1
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Choy YMM, Walter GM, Mirth CK, Sgrò CM. Within-population plastic responses to combined thermal-nutritional stress differ from those in response to single stressors, and are genetically independent across traits in both males and females. J Evol Biol 2024; 37:717-731. [PMID: 38757509 DOI: 10.1093/jeb/voae061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2023] [Revised: 03/25/2024] [Accepted: 05/16/2024] [Indexed: 05/18/2024]
Abstract
Phenotypic plasticity helps animals to buffer the effects of increasing thermal and nutritional stress created by climate change. Plastic responses to single and combined stressors can vary among genetically diverged populations. However, less is known about how plasticity in response to combined stress varies among individuals within a population or whether such variation changes across life-history traits. This is important because individual variation within populations shapes population-level responses to environmental change. Here, we used isogenic lines of Drosophila melanogaster to assess the plasticity of egg-to-adult viability and sex-specific body size for combinations of 2 temperatures (25 °C or 28 °C) and 3 diets (standard diet, low caloric diet, or low protein:carbohydrate ratio diet). Our results reveal substantial within-population genetic variation in plasticity for egg-to-adult viability and wing size in response to combined thermal-nutritional stress. This genetic variation in plasticity was a result of cross-environment genetic correlations that were often < 1 for both traits, as well as changes in the expression of genetic variation across environments for egg-to-adult viability. Cross-sex genetic correlations for body size were weaker when the sexes were reared in different conditions, suggesting that the genetic basis of traits may change with the environment. Furthermore, our results suggest that plasticity in egg-to-adult viability is genetically independent from plasticity in body size. Importantly, plasticity in response to diet and temperature individually differed from plastic shifts in response to diet and temperature in combination. By quantifying plasticity and the expression of genetic variance in response to combined stress across traits, our study reveals the complexity of animal responses to environmental change, and the need for a more nuanced understanding of the potential for populations to adapt to ongoing climate change.
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Affiliation(s)
- Yeuk Man Movis Choy
- School of Biological Sciences, Monash University, Wellington Rd, Clayton, Melbourne, Victoria, Australia
| | - Greg M Walter
- School of Biological Sciences, Monash University, Wellington Rd, Clayton, Melbourne, Victoria, Australia
| | - Christen K Mirth
- School of Biological Sciences, Monash University, Wellington Rd, Clayton, Melbourne, Victoria, Australia
| | - Carla M Sgrò
- School of Biological Sciences, Monash University, Wellington Rd, Clayton, Melbourne, Victoria, Australia
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2
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Weber JN, Kojima W, Boisseau RP, Niimi T, Morita S, Shigenobu S, Gotoh H, Araya K, Lin CP, Thomas-Bulle C, Allen CE, Tong W, Lavine LC, Swanson BO, Emlen DJ. Evolution of horn length and lifting strength in the Japanese rhinoceros beetle Trypoxylus dichotomus. Curr Biol 2023; 33:4285-4297.e5. [PMID: 37734374 DOI: 10.1016/j.cub.2023.08.066] [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: 03/13/2023] [Revised: 06/28/2023] [Accepted: 08/23/2023] [Indexed: 09/23/2023]
Abstract
What limits the size of nature's most extreme structures? For weapons like beetle horns, one possibility is a tradeoff associated with mechanical levers: as the output arm of the lever system-the beetle horn-gets longer, it also gets weaker. This "paradox of the weakening combatant" could offset reproductive advantages of additional increases in weapon size. However, in contemporary populations of most heavily weaponed species, males with the longest weapons also tend to be the strongest, presumably because selection drove the evolution of compensatory changes to these lever systems that ameliorated the force reductions of increased weapon size. Therefore, we test for biomechanical limits by reconstructing the stages of weapon evolution, exploring whether initial increases in weapon length first led to reductions in weapon force generation that were later ameliorated through the evolution of mechanisms of mechanical compensation. We describe phylogeographic relationships among populations of a rhinoceros beetle and show that the "pitchfork" shaped head horn likely increased in length independently in the northern and southern radiations of beetles. Both increases in horn length were associated with dramatic reductions to horn lifting strength-compelling evidence for the paradox of the weakening combatant-and these initial reductions to horn strength were later ameliorated in some populations through reductions to horn length or through increases in head height (the input arm for the horn lever system). Our results reveal an exciting geographic mosaic of weapon size, weapon force, and mechanical compensation, shedding light on larger questions pertaining to the evolution of extreme structures.
