1
|
Petino Zappala MA, Satorre I, Fanara JJ. Stage- and thermal-specific genetic architecture for preadult viability in natural populations of Drosophila melanogaster. J Evol Biol 2019; 32:683-693. [PMID: 30924196 DOI: 10.1111/jeb.13448] [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: 11/13/2018] [Revised: 03/18/2019] [Accepted: 03/20/2019] [Indexed: 11/29/2022]
Abstract
Studying the processes affecting variation for preadult viability is essential to understand the evolutionary trajectories followed by natural populations. This task requires focusing on the complex nature of the phenotype-genotype relationship by taking into account usually neglected aspects of the phenotype and recognizing the modularity between different ontogenetic stages. Here, we describe phenotypic variability for viability during the larval and pupal stages in lines derived from three natural populations of Drosophila melanogaster, as well as the variability for phenotypic plasticity and canalization at two different rearing temperatures. The results indicate that the three populations present significant phenotypic differences for preadult viability. Furthermore, distinct aspects of the phenotype (means, plasticity, canalization, plasticity of canalization) are affected by different genetic bases underlying changes in viability in a stage- and environment-specific manner. These findings explain the generalized maintenance of genetic variability for this fitness trait.
Collapse
Affiliation(s)
- María Alejandra Petino Zappala
- Departamento de Ecologia, Genetica y Evolucion - IEGEBA (CONICET-UBA), Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, CABA, Argentina
| | - Ignacio Satorre
- Departamento de Ecologia, Genetica y Evolucion - IEGEBA (CONICET-UBA), Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, CABA, Argentina
| | - Juan José Fanara
- Departamento de Ecologia, Genetica y Evolucion - IEGEBA (CONICET-UBA), Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, CABA, Argentina
| |
Collapse
|
2
|
Study of Natural Genetic Variation in Early Fitness Traits Reveals Decoupling Between Larval and Pupal Developmental Time in Drosophila melanogaster. Evol Biol 2018. [DOI: 10.1007/s11692-018-9461-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
|
3
|
Yohe LR, Brand P. Evolutionary ecology of chemosensation and its role in sensory drive. Curr Zool 2018; 64:525-533. [PMID: 30108633 PMCID: PMC6084603 DOI: 10.1093/cz/zoy048] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2018] [Accepted: 06/20/2018] [Indexed: 11/14/2022] Open
Abstract
All behaviors of an organism are rooted in sensory processing of signals from its environment, and natural selection shapes sensory adaptations to ensure successful detection of cues that maximize fitness. Sensory drive, or divergent selection for efficient signal transmission among heterogeneous environments, has been a useful hypothesis for describing sensory adaptations, but its current scope has primarily focused on visual and acoustic sensory modalities. Chemosensation, the most widespread sensory modality in animals that includes the senses of smell and taste, is characterized by rapid evolution and has been linked to sensory adaptations to new environments in numerous lineages. Yet, olfaction and gustation have been largely underappreciated in light of the sensory drive hypothesis. Here, we examine why chemosensory systems have been overlooked and discuss the potential of chemosensation to shed new insight on the sensory drive hypothesis and vice versa. We provide suggestions for developing a framework to better incorporate studies of chemosensory adaptation that have the potential to shape a more complete, coherent, and holistic interpretation of the sensory drive.
