1
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Levis NA, Ragsdale EJ. A histone demethylase links the loss of plasticity to nongenetic inheritance and morphological change. Nat Commun 2023; 14:8439. [PMID: 38114491 PMCID: PMC10730525 DOI: 10.1038/s41467-023-44306-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Accepted: 12/07/2023] [Indexed: 12/21/2023] Open
Abstract
Plasticity is a widespread feature of development, enabling phenotypic change based on the environment. Although the evolutionary loss of plasticity has been linked both theoretically and empirically to increased rates of phenotypic diversification, molecular insights into how this process might unfold are generally lacking. Here, we show that a regulator of nongenetic inheritance links evolutionary loss of plasticity in nature to changes in plasticity and morphology as selected in the laboratory. Across nematodes of Diplogastridae, which ancestrally had a polyphenism, or discrete plasticity, in their feeding morphology, we use molecular evolutionary analyses to screen for change associated with independent losses of plasticity. Having inferred a set of ancestrally polyphenism-biased genes from phylogenetically informed gene-knockouts and gene-expression comparisons, selection signatures associated with plasticity's loss identify the histone H3K4 di/monodemethylase gene spr-5/LSD1/KDM1A. Manipulations of this gene affect both sensitivity and variation in plastic morphologies, and artificial selection of manipulated lines drive multigenerational shifts in these phenotypes. Our findings thus give mechanistic insight into how traits are modified as they traverse the continuum of greater to lesser environmental sensitivity.
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Affiliation(s)
- Nicholas A Levis
- Department of Biology, Indiana University, Bloomington, IN, 47405, USA.
| | - Erik J Ragsdale
- Department of Biology, Indiana University, Bloomington, IN, 47405, USA.
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2
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Isdaner AJ, Levis NA, Pfennig DW. Comparative transcriptomics reveals that a novel form of phenotypic plasticity evolved via lineage-specific changes in gene expression. Ecol Evol 2023; 13:e10646. [PMID: 37869437 PMCID: PMC10589077 DOI: 10.1002/ece3.10646] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2023] [Accepted: 10/09/2023] [Indexed: 10/24/2023] Open
Abstract
Novel forms of phenotypic plasticity may evolve by lineage-specific changes or by co-opting mechanisms from more general forms of plasticity. Here, we evaluated whether a novel resource polyphenism in New World spadefoot toads (genus Spea) evolved by co-opting mechanisms from an ancestral form of plasticity common in anurans-accelerating larval development rate in response to pond drying. We compared overlap in differentially expressed genes between alternative trophic morphs constituting the polyphenism in Spea versus those found between tadpoles of Old World spadefoot toads (genus Pelobates) when experiencing different pond-drying regimes. Specifically, we (1) generated a de novo transcriptome and conducted differential gene expression analysis in Spea multiplicata, (2) utilized existing gene expression data and a recently published transcriptome for Pelobates cultripes when exposed to different drying regimes, and (3) identified unique and overlapping differentially expressed transcripts. We found thousands of differentially expressed genes between S. multiplicata morphs that were involved in major developmental reorganization, but the vast majority of these were not differentially expressed in P. cultripes. Thus, S. multiplicata's novel polyphenism appears to have arisen primarily through lineage-specific changes in gene expression and not by co-opting existing patterns of gene expression involved in pond-drying plasticity. Therefore, although ancestral stress responses might jump-start evolutionary innovation, substantial lineage-specific modification might be needed to refine these responses into more complex forms of plasticity.
