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Ospina OE, Lemmon AR, Dye M, Zdyrski C, Holland S, Stribling D, Kortyna ML, Lemmon EM. Neurogenomic divergence during speciation by reinforcement of mating behaviors in chorus frogs (Pseudacris). BMC Genomics 2021; 22:711. [PMID: 34600496 PMCID: PMC8487493 DOI: 10.1186/s12864-021-07995-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2020] [Accepted: 09/10/2021] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Species interactions can promote mating behavior divergence, particularly when these interactions are costly due to maladaptive hybridization. Selection against hybridization can indirectly cause evolution of reproductive isolation within species, a process termed cascade reinforcement. This process can drive incipient speciation by generating divergent selection pressures among populations that interact with different species assemblages. Theoretical and empirical studies indicate that divergent selection on gene expression networks has the potential to increase reproductive isolation among populations. After identifying candidate synaptic transmission genes derived from neurophysiological studies in anurans, we test for divergence of gene expression in a system undergoing cascade reinforcement, the Upland Chorus Frog (Pseudacris feriarum). RESULTS Our analyses identified seven candidate synaptic transmission genes that have diverged between ancestral and reinforced populations of P. feriarum, including five that encode synaptic vesicle proteins. Our gene correlation network analyses revealed four genetic modules that have diverged between these populations, two possessing a significant concentration of neurotransmission enrichment terms: one for synaptic membrane components and the other for metabolism of the neurotransmitter nitric oxide. We also ascertained that a greater number of genes have diverged in expression by geography than by sex. Moreover, we found that more genes have diverged within females as compared to males between populations. Conversely, we observed no difference in the number of differentially-expressed genes within the ancestral compared to the reinforced population between the sexes. CONCLUSIONS This work is consistent with the idea that divergent selection on mating behaviors via cascade reinforcement contributed to evolution of gene expression in P. feriarum. Although our study design does not allow us to fully rule out the influence of environment and demography, the fact that more genes diverged in females than males points to a role for cascade reinforcement. Our discoveries of divergent candidate genes and gene networks related to neurotransmission support the idea that neural mechanisms of acoustic mating behaviors have diverged between populations, and agree with previous neurophysiological studies in frogs. Increasing support for this hypothesis, however, will require additional experiments under common garden conditions. Our work points to the importance of future replicated and tissue-specific studies to elucidate the relative contribution of gene expression divergence to the evolution of reproductive isolation during incipient speciation.
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Affiliation(s)
- Oscar E Ospina
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, 1800 Christensen Drive, 50011, Ames, IA, USA
- Present address: Department of Biostatistics and Bioinformatics, Moffitt Cancer Center, 13131 USF Magnolia Drive, Tampa, FL, 33612, USA
| | - Alan R Lemmon
- Department of Scientific Computing, Florida State University, 400 Dirac Science Library, Tallahassee, FL, 32306, USA
| | - Mysia Dye
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, 1800 Christensen Drive, 50011, Ames, IA, USA
| | - Christopher Zdyrski
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, 1800 Christensen Drive, 50011, Ames, IA, USA
- Present address: Genetics and Genomics Program, Iowa State University, 2437 Pammel Drive, Ames, IA, 50011, USA
| | - Sean Holland
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, 1800 Christensen Drive, 50011, Ames, IA, USA
| | - Daniel Stribling
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, 1800 Christensen Drive, 50011, Ames, IA, USA
- Present address: Department of Molecular Genetics and Microbiology, Genetics Institute, University of Florida, Gainesville, FL, 32610, USA
| | - Michelle L Kortyna
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, 1800 Christensen Drive, 50011, Ames, IA, USA
| | - Emily Moriarty Lemmon
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, 1800 Christensen Drive, 50011, Ames, IA, USA.
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Wang X, Verschut TA, Billeter JC, Maan ME. Seven Questions on the Chemical Ecology and Neurogenetics of Resource-Mediated Speciation. Front Ecol Evol 2021. [DOI: 10.3389/fevo.2021.640486] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Adaptation to different environments can result in reproductive isolation between populations and the formation of new species. Food resources are among the most important environmental factors shaping local adaptation. The chemosensory system, the most ubiquitous sensory channel in the animal kingdom, not only detects food resources and their chemical composition, but also mediates sexual communication and reproductive isolation in many taxa. Chemosensory divergence may thus play a crucial role in resource-mediated adaptation and speciation. Understanding how the chemosensory system can facilitate resource-mediated ecological speciation requires integrating mechanistic studies of the chemosensory system with ecological studies, to link the genetics and physiology of chemosensory properties to divergent adaptation. In this review, we use examples of insect research to present seven key questions that can be used to understand how the chemosensory system can facilitate resource-mediated ecological speciation in consumer populations.