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Affiliation(s)
- Jesse N Weber
- Department of Integrative Biology, University of Wisconsin-Madison, Madison, WI 53706, USA.
| | - Wataru Kojima
- Graduate School of Sciences and Technology for Innovation, Yamaguchi University, 1677-1 Yoshida, Yamaguchi 753-8511, Japan
| | - Romain P Boisseau
- Division of Biological Sciences, The University of Montana, Missoula, MT 59812, USA
| | - Teruyuki Niimi
- Division of Evolutionary Developmental Biology, National Institute for Basic Biology, 38 Nishigonaka Myodaiji, Okazaki 444-8585, Japan
| | - Shinichi Morita
- Division of Evolutionary Developmental Biology, National Institute for Basic Biology, 38 Nishigonaka Myodaiji, Okazaki 444-8585, Japan
| | - Shuji Shigenobu
- Trans-Scale Biology Center, National Institute for Basic Biology, 38 Nishigonaka Myodaiji, Okazaki 444-8585, Japan
| | - Hiroki Gotoh
- Department of Science, Graduate School of Integrated Science and Technology, Shizuoka University, 836 Oya, Suruga Ward, Shizuoka, Japan
| | - Kunio Araya
- Faculty of Social and Cultural Studies, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka-city Fukuoka 819-0395, Japan
| | - Chung-Ping Lin
- Department of Life Science, National Taiwan Normal University, No.88 Sec. 4, Tingzhou Rd, Taipei 11677, Taiwan
| | - Camille Thomas-Bulle
- Division of Biological Sciences, The University of Montana, Missoula, MT 59812, USA; Department of Biological Sciences, University of Denver, Denver, CO 80208, USA
| | - Cerisse E Allen
- Division of Biological Sciences, The University of Montana, Missoula, MT 59812, USA
| | - Wenfei Tong
- Cornell Laboratory of Ornithology, Ithaca, NY 14850, USA
| | - Laura Corley Lavine
- Department of Entomology, Washington State University, Pullman, WA 99164, USA
| | - Brook O Swanson
- Department of Biology, Gonzaga University, 502 East Boone Avenue, Spokane, WA 99258-0102, USA
| | - Douglas J Emlen
- Division of Biological Sciences, The University of Montana, Missoula, MT 59812, USA.
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3
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Wilcox AS, Vea IM, Frankino WA, Shingleton AW. Genetic variation of morphological scaling in Drosophila melanogaster. Heredity (Edinb) 2023; 130:302-311. [PMID: 36878946 PMCID: PMC10162999 DOI: 10.1038/s41437-023-00603-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Revised: 02/09/2023] [Accepted: 02/10/2023] [Indexed: 03/08/2023] Open
Abstract
Morphological scaling relationships between the sizes of individual traits and the body captures the characteristic shape of a species, and their evolution is the primary mechanism of morphological diversification. However, we have almost no knowledge of the genetic variation of scaling, which is critical if we are to understand how scaling evolves. Here we explore the genetics of population scaling relationships (scaling relationships fit to multiple genetically-distinct individuals in a population) by describing the distribution of individual scaling relationships (genotype-specific scaling relationships that are unseen or cryptic). These individual scaling relationships harbor the genetic variation in the developmental mechanisms that regulate trait growth relative to body growth, and theoretical studies suggest that their distribution dictates how the population scaling relationship will respond to selection. Using variation in nutrition to generate size variation within 197 isogenic lineages of Drosophila melanogaster, we reveal extensive variation in the slopes of the wing-body and leg-body individual scaling relationships among genotypes. This variation reflects variation in the nutritionally-induced size plasticity of the wing, leg, and body. Surprisingly, we find that variation in the slope of individual scaling relationships primarily results from variation in nutritionally-induced plasticity of body size, not leg or wing size. These data allow us to predict how different selection regimes affect scaling in Drosophila, and is the first step in identifying the genetic targets of such selection. More generally, our approach provides a framework for understanding the genetic variation of scaling, an important prerequisite to explaining how selection changes scaling and morphology.
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Affiliation(s)
- Austin S Wilcox
- Department of Biological Sciences, University of Illinois Chicago, 840 W Taylor St, Chicago, IL, 60607, USA
| | - Isabelle M Vea
- Department of Biological Sciences, University of Illinois Chicago, 840 W Taylor St, Chicago, IL, 60607, USA
| | - W Anthony Frankino
- Department of Biology and Biochemistry, University of Houston, Houston, TX, 77204, USA
| | - Alexander W Shingleton
- Department of Biological Sciences, University of Illinois Chicago, 840 W Taylor St, Chicago, IL, 60607, USA.