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Affiliation(s)
- Andrew J. Isdaner
- Department of BiologyUniversity of North CarolinaChapel HillNorth CarolinaUSA
| | - Nicholas A. Levis
- Department of BiologyUniversity of North CarolinaChapel HillNorth CarolinaUSA
- Department of BiologyIndiana UniversityBloomingtonIndianaUSA
| | - David W. Pfennig
- Department of BiologyUniversity of North CarolinaChapel HillNorth CarolinaUSA
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3
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Dantzer B, Mabry KE, Bernhardt JR, Cox RM, Francis CD, Ghalambor CK, Hoke KL, Jha S, Ketterson E, Levis NA, McCain KM, Patricelli GL, Paull SH, Pinter-Wollman N, Safran RJ, Schwartz TS, Throop HL, Zaman L, Martin LB. Understanding Organisms Using Ecological Observatory Networks. Integr Org Biol 2023; 5:obad036. [PMID: 37867910 PMCID: PMC10586040 DOI: 10.1093/iob/obad036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2023] [Revised: 06/07/2023] [Accepted: 09/21/2023] [Indexed: 10/24/2023] Open
Abstract
Human activities are rapidly changing ecosystems around the world. These changes have widespread implications for the preservation of biodiversity, agricultural productivity, prevalence of zoonotic diseases, and sociopolitical conflict. To understand and improve the predictive capacity for these and other biological phenomena, some scientists are now relying on observatory networks, which are often composed of systems of sensors, teams of field researchers, and databases of abiotic and biotic measurements across multiple temporal and spatial scales. One well-known example is NEON, the US-based National Ecological Observatory Network. Although NEON and similar networks have informed studies of population, community, and ecosystem ecology for years, they have been minimally used by organismal biologists. NEON provides organismal biologists, in particular those interested in NEON's focal taxa, with an unprecedented opportunity to study phenomena such as range expansions, disease epidemics, invasive species colonization, macrophysiology, and other biological processes that fundamentally involve organismal variation. Here, we use NEON as an exemplar of the promise of observatory networks for understanding the causes and consequences of morphological, behavioral, molecular, and physiological variation among individual organisms.
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Affiliation(s)
- B Dantzer
- Department of Psychology, University of Michigan, Ann Arbor, MI 48109,USA
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI 48109,USA
| | - K E Mabry
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI 48109,USA
- Department of Biology, New Mexico State University, Las Cruces, NM 88003,USA
| | - J R Bernhardt
- Department of Biology, New Mexico State University, Las Cruces, NM 88003,USA
- Department of Integrative Biology, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - R M Cox
- Department of Biology, University of Virginia, Charlottesville, VA 22940,USA
- Department of Biological Sciences, California Polytechnic State University, San Luis Obispo, CA 93407,USA
| | - C D Francis
- Department of Biological Sciences, California Polytechnic State University, San Luis Obispo, CA 93407,USA
- Department of Biology, Centre for Biodiversity Dynamics (CBD), Norwegian University of Science and Technology (NTNU), N‐7491 Trondheim, Norway
| | - C K Ghalambor
- Department of Biology, Centre for Biodiversity Dynamics (CBD), Norwegian University of Science and Technology (NTNU), N‐7491 Trondheim, Norway
- Department of Biology, Colorado State University, Fort Collins, CO 80523, USA
| | - K L Hoke
- Department of Biology, Colorado State University, Fort Collins, CO 80523, USA
| | - S Jha
- Department of Integrative Biology, University of Texas at Austin, Austin, TX 78712,USA
| | - E Ketterson
- Department of Biology, Indiana University, 1001 E. Third Street, Bloomington, IN 47405,USA
| | - N A Levis
- Department of Biology, Indiana University, 1001 E. Third Street, Bloomington, IN 47405,USA
| | - K M McCain
- Global Health and Infectious Disease Research Center, College of Public Health, University of South Florida, Tampa, FL 33612,USA
| | - G L Patricelli
- Department of Evolution and Ecology, University of California, Davis, CA 95616,USA
| | - S H Paull
- Battelle, National Ecological Observatory Network, 1685 38th Street, Boulder, CO 80301, USA
| | - N Pinter-Wollman
- Department of Ecology and Evolutionary Biology, University of California Los Angeles, 621 Charles E. Young Drive South, Los Angeles, CA 90095, USA
| | - R J Safran
- Department of Ecology and Evolutionary Biology, University of Colorado, Boulder 80309,USA
| | - T S Schwartz
- Department of Biological Sciences, Auburn University, Auburn, AL 36849, USA
| | - H L Throop
- School of Earth and Space Exploration and School of Life Sciences, Arizona State University, Tempe, AZ 85287, USA
| | - L Zaman
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI 48109,USA
- Center for the Study of Complex Systems, University of Michigan, Ann Arbor, MI 48109, USA
| | - L B Martin
- Global Health and Infectious Disease Research Center and Center for Genomics, College of Public Health, University of South Florida, Tampa, FL 33612,USA
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4
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Levis NA, McKay DJ, Pfennig DW. Disentangling the developmental origins of a novel phenotype: enhancement versus reversal of environmentally induced gene expression. Proc Biol Sci 2022; 289:20221764. [PMID: 36285495 PMCID: PMC9597403 DOI: 10.1098/rspb.2022.1764] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Accepted: 10/03/2022] [Indexed: 11/12/2022] Open
Abstract
Increasing evidence suggests that many novel traits might have originated via plasticity-led evolution (PLE). Yet, little is known of the developmental processes that underpin PLE, especially in its early stages. One such process is 'phenotypic accommodation', which occurs when, in response to a change in the environment, an organism experiences adjustments across variable parts of its phenotype that improve its fitness. Here, we asked if environmentally induced changes in gene expression are enhanced or reversed during phenotypic accommodation of a novel, complex phenotype in spadefoot toad tadpoles (Spea multiplicata). More genes than expected were affected by both the environment and phenotypic accommodation in the liver and brain. However, although phenotypic accommodation primarily reversed environmentally induced changes in gene expression in liver tissue, it enhanced these changes in brain tissue. Thus, depending on the tissue, phenotypic accommodation may either minimize functional disruption via reversal of gene expression patterns or promote novelty via enhancement of existing expression patterns. Our study thereby provides insights into the developmental origins of a novel phenotype and the incipient stages of PLE.