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St John ME, Fuller RC. Asymmetric reinforcement in Lucania killifish: assessing reproductive isolation when both sexes choose. Curr Zool 2020; 67:215-224. [PMID: 33854539 PMCID: PMC8026148 DOI: 10.1093/cz/zoaa049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2020] [Accepted: 08/25/2020] [Indexed: 11/21/2022] Open
Abstract
Reinforcement can occur when maladaptive hybridization in sympatry favors the evolution of conspecific preferences and target traits that promote behavioral isolation (BI). In many systems, enhanced BI is due to increased female preference for conspecifics. In others, BI is driven by male preference, and in other systems both sexes exert preferences. Some of these patterns can be attributed to classic sex-specific costs and benefits of preference. Alternatively, sex differences in conspecific preference can emerge due to asymmetric postzygotic isolation (e.g., hybrid offspring from female A × male B have lower fitness than hybrid offspring from female B × male A), which can lead to asymmetric BI (e.g., female A and male B are less likely to mate than female B and male A). Understanding reinforcement requires understanding how conspecific preferences evolve in sympatry. Yet, estimating conspecific preferences can be difficult when both sexes are choosy. In this study, we use Lucania killifish to test the hypothesis that patterns of reinforcement are driven by asymmetric postzygotic isolation between species. If true, we predicted that sympatric female Lucania goodei and sympatric male L. parva should have lower levels of BI compared with their sympatric counterparts, as they produce hybrid offspring with the highest fitness. To address the problem of measuring BI when both sexes are choosy, we inferred the contribution to BI of each partner using assays where one sex in the mating pair comes from an allopatric population with potentially low preference, whereas the other comes from a sympatric population with high preference. For one hybrid cross direction, we found that both female L. parva and male L. goodei have high contributions to BI in sympatry. In the other hybrid cross direction, we found that only female L. goodei contribute to BI. Sympatric male L. parva readily engaged in hybrid spawnings with allopatric L. goodei females. These results indicate that both asymmetric postzygotic isolation and the traditional sex-specific costs to preference likely affect the nature of selection on conspecific preferences and target traits.
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Affiliation(s)
- Michelle E St John
- School of Integrative Biology, University of Illinois Urbana-Champaign, Champaign, IL 61820, USA
| | - Rebecca C Fuller
- School of Integrative Biology, University of Illinois Urbana-Champaign, Champaign, IL 61820, USA
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Larson EL, Brassil MM, Maslan J, Juárez D, Lilagan F, Tipton H, Schweitzer A, Skillman J, Monsen-Collar KJ, Peterson MA. The effects of heterospecific mating frequency on the strength of cryptic reproductive barriers. J Evol Biol 2019; 32:900-912. [PMID: 31162735 DOI: 10.1111/jeb.13495] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2019] [Revised: 05/22/2019] [Accepted: 05/28/2019] [Indexed: 01/02/2023]
Abstract
Heterospecific mating frequency is critical to hybrid zone dynamics and can directly impact the strength of reproductive barriers and patterns of introgression. The effectiveness of post-mating prezygotic (PMPZ) reproductive barriers, which include reduced fecundity via heterospecific matings and conspecific sperm precedence, may depend on the number, identity and order of mates. Studies of PMPZ barriers suggest that they may be important in many systems, but whether these barriers are effective at realistic heterospecific mating frequencies has not been tested. Here, we evaluate the strength of cryptic reproductive isolation in two leaf beetles (Chrysochus auratus and C. cobaltinus) in the context of a range of heterospecific mating frequencies observed in natural populations. We found both species benefited from multiple matings, but the benefits were greater in C. cobaltinus and extended to heterospecific matings. We found that PMPZ barriers greatly limited hybrid production by C. auratus females with moderate heterospecific mating frequencies, but that their effectiveness diminished at higher heterospecific mating frequencies. In contrast, there was no evidence for PMPZ barriers in C. cobaltinus females at any heterospecific mating frequency. We show that integrating realistic estimates of cryptic isolation with information on relative abundance and heterospecific mating frequency in the field substantially improves our understanding of the strong directional bias in F1 production previously documented in the Chrysochus hybrid zone. Our results demonstrate that heterospecific mating frequency is critical to understanding the impact of cryptic post-copulatory barriers on hybrid zone structure and dynamics, and that future studies of such barriers should incorporate field-relevant heterospecific mating frequencies.
