DOCSLIB.ORG

Genetic and Developmental Analysis of Evolved Stickleback Gill Raker Reduction

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Genetic and Developmental Analysis of Evolved Stickleback Gill Raker Reduction Genetic and Developmental Analysis of Evolved Stickleback Gill Raker Reduction by Andrew Michael Glazer A dissertation submitted in partial satisfaction of the requirements for the degree of Doctor of Philosophy in Molecular and Cell Biology in the Graduate Division of the University of California, Berkeley Committee in charge: Professor Craig Miller, Chair Professor Daniel Rokhsar Professor Richard Harland Professor Marvalee Wake Spring 2015 Genetic and Developmental Analysis of Evolved Stickleback Gill Raker Reduction Copyright 2015 By Andrew Michael Glazer Abstract Genetic and Developmental Analysis of Evolved Stickleback Gill Raker Reduction by Andrew Michael Glazer Doctor of Philosophy in Molecular and Cellular Biology University of California, Berkeley Professor Craig Miller, Chair Much is known about the genetic and developmental basis of mutant phenotypes in the laboratory. However, much less is known about the mechanisms that control naturally evolved phenotypes in the wild. Are specific types of genes or mutations preferred? How are developmental programs modified to generate altered phenotypes? Finally, in cases where the same phenotype has evolved in independent lineages (convergent evolution), are the same genes or mutations used? The threespine stickleback fish (Gasterosteus aculeatus) is an emerging model organism in which the approaches and tools of developmental biology, genetics, and genomics can be applied to understand evolutionary changes. Marine sticklebacks have repeatedly colonized and adapted to new freshwater environments throughout the Northern Hemisphere. Freshwater sticklebacks have evolved many changes in their skeleton relative to marine fish. For example, freshwater sticklebacks have evolved changes to their defensive armor in response to decreased predation and changes in bones used for feeding in response to differences in diet. Despite their phenotypic differences, marine and freshwater sticklebacks can be bred in the lab. Crosses between marine and freshwater sticklebacks can be used to decipher the genetic basis of their evolved phenotypic differences. In chapter 2 of this thesis, I present the results of a large quantitative genetic study of stickleback skeletal evolution. I mapped regions of the genome, known as quantitative trait loci (QTL), affecting a wide range of skeletal traits. Over 100 QTL were mapped, and a meta-analysis of their properties was performed. Using these QTL, several general questions in evolutionary genetics were addressed. First, I explored the dominance of the QTL. The dominance of a QTL is a genetic property that might affect likelihood of being used during adaptation. Surprisingly, a large proportion of skeletal QTL had an additive (intermediate) dominance. Second, I investigated the modularity of QTL. To do this, I examined serially repeating skeletal elements such as vertebrae. Most (76%) QTL that influenced such traits had specific, modular effects on just a subset of the possible 1 domains of the phenotype. Finally, I examined whether the QTL clustered in the genome. Many large-effect skeletal QTL were clustered on chromosomes 4, 20, and 21. Inheritance of these clusters of linked adaptive alleles might allow multiple aspects of skeletal morphology to evolve rapidly and simultaneously. In summary, the large set of skeletal QTL was used to explore the genetic properties of evolved mutations. These QTL are a starting point for the identification of the molecular basis of evolved changes in the vertebrate skeleton. In chapter 3 of this thesis, I focus on one skeletal trait, gill raker number. Gill rakers are periodically patterned bones in a fish’s throat important for feeding. In response to a change in diet in freshwater populations, hundreds of freshwater stickleback populations have independently evolved a reduction in gill raker number. This phenomenon is known as gill raker reduction. I found that heritable marine/freshwater differences in gill raker number were present early in development. The gill raker number differences were due to a difference in the spacing between adjacent gill rakers. The marine/freshwater number and spacing differences were present at the earliest detectable point of gill raker specification. This result suggests that gill raker reduction is caused by an early-acting change to a lateral inhibition process controlling raker bud spacing. Next, I performed linkage mapping in F2 fish from crosses with three independently derived freshwater populations. In all three crosses, gill raker QTL mapped to chromosomes 4 and 20, suggesting a similar genetic basis. Finally, the chromosome 4 and 20 QTL affected the early