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Affiliation(s)
- Nicholas A. Levis
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Daniel J. McKay
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA
| | - David W. Pfennig
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA
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5
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Levis NA, Ragsdale EJ. Linking Molecular Mechanisms and Evolutionary Consequences of Resource Polyphenism. Front Integr Neurosci 2022; 16:805061. [PMID: 35210995 PMCID: PMC8861301 DOI: 10.3389/fnint.2022.805061] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Accepted: 01/10/2022] [Indexed: 11/13/2022] Open
Abstract
Resource polyphenism—the occurrence of environmentally induced, discrete, and intraspecific morphs showing differential niche use—is taxonomically widespread and fundamental to the evolution of ecological function where it has arisen. Despite longstanding appreciation for the ecological and evolutionary significance of resource polyphenism, only recently have its proximate mechanisms begun to be uncovered. Polyphenism switches, especially those influencing and influenced by trophic interactions, offer a route to integrating proximate and ultimate causation in studies of plasticity, and its potential influence on evolution more generally. Here, we use the major events in generalized polyphenic development as a scaffold for linking the molecular mechanisms of polyphenic switching with potential evolutionary outcomes of polyphenism and for discussing challenges and opportunities at each step in this process. Not only does the study of resource polyphenism uncover interesting details of discrete plasticity, it also illuminates and informs general principles at the intersection of development, ecology, and evolution.
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6
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Levis NA, Kelly PW, Harmon EA, Ehrenreich IM, McKay DJ, Pfennig DW. Transcriptomic bases of a polyphenism. J Exp Zool B Mol Dev Evol 2021; 336:482-495. [PMID: 34142757 DOI: 10.1002/jez.b.23066] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Revised: 03/22/2021] [Accepted: 05/22/2021] [Indexed: 11/06/2022]
Abstract
Polyphenism-in which multiple distinct phenotypes are produced from a single genotype owing to differing environmental conditions-is commonplace, but its molecular bases are poorly understood. Here, we examine the transcriptomic bases of a polyphenism in Mexican spadefoot toads (Spea multiplicata). Depending on their environment, their tadpoles develop into either a default "omnivore" morph or a novel "carnivore" morph. We compared patterns of gene expression among sibships that exhibited high versus low production of carnivores when reared in conditions that induce the carnivore morph versus those that do not. We found that production of the novel carnivore morph actually involved changes in fewer genes than did the maintenance of the default omnivore morph in the inducing environment. However, only body samples showed this pattern; head samples showed the opposite pattern. We also found that changes to lipid metabolism (especially cholesterol biosynthesis) and peroxisome contents and function might be crucial for establishing and maintaining differences between the morphs. Thus, our findings suggest that carnivore phenotype might have originally evolved following the breakdown of robustness mechanisms that maintain the default omnivore phenotype, and that the carnivore morph is developmentally regulated by lipid metabolism and peroxisomal form, function, and/or signaling. This study also serves as a springboard for further exploration into the nature and causes of plasticity in an emerging model system.