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Affiliation(s)
- Erica L Larson
- Department of Biological Sciences, University of Denver, Denver, Colorado, USA.,Biology Department, Western Washington University, Bellingham, Washington, USA
| | - Margaret M Brassil
- Biology Department, Western Washington University, Bellingham, Washington, USA
| | - Jonathan Maslan
- Biology Department, Western Washington University, Bellingham, Washington, USA
| | - Danielle Juárez
- Biology Department, Western Washington University, Bellingham, Washington, USA
| | - Flordeliza Lilagan
- Biology Department, Western Washington University, Bellingham, Washington, USA
| | - Hallie Tipton
- Biology Department, Western Washington University, Bellingham, Washington, USA
| | - Andrew Schweitzer
- Biology Department, Western Washington University, Bellingham, Washington, USA
| | - Joe Skillman
- Biology Department, Western Washington University, Bellingham, Washington, USA
| | | | - Merrill A Peterson
- Biology Department, Western Washington University, Bellingham, Washington, USA
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Dyer KA, Bewick ER, White BE, Bray MJ, Humphreys DP. Fine-scale geographic patterns of gene flow and reproductive character displacement in Drosophila subquinaria and Drosophila recens. Mol Ecol 2018; 27:10.1111/mec.14825. [PMID: 30074656 PMCID: PMC6360132 DOI: 10.1111/mec.14825] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2018] [Revised: 07/13/2018] [Accepted: 07/14/2018] [Indexed: 12/12/2022]
Abstract
When two species are incompletely isolated, strengthening premating isolation barriers in response to the production of low fitness hybrids may complete the speciation process. Here, we use the sister species Drosophila subquinaria and Drosophila recens to study the conditions under which this reinforcement of species boundaries occurs in natural populations. We first extend the region of known sympatry between these species, and then we conduct a fine-scale geographic survey of mate discrimination coupled with estimates of gene flow within and admixture between species. Within D. subquinaria, reinforcement is extremely effective: we find variation in mate discrimination both against D. recens males and against conspecific allopatric males on the scale of a few kilometres and in the face of gene flow both from conspecific populations and introgression from D. recens. In D. recens, we do not find evidence for increased mate discrimination in sympatry, even where D. recens is rare, consistent with substantial gene flow throughout the species' range. Finally, we find that introgression between species is asymmetric, with more from D. recens into D. subquinaria than vice versa. Within each species, admixture is highest in the geographic region where it is rare relative to the other species, suggesting that when hybrids are produced they are of low fitness. In sum, reinforcement within D. subquinaria is effective at maintaining species boundaries, but even when reinforcing selection is strong it may not always result in a pattern of strong reproductive character displacement due to variation in the frequency of hybridization and gene flow from neighbouring populations.
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Affiliation(s)
- Kelly A. Dyer
- Department of Genetics; University of Georgia; Athens, GA 30602; USA
| | | | - Brooke E. White
- Department of Genetics; University of Georgia; Athens, GA 30602; USA
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Siepielski AM, McPeek SJ, McPeek MA. Female mate preferences on high-dimensional shape variation for male species recognition traits. J Evol Biol 2018; 31:1239-1250. [PMID: 29876989 DOI: 10.1111/jeb.13302] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Revised: 05/14/2018] [Accepted: 05/31/2018] [Indexed: 01/01/2023]
Abstract
Females in many animal species must discriminate between conspecific and heterospecific males when choosing mates. Such mating preferences that discriminate against heterospecifics may inadvertently also affect the mating success of conspecific males, particularly those with more extreme phenotypes. From this expectation, we hypothesized that female mate choice should cause Enallagma females (Odonata: Coenagrionidae) to discriminate against conspecific males with more extreme phenotypes of the claspers males use to grasp females while mating - the main feature of species mate recognition in these species. To test this, we compared cerci sizes and shapes between males that were captured while mating with females to males that were captured at the same time but not mating in three Enallagma species. In contrast to our hypothesis, we found only one of forty comparisons of shape variation that was consistent with females discriminating against males with more extreme cerci shapes. Instead, differences in cerci shape between mating and single males suggested that females displayed directional preferences on 1-4 aspects of cerci shape in two of the species in our samples. These results suggest that whereas some directional biases in mating based on cerci shape occur, the intraspecific phenotypic variation in male cerci size and shape is likely not large enough for females to express any significant incidental discrimination among conspecifics with more extreme shapes.