Collapse
Affiliation(s)
- Laurel R Yohe
- Department of Ecology and Evolution, Stony Brook University, Stony Brook, NY, USA
- Department of Geology & Geophysics, Yale University, New Haven, CT, USA
| | - Philipp Brand
- Department of Evolution and Ecology, Center for Population Biology, University of California, Davis, CA, USA
| | | |
Collapse
|
4
|
Changes Across Development Influence Visible and Cryptic Natural Variation of Drosophila melanogaster Olfactory Response. Evol Biol 2015. [DOI: 10.1007/s11692-015-9352-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
5
|
Du Y, Feng B, Li H, Liu C, Zeng J, Pan L, Yu Q. Field Evaluation of Agrotis ipsilon (Lepidoptera: Noctuidae) Pheromone Blends and Their Application to Monitoring Moth Populations in China. ENVIRONMENTAL ENTOMOLOGY 2015; 44:724-733. [PMID: 26313979 DOI: 10.1093/ee/nvv043] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2014] [Accepted: 03/11/2015] [Indexed: 06/04/2023]
Abstract
The attractiveness of a series of mixtures of (Z)-7-dodecenyl acetate (Z7-12:Ac), (Z)-9-tetradecenyl acetate (Z9-14:Ac), and (Z)-11-hexadecenyl acetate (Z11-16:Ac), the Agrotis ipsilon (Hufnagel) (Lepidoptera: Noctuidae) pheromone, were evaluated in four locations in China. The ternary blend of Z7-12:Ac, Z9-14:Ac, and Z11-16:Ac was the complete pheromone blend for A. ipsilon and the ratio of Z7-12:Ac and Z9-14:Ac was optimal at 3:1. The most attractive ratio of Z11-16:Ac to the other components depended on geographic location. The optimal ratio was 3:1:6 in Yunnan and Shanxi, 3:1:2 in Sichuan and ranged from 3:1:2 to 3:1:12 in Shanghai, which differs significantly from the ratio of 3:1:16 in Japan. The dose of the blend in the pheromone lure influenced attractiveness to male moths and was related to the temperature in the test locations. Attractiveness of sugar-acetic acid-baited and pheromone-baited traps to male and female moths was different before and after the start of flowering of the oilseed rape crop; large numbers of female moths were attracted to sugar-acetic acid traps before flowering but none after flowering had started. This was similar for male moths and there was no synergistic effect when sugar-acetic acid solutions and pheromone were used together. These studies suggest that pheromone trapping based on the blends of three components can be an effective tool to improve the efficiency of monitoring of this pest in China.
Collapse
Affiliation(s)
- Yongjun Du
- Institute of Health and Environmental Ecology, Wenzhou Medical University, University Park at Chashan Town, Wenzhou 325035, China.
| | - Bo Feng
- Institute of Health and Environmental Ecology, Wenzhou Medical University, University Park at Chashan Town, Wenzhou 325035, China
| | | | | | - Juan Zeng
- National Extension and Service Center of Agricultural Technology, Beijing 100125, China
| | - Lieming Pan
- Department of Research and Development, NewCon Inc., Ningbo 315860, China
| | - Qing Yu
- Yunnan Academy of Tobacco Agricultural Sciences, Kunming, Yunnan 650031, China
| |
Collapse
|
6
|
Fallis LC, Fanara JJ, Morgan TJ. Developmental thermal plasticity among Drosophila melanogaster populations. J Evol Biol 2014; 27:557-64. [PMID: 26230171 DOI: 10.1111/jeb.12321] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2013] [Revised: 12/16/2013] [Accepted: 12/17/2013] [Indexed: 11/30/2022]
Abstract
Many biotic and abiotic variables influence the dispersal and distribution of organisms. Temperature has a major role in determining these patterns because it changes daily, seasonally and spatially, and these fluctuations have a significant impact on an organism's behaviour and fitness. Most ecologically relevant phenotypes that are adaptive are also complex and thus they are influenced by many underlying loci that interact with the environment. In this study, we quantified the degree of thermal phenotypic plasticity within and among populations by measuring chill-coma recovery times of lines reared from egg to adult at two different environmental temperatures. We used sixty genotypes from six natural populations of Drosophila melanogaster sampled along a latitudinal gradient in South America. We found significant variation in thermal plasticity both within and among populations. All populations exhibit a cold acclimation response, with flies reared at lower temperatures having increased resistance to cold. We tested a series of environmental parameters against the variation in population mean thermal plasticity and discovered the mean thermal plasticity was significantly correlated with altitude of origin of the population. Pairing our data with previous experiments on viability fitness assays in the same populations in fixed and variable environments suggests an adaptive role of this thermal plasticity in variable laboratory environments. Altogether, these data demonstrate abundant variation in adaptive thermal plasticity within and among populations.
