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Gao JJ, Barmina O, Thompson A, Kim BY, Suvorov A, Tanaka K, Watabe H, Toda MJ, Chen JM, Katoh TK, Kopp A. Secondary reversion to sexual monomorphism associated with tissue-specific loss of doublesex expression. Evolution 2022; 76:2089-2104. [PMID: 35841603 DOI: 10.1111/evo.14564] [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] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2022] [Revised: 06/23/2022] [Accepted: 06/27/2022] [Indexed: 01/22/2023]
Abstract
Animal evolution is characterized by frequent turnover of sexually dimorphic traits-new sex-specific characters are gained, and some ancestral sex-specific characters are lost, in many lineages. In insects, sexual differentiation is predominantly cell autonomous and depends on the expression of the doublesex (dsx) transcription factor. In most cases, cells that transcribe dsx have the potential to undergo sex-specific differentiation, while those that lack dsx expression do not. Consistent with this mode of development, comparative research has shown that the origin of new sex-specific traits can be associated with the origin of new spatial domains of dsx expression. In this report, we examine the opposite situation-a secondary loss of the sex comb, a male-specific grasping structure that develops on the front legs of some drosophilid species. We show that while the origin of the sex comb is linked to an evolutionary gain of dsx expression in the leg, sex comb loss in a newly identified species of Lordiphosa (Drosophilidae) is associated with a secondary loss of dsx expression. We discuss how the developmental control of sexual dimorphism affects the mechanisms by which sex-specific traits can evolve.
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Affiliation(s)
- Jian-Jun Gao
- Yunnan Key Laboratory of Plant Reproductive Adaptation and Evolutionary Ecology, Yunnan University, China.,State Key Laboratory for Conservation and Utilization of Bioresources in Yunnan, Yunnan University, China
| | - Olga Barmina
- Department of Evolution and Ecology, University of California Davis, Davis, CA, 95616, USA
| | - Ammon Thompson
- Department of Evolution and Ecology, University of California Davis, Davis, CA, 95616, USA
| | - Bernard Y Kim
- Department of Biology, Stanford University, Stanford, CA, 94305, USA
| | - Anton Suvorov
- Department of Genetics, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Kohtaro Tanaka
- Department of Evolution and Ecology, University of California Davis, Davis, CA, 95616, USA
| | - Hideaki Watabe
- The Hokkaido University Museum, Kita-10, Nishi-8, Kitaku, Sapporo, 060-0810, Japan
| | - Masanori J Toda
- The Hokkaido University Museum, Kita-10, Nishi-8, Kitaku, Sapporo, 060-0810, Japan
| | - Ji-Min Chen
- State Key Laboratory for Conservation and Utilization of Bioresources in Yunnan, Yunnan University, China
| | - Takehiro K Katoh
- Yunnan Key Laboratory of Plant Reproductive Adaptation and Evolutionary Ecology, Yunnan University, China
| | - Artyom Kopp
- Department of Evolution and Ecology, University of California Davis, Davis, CA, 95616, USA
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Mittleman BE, Manzano-Winkler B, Hall JB, Korunes KL, Noor MAF. The large X-effect on secondary sexual characters and the genetics of variation in sex comb tooth number in Drosophila subobscura. Ecol Evol 2016; 7:533-540. [PMID: 28116050 PMCID: PMC5243774 DOI: 10.1002/ece3.2634] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [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: 10/12/2016] [Revised: 10/21/2016] [Accepted: 10/24/2016] [Indexed: 02/05/2023] Open
Abstract
Genetic studies of secondary sexual traits provide insights into whether and how selection drove their divergence among populations, and these studies often focus on the fraction of variation attributable to genes on the X-chromosome. However, such studies may sometimes misinterpret the amount of variation attributable to the X-chromosome if using only simple reciprocal F1 crosses, or they may presume sexual selection has affected the observed phenotypic variation. We examined the genetics of a secondary sexual trait, male sex comb size, in Drosophila subobscura. This species bears unusually large sex combs for its species group, and therefore, this trait may be a good candidate for having been affected by natural or sexual selection. We observed significant heritable variation in number of teeth of the distal sex comb across strains. While reciprocal F1 crosses seemed to implicate a disproportionate X-chromosome effect, further examination in the F2 progeny showed that transgressive autosomal effects inflated the estimate of variation associated with the X-chromosome in the F1. Instead, the X-chromosome appears to confer the smallest contribution of all major chromosomes to the observed phenotypic variation. Further, we failed to detect effects on copulation latency or duration associated with the observed phenotypic variation. Overall, this study presents an examination of the genetics underlying segregating phenotypic variation within species and illustrates two common pitfalls associated with some past studies of the genetic basis of secondary sexual traits.