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Affiliation(s)
- Adam M Siepielski
- Department of Biological Sciences, University of Arkansas, Fayetteville, AR, USA
| | - Sarah J McPeek
- Department of Biological Sciences, Dartmouth College, Hanover, NH, USA
| | - Mark A McPeek
- Department of Biological Sciences, Dartmouth College, Hanover, NH, USA
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De Lisle SP, Svensson EI. On the standardization of fitness and traits in comparative studies of phenotypic selection. Evolution 2017; 71:2313-2326. [PMID: 28804878 DOI: 10.1111/evo.13325] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2017] [Accepted: 08/03/2017] [Indexed: 02/02/2023]
Abstract
Comparisons of the strength and form of phenotypic selection among groups provide a powerful approach for testing adaptive hypotheses. A central and largely unaddressed issue is how fitness and phenotypes are standardized in such studies; standardization across or within groups can qualitatively change conclusions whenever mean fitness differs between groups. We briefly reviewed recent relevant literature, and found that selection studies vary widely in their scale of standardization, but few investigators motivated their rationale for chosen standardization approaches. Here, we propose that the scale at which fitness should be relativized should reflect whether selection is likely to be hard or soft; that is, the scale at which populations (or hypothetical populations in the case of a contrived experiment) are regulated. We argue that many comparative studies of selection are implicitly or explicitly focused on soft selection (i.e., frequency and density-dependent selection). In such studies, relative fitness should preferably be calculated using within-group means, although this approach is taken only occasionally. Related difficulties arise for the standardization of phenotypes. The appropriate scale at which standardization should take place depends on whether groups are considered to be fixed or random. We emphasize that the scale of standardization is a critical decision in empirical studies of selection that should always warrant explicit justification.
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Affiliation(s)
- Stephen P De Lisle
- Evolutionary Ecology Unit, Department of Biology, Lund University, Sölvegatan 37, 223 62 Lund, Sweden
| | - Erik I Svensson
- Evolutionary Ecology Unit, Department of Biology, Lund University, Sölvegatan 37, 223 62 Lund, Sweden
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Fuller RC. Reconciling concepts, theory, and empirical patterns surrounding cascade reinforcement. Curr Zool 2016; 62:131-134. [PMID: 29491900 PMCID: PMC5804233 DOI: 10.1093/cz/zow011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- Rebecca C Fuller
- Department of Animal Biology, University of Illinois, Urbana, IL 61801, USA
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9
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Humphreys DP, Rundle HD, Dyer KA. Patterns of reproductive isolation in the Drosophila subquinaria complex: can reinforced premating isolation cascade to other species? Curr Zool 2016; 62:183-191. [PMID: 29491905 PMCID: PMC5804228 DOI: 10.1093/cz/zow005] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Accepted: 12/17/2015] [Indexed: 12/29/2022] Open
Abstract
The reinforcement of premating barriers due to reduced hybrid fitness in sympatry may cause secondary sexual isolation within a species as a by-product. Consistent with this, in the fly Drosophila subquinaria, females that are sympatric with D. recens mate at very low rates not only with D. recens, but also with conspecific D. subquinaria males from allopatry. Here, we ask if these effects of reinforcement cascade more broadly to affect sexual isolation with other closely related species. We assay reproductive isolation of these species with D. transversa and find that choosy D. subquinaria females from the region sympatric with D. recens discriminate strongly against male D. transversa, whereas D. subquinaria from the allopatric region do not. This increased sexual isolation cannot be explained by natural selection to avoid mating with this species, as they are allopatric in geographic range and we do not identify any intrinsic postzygotic isolation between D. subquinaria and D. transversa. Variation in epicuticular hydrocarbons, which are used as mating signals in D. subquinaria, follow patterns of premating isolation: D. transversa and allopatric D. subquinaria are most similar to each other and differ from sympatric D. subquinaria, and those of D. recens are distinct from the other two species. We suggest that the secondary effects of reinforcement may cascade to strengthen reproductive isolation with other species that were not a target of selection. These effects may enhance the divergence that occurs in allopatry to help explain why some species are already sexually isolated upon secondary contact.
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Affiliation(s)
- Devon P Humphreys
- Department of Genetics, University of Georgia, Athens, GA 30602, USA
| | - Howard D Rundle
- Department of Biology, University of Ottawa, Ottawa, ON K1N 6N5; Canada
| | - Kelly A Dyer
- Department of Genetics, University of Georgia, Athens, GA 30602, USA
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