Collapse
Affiliation(s)
- L C Fallis
- The Division of Biology, The Ecological Genomics Institute, Kansas State University, Manhattan, KS, USA
| | - J J Fanara
- Departamento de Ecologia, Genetica y Evolucion-IEGEBA (CONICET-UBA), FCEN, UBA, Buenos Aires, Argentina
| | - T J Morgan
- The Division of Biology, The Ecological Genomics Institute, Kansas State University, Manhattan, KS, USA
| |
Collapse
|
7
|
Latitudinal Variation in Starvation Resistance is Explained by Lipid Content in Natural Populations of Drosophila melanogaster. Evol Biol 2013. [DOI: 10.1007/s11692-013-9235-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
|
8
|
Lavagnino NJ, Arya GH, Korovaichuk A, Fanara JJ. Genetic architecture of olfactory behavior in Drosophila melanogaster: differences and similarities across development. Behav Genet 2013; 43:348-59. [PMID: 23563598 DOI: 10.1007/s10519-013-9592-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2012] [Accepted: 03/18/2013] [Indexed: 01/22/2023]
Abstract
In the holometabolous insect Drosophila melanogaster, genetic, physiological and anatomical aspects of olfaction are well known in the adult stage, while larval stages olfactory behavior has received some attention it has been less studied than its adult counterpart. Most of these studies focus on olfactory receptor (Or) genes that produce peripheral odor recognition. In this paper, through a loss-of-function screen using P-element inserted lines and also by means of expression analyses of larval olfaction candidate genes, we extended the uncovering of the genetic underpinnings of D. melanogaster larval olfactory behavior by demonstrating that larval olfactory behavior is, in addition to Or genes, orchestrated by numerous genes with diverse functions. Also, our results point out that the genetic architecture of olfactory behavior in D. melanogaster presents a dynamic and changing organization across environments and ontogeny.
Collapse
Affiliation(s)
- N J Lavagnino
- Departamento de Ecología, Genética y Evolución, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellón II, 1428, Buenos Aires, Argentina.
| | | | | | | |
Collapse
|
9
|
Fallis LC, Fanara JJ, Morgan TJ. Genetic variation in heat-stress tolerance among South American Drosophila populations. Genetica 2012; 139:1331-7. [PMID: 22350564 DOI: 10.1007/s10709-012-9635-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2011] [Accepted: 02/02/2012] [Indexed: 10/14/2022]
Abstract
Spatial or temporal differences in environmental variables, such as temperature, are ubiquitous in nature and impose stress on organisms. This is especially true for organisms that are isothermal with the environment, such as insects. Understanding the means by which insects respond to temperature and how they will react to novel changes in environmental temperature is important for understanding the adaptive capacity of populations and to predict future trajectories of evolutionary change. The organismal response to heat has been identified as an important environmental variable for insects that can dramatically influence life history characters and geographic range. In the current study we surveyed the amount of variation in heat tolerance among Drosophila melanogaster populations collected at diverse sites along a latitudinal gradient in Argentina (24°-38°S). This is the first study to quantify heat tolerance in South American populations and our work demonstrates that most of the populations surveyed have abundant within-population phenotypic variation, while still exhibiting significant variation among populations. The one exception was the most heat tolerant population that comes from a climate exhibiting the warmest annual mean temperature. All together our results suggest there is abundant genetic variation for heat-tolerance phenotypes within and among natural populations of Drosophila and this variation has likely been shaped by environmental temperature.