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4
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Chakraborty A, Walter GM, Monro K, Alves AN, Mirth CK, Sgrò CM. Within-population variation in body size plasticity in response to combined nutritional and thermal stress is partially independent from variation in development time. J Evol Biol 2023; 36:264-279. [PMID: 36208146 PMCID: PMC10092444 DOI: 10.1111/jeb.14099] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2021] [Revised: 06/16/2022] [Accepted: 06/21/2022] [Indexed: 01/11/2023]
Abstract
Ongoing climate change has forced animals to face changing thermal and nutritional environments. Animals can adjust to such combinations of stressors via plasticity. Body size is a key trait influencing organismal fitness, and plasticity in this trait in response to nutritional and thermal conditions varies among genetically diverse, locally adapted populations. The standing genetic variation within a population can also influence the extent of body size plasticity. We generated near-isogenic lines from a newly collected population of Drosophila melanogaster at the mid-point of east coast Australia and assayed body size for all lines in combinations of thermal and nutritional stress. We found that isogenic lines showed distinct underlying patterns of body size plasticity in response to temperature and nutrition that were often different from the overall population response. We then tested whether plasticity in development time could explain, and therefore regulate, variation in body size to these combinations of environmental conditions. We selected five genotypes that showed the greatest variation in response to combined thermal and nutritional stress and assessed the correlation between response of developmental time and body size. While we found significant genetic variation in development time plasticity, it was a poor predictor of body size among genotypes. Our results therefore suggest that multiple developmental pathways could generate genetic variation in body size plasticity. Our study emphasizes the need to better understand genetic variation in plasticity within a population, which will help determine the potential for populations to adapt to ongoing environmental change.
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Affiliation(s)
| | - Greg M Walter
- School of Biological Sciences, Monash University, Melbourne, Victoria, Australia
| | - Keyne Monro
- School of Biological Sciences, Monash University, Melbourne, Victoria, Australia
| | - André N Alves
- School of Biological Sciences, Monash University, Melbourne, Victoria, Australia
| | - Christen K Mirth
- School of Biological Sciences, Monash University, Melbourne, Victoria, Australia
| | - Carla M Sgrò
- School of Biological Sciences, Monash University, Melbourne, Victoria, Australia
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5
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Summers TC, Ord TJ. Signal detection shapes ornament allometry in functionally convergent Caribbean Anolis and Southeast Asian Draco lizards. J Evol Biol 2022; 35:1508-1523. [PMID: 36177770 PMCID: PMC9828585 DOI: 10.1111/jeb.14102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Revised: 07/10/2022] [Accepted: 07/21/2022] [Indexed: 01/12/2023]
Abstract
Visual ornaments have long been assumed to evolve hyper-allometry as an outcome of sexual selection. Yet growing evidence suggests many sexually selected morphologies can exhibit other scaling patterns with body size, including hypo-allometry. The large conspicuous throat fan, or dewlap, of arboreal Caribbean Anolis lizards was one ornament previously thought to conform to the classical expectation of hyper-allometry. We re-evaluated this classic example alongside a second arboreal group of lizards that has also independently evolved a functionally equivalent dewlap, the Southeast Asian Draco lizards. Across multiple closely related species in both genera, the Anolis and Draco dewlaps were either isometric or had hypo-allometric scaling patterns. In the case of the Anolis dewlap, variation in dewlap allometry was predicted by the distance of conspecifics and the light environment in which the dewlap was typically viewed. Signal efficacy, therefore, appears to have driven the evolution of hypo-allometry in what was originally thought to be a sexually selected ornament with hyper-allometry. Our findings suggest that other elaborate morphological structures used in social communication might similarly exhibit isometric or hypo-allometric scaling patterns because of environmental constraints on signal detection.
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Affiliation(s)
- Thomas C. Summers
- Evolution and Ecology Research Centre, and the School of Biological, Earth and Environmental SciencesUniversity of New South WalesKensingtonNew South WalesAustralia
| | - Terry J. Ord
- Evolution and Ecology Research Centre, and the School of Biological, Earth and Environmental SciencesUniversity of New South WalesKensingtonNew South WalesAustralia
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6
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Abstract
Abstract
Background
Organisms show an incredibly diverse array of body and organ shapes that are both unique to their taxon and important for adapting to their environment. Achieving these specific shapes involves coordinating the many processes that transform single cells into complex organs, and regulating their growth so that they can function within a fully-formed body.