spacing of gill raker buds. Collectively, these data demonstrated that parallel developmental genetic features underlie the convergent evolution of gill raker reduction in freshwater sticklebacks. These results suggest that even highly polygenic adaptive traits can have a predictable developmental genetic basis. In chapter 4 of this thesis, I present an economical method that uses next- generation sequencing to perform genome-wide genotyping of hundreds of multiplexed samples. This method was used to genotype two large marine by freshwater F2 crosses of over 350 fish each. The resulting maps significantly improved the stickleback genome assembly by making over 100 changes to the order and orientation of the scaffolds that compose the genome assembly. In the revised genome assembly, 95% of the assembly was anchored to a chromosome, compared to 87% in the original assembly. To assess linkage map quality, I mapped quantitative trait loci (QTL) controlling lateral plate number. Plate number mapped as expected to a 200 kilobase genomic region containing Ectodysplasin. In addition, plate number mapped to a chromosome 7 QTL overlapping a previously identified modifier QTL. Finally, I examined gill raker length. I found that the two freshwater populations convergently evolved shorter gill rakers relative to marine fish. I mapped eight QTL controlling gill raker length in the two crosses. However, none of the QTL were overlapping between the two crosses. Thus, the convergent evolution gill raker length reduction has a surprisingly non-parallel genetic basis. In chapter 5 of this thesis, I present additional experiments to determine the genetic basis of evolved reduction in gill raker number. Using the genotyping method developed in chapter 4, I mapped QTL controlling raker number and spacing in two large 2 marine by freshwater F2 crosses of over 350 fish each. Overlapping QTL on chromosomes 4, 16, and 20 were found in both crosses. In addition, 14 unique modifier QTL were mapped. Together these results indicate that a combination of similar and different genetic basis underlies the convergent evolution of gill raker number. Using crosses with recombinant chromosomes, I fine-mapped the chromosome 4 and 20 QTL, substantially narrowing the interval sizes. Surprisingly, the chromosome 4 QTL in the two crosses mapped to non-overlapping regions. Therefore, even though the chromosome 4 QTL appeared to map to similar genomic regions in the two crosses, a different genetic basis was actually used. An excellent candidate gene, Fibroblast Growth Factor 20 (Fgf20) was located within one of the fine-mapped chromosome 4 QTL. I mutated the coding region of Fgf20 with a genome-editing technology called Transcription Activator- Like Effector Nucleases (TALENs). Induced loss of function mutations in Fgf20 resulted in a decrease in gill raker number. The Fgf20 mutants had a concomitant increase in gill raker spacing, similar to the evolved freshwater phenotype. Induced mutations in a second gene, Smad5, also resulted in a raker phenotype. However, Smad5 was excluded from the fine-mapped QTL intervals, so it likely does not underlie gill raker evolution. No coding changes in Fgf20 likely cause evolved gill raker reduction. These results suggest a model in which cis-regulatory mutations that affect Fgf20 expression levels or spatial patterns contribute to evolved gill raker reduction. Together, this work makes significant progress towards understanding the genetic and developmental basis of skeletal evolution in stickleback fish. The results have broad implications for understanding the process of how genetic variation contributes to adaptive evolution. 3 Table of Contents Abstract ............................................................................................ 1 Table of Contents ............................................................................................ i List of Figures ............................................................................................ iii List of Tables ............................................................................................ v Acknowledgements ............................................................................................ vi Chapter 1: An introduction to evolutionary genetics, stickleback adaptive radiation, and gill raker evolution Title ............................................................................................ 1 Introduction ............................................................................................ 2 References ............................................................................................ 14 Chapter 2: Additive and clustered quantitative trait loci control anatomically regional skeletal evolution in sticklebacks Title ...........................................................................................