Collapse
Affiliation(s)
- Lindsey C Fallis
- The Division of Biology, The Ecological Genomics Institute, Kansas State University, 116 Ackert Hall, Manhattan, KS 66506, USA
| | | | | |
Collapse
|
10
|
Lavagnino N, Serra F, Arbiza L, Dopazo H, Hasson E. Evolutionary Genomics of Genes Involved in Olfactory Behavior in the Drosophila melanogaster Species Group. Evol Bioinform Online 2012; 8:89-104. [PMID: 22346339 PMCID: PMC3273929 DOI: 10.4137/ebo.s8484] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
Previous comparative genomic studies of genes involved in olfactory behavior in Drosophila focused only on particular gene families such as odorant receptor and/or odorant binding proteins. However, olfactory behavior has a complex genetic architecture that is orchestrated by many interacting genes. In this paper, we present a comparative genomic study of olfactory behavior in Drosophila including an extended set of genes known to affect olfactory behavior. We took advantage of the recent burst of whole genome sequences and the development of powerful statistical tools to analyze genomic data and test evolutionary and functional hypotheses of olfactory genes in the six species of the Drosophila melanogaster species group for which whole genome sequences are available. Our study reveals widespread purifying selection and limited incidence of positive selection on olfactory genes. We show that the pace of evolution of olfactory genes is mostly independent of the life cycle stage, and of the number of life cycle stages, in which they participate in olfaction. However, we detected a relationship between evolutionary rates and the position that the gene products occupy in the olfactory system, genes occupying central positions tend to be more constrained than peripheral genes. Finally, we demonstrate that specialization to one host does not seem to be associated with bursts of adaptive evolution in olfactory genes in D. sechellia and D. erecta, the two specialists species analyzed, but rather different lineages have idiosyncratic evolutionary histories in which both historical and ecological factors have been involved.
Collapse
Affiliation(s)
- Nicolás Lavagnino
- Departamento de Ecología, Genética y Evolución; Facultad de Ciencias Exactas y Naturales; Universidad de Buenos Aires; Buenos Aires; Argentina
| | | | | | | | | |
Collapse
|
11
|
A quantitative genetic study of starvation resistance at different geographic scales in natural populations of Drosophila melanogaster. Genet Res (Camb) 2010; 92:253-9. [DOI: 10.1017/s0016672310000327] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
SummaryFood shortage is a stress factor that commonly affects organisms in nature. Resistance to food shortage or starvation resistance (SR) is a complex quantitative trait with direct implications on fitness. However, surveys of natural genetic variation in SR at different geographic scales are scarce. Here, we have measured variation in SR in sets of lines derived from nine natural populations of Drosophila melanogaster collected in western Argentina. Our study shows that within population variation explained a larger proportion of overall phenotypic variance (80%) than among populations (7·2%). We also noticed that an important fraction of variation was sex-specific. Overall females were more resistant to starvation than males; however, the magnitude of the sexual dimorphism (SD) in SR varied among lines and explained a significant fraction of phenotypic variance in all populations. Estimates of cross-sex genetic correlations suggest that the genetic architecture of SR is only partially shared between sexes in the populations examined, thus, facilitating further evolution of the SD.
Collapse
|
12
|
Houot B, Svetec N, Godoy-Herrera R, Ferveur JF. Effect of laboratory acclimation on the variation of reproduction-related characters in Drosophila melanogaster. J Exp Biol 2010; 213:2322-31. [DOI: 10.1242/jeb.041566] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARY
The natural variation of sex-specific characters between populations can favor their behavioral isolation, eventually leading to the formation of new species. Marked variations for male courtship, mating and the production of sex pheromones – three complex characters potentially inducing sexual isolation – were found between Drosophila melanogaster populations of various origins acclimated for many generations in research laboratories. However, the natural variation of these three characters between natural populations and their evolution after long-term acclimation in the laboratory remains unknown. We measured many traits involved in these characters in six stocks initiated with distinct populations sampled in a restricted geographic area. Several sex-specific traits varied between stocks freshly brought back to the laboratory. After 100 generations spent in the laboratory without any experimental selection, traits varied in a strain-dependent manner. This variation was not related to a reduction of their variance except for copulation duration. This indicates that reproduction-related characters can diverge between neighboring D. melanogaster populations, and differently adapt to stable laboratory conditions.
