divergence. Our findings favour Gould's view that evolution is often the unrepeatable result of stochastic events with highly contingent effects.
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Affiliation(s)
- Markus Pfenninger
- Molecular Ecology Group, Senckenberg Biodiversity and Climate Research Centre (BiK-F), Senckenberganlage 25, D-60325 Frankfurt am Main, Hessen, Germany
| | - Simit Patel
- Molecular Ecology Group, Senckenberg Biodiversity and Climate Research Centre (BiK-F), Senckenberganlage 25, D-60325 Frankfurt am Main, Hessen, Germany
| | - Lenin Arias-Rodriguez
- División Académica de Ciencias Biológicas, Universidad Juárez Autónoma de Tabasco (UJAT), Villahermosa, C.P. 86150 Tabasco, México
| | - Barbara Feldmeyer
- Molecular Ecology Group, Senckenberg Biodiversity and Climate Research Centre (BiK-F), Senckenberganlage 25, D-60325 Frankfurt am Main, Hessen, Germany
| | - Rüdiger Riesch
- School of Biological Sciences, Centre for Ecology, Evolution and Behaviour, Royal Holloway University of London, Egham Hill, Egham, Surrey TW20 0EX, UK
| | - Martin Plath
- College of Animal Science and Technology, Northwest A&F University, Xinong Road 22, 712100 Yangling, China
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15
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Kelley JL, Arias-Rodriguez L, Patacsil Martin D, Yee MC, Bustamante CD, Tobler M. Mechanisms Underlying Adaptation to Life in Hydrogen Sulfide-Rich Environments. Mol Biol Evol 2016; 33:1419-34. [PMID: 26861137 PMCID: PMC4868117 DOI: 10.1093/molbev/msw020] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Hydrogen sulfide (H2S) is a potent toxicant interfering with oxidative phosphorylation in mitochondria and creating extreme environmental conditions in aquatic ecosystems. The mechanistic basis of adaptation to perpetual exposure to H2S remains poorly understood. We investigated evolutionarily independent lineages of livebearing fishes that have colonized and adapted to springs rich in H2S and compared their genome-wide gene expression patterns with closely related lineages from adjacent, nonsulfidic streams. Significant differences in gene expression were uncovered between all sulfidic and nonsulfidic population pairs. Variation in the number of differentially expressed genes among population pairs corresponded to differences in divergence times and rates of gene flow, which is consistent with neutral drift driving a substantial portion of gene expression variation among populations. Accordingly, there was little evidence for convergent evolution shaping large-scale gene expression patterns among independent sulfide spring populations. Nonetheless, we identified a small number of genes that was consistently differentially expressed in the same direction in all sulfidic and nonsulfidic population pairs. Functional annotation of shared differentially expressed genes indicated upregulation of genes associated with enzymatic H2S detoxification and transport of oxidized sulfur species, oxidative phosphorylation, energy metabolism, and pathways involved in responses to oxidative stress. Overall, our results suggest that modification of processes associated with H2S detoxification and toxicity likely complement each other to mediate elevated H2S tolerance in sulfide spring fishes. Our analyses allow for the development of novel hypotheses about biochemical and physiological mechanisms of adaptation to extreme environments.
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Affiliation(s)
| | - Lenin Arias-Rodriguez
- División Académica de Ciencias Biológicas, Universidad Juárez Autónoma de Tabasco, Villahermosa, Tabasco, México
| | | | - Muh-Ching Yee
- Department of Plant Biology, Carnegie Institution for Science, Stanford, CA
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16
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Fišer C, Luštrik R, Sarbu S, Flot JF, Trontelj P. Morphological evolution of coexisting amphipod species pairs from sulfidic caves suggests competitive interactions and character displacement, but no environmental filtering and convergence. PLoS One 2015; 10:e0123535. [PMID: 25905793 PMCID: PMC4407961 DOI: 10.1371/journal.pone.0123535] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2014] [Accepted: 02/19/2015] [Indexed: 11/18/2022] Open
Abstract
Phenotypically similar species coexisting in extreme environments like sulfidic water are subject to two opposing eco-evolutionary processes: those favoring similarity of environment-specific traits, and those promoting differences of traits related to resource use. The former group of processes includes ecological filtering and convergent or parallel evolution, the latter competitive exclusion, character displacement and divergent evolution. We used a unique eco-evolutionary study system composed of two independent pairs of coexisting amphipod species (genus Niphargus) from the sulfidic caves Movile in Romania and Frasassi in Italy to study the relative contribution and interaction of both processes. We looked at the shape of the multifunctional ventral channel as a trait ostensibly related to oxygenation and sulfide detoxification, and at body size as a resource-related trait. Phylogenetic analysis suggests that the sulfidic caves were colonized separately by ancestors of each species. Species within pairs were more dissimilar in their morphology than expected according to a null model based on regional species pool. This might indicate competitive interactions shaping the morphology of these amphipod species. Moreover, our results suggest that the shape of the ventral channel is not subject to long-term convergent selection or to the process of environmental filtering, and as such probably does not play a role in sulfide tolerance. Nevertheless, the ancestral conditions reconstructed using the comparative method tended to be more similar than null-model expectations. This shift in patterns may reflect a temporal hierarchy of eco-evolutionary processes, in which initial environmental filtering became later on superseded by character displacement or other competition-driven divergent evolutionary processes.