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Affiliation(s)
- Nicholas A Levis
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina, USA.,Current affiliation: Department of Biology, Indiana University, Bloomington, Indiana, USA
| | - Patrick W Kelly
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina, USA
| | - Emily A Harmon
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina, USA
| | - Ian M Ehrenreich
- Molecular and Computational Biology Section, University of Southern, Los Angeles, California, USA
| | - Daniel J McKay
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina, USA
| | - David W Pfennig
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina, USA
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7
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Levis NA, Fuller CG, Pfennig DW. An experimental investigation of how intraspecific competition and phenotypic plasticity can promote the evolution of novel, complex phenotypes. Biol J Linn Soc Lond 2020. [DOI: 10.1093/biolinnean/blaa095] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
Abstract
Intraspecific competition has long been considered a key driver of evolutionary diversification, but whether it can also promote evolutionary innovation is less clear. Here we examined the interplay between competition and phenotypic plasticity in fuelling the origins of a novel, complex phenotype – a distinctive carnivore morph found in spadefoot toad tadpoles (genus Spea) that specializes on fairy shrimp. We specifically sought to explore the possible origins of this phenotype by providing shrimp to Scaphiopus holbrookii tadpoles (the sister genus to Spea that does not produce carnivores) while subjecting them to competition for their standard diet of detritus. Previous research had shown that this species will eat shrimp when detritus is limited, and that these shrimp-fed individuals produce features that are redolent of a rudimentary Spea carnivore. In this study, we found that: (1) behavioural and morphological plasticity enabled some individuals to expand their diet to include shrimp; (2) there was heritable variation in this plasticity; and (3) individuals received a growth and development benefit by eating shrimp. Thus, novel resource use can arise via plasticity as an adaptive response to intraspecific competition. More generally, our results show how competition and plasticity may interact to pave the way for the evolution of complex, novel phenotypes, such as the distinctive carnivore morph in present-day Spea.
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Affiliation(s)
- Nicholas A Levis
- Department of Biology, CB#3280, University of North Carolina, Chapel Hill, NC, USA
| | - Carly G Fuller
- Department of Biology, CB#3280, University of North Carolina, Chapel Hill, NC, USA
| | - David W Pfennig
- Department of Biology, CB#3280, University of North Carolina, Chapel Hill, NC, USA
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8
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Levis NA, Reed EMX, Pfennig DW, Burford Reiskind MO. Identification of candidate loci for adaptive phenotypic plasticity in natural populations of spadefoot toads. Ecol Evol 2020; 10:8976-8988. [PMID: 32884672 PMCID: PMC7452772 DOI: 10.1002/ece3.6602] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2020] [Revised: 06/30/2020] [Accepted: 07/01/2020] [Indexed: 12/24/2022] Open
Abstract
Phenotypic plasticity allows organisms to alter their phenotype in direct response to changes in the environment. Despite growing recognition of plasticity's role in ecology and evolution, few studies have probed plasticity's molecular bases-especially using natural populations. We investigated the genetic basis of phenotypic plasticity in natural populations of spadefoot toads (Spea multiplicata). Spea tadpoles normally develop into an "omnivore" morph that is favored in long-lasting, low-density ponds. However, if tadpoles consume freshwater shrimp or other tadpoles, they can alternatively develop (via plasticity) into a "carnivore" morph that is favored in ephemeral, high-density ponds. By combining natural variation in pond ecology and morph production with population genetic approaches, we identified candidate loci associated with each morph (carnivores vs. omnivores) and loci associated with adaptive phenotypic plasticity (adaptive vs. maladaptive morph choice). Our candidate morph loci mapped to two genes, whereas our candidate plasticity loci mapped to 14 genes. In both cases, the identified genes tended to have functions related to their putative role in spadefoot tadpole biology. Our results thereby form the basis for future studies into the molecular mechanisms that mediate plasticity in spadefoots. More generally, these results illustrate how diverse loci might mediate adaptive plasticity.
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Affiliation(s)
| | - Emily M. X. Reed
- Department of Biological SciencesNorth Carolina State UniversityRaleighNCUSA
| | - David W. Pfennig
- Department of BiologyUniversity of North CarolinaChapel HillNCUSA
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9
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Abstract
Explaining the origins of adaptive features is a perennial challenge in evolutionary biology. A study on thermophilic cyanobacteria reveals how environmentally induced phenotypic change (plasticity) can pave the way for evolutionary innovation and subsequent adaptation to extreme conditions.