Collapse
Affiliation(s)
- Benjamin Houot
- Unité Mixte de Recherche 6265 Associée au Centre National de la Recherche Scientifique, Université de Bourgogne, Faculté des Sciences, 6, Bd Gabriel, 21 000 Dijon, France
| | - Nicolas Svetec
- Unité Mixte de Recherche 6265 Associée au Centre National de la Recherche Scientifique, Université de Bourgogne, Faculté des Sciences, 6, Bd Gabriel, 21 000 Dijon, France
| | - Raùl Godoy-Herrera
- Instituto de Ciencias, Biomédicas, Facultad de Medicina, Universidad de Chile, Independencia 1027, Santiago-7, Casilla 70061, Chile
| | - Jean-François Ferveur
- Unité Mixte de Recherche 6265 Associée au Centre National de la Recherche Scientifique, Université de Bourgogne, Faculté des Sciences, 6, Bd Gabriel, 21 000 Dijon, France
| |
Collapse
|
13
|
The transcriptional landscape of cross-specific hybrids and its possible link with growth in brook charr (Salvelinus fontinalis Mitchill). Genetics 2010; 186:97-107. [PMID: 20551437 DOI: 10.1534/genetics.110.118158] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The genetic mechanisms underlying hybridization are poorly understood despite their potentially important roles in speciation processes, adaptative evolution, and agronomical innovation. In this study, transcription profiles were compared among three populations of brook charr and their hybrids using microarrays to assess the influence of hybrid origin on modes of transcription regulation inheritance and on the mechanisms underlying growth. We found that twice as many transcripts were differently expressed between the domestic population and the two wild populations (Rupert and Laval) than between wild ones, despite their deeper genetic distance. This could reflect the consequence of artificial selection during domestication. We detected that hybrids exhibited strikingly different patterns of mode of transcription regulation, being mostly additive (94%) for domestic × Rupert, and nonadditive for Laval × domestic (45.7%) and Rupert × Laval hybrids (37.5%). Both heterosis and outbreeding depression for growth were observed among the crosses. Our results indicated that prevalence of dominance in transcription regulation seems related to growth heterosis, while prevalence of transgressive transcription regulation may be more related to outbreeding depression. Our study clearly shows, for the first time in vertebrates, that the consequences of hybridization on both the transcriptome level and the phenotype are highly dependent on the specific genetic architectures of crossed populations and therefore hardly predictable.
Collapse
|
14
|
Corrigendum. J Evol Biol 2009. [DOI: 10.1111/j.1420-9101.2009.01812.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
15
|
Renn SCP, Carleton JB, Magee H, Nguyen MLT, Tanner ACW. Maternal care and altered social phenotype in a recently collected stock of Astatotilapia burtoni cichlid fish. Integr Comp Biol 2009; 49:660-73. [DOI: 10.1093/icb/icp085] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
|
16
|
Normandeau E, Hutchings JA, Fraser DJ, Bernatchez L. Population-specific gene expression responses to hybridization between farm and wild Atlantic salmon. Evol Appl 2009; 2:489-503. [PMID: 25567894 PMCID: PMC3352448 DOI: 10.1111/j.1752-4571.2009.00074.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2009] [Accepted: 04/29/2009] [Indexed: 11/29/2022] Open
Abstract
Because of intrinsic differences in their genetic architectures, wild populations invaded by domesticated individuals could experience population-specific consequences following introgression by genetic material of domesticated origin. Expression levels of 16 000 transcripts were quantified by microarrays in liver tissue from farm, wild, and farm-wild backcross (i.e. F1 farm-wild hybrid × wild; total n = 50) Atlantic salmon (Salmo salar) raised under common environmental conditions. The wild populations and farm strain originated from three North American rivers in eastern Canada (Stewiacke, Tusket, and Saint John rivers, respectively). Analysis of variance revealed 177 transcripts with different expression levels among the five strains compared. Five times more of these transcripts were differentiated between farmed parents and Tusket backcrosses (n = 53) than between Stewiacke backcrosses and their farmed parents (n = 11). Altered biological processes in backcrosses also differed between populations both in number and in the type of processes impacted (metabolism vs immunity). Over-dominant gene expression regulation in backcrosses varied considerably between populations (23% in Stewiacke vs 44% in Tusket). Hence, the consequences of introgression of farm genetic material on gene expression depended on population-specific genetic architectures. These results support the need to evaluate impacts of farm-wild genetic interactions at the population scale.