Load more

Recommended publications
  • Evidence for Rapid Phenotypic and Behavioural Shifts in a Recently Established Cavefish Population
    applyparastyle “fig//caption/p[1]” parastyle “FigCapt” Biological Journal of the Linnean Society, 2020, 129, 143–161. With 5 figures. Downloaded from https://academic.oup.com/biolinnean/article-abstract/129/1/143/5637080 by University of Minnesota Libraries - Twin Cities user on 13 January 2020 Evidence for rapid phenotypic and behavioural shifts in a recently established cavefish population SUZANNE E. McGAUGH1*, SAM WEAVER1, ERIN N. GILBERTSON1, BRIANNA GARRETT1, MELISSA L. RUDEEN1, STEPHANIE GRIEB1, JENNIFER ROBERTS1, ALEXANDRA DONNY1, PETER MARCHETTO2 and ANDREW G. GLUESENKAMP3 1Ecology, Evolution, and Behavior, University of Minnesota, 140 Gortner Lab, 1479 Gortner Ave, Saint Paul, MN 55108, USA 2Department of Bioproducts and Biosystems Engineering, University of Minnesota, 218 BAE, 1390 Eckles Ave., Saint Paul, MN 55108, USA 3Center for Conservation and Research, San Antonio Zoo, 3903 N St Mary’s St., San Antonio, TX 78212, USA Received 25 August 2019; revised 16 September 2019; accepted for publication 17 September 2019 Cave colonization offers a natural laboratory to study an extreme environmental shift, and diverse cave species from around the world often have converged on robust morphological, physiological and behavioural traits. The Mexican tetra (Astyanax mexicanus) has repeatedly colonized caves in the Sierra de El Abra and Sierra de Guatemala regions of north-east Mexico ~0.20–1 Mya, indicating an ability to adapt to the cave environment. The time frame for the evolution of these traits in any cave animal, however, is poorly understood. Astyanax mexicanus from the Río Grande in South Texas were brought to Central Texas beginning in the early 1900s and colonized underground environments.
    [Show full text]
  • Summary Report of Freshwater Nonindigenous Aquatic Species in U.S
    Summary Report of Freshwater Nonindigenous Aquatic Species in U.S. Fish and Wildlife Service Region 4—An Update April 2013 Prepared by: Pam L. Fuller, Amy J. Benson, and Matthew J. Cannister U.S. Geological Survey Southeast Ecological Science Center Gainesville, Florida Prepared for: U.S. Fish and Wildlife Service Southeast Region Atlanta, Georgia Cover Photos: Silver Carp, Hypophthalmichthys molitrix – Auburn University Giant Applesnail, Pomacea maculata – David Knott Straightedge Crayfish, Procambarus hayi – U.S. Forest Service i Table of Contents Table of Contents ...................................................................................................................................... ii List of Figures ............................................................................................................................................ v List of Tables ............................................................................................................................................ vi INTRODUCTION ............................................................................................................................................. 1 Overview of Region 4 Introductions Since 2000 ....................................................................................... 1 Format of Species Accounts ...................................................................................................................... 2 Explanation of Maps ................................................................................................................................
    [Show full text]
  • Developmental Genetic Modularity of Cichlid Fish Dentitions
    This is a repository copy of Biting into the Genome to Phenome Map: Developmental Genetic Modularity of Cichlid Fish Dentitions. White Rose Research Online URL for this paper: http://eprints.whiterose.ac.uk/109900/ Version: Accepted Version Article: Hulsey, C.D., Fraser, G.J. orcid.org/0000-0002-7376-0962 and Meyer, A. (2016) Biting into the Genome to Phenome Map: Developmental Genetic Modularity of Cichlid Fish Dentitions. Integrative and Comparative Biology, 56 (3). pp. 373-388. ISSN 1540-7063 https://doi.org/10.1093/icb/icw059 This is a pre-copyedited, author-produced version of an article accepted for publication in Integrative and Comparative Biology following peer review. The version of record Integr. Comp. Biol. (2016) 56 (3): 373-388 is available online at: https://doi.org/10.1093/icb/icw059. Reuse Unless indicated otherwise, fulltext items are protected by copyright with all rights reserved. The copyright exception in section 29 of the Copyright, Designs and Patents Act 1988 allows the making of a single copy solely for the purpose of non-commercial research or private study within the limits of fair dealing. The publisher or other rights-holder may allow further reproduction and re-use of this version - refer to the White Rose Research Online record for this item. Where records identify the publisher as the copyright holder, users can verify any specific terms of use on the publisher’s website. Takedown If you consider content in White Rose Research Online to be in breach of UK law, please notify us by emailing [email protected] including the URL of the record and the reason for the withdrawal request.