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Maraqa MS, Griffin R, Sharma MD, Wilson AJ, Hunt J, Hosken DJ, House CM. Constrained evolution of the sex comb in Drosophila simulans. J Evol Biol 2016; 30:388-400. [PMID: 27859860 PMCID: PMC5324616 DOI: 10.1111/jeb.13015] [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] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2016] [Revised: 11/03/2016] [Accepted: 11/07/2016] [Indexed: 11/30/2022]
Abstract
Male fitness is dependent on sexual traits that influence mate acquisition (precopulatory sexual selection) and paternity (post-copulatory sexual selection), and although many studies have documented the form of selection in one or the other of these arenas, fewer have done it for both. Nonetheless, it appears that the dominant form of sexual selection is directional, although theoretically, populations should converge on peaks in the fitness surface, where selection is stabilizing. Many factors, however, can prevent populations from reaching adaptive peaks. Genetic constraints can be important if they prevent the development of highest fitness phenotypes, as can the direction of selection if it reverses across episodes of selection. In this study, we examine the evidence that these processes influence the evolution of the multivariate sex comb morphology of male Drosophila simulans. To do this, we conduct a quantitative genetic study together with a multivariate selection analysis to infer how the genetic architecture and selection interact. We find abundant genetic variance and covariance in elements of the sex comb. However, there was little evidence for directional selection in either arena. Significant nonlinear selection was detected prior to copulation when males were mated to nonvirgin females, and post-copulation during sperm offence (again with males mated to nonvirgins). Thus, contrary to our predictions, the evolution of the D. simulans sex comb is limited neither by genetic constraints nor by antagonistic selection between pre- and post-copulatory arenas, but nonlinear selection on the multivariate phenotype may prevent sex combs from evolving to reach some fitness maximizing optima.
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Affiliation(s)
- M S Maraqa
- Centre for Ecology and Conservation, College of Life & Environmental Sciences, University of Exeter, Cornwall, UK
| | - R Griffin
- Department of Biology, University of Turku, Turun Yliopisto, Finland
| | - M D Sharma
- Centre for Ecology and Conservation, College of Life & Environmental Sciences, University of Exeter, Cornwall, UK
| | - A J Wilson
- Centre for Ecology and Conservation, College of Life & Environmental Sciences, University of Exeter, Cornwall, UK
| | - J Hunt
- School of Science and Health, Western Sydney University, Penrith, NSW, Australia
| | - D J Hosken
- Centre for Ecology and Conservation, College of Life & Environmental Sciences, University of Exeter, Cornwall, UK
| | - C M House
- School of Science and Health, Western Sydney University, Penrith, NSW, Australia
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Travers LM, Garcia-Gonzalez F, Simmons LW. Genetic variation but weak genetic covariation between pre- and post-copulatory episodes of sexual selection in Drosophila melanogaster. J Evol Biol 2016; 29:1535-52. [PMID: 27159063 DOI: 10.1111/jeb.12890] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [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: 01/22/2016] [Revised: 04/20/2016] [Accepted: 04/29/2016] [Indexed: 12/16/2022]
Abstract
When females mate polyandrously, male reproductive success depends both on the male's ability to attain matings and on his ability to outcompete rival males in the fertilization of ova post-copulation. Increased investment in ejaculate components may trade off with investment in precopulatory traits due to resource allocation. Alternatively, pre- and post-copulatory traits could be positively related if individuals can afford to invest heavily in traits advantageous at both episodes of selection. There is empirical evidence for both positive and negative associations between pre- and post-copulatory episodes, but little is known about the genetic basis of these correlations. In this study, we measured morphological, chemical and behavioural precopulatory male traits and investigated their relationship with measures of male fitness (male mating success, remating inhibition and offensive sperm competitiveness) across 40 isofemale lines of Drosophila melanogaster. We found significant variation among isofemale lines, indicating a genetic basis for most of the traits investigated. However, we found weak evidence for genetic correlations between precopulatory traits and our indices of male fitness. Moreover, pre- and post-copulatory episodes of selection were uncorrelated, suggesting selection may act independently at the different episodes to maximize male reproductive success.
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Affiliation(s)
- L M Travers
- Centre for Evolutionary Biology, School of Animal Biology (M092), The University of Western Australia, Crawley, WA, Australia
| | - F Garcia-Gonzalez
- Centre for Evolutionary Biology, School of Animal Biology (M092), The University of Western Australia, Crawley, WA, Australia.,Doñana Biological Station, Spanish Research Council CSIC, Isla de la Cartuja, Seville, Spain
| | - L W Simmons
- Centre for Evolutionary Biology, School of Animal Biology (M092), The University of Western Australia, Crawley, WA, Australia
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Abstract
The dominant autosomal gene Msc (Multiple sex combs) of Drosophila causes the appearance of sex combs on the second and third legs and a reduction of size of sex combs on first legs. The effect of Msc was studied in mosaic flies in which non-Msc spots were present on a Msc background. Mosaics were due to somatic crossing-over induced by x-rays. Analysis of mosaics suggested autonomy of the action of Msc, provided that the somatic crossing-over occurs less frequently proximally to the Msc locus than distally. This unusual ratio of somatic crossing-over was confirmed by a separate experiment with the gene Kinked, whose locus is very close to Msc.
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