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Affiliation(s)
- Cene Fišer
- Department of Biology, Biotechnical Faculty, University of Ljubljana, 1000 Ljubljana, Slovenia
- * E-mail:
| | - Roman Luštrik
- Department of Biology, Biotechnical Faculty, University of Ljubljana, 1000 Ljubljana, Slovenia
| | - Serban Sarbu
- Grupul de Explorări Subacvatice şi Speologice, Strada Frumoasă 31, 010986 Bucureşti, Romania
| | - Jean-François Flot
- Department of Genetics, Evolution and Environment, University College London, Darwin Building, Gower Street, London WC1E 6BT, United Kingdom
| | - Peter Trontelj
- Department of Biology, Biotechnical Faculty, University of Ljubljana, 1000 Ljubljana, Slovenia
- Museum für Naturkunde, Leibniz-Institut für Evolutions- und Biodiversitätsforschung an der Humboldt-Universität zu Berlin, Invalidenstrasse 43, Berlin 10115, Germany
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17
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Passow CN, Greenway R, Arias-Rodriguez L, Jeyasingh PD, Tobler M. Reduction of Energetic Demands through Modification of Body Size and Routine Metabolic Rates in Extremophile Fish. Physiol Biochem Zool 2015; 88:371-83. [PMID: 26052634 DOI: 10.1086/681053] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Variation in energy availability or maintenance costs in extreme environments can exert selection for efficient energy use, and reductions in organismal energy demand can be achieved in two ways: reducing body mass or metabolic suppression. Whether long-term exposure to extreme environmental conditions drives adaptive shifts in body mass or metabolic rates remains an open question. We studied body size variation and variation in routine metabolic rates in locally adapted populations of extremophile fish (Poecilia mexicana) living in toxic, hydrogen sulfide-rich springs and caves. We quantified size distributions and routine metabolic rates in wild-caught individuals from four habitat types. Compared with ancestral populations in nonsulfidic surface habitats, extremophile populations were characterized by significant reductions in body size. Despite elevated metabolic rates in cave fish, the body size reduction precipitated in significantly reduced energy demands in all extremophile populations. Laboratory experiments on common garden-raised fish indicated that elevated routine metabolic rates in cave fish likely have a genetic basis. The results of this study indicate that adaptation to extreme environments directly impacts energy metabolism, with fish living in cave and sulfide spring environments expending less energy overall during routine metabolism.
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Affiliation(s)
- Courtney N Passow
- Department of Zoology, Oklahoma State University, 501 Life Sciences West, Stillwater, Oklahoma 74078; 2División Académica de Ciencias Biológicas, Universidad Juárez Autónoma de Tabasco, Villahermosa, Tabasco, Mexico
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18
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Patterns of Macroinvertebrate and Fish Diversity in Freshwater Sulphide Springs. DIVERSITY-BASEL 2014. [DOI: 10.3390/d6030597] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Extreme environments are characterised by the presence of physicochemical stressors and provide unique study systems to address problems in evolutionary ecology research. Sulphide springs provide an example of extreme freshwater environments; because hydrogen sulphide’s adverse physiological effects induce mortality in metazoans even at micromolar concentrations. Sulphide springs occur worldwide, but while microbial communities in sulphide springs have received broad attention, little is known about macroinvertebrates and fish inhabiting these toxic environments. We reviewed qualitative occurrence records of sulphide spring faunas on a global scale and present a quantitative case study comparing diversity patterns in sulphidic and adjacent non-sulphidic habitats across replicated river drainages in Southern Mexico. While detailed studies in most regions of the world remain scarce, available data suggests that sulphide spring faunas are characterised by low species richness. Dipterans (among macroinvertebrates) and cyprinodontiforms (among fishes) appear to dominate the communities in these habitats. At least in fish, there is evidence for the presence of highly endemic species and populations exclusively inhabiting sulphide springs. We provide a detailed discussion of traits that might predispose certain taxonomic groups to colonize sulphide springs, how colonizers subsequently adapt to cope with sulphide toxicity, and how adaptation may be linked to speciation processes.
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19
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Parallel evolution of cox genes in H2S-tolerant fish as key adaptation to a toxic environment. Nat Commun 2014; 5:3873. [PMID: 24815812 DOI: 10.1038/ncomms4873] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2013] [Accepted: 04/14/2014] [Indexed: 01/30/2023] Open
Abstract
Populations that repeatedly adapt to the same environmental stressor offer a unique opportunity to study adaptation, especially if there are a priori predictions about the genetic basis underlying phenotypic evolution. Hydrogen sulphide (H2S) blocks the cytochrome-c oxidase complex (COX), predicting the evolution of decreased H2S susceptibility of the COX in three populations in the Poecilia mexicana complex that have colonized H2S-containing springs. Here, we demonstrate that decreased H2S susceptibility of COX evolved in parallel in two sulphide lineages, as evidenced by shared amino acid substitutions in cox1 and cox3 genes. One of the shared substitutions likely triggers conformational changes in COX1 blocking the access of H2S. In a third sulphide population, we detect no decreased H2S susceptibility of COX, suggesting that H2S resistance is achieved through another mechanism. Our study thus demonstrates that even closely related lineages follow both parallel and disparate molecular evolutionary paths to adaptation in response to the same selection pressure.
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