    [Show full text]
  • Investigating the Genetic Basis of Altered Activity Profiles in the Blind
    Investigating the genetic basis of altered activity profiles in the blind Mexican cavefish, Astyanax mexicanus A dissertation submitted to the Graduate School of the University of Cincinnati in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Biological Sciences of the McMicken College of Arts and Sciences by by Brian M. Carlson B.S. Biology, Xavier University, May 2010 Committee Chair: Dr. Joshua B. Gross June 2015 ABSTRACT Organisms that have evolved to exploit extreme ecological niches may alter or abandon survival strategies that no longer provide a benefit, or may even impose a cost, in the environment to which they have adapted. Cave environments are characterized by perpetual darkness, isolation and relatively constant temperature and humidity. Accordingly, cave-adapted species tend to converge on a suite of regressive and constructive morphological, physiological and behavioral alterations, including loss or reduction of eyes and pigmentation, increased locomotor activity and reduction or alteration of behavioral rhythmicity. The cave environment and the associated changes in locomotor behavior make species of cavefish prime natural models in which to examine the complex genetic architecture underlying these behavioral phenotypes. The principal goal of this dissertation was to investigate the genetic basis of altered locomotor activity patterns in the blind Mexican tetra, Astyanax mexicanus. Initially, a custom locomotor assay rig and experimental protocols were developed to assess, characterize and compare activity patterns in surface and Pachón cavefish. The results of these assays clarified differences between the morphotypes, provided evidence that Pachón cavefish retain a weakly-entrainable circadian oscillator with limited capacity to self-sustain entrained rhythms and suggested that patterns in spatial “tank usage” data may be the result of a positive masking effect in response to light stimulus in both morphotypes.
    [Show full text]
  • Luis Espinasa Selected Publications Herman, A., Brandvain, Y., Weagley
    Luis Espinasa Selected Publications Herman, A., Brandvain, Y., Weagley, J., Jeffery, W.R., Keene, A.C., Kono, T.J.Y., Bilandžija, H., Borowsky, R.. Espinasa, L.. O'Quin, K., Ornelas-García, C.P., Yoshizawa, M., Carlson, B., Maldonado, E., Gross, J.B., Cartwright, R.A., Rohner, N., Warren, W.C., and McGaugh. S.E. (2018) The role of gene flow in rapid and repeated evolution of cave related traits in Mexican tetra, Astyanax mexicanus. Molecular Ecology. bioRxiv https://doi.org/10.1101/335182 Espinasa, L., Robinson, J., and Espinasa, M. (2018) Mc1r gene in Astroblepus pholeter and Astyanax mexicanus: Convergent regressive evolution of pigmentation across cavefish species. Developmental Biology 441: 305-310 Espinasa, L., Hoese, G., Toulkeridis, T., and Toomey, R. (2018) Corroboration that theMc1r Gly/Ser mutation correlates with the phenotypic expression of pigmentation in Astroblepus. Developmental Biology 441: 311-312 Blin, M., Tine, E., Meister, L., Elipot, Y., Bibliowicz, J., Espinasa, L., and Rétaux, S. (2018) Developmental evolution and developmental plasticity of the olfactory epithelium and olfactory skills in Mexican cavefish. Developmental Biology 441: 242-251 Espinasa, L., Robinson, J., Soares, D., Hoese, G., Toulkeridis, T., and Toomey, R. (2018) Troglomorphic features of Astroblepus pholeter, a cavefish from Ecuador, and possible introgressive hybridization. Subterranean Biology 27:17-29 Kopp, J., Avasthi, S., and Espinasa, L. (2018) Phylogeographical convergence between Astyanax cavefish and mysid shrimps in the Sierra de El Abra, Mexico. Subterranean Biology 26: 39-53 Espinasa, L., Legendre, L., Fumey, F., Blin, M., Rétaux, S., and Espinasa, M. (2018) A new cave locality for Astyanax cavefish in Sierra de El Abra, Mexico.