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Affiliation(s)
- Nicholas A Levis
- Department of Biology, CB#3280, University of North Carolina, Chapel Hill, NC 27599, USA.
| | - David W Pfennig
- Department of Biology, CB#3280, University of North Carolina, Chapel Hill, NC 27599, USA
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10
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Seidl F, Levis NA, Schell R, Pfennig DW, Pfennig KS, Ehrenreich IM. Genome of Spea multiplicata, a Rapidly Developing, Phenotypically Plastic, and Desert-Adapted Spadefoot Toad. G3 (Bethesda) 2019; 9:3909-3919. [PMID: 31578218 PMCID: PMC6893194 DOI: 10.1534/g3.119.400705] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Accepted: 09/23/2019] [Indexed: 12/22/2022]
Abstract
Frogs and toads (anurans) are widely used to study many biological processes. Yet, few anuran genomes have been sequenced, limiting research on these organisms. Here, we produce a draft genome for the Mexican spadefoot toad, Spea multiplicata, which is a member of an unsequenced anuran clade. Atypically for amphibians, spadefoots inhabit deserts. Consequently, they possess many unique adaptations, including rapid growth and development, prolonged dormancy, phenotypic (developmental) plasticity, and adaptive, interspecies hybridization. We assembled and annotated a 1.07 Gb Sp. multiplicata genome containing 19,639 genes. By comparing this sequence to other available anuran genomes, we found gene amplifications in the gene families of nodal, hyas3, and zp3 in spadefoots, and obtained evidence that anuran genome size differences are partially driven by variability in intergenic DNA content. We also used the genome to identify genes experiencing positive selection and to study gene expression levels in spadefoot hybrids relative to their pure-species parents. Completion of the Sp. multiplicata genome advances efforts to determine the genetic bases of spadefoots' unique adaptations and enhances comparative genomic research in anurans.
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Affiliation(s)
- Fabian Seidl
- Molecular and Computational Biology Section, Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089, and
| | - Nicholas A Levis
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599
| | - Rachel Schell
- Molecular and Computational Biology Section, Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089, and
| | - David W Pfennig
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599
| | - Karin S Pfennig
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599
| | - Ian M Ehrenreich
- Molecular and Computational Biology Section, Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089, and
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11
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Seidl F, Levis NA, Jones CD, Monroy-Eklund A, Ehrenreich IM, Pfennig KS. Variation in hybrid gene expression: Implications for the evolution of genetic incompatibilities in interbreeding species. Mol Ecol 2019; 28:4667-4679. [PMID: 31541560 DOI: 10.1111/mec.15246] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2017] [Revised: 08/27/2019] [Accepted: 09/09/2019] [Indexed: 02/06/2023]
Abstract
Interbreeding species often produce low-fitness hybrids due to genetic incompatibilities between parental genomes. Whether these incompatibilities reflect fixed allelic differences between hybridizing species, or, alternatively, standing variants that segregate within them, remains unknown for many natural systems. Yet, evaluating these alternatives is important for understanding the origins and nature of species boundaries. We examined these alternatives using spadefoot toads (genus Spea), which naturally hybridize. Specifically, we contrasted patterns of gene expression in hybrids relative to pure-species types in experimentally produced tadpoles from allopatric parents versus those from sympatric parents. We evaluated the prediction that segregating variation should result in gene expression differences between hybrids derived from sympatric parents versus hybrids derived from allopatric parents, and found that 24% of the transcriptome showed such differences. Our results further suggest that gene expression in hybrids has evolved in sympatry owing to evolutionary pressures associated with ongoing hybridization. Although we did not measure hybrid incompatibilities directly, we discuss the implications of our findings for understanding the nature of hybrid incompatibilities, how they might vary across populations over time, and the resulting effects on the evolutionary maintenance - or breakdown - of reproductive barriers between species.