Main text
Conceptually, body and organ shape can be separated in two categories, although in practice these categories need not be mutually exclusive. Body shape results from the extent to which organs, or parts of organs, grow relative to each other. The patterns of relative organ size are characterized using allometry. Organ shape, on the other hand, is defined as the geometric features of an organ’s component parts excluding its size. Characterization of organ shape is frequently described by the relative position of homologous features, known as landmarks, distributed throughout the organ. These descriptions fall into the domain of geometric morphometrics.
Conclusion
In this review, we discuss the methods of characterizing body and organ shape, the developmental programs thought to underlie each, highlight when and how the mechanisms regulating body and organ shape might overlap, and provide our perspective on future avenues of research.
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7
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Del Sol JF, Hongo Y, Boisseau RP, Berman GH, Allen CE, Emlen DJ. Population differences in the strength of sexual selection match relative weapon size in the Japanese rhinoceros beetle, Trypoxylus dichotomus (Coleoptera: Scarabaeidae)†. Evolution 2020; 75:394-413. [PMID: 33009663 DOI: 10.1111/evo.14101] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2020] [Revised: 07/07/2020] [Accepted: 09/07/2020] [Indexed: 12/21/2022]
Abstract
Exaggerated weapons of sexual selection often diverge more rapidly and dramatically than other body parts, suggesting that relevant agents of selection may be discernible in contemporary populations. We examined the ecology, reproductive behavior, and strength of sexual selection on horn length in five recently diverged rhinoceros beetle (Trypoxylus dichotomus) populations that differ in relative horn size. Males with longer horns were better at winning fights in all locations, but the link between winning fights and mating success differed such that selection favored large males with long horns at the two long-horned populations, but was relaxed or nonexistent at the populations with relatively shorter horns. Observations of local habitat conditions and breeding ecology point to shifts in the relative abundance of feeding territories as the most likely cause of population differences in selection on male weapon size in this species. Comparisons of ecological conditions and selection strength across populations offer critical first steps toward meaningfully linking mating system dynamics, selection patterns, and diversity in sexually selected traits.
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Affiliation(s)
- Jillian F Del Sol
- Division of Biological Sciences, University of Montana, Missoula, Montana, 59812
| | - Yoshihito Hongo
- Department of Life Sciences, Ritsumeikan University, Kyoto, 603-8577, Japan
| | - Romain P Boisseau
- Division of Biological Sciences, University of Montana, Missoula, Montana, 59812
| | - Gabriella H Berman
- Division of Biological Sciences, University of Montana, Missoula, Montana, 59812
| | - Cerisse E Allen
- Division of Biological Sciences, University of Montana, Missoula, Montana, 59812
| | - Douglas J Emlen
- Division of Biological Sciences, University of Montana, Missoula, Montana, 59812
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8
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Houle D, Jones LT, Fortune R, Sztepanacz JL. Why does allometry evolve so slowly? Integr Comp Biol 2020; 59:1429-1440. [PMID: 31198948 DOI: 10.1093/icb/icz099] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Morphological allometry is striking due to its evolutionary conservatism, making it an example of a certain sort of evolutionary stasis. Organisms that vary in size, whether for developmental, environmental, or evolutionary reasons, adopt shapes that are predictable from that size alone. There are two major hypotheses to explain this. It may be that natural selection strongly favors each allometric pattern, or that organisms lack the development and genetic capacity to produce variant shapes for selection to act on. Using a high-throughput system for measuring the size and shape of Drosophila wings, we documented an allometric pattern that has been virtually unchanged for 40 million years. We performed an artificial selection experiment on the static allometric slope within one species. In just 26 generations, we were able to increase the slope from 1.1 to 1.4, and decrease it to 0.8. Once artificial selection was suspended, the slope rapidly evolved back to a value near the initial static slope. This result decisively rules out the hypothesis that allometry is preserved due to a lack of genetic variation, and provides evidence that natural selection acts to maintain allometric relationships. On the other hand, it seems implausible that selection on allometry in the wing alone could be sufficiently strong to maintain static allometries over millions of years. This suggests that a potential explanation for stasis is selection on a potentially large number of pleiotropic effects. This seems likely in the case of allometry, as the sizes of all parts of the body may be altered when the allometric slope of one body part is changed. Unfortunately, hypotheses about pleiotropy have been very difficult to test. We lay out an approach to begin the systematic study of pleiotropic effects using genetic manipulations and high-throughput phenotyping.