    [Show full text]
  • Identifying Fish in Aquarium
    What fish are in my aquarium? What fish are in the aquarium? What family do they belong to? How do they reproduce? What are their feeding strategies? Minnows Tetras Armored Catfish Family: Cyprinidae Family: Characidae Family: Callichthyidae Over 2000 species Over 900 species Over 130 species zebra danio black tetra leopard corydora Common Species in FL Common Species in FL Common Species in FL • Barbs • Neon tetra • Leopard corydora • Danios • Black tetra • Bronze corydora • Goldfish • Pacu • Panda corydora • Koi • Lemon tetra • Hoplo catfish • Rasboras • Mexican tetra • Tons of color variants • Freshwater sharks • Firehead tetra Reproduction: Reproduction: Reproduction: Egg layers/Broadcast spawner Egg layers/Broadcast spawner Adhesive eggs/bubble nests Feeding: Omnivore Feeding: Omnivore Feeding: Insectivore Commonly Cultured Freshwater Fish Groups Photo credit: UF-IFAS Publication Circular #54 Photos from: UF/IFAS Circular 54 Suckermouth Rainbowfishes Cichlids Catfish Family: Melanotaeniidae etc. Family: Callichthyidae Family: Loricariidae 53 species in 6 genera Over 1500 species Over 550 species banded rainbowfish zebra cichilid Common Species in FL Pleco catfish Common Species in FL Common Species in FL • Red rainbowfish • Angelfish • Discus • Common pleco • Australian rainbowfish • Oscar • Bristle-nose pleco • Boeseman’s rainbowfish • Jewel cichilid • Sailfin pleco • Neon dwarf rainbowfish zebra cichilid banded rainbowfish • Mbuna cichilid • Kribs cichilid Reproduction: Reproduction: Reproduction: Adhesive eggs/Male guards eggs
    [Show full text]
  • Science & Literacy Activity
    Life at the Limits: Stories of Amazing Species GRADES 9-10 Science & Literacy Activity ACTIVITY OVERVIEW Common Core State Standards This activity, which is aligned to the Common Core State RST.9-10.1 Cite specific textual evidence to support analysis of science and technical texts, Standards (CCSS) for English Language Arts, introduces attending to the precise details of explanations students to scientific knowledge and language related to animal or descriptions. adaptations. RST.9-10.2 Determine the central ideas or con- clusions of a text; trace the text’s explanation or depiction of a complex process, phenomenon, This activity has three components: or concept; provide an accurate summary of the text. 1. Before your visit, students will read a content-rich article about scientists who WHST.9-10.2 Write informative/explanatory study cave fish to understand how blindness evolves in organisms that live in texts, including the narration of historical events, dark environments. This article will provide context for the visit, and also help scientific procedures/ experiments, or technical them complete the post-visit writing task. processes. 2. At the Museum, students will read and engage with additional texts (including printed text, digital and physical/hands-on interactives, videos, diagrams, and New York State Science Core Curriculum models). This information will help them complete the post-visit writing task. LE 3.1g 3. Back in the classroom, students will draw on the first two components of the activity to complete a CCSS-aligned explanatory writing task about biological, Next Generation Science Standards behavioral, and physiological adaptations. DCI: LS4.C: Adaptation Natural selection leads to adaptation, that is, to Materials in this packet include: a population dominated by organisms that are anatomically, behaviorally, and physiologically For Teachers well suited to survive and reproduce in a specific environment.
    [Show full text]
  • Why Do Cave Fish Lose Their Eyes?
    Why Do Cave Fish Lose Their Eyes? This StepRead is based on an article provided by the American Museum of Natural History. Carlsbad Caverns National Park There are caves deep under the ground where the sun never shines. If you went into one of these caves without a flashlight, you would see nothing at all. There would just be blackness. In some of these caves, there are animals that live without light. They include salamanders, crustaceans, and fishes. In fact, more than one hundred species, or kinds, of cave fishes live in constant darkness. They depend on senses other than sight to hunt, eat, and reproduce. These fishes have evolved, or changed over many generations, to live without light. Many of these species of fish are blind or nearly blind. Some don’t even have eyes. Yet they all evolved from fishes that could see. Somehow, over millions of years, these fishes both lost the ability to see and gained the ability to live without sight. How did that happen? How can evolution cause a species to lose a trait such as the ability to see? That is a mystery that scientists have been trying to solve. Their search for an answer gives us a fascinating look at how evolution works. Regressive Evolution We usually think of evolution as a process in which species gain new traits. But in cave fishes we have an example of regressive evolution. This type of evolution is a process in which species lose a trait. In cave fishes, that trait is the ability to see.