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Affiliation(s)
- Fabian Seidl
- Molecular and Computational Biology Section, Department of Biological Sciences, University of Southern California, Los Angeles, CA, USA
| | - Nicholas A Levis
- Department of Biology, University of North Carolina, Chapel Hill, NC, USA
| | - Corbin D Jones
- Department of Biology, University of North Carolina, Chapel Hill, NC, USA.,Integrative Program for Biological & Genome Sciences, University of North Carolina, Chapel Hill, NC, USA
| | | | - Ian M Ehrenreich
- Molecular and Computational Biology Section, Department of Biological Sciences, University of Southern California, Los Angeles, CA, USA
| | - Karin S Pfennig
- Department of Biology, University of North Carolina, Chapel Hill, NC, USA
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12
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Affiliation(s)
- Nicholas A. Levis
- Department of Biology University of North Carolina Chapel Hill North Carolina
| | - David W. Pfennig
- Department of Biology University of North Carolina Chapel Hill North Carolina
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13
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Levis NA, Pfennig DW. How stabilizing selection and nongenetic inheritance combine to shape the evolution of phenotypic plasticity. J Evol Biol 2019; 32:706-716. [PMID: 30968503 DOI: 10.1111/jeb.13475] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Revised: 04/01/2019] [Accepted: 04/03/2019] [Indexed: 12/22/2022]
Abstract
Relatively little is known about whether and how nongenetic inheritance interacts with selection to impact the evolution of phenotypic plasticity. Here, we empirically evaluated how stabilizing selection and a common form of nongenetic inheritance-maternal environmental effects-jointly influence the evolution of phenotypic plasticity in natural populations of spadefoot toads. We compared populations that previous fieldwork has shown to have evolved conspicuous plasticity in resource-use phenotypes ("resource polyphenism") with those that, owing to stabilizing selection favouring a narrower range of such phenotypes, appear to have lost this plasticity. We show that: (a) this apparent loss of plasticity in nature reflects a condition-dependent maternal effect and not a genetic loss of plasticity, that is "genetic assimilation," and (b) this plasticity is not costly. By shielding noncostly plasticity from selection, nongenetic inheritance generally, and maternal effects specifically, can preclude genetic assimilation from occurring and consequently impede adaptive (genetic) evolution.
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Affiliation(s)
- Nicholas A Levis
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina
| | - David W Pfennig
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina
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14
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Levis NA, Pfennig DW. Plasticity-led evolution: evaluating the key prediction of frequency-dependent adaptation. Proc Biol Sci 2019; 286:20182754. [PMID: 30963848 PMCID: PMC6408876 DOI: 10.1098/rspb.2018.2754] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Accepted: 02/05/2019] [Indexed: 01/20/2023] Open
Abstract
Plasticity-led evolution occurs when a change in the environment triggers a change in phenotype via phenotypic plasticity, and this pre-existing plasticity is subsequently refined by selection into an adaptive phenotype. A critical, but largely untested prediction of plasticity-led evolution (and evolution by natural selection generally) is that the rate and magnitude of evolutionary change should be positively associated with a phenotype's frequency of expression in a population. Essentially, the more often a phenotype is expressed and exposed to selection, the greater its opportunity for adaptive refinement. We tested this prediction by competing against each other spadefoot toad tadpoles from different natural populations that vary in how frequently they express a novel, environmentally induced carnivore ecomorph. As expected, laboratory-reared tadpoles whose parents were derived from populations that express the carnivore ecomorph more frequently were superior competitors for the resource for which this ecomorph is specialized-fairy shrimp. These tadpoles were better at using this resource both because they were more efficient at capturing and consuming shrimp and because they produced more exaggerated carnivore traits. Moreover, they exhibited these more carnivore-like features even without experiencing the inducing cue, suggesting that this ecomorph has undergone an extreme form of plasticity-led evolution-genetic assimilation. Thus, our findings provide evidence that the frequency of trait expression drives the magnitude of adaptive refinement, thereby validating a key prediction of plasticity-led evolution specifically and adaptive evolution generally.
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Affiliation(s)
- Nicholas A. Levis
- Department of Biology, University of North Carolina, CB no. 3280, Chapel Hill, NC 27599, USA
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15
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Levis NA, Pfennig DW. Phenotypic plasticity, canalization, and the origins of novelty: Evidence and mechanisms from amphibians. Semin Cell Dev Biol 2018; 88:80-90. [PMID: 29408711 DOI: 10.1016/j.semcdb.2018.01.012] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Revised: 01/25/2018] [Accepted: 01/29/2018] [Indexed: 12/20/2022]
Abstract
A growing number of biologists have begun asking whether environmentally induced phenotypic change--'phenotypic plasticity'--precedes and facilitates the origin and canalization of novel, complex phenotypes. However, such 'plasticity-first evolution' (PFE) remains controversial. Here, we summarize the PFE hypothesis and describe how it can be evaluated in natural systems. We then review the evidence for PFE from amphibians (a group in which phenotypic plasticity is especially widespread) and describe how phenotypic plasticity might have facilitated macroevolutionary change. Finally, we discuss what is known about the proximate mechanisms of PFE in amphibians. We close with suggestions for future research. As we describe, amphibians offer some of the best support for plasticity's role in the origin of evolutionary novelties.