Collapse
Affiliation(s)
| | | | - Dylan J Fraser
- Department of Biology, Dalhousie University Halifax, Nova Scotia, Canada
| | | |
Collapse
|
17
|
Dangles O, Irschick D, Chittka L, Casas J. Variability in Sensory Ecology: Expanding the Bridge Between Physiology and Evolutionary Biology. QUARTERLY REVIEW OF BIOLOGY 2009; 84:51-74. [DOI: 10.1086/596463] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
|
18
|
Genetic changes accompanying the evolution of host specialization in Drosophila sechellia. Genetics 2008; 181:721-36. [PMID: 19033155 DOI: 10.1534/genetics.108.093419] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Changes in host specialization contribute to the diversification of phytophagous insects. When shifting to a new host, insects evolve new physiological, morphological, and behavioral adaptations. Our understanding of the genetic changes responsible for these adaptations is limited. For instance, we do not know how often host shifts involve gain-of-function vs. loss-of-function alleles. Recent work suggests that some genes involved in odor recognition are lost in specialists. Here we show that genes involved in detoxification and metabolism, as well as those affecting olfaction, have reduced gene expression in Drosophila sechellia-a specialist on the fruit of Morinda citrifolia. We screened for genes that differ in expression between D. sechellia and its generalist sister species, D. simulans. We also screened for genes that are differentially expressed in D. sechellia when these flies chose their preferred host vs. when they were forced onto other food. D. sechellia increases expression of genes involved with oogenesis and fatty acid metabolism when on its host. The majority of differentially expressed genes, however, appear downregulated in D. sechellia. For several functionally related genes, this decrease in expression is associated with apparent loss-of-function alleles. For example, the D. sechellia allele of Odorant binding protein 56e (Obp56e) harbors a premature stop codon. We show that knockdown of Obp56e activity significantly reduces the avoidance response of D. melanogaster toward M. citrifolia. We argue that apparent loss-of-function alleles like Obp56e potentially contributed to the initial adaptation of D. sechellia to its host. Our results suggest that a subset of genes reduce or lose function as a consequence of host specialization, which may explain why, in general, specialist insects tend to shift to chemically similar hosts.
Collapse
|
19
|
Ruebenbauer A, Schlyter F, Hansson BS, Löfstedt C, Larsson MC. Genetic variability and robustness of host odor preference in Drosophila melanogaster. Curr Biol 2008; 18:1438-43. [PMID: 18804372 DOI: 10.1016/j.cub.2008.08.062] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2008] [Revised: 08/04/2008] [Accepted: 08/15/2008] [Indexed: 11/19/2022]
Abstract
Chemosensory stimuli play a crucial role for host selection in insects, including the fruit fly Drosophila melanogaster. Drosophila has been instrumental in unraveling the neurological basis of olfactory processing in insects. Basic knowledge regarding chemical ecology and thorough studies of olfactory preferences are still lacking to a great extent in D. melanogaster, however. We have characterized repeatable variation in olfactory preference between five classical D. melanogaster wild-type strains toward a large array of natural host odors and synthetic compounds. By recording the rate of attraction over up to 24 hr, we could compare stimuli varying in attractiveness and characterize phenotypic parameters on the basis of individual stimuli and the whole stimulus array. Behavioral differences between strains were predominantly due to variation in a single phenotypic parameter: their overall responsiveness toward optimal and suboptimal olfactory stimuli. These differences were not explained by variation in olfactory sensitivity, locomotory activity, or general vigor monitored by survival. Comparisons with three recently established wild-type strains indicated that a high behavioral threshold against accepting suboptimal olfactory stimuli is the characteristic phenotype of wild D. melanogaster.
Collapse
|