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Affiliation(s)
- David Houle
- Department of Biology, Florida State University, Tallahassee, FL, USA
| | - Luke T Jones
- Department of Biology, Florida State University, Tallahassee, FL, USA
| | - Ryan Fortune
- Department of Biology, Florida State University, Tallahassee, FL, USA
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9
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Varón-González C, Fraimout A, Delapré A, Debat V, Cornette R. Limited thermal plasticity and geographical divergence in the ovipositor of Drosophila suzukii. ROYAL SOCIETY OPEN SCIENCE 2020; 7:191577. [PMID: 32218976 PMCID: PMC7029920 DOI: 10.1098/rsos.191577] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/23/2019] [Accepted: 11/27/2019] [Indexed: 06/10/2023]
Abstract
Phenotypic plasticity has been repeatedly suggested to facilitate adaptation to new environmental conditions, as in invasions. Here, we investigate this possibility by focusing on the worldwide invasion of Drosophila suzukii: an invasive species that has rapidly colonized all continents over the last decade. This species is characterized by a highly developed ovipositor, allowing females to lay eggs through the skin of ripe fruits. Using a novel approach based on the combined use of scanning electron microscopy and photogrammetry, we quantified the ovipositor size and three-dimensional shape, contrasting invasive and native populations raised at three different developmental temperatures. We found a small but significant effect of temperature and geographical origin on the ovipositor shape, showing the occurrence of both geographical differentiation and plasticity to temperature. The shape reaction norms are in turn strikingly similar among populations, suggesting very little difference in shape plasticity among invasive and native populations, and therefore rejecting the hypothesis of a particular role for the plasticity of the ovipositor in the invasion success. Overall, the ovipositor shape seems to be a fairly robust trait, indicative of stabilizing selection. The large performance spectrum rather than the flexibility of the ovipositor would thus contribute to the success of D. suzukii worldwide invasion.
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Affiliation(s)
- Ceferino Varón-González
- Institut de Systématique, Evolution, Biodiversité (ISYEB), Muséum National d'Histoire Naturelle, CNRS, Sorbonne Université, EPHE, Université des Antilles, 57 rue Cuvier, CP 50, 75005 Paris, France
| | - Antoine Fraimout
- Centre de Biologie pour la Gestion des Populations, UMR CBGP, INRA, CIRAD, IRD, Montpellier SupAgro, University of Montpellier, 755 avenue du Campus Agropolis CS 30016, 34988 Montferrier sur Lez cedex, France
| | - Arnaud Delapré
- Institut de Systématique, Evolution, Biodiversité (ISYEB), Muséum National d'Histoire Naturelle, CNRS, Sorbonne Université, EPHE, Université des Antilles, 57 rue Cuvier, CP 50, 75005 Paris, France
| | - Vincent Debat
- Institut de Systématique, Evolution, Biodiversité (ISYEB), Muséum National d'Histoire Naturelle, CNRS, Sorbonne Université, EPHE, Université des Antilles, 57 rue Cuvier, CP 50, 75005 Paris, France
| | - Raphaël Cornette
- Institut de Systématique, Evolution, Biodiversité (ISYEB), Muséum National d'Histoire Naturelle, CNRS, Sorbonne Université, EPHE, Université des Antilles, 57 rue Cuvier, CP 50, 75005 Paris, France
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10
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Dreyer AP, Shingleton AW. Insulin-insensitivity of male genitalia maintains reproductive success in Drosophila. Biol Lett 2019; 15:20190057. [PMID: 31088279 DOI: 10.1098/rsbl.2019.0057] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
For most arthropod species, male genital size is relatively implastic in response to variation in developmental nutrition, such that the genitals in large well-fed males are similar in size to those in small poorly-fed males. In Drosophila melanogaster, reduced nutritional plasticity of the male genitalia is a consequence of low insulin sensitivity through a tissue-specific reduction in the expression of FOXO, a negative growth regulator . Despite an understanding of the proximate developmental mechanisms regulating organ size, the ultimate evolutionary mechanisms that may have led to reduced FOXO expression in the genitalia have not been fully elucidated. Here we show that restoring FOXO activity in the developing genitalia reduces the male genital size and decreases various aspects of male reproductive success. These data support the hypothesis that sexual selection has acted on the male genitalia to limit their nutritional plasticity through a reduction in FOXO expression, linking proximate with ultimate mechanisms of genital evolution.