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Affiliation(s)
- Nicholas A Levis
- Department of Biology, CB#3280, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - David W Pfennig
- Department of Biology, CB#3280, University of North Carolina, Chapel Hill, NC, 27599, USA.
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Levis NA, Martin RA, O'Donnell KA, Pfennig DW. Intraspecific adaptive radiation: Competition, ecological opportunity, and phenotypic diversification within species. Evolution 2017; 71:2496-2509. [PMID: 28841748 DOI: 10.1111/evo.13313] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2017] [Revised: 06/21/2017] [Accepted: 06/30/2017] [Indexed: 11/30/2022]
Abstract
Intraspecific variation in resource-use traits can have profound ecological and evolutionary implications. Among the most striking examples are resource polymorphisms, where alternative morphs that utilize different resources evolve within a population. An underappreciated aspect of their evolution is that the same conditions that favor resource polymorphism-competition and ecological opportunity-might foster additional rounds of diversification within already existing morphs. We examined these issues in spadefoot toad tadpoles that develop into either a generalist "omnivore" or a specialist "carnivore" morph. Specifically, we assessed the morphological diversity of tadpoles from natural ponds and experimentally induced carnivores reared on alternative diets. We also surveyed natural ponds to determine if the strength of intramorph competition and the diversity and abundance of dietary resources (measures of ecological opportunity) influenced the diversity of within-morph variation. We found that five omnivore and four carnivore types were present in natural ponds; alternative diets led to shape differences, some of which mirrored variation in the wild; and both competition and ecological opportunity were associated with enhanced morphological diversity in natural ponds. Such fine-scale intraspecific variation might represent an underappreciated form of biodiversity and might constitute a crucible of evolutionary innovation and diversification.
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Affiliation(s)
- Nicholas A Levis
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina, 27599
| | - Ryan A Martin
- Department of Biology, Case Western Reserve University, Cleveland, Ohio, 44106
| | - Kerry A O'Donnell
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina, 27599
| | - David W Pfennig
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina, 27599
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Affiliation(s)
- Nicholas A. Levis
- Department of Biology; University of North Carolina; Chapel Hill North Carolina 27599
| | - David W. Pfennig
- Department of Biology; University of North Carolina; Chapel Hill North Carolina 27599
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Levis NA, Schooler ML, Johnson JR, Collyer ML. Non-adaptive phenotypic plasticity: the effects of terrestrial and aquatic herbicides on larval salamander morphology and swim speed. Biol J Linn Soc Lond 2016. [DOI: 10.1111/bij.12761] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Nicholas A. Levis
- Department of Biology; Western Kentucky University; Bowling Green KY 42101 USA
| | | | - Jarrett R. Johnson
- Department of Biology; Western Kentucky University; Bowling Green KY 42101 USA
| | - Michael L. Collyer
- Department of Biology; Western Kentucky University; Bowling Green KY 42101 USA
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Levis NA, Johnson JR. Level of UV-B radiation influences the effects of glyphosate-based herbicide on the spotted salamander. Ecotoxicology 2015; 24:1073-86. [PMID: 25794558 DOI: 10.1007/s10646-015-1448-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 03/11/2015] [Indexed: 06/04/2023]
Abstract
Glyphosate-based herbicides are the number one pesticide in the United States and are used commonly around the world. Understanding the affects of glyphosate-based herbicides on non-target wildlife, for example amphibians, is critical for evaluation of regulations pertaining to the use of such herbicides. Additionally, it is important to understand how variation in biotic and abiotic environmental conditions, such as UV-B light regime, could potentially affect how glyphosate-based herbicides interact with non-target species. This study used artificial pond mesocosms to identify the effects of generic glyphosate-based herbicide (GLY-4 Plus) on mortality, cellular immune response, body size, and morphological plasticity of larvae of the spotted salamander (Ambystoma maculatum) under conditions that reflect moderate (UV(M)) and low (UV(L)) UV-B light regimes. Survival within a given UV-B level was unaffected by herbicide presence or absence. However, when herbicide was present, survival varied between UV-B levels with higher survival in UV(M) conditions. Herbicide presence in the UV(M) treatments also decreased body size and reduced cellular immune response. In the UV(L) treatments, the presence of herbicide increased body size and affected tail morphology. Finally, in the absence of herbicide, body size and cellular immune response were higher in UV(M) treatments compared to UV(L) treatments. Thus, the effects of herbicide on salamander fitness were dependent on UV-B level. As anthropogenic habitat modifications continue to alter landscapes that contain amphibian breeding ponds, salamanders may increasingly find themselves in locations with reduced canopy cover and increased levels of UV light. Our findings suggest that the probability of surviving exposure to the glyphosate-based herbicide used in this study may be elevated in more open canopy ponds, but the effects on other components of fitness may be varied and unexpected.