    [Show full text]
  • Astyanax Cavefish Bibliography, Chronological
    Astyanax Cavefish Bibliography, chronological 552 citations from the Cave Life Bibliography William R. Elliott, [email protected] Hubbs, Carl L., and William T. Innes. 1936. The first known blind fish of the family Characidae: A new genus from Mexico. Occasional Papers of the Museum of Zoology, University of Michigan, no. 342. 7 pp., 1 pl. Muir, JM. 1936. Geology of the Tampico Region, Mexico. Special Volume ed. Tulsa, Oklahoma. American Association of Petroleum Geologists, Tulsa, 280 pp. Hykes, O.V. 1937. _Anoptichthys jordani_, Hubbs und Innes. Akvaristické listy, 11:108-109. Innes, William T. 1937. A cavern characin _Anoptichthys jordani_, Hubbs & Innes. Aquarium, Philadelphia, 5(10):200-202. Jordan, C. Basil. 1937. Bringing in the new cave fish _Anoptichthys jordani_ Hubbs and Innes. Aquarium, Philadelphia, 5(10):203-204. Anonymous. 1940. Expedición para recoger peces ciegos en México. Ciencia, 1:221. Bridges, William. 1940. The blind fish of La Cueva Chica. Bulletin of the New York Zoological Society. 43:74-97. De Buen, Fernando. 1940. Lista de peces de agua dulce de México. En preparación de su catálogo. Trabajos de Estación Limnológica de Pátzcuaro, 2. 66 pp. Gresser, E. B., and C. M. Breder, Jr. 1940. The histology of the eye of the cave characin, _Anoptichthys_. Zoologica, New York, 25(10):113-116, pls. I- III. Heim, A. 1940. The front ranges of the Sierra Madre Oriental, Mexico, from Ciudad Victoria to Tamazunchale. Eclogae Geolicae Helvetiae, 33:313-352. Breder, Charles M., Jr., and Edward B. Gresser. 1941. Correlations between structural eye defects and behavior in the Mexican blind characin.
    [Show full text]
  • Raising the Mexican Tetra Astyanax Mexicanus for Analysis of Post-Larval Phenotypes and Whole-Mount Immunohistochemistry
    Journal of Visualized Experiments www.jove.com Video Article Raising the Mexican Tetra Astyanax mexicanus for Analysis of Post-larval Phenotypes and Whole-mount Immunohistochemistry Misty Riddle1, Brian Martineau1, Megan Peavey1, Clifford Tabin1 1 Harvard Medical School Correspondence to: Clifford Tabin at [email protected] URL: https://www.jove.com/video/58972 DOI: doi:10.3791/58972 Keywords: Genetics, Issue 142, Astyanax mexicanus, immunohistochemistry, fish husbandry, cavefish, aquaculture, whole-mount immunostaining Date Published: 12/28/2018 Citation: Riddle, M., Martineau, B., Peavey, M., Tabin, C. Raising the Mexican Tetra Astyanax mexicanus for Analysis of Post-larval Phenotypes and Whole-mount Immunohistochemistry. J. Vis. Exp. (142), e58972, doi:10.3791/58972 (2018). Abstract River and cave-adapted populations of Astyanax mexicanus show differences in morphology, physiology, and behavior. Research focused on comparing adult forms has revealed the genetic basis of some of these differences. Less is known about how the populations differ at post- larval stages (at the onset of feeding). Such studies may provide insight into how cavefish survive through adulthood in their natural environment. Methods for comparing post-larval development in the laboratory require standardized aquaculture and feeding regimes. Here we describe how to raise fish on a diet of nutrient-rich rotifers in non-recirculating water for up to two-weeks post fertilization. We demonstrate how to collect post-larval fish from this nursery system and perform whole-mount immunostaining. Immunostaining is an attractive alternative to transgene expression analysis for investigating development and gene function in A. mexicanus. The nursery method can also be used as a standard protocol for establishing density-matched populations for growth into adults.