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Affiliation(s)
- Austin P Dreyer
- 1 Department of Biology, Loyola University of Chicago , 1050 West Sheridan Road, Chicago, IL 60660 , USA
| | - Alexander W Shingleton
- 2 Department of Biological Sciences, University of Illinois Chicago , 845 West Taylor Street, Chicago, IL 60607 , USA
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11
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Frankino WA, Bakota E, Dworkin I, Wilkinson GS, Wolf JB, Shingleton AW. Individual Cryptic Scaling Relationships and the Evolution of Animal Form. Integr Comp Biol 2019; 59:1411-1428. [PMID: 31364716 PMCID: PMC6863759 DOI: 10.1093/icb/icz135] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Artificial selection offers a powerful tool for the exploration of how selection and development shape the evolution of morphological scaling relationships. An emerging approach models the expression and evolution of morphological scaling relationships as a function of variation among individuals in the developmental mechanisms that regulate trait growth. These models posit the existence of genotype-specific morphological scaling relationships that are unseen or "cryptic." Within-population allelic variation at growth-regulating loci determines how these individual cryptic scaling relationships are distributed, and exposure to environmental factors that affect growth determines the size phenotype expressed by each individual on their cryptic, genotype-specific scaling relationship. These models reveal that evolution of the intercept and slope of the population-level static allometry is determined, often in counterintuitive ways, largely by the shape of the distribution of these underlying individual-level scaling relationships. Here we review this modeling framework and present the wing-body size individual cryptic scaling relationships from a population of Drosophila melanogaster. To determine how these models might inform interpretation of published work on scaling relationship evolution, we review studies where artificial selection was applied to alter the parameters of population-level static allometries. Finally, motivated by our review, we outline areas in need of empirical work and describe a research program to address these topics; the approach includes describing the distribution of individual cryptic scaling relationships across populations and environments, empirical testing of the model's predictions, and determining the effects of environmental heterogeneity on realized trait distributions and how this affects allometry evolution.
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Affiliation(s)
- W Anthony Frankino
- Department of Biology and Biochemistry, University of Houston, Houston, TX 77204-5001, USA
| | - Eric Bakota
- Department of Biology and Biochemistry, University of Houston, Houston, TX 77204-5001, USA
| | - Ian Dworkin
- Department of Biology, McMaster University, Hamilton, Ontario, Canada L9H 6X9
| | - Gerald S Wilkinson
- Department of Biology, University of Maryland, College Park, MD 20742, USA
| | - Jason B Wolf
- Milner Centre for Evolution and Department of Biology and Biochemistry, University of Bath, Bath BA2 7AY, UK
| | - Alexander W Shingleton
- Department of Biological Sciences, University of Illinois at Chicago, Chicago, IL 60607, USA
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12
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Casasa S, Moczek AP. Evolution of, and via, Developmental Plasticity: Insights through the Study of Scaling Relationships. Integr Comp Biol 2019; 59:1346-1355. [PMID: 31147701 DOI: 10.1093/icb/icz086] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Scaling relationships emerge from differential growth of body parts relative to each other. As such, scaling relationships are at least in part the product of developmental plasticity. While some of the developmental genetic mechanisms underlying scaling relationships are starting to be elucidated, how these mechanisms evolve and give rise to the enormous diversity of allometric scaling observed in nature is less understood. Furthermore, developmental plasticity has itself been proposed as a mechanism that facilitates adaptation and diversification, yet its role in the developmental evolution of scaling relationships remains largely unknown. In this review, we first explore how the mechanisms of scaling relationships have evolved. We primarily focus on insect development and review how pathway components and pathway interactions have evolved across taxa to regulate scaling relationships across diverse traits. We then discuss the potential role of developmental plasticity in the evolution of scaling relationships. Specifically, we address the potential role of allometric plasticity and cryptic genetic variation in allometry in facilitating divergence via genetic accommodation. Collectively, in this article, we aim to bring together two aspects of developmental plasticity: the mechanistic underpinnings of scaling relationships and their evolution, and the potential role that plasticity plays in the evolutionary diversification of scaling relationships.