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Affiliation(s)
- Nicholas A Levis
- Department of Biology, Western Kentucky University, Bowling Green, KY, 42101, USA,
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Levis NA, de la Serna Buzón S, Pfennig DW. An inducible offense: carnivore morph tadpoles induced by tadpole carnivory. Ecol Evol 2015; 5:1405-11. [PMID: 25897380 PMCID: PMC4395170 DOI: 10.1002/ece3.1448] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Revised: 02/03/2015] [Accepted: 02/08/2015] [Indexed: 01/11/2023] Open
Abstract
Phenotypic plasticity is commonplace, and plasticity theory predicts that organisms should often evolve mechanisms to detect and respond to environmental cues that accurately predict future environmental conditions. Here, we test this prediction in tadpoles of spadefoot toads, Spea multiplicata. These tadpoles develop into either an omnivore ecomorph, which is a dietary generalist, or a carnivore ecomorph, which specializes on anostracan shrimp and other tadpoles. We investigated a novel proximate cue - ingestion of Scaphiopus tadpoles - and its propensity to produce carnivores by rearing tadpoles on different diets. We found that diets containing tadpoles from the genus Scaphiopus produced more carnivores than diets without Scaphiopus tadpoles. We discuss why Scaphiopus tadpoles are an excellent food source and why it is therefore advantageous for S. multiplicata tadpoles to produce an inducible offense that allows them to better utilize this resource. In general, such inducible offenses provide an excellent setting for investigating the proximate and evolutionary basis of phenotypic plasticity.
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Affiliation(s)
- Nicholas A Levis
- Department of Biology, University of North Carolina CB#3280, Chapel Hill, NC, 27599
| | | | - David W Pfennig
- Department of Biology, University of North Carolina CB#3280, Chapel Hill, NC, 27599
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Levis NA, Yi SX, Lee RE. Mild desiccation rapidly increases freeze tolerance of the goldenrod gall fly, Eurosta solidaginis: evidence for drought-induced RCH. J Exp Biol 2012; 215:3768-73. [DOI: 10.1242/jeb.076885] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Summary
Overwintering insects may experience extreme cold and desiccation stress. Both freezing and desiccation require cells to tolerate osmotic challenge as solutes become concentrated in the hemolymph. Not surprisingly, physiological responses to low temperature and desiccation share common features and may confer cross-tolerance against these stresses. Freeze-tolerant larvae of the goldenrod gall fly, Eurosta solidaginis (Fitch) (Diptera: Tephritidae), experience extremely dry and cold conditions in winter. To determine whether mild desiccation can improve freeze tolerance at organismal and cellular levels, we assessed survival, hemolymph osmolality, and glycerol levels of control and desiccated larvae. Larvae that lost only 6-10% of their body mass, in as little as 6 h, had markedly higher levels of freeze tolerance. Mild, rapid desiccation increased freezing tolerance at -15°C in September- (33.3±6.7 to 73.3±12%) and at -20°C in October-collected (16.7±6.7 to 46.7±3.3%) larvae. Similarly, 6 h of desiccation improved in vivo survival by 17-43% in fat body, Malpighian tubule, salivary gland, and tracheal cells at -20°C. Desiccation, also, enhanced intrinsic levels of cold tolerance in midgut cells frozen ex vivo (38.7±4.6 to 89.2±5.5 %). Whereas hemolymph osmolality increased significantly with desiccation treatment from 544±16 to 720±26 mOsm, glycerol levels did not differ between control and desiccated groups. The rapidity with which a mild desiccation stress increased freeze tolerance closely resembles the rapid cold-hardening (RCH) response, which occurs during brief sub-lethal chilling, and suggests that drought stress can induce RCH.
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