    [Show full text]
  • Phenotypic Plasticity As a Mechanism of Cave Colonization and Adaptation
    RESEARCH ARTICLE Phenotypic plasticity as a mechanism of cave colonization and adaptation Helena Bilandzˇija1,2, Breanna Hollifield1, Mireille Steck3, Guanliang Meng4,5, Mandy Ng1, Andrew D Koch6, Romana Gracˇan7, Helena C´ etkovic´ 2, Megan L Porter3, Kenneth J Renner6, William Jeffery1* 1Department of Biology, University of Maryland, College Park, United States; 2Department of Molecular Biology, Ruđer Bosˇkovic´ Institute, Zagreb, Croatia; 3Department of Biology, University of Hawai’i at Manoa, Honolulu, United States; 4BGI-Shenzhen, Shenzhen, China; 5China National GeneBank, BGI-Shenzhen, Shenzhen, China; 6Department of Biology, University of South Dakota, Vermillion, United States; 7Department of Biology, Faculty of Science, University of Zagreb, Zagreb, Croatia Abstract A widely accepted model for the evolution of cave animals posits colonization by surface ancestors followed by the acquisition of adaptations over many generations. However, the speed of cave adaptation in some species suggests mechanisms operating over shorter timescales. To address these mechanisms, we used Astyanax mexicanus, a teleost with ancestral surface morphs (surface fish, SF) and derived cave morphs (cavefish, CF). We exposed SF to completely dark conditions and identified numerous altered traits at both the gene expression and phenotypic levels. Remarkably, most of these alterations mimicked CF phenotypes. Our results indicate that many cave-related traits can appear within a single generation by phenotypic plasticity. In the next generation, plasticity can be further refined. The initial plastic responses are random in adaptive outcome but may determine the subsequent course of evolution. Our study suggests that phenotypic plasticity contributes to the rapid evolution of cave-related traits in A. mexicanus. *For correspondence: [email protected] Competing interests: The Introduction authors declare that no A major problem in modern biology is understanding how organisms adapt to an environmental competing interests exist.
    [Show full text]
  • DNA Sequences of Troglobitic Nicoletiid Insects Support Sierra De El Abra and the Sierra De Guatemala As a Single Biogeographical Area: Implications for Astyanax
    A peer-reviewed open-access journal Subterranean Biology 13: 35–44DNA (2014) sequences of troglobitic nicoletiid insects support... 35 doi: 10.3897/subtbiol.13.7256 RESEARCH ARTICLE Subterranean Published by www.pensoft.net/journals/subtbiol The International Society Biology for Subterranean Biology DNA sequences of troglobitic nicoletiid insects support Sierra de El Abra and the Sierra de Guatemala as a single biogeographical area: Implications for Astyanax Luis Espinasa1, Nicole D. Bartolo1, Catherine E. Newkirk1 1 School of Science, Marist College, 3399 North Rd, Poughkeepsie, New York 12601, USA Corresponding author: Luis Espinasa ([email protected]) Academic editor: O. Moldovan | Received 14 February 2013 | Accepted 7 March 2014 | Published 18 March 2014 Citation: Espinasa L, Bartolo ND, Newkirk CE (2014) DNA sequences of troglobitic nicoletiid insects support Sierra de El Abra and the Sierra de Guatemala as a single biogeographical area: Implications for Astyanax. Subterranean Biology 13: 35–44. doi: 10.3897/subtbiol.13.7256 Abstract The blind Mexican tetra fish, Astyanax mexicanus, has become the most influential model for research of cave adapted organisms. Many authors assume that the Sierra de Guatemala populations and the Sierra de El Abra populations are derived from two independent colonizations. This assumption arises in part from biogeography. The 100 m high, 100 m wide Servilleta Canyon of the Boquillas River separates both mountain ranges and is an apparent barrier for troglobite dispersion. Anelpistina quinterensis (Nicoletiidae, Zygentoma, Insecta) is one of the most troglomorphic nicoletiid silverfish insects ever described. 16S rRNA sequences support that this species migrated underground to reach both mountain ranges within less than 12,000 years.
    [Show full text]