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Affiliation(s)
- Sofia Casasa
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
| | - Armin P Moczek
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
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13
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Shingleton AW. Which Line to Follow? The Utility of Different Line-Fitting Methods to Capture the Mechanism of Morphological Scaling. Integr Comp Biol 2019; 59:1399-1410. [PMID: 31120495 DOI: 10.1093/icb/icz059] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Bivariate morphological scaling relationships describe how the sizes of two traits co-vary among adults in a population. In as much as body shape is reflected by the relative size of various traits within the body, morphological scaling relationships capture how body shape varies with size, and therefore have been used widely as descriptors of morphological variation within and among species. Despite their extensive use, there is continuing discussion over which line-fitting method should be used to describe linear morphological scaling relationships. Here I argue that the "best" line-fitting method is the one that most accurately captures the proximate developmental mechanisms that generate scaling relationships. Using mathematical modeling, I show that the "best" line-fitting method depends on the pattern of variation among individuals in the developmental mechanisms that regulate trait size. For Drosophila traits, this pattern of variation indicates that major axis regression is the best line-fitting method. For morphological traits in other animals, however, other line-fitting methods may be more accurate. I provide a simple web-based application for researchers to explore how different line-fitting methods perform on their own morphological data.
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Affiliation(s)
- Alexander W Shingleton
- Department of Biological Sciences, University of Illinois at Chicago, Chicago, IL 60607, USA
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14
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Variation in an Extreme Weapon: Horn Performance Differences across Rhinoceros Beetle ( Trypoxylus dichotomus) Populations. INSECTS 2019; 10:insects10100346. [PMID: 31618906 PMCID: PMC6835817 DOI: 10.3390/insects10100346] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Revised: 10/01/2019] [Accepted: 10/03/2019] [Indexed: 01/02/2023]
Abstract
Japanese rhinoceros beetle (Trypoxylus dichotomus) males have exaggerated head horns that they use as weapons in combat over reproductive opportunities. In these contests, there is an advantage to having a longer horn, and there seems to be little cost to horn exaggeration. However, populations vary in the amount of horn exaggeration across this widespread species. Here, we examine four populations and quantify scaling and functional morphology of the horn. We then measure force production by the horn system in a combat-relevant movement. We find that not only does horn length vary among populations, but allometry of lever mechanics and force production varies in a complex way. For instance, some beetle populations make relatively long horns, but exert relatively low forces. Other populations make shorter horns and produce higher forces during fights. We suggest that this performance variation could be associated with differences in the intensity or type of sexual selection across the species.
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McKenna KZ, Tao D, Nijhout HF. Exploring the Role of Insulin Signaling in Relative Growth: A Case Study on Wing-Body Scaling in Lepidoptera. Integr Comp Biol 2019; 59:1324-1337. [DOI: 10.1093/icb/icz080] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Abstract
Adult forms emerge from the relative growth of the body and its parts. Each appendage and organ has a unique pattern of growth that influences the size and shape it attains. This produces adult size relationships referred to as static allometries, which have received a great amount of attention in evolutionary and developmental biology. However, many questions remain unanswered, for example: What sorts of developmental processes coordinate growth? And how do these processes change given variation in body size? It has become increasingly clear that nutrition is one of the strongest influences on size relationships. In insects, nutrition acts via insulin/TOR signaling to facilitate inter- and intra-specific variation in body size and appendage size. Yet, the mechanism by which insulin signaling influences the scaling of growth remains unclear. Here we will discuss the potential roles of insulin signaling in wing-body scaling in Lepidoptera. We analyzed the growth of wings in animals reared on different diet qualities that induce a range of body sizes not normally present in our laboratory populations. By growing wings in tissue culture, we survey how perturbation and stimulation of insulin/TOR signaling influences wing growth. To conclude, we will discuss the implications of our findings for the development and evolution of organismal form.
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Affiliation(s)
| | - Della Tao
- Department of Biology, Duke University, Durham, NC 27708, USA
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Kaliontzopoulou A, Pinho C, Martínez-Freiría F. Where does diversity come from? Linking geographical patterns of morphological, genetic, and environmental variation in wall lizards. BMC Evol Biol 2018; 18:124. [PMID: 30134828 PMCID: PMC6113677 DOI: 10.1186/s12862-018-1237-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2018] [Accepted: 08/09/2018] [Indexed: 02/08/2023] Open
Abstract
BACKGROUND Understanding how phenotypic variation scales from individuals, through populations, up to species, and how it relates to genetic and environmental factors, is essential for deciphering the evolutionary mechanisms that drive biodiversity. We used two species of Podarcis wall lizards to test whether phenotypic diversity within and divergence across populations follow concordant patterns, and to examine how phenotypic variation responds to genetic and environmental variability across different hierarchical levels of biological organization, in an explicit geographic framework. RESULTS We found a general concordance of phenotypic variation across hierarchical levels (i.e. individuals and populations). However, we also found that within-population diversity does not exhibit a coherent geographic structure for most traits, while among-population divergence does, suggesting that different mechanisms may underlie the generation of diversity at these two levels. Furthermore, the association of phenotypic variation with genetic and environmental factors varied extensively between hierarchical levels and across traits, hampering the identification of simple rules to explain what yields diversity. CONCLUSIONS Our results in some cases comply with general ecological and evolutionary predictions, but in others they are difficult to explain in the geographic framework used, suggesting that habitat characteristics and other regulatory mechanisms may have a more substantial contribution in shaping phenotypic diversity.
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Affiliation(s)
- Antigoni Kaliontzopoulou
- CIBIO/InBIO Research Centre in Biodiversity and Genetic Resources, University of Porto, Campus de Vairão, Rua Padre Armando Quintas, N° 7.4485-661 Vairão, Vila do Conde, Portugal.
| | - Catarina Pinho
- CIBIO/InBIO Research Centre in Biodiversity and Genetic Resources, University of Porto, Campus de Vairão, Rua Padre Armando Quintas, N° 7.4485-661 Vairão, Vila do Conde, Portugal
| | - Fernando Martínez-Freiría
- CIBIO/InBIO Research Centre in Biodiversity and Genetic Resources, University of Porto, Campus de Vairão, Rua Padre Armando Quintas, N° 7.4485-661 Vairão, Vila do Conde, Portugal
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O'Brien DM, Katsuki M, Emlen DJ. Selection on an extreme weapon in the frog‐legged leaf beetle (
Sagra femorata
). Evolution 2017; 71:2584-2598. [DOI: 10.1111/evo.13336] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Revised: 07/21/2017] [Accepted: 08/10/2017] [Indexed: 12/15/2022]
Affiliation(s)
- Devin M. O'Brien
- Division of Biological Sciences University of Montana Missoula Montana
| | - Masako Katsuki
- Department of Arts and Sciences University of Tokyo Tokyo Japan
| | - Douglas J. Emlen
- Division of Biological Sciences University of Montana Missoula Montana
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Shingleton AW, Masandika JR, Thorsen LS, Zhu Y, Mirth CK. The sex-specific effects of diet quality versus quantity on morphology in Drosophila melanogaster. ROYAL SOCIETY OPEN SCIENCE 2017; 4:170375. [PMID: 28989746 PMCID: PMC5627086 DOI: 10.1098/rsos.170375] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/26/2017] [Accepted: 08/03/2017] [Indexed: 06/07/2023]
Abstract
Variation in the quality and quantity of nutrition is a major contributor to phenotypic variation in animal populations. Although we know much of how dietary restriction impacts phenotype, and of the molecular-genetic and physiological mechanisms that underlie this response, we know much less of the effects of dietary imbalance. Specifically, although dietary imbalance and restriction both reduce overall body size, it is unclear whether both have the same effect on the size of individual traits. Here, we use the fruit fly Drosophila melanogaster to explore the effect of dietary food versus protein-to-carbohydrate ratio on body proportion and trait size. Our results indicate that body proportion and trait size respond differently to changes in diet quantity (food concentration) versus diet quality (protein-to-carbohydrate ratio), and that these effects are sex specific. While these differences suggest that Drosophila use at least partially distinct developmental mechanisms to respond to diet quality versus quantity, further analysis indicates that the responses can be largely explained by the independent and contrasting effects of protein and carbohydrate concentration on trait size. Our data highlight the importance of considering macronutrient composition when elucidating the effect of nutrition on trait size, at the levels of both morphology and developmental physiology.
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Affiliation(s)
| | | | - Lily S. Thorsen
- Department of Biology, Lake Forest College, Lake Forest, IL 60045, USA
| | - Yuqing Zhu
- Department of Biology, Lake Forest College, Lake Forest, IL 60045, USA
- Division of Biology and Biomedical Sciences, Washington University, St Louis, MO 63110, USA
| | - Christen K. Mirth
- School of Biological Sciences, Monash University, Clayton, Victoria, Australia
- Instituto Gulbenkian de Ciência, Rua da Quinta Grande 6, 2780-156 Oeiras